Search

In high-altitude areas, suppressing the flicker of methane laminar diffusion flame and reducing carbon emissions simultaneously is a challenge. This paper proposes a combustion strategy involving sub-atmospheric pressure and ammonia mixing. Through high-speed imaging and schlieren techniques, the study explores the flame flicker patterns under mixing ratios of 0–60% ammonia at 0.5–1.0 atm, as well as the structural and dynamic characteristics of shear layers and vortices. The stable combustion mechanism of sub-atmospheric pressure and ammonia mixing is also analyzed. It was found that reducing the pressure reduced the flame Richardson number, eased the formation of vortices and weakened the interaction with the flame. The heat release rate of the flame decreases after mixing ammonia, which leads to a decrease in the density gradient of the shear layer and also slows down the formation of vortices. The characteristic values of flicker were quantified. Decreasing the pressure, the flicker frequency decreases. Increasing the ammonia mixing ratio, the flicker frequency increases and the oscillation amplitude shows a highly nonlinear decreasing trend. It is verified that the flicker frequency still satisfies the function form of the Strouhal-Froude number under sub-atmospheric pressure and ammonia mixed combustion. • Established a combustion chamber capable of simulating plateau areas' pressure. • Provided vortex characteristic information through high-speed Schlieren imaging. • Complete suppression of flame flicker observed at 0.5 atm/50% ammonia mixture. • Ammonia mixture can both reduce carbon emissions and suppress flame flicker. • Pressure reduction and ammonia mixture alter density gradients in the shear layer. [ABSTRACT FROM AUTHOR]

The paper presents the results of numerical experiments on the implementation of Over Fire Air (OFA) technology at a coal burning thermal power plant (TPP) in order to reduce emissions of harmful substances into the atmosphere. To implement the OFA technology, various options for supplying additional air through injectors in the upper part of the combustion chamber have been studied. For the first time, various heights (h = 8 m, 9 m, 10 m, 11 m, 12 m) of the location of OFA injectors in the combustion chamber at the kazakh TPP were studied. For the first time, different volumes of additional air supply through the injectors are simulated when OFA is 0% - this is the base case (traditional combustion) and when OFA is 5%, 10%, 15%, 18%, 20%, 25% and 30% of the total volume air required for complete combustion of the fuel. It is shown that at the optimal location height of OFA injectors (h = 9 m), an increase in the volume of additional air to 18% leads to a decrease in the concentrations of carbon monoxide CO by about 36%, and nitrogen dioxide NO 2 by 25% compared with the base case (OFA = 0%). • The effect of Over Fire Air (OFA) technology on furnace processes has been studied. • Found the optimal location of OFA-injectors in the combustion chamber. • Found the optimal amount of additional air flowing through the injectors. • OFA technologies optimize the combustion process and reduce harmful emissions. [ABSTRACT FROM AUTHOR]

The paper provides a discussion on environmental and energy performance of coal fuelled boilers falling into the group of small combustion installations and medium combustion plants. In particular, new technical measure for reducing emissions, mainly of particulate matter is described. The paper presents a new cyclone type deduster, combined with known technique of external flue gas recycle. A new technical solution offers efficient removal of particulate matter from flue gasses, by centrifugal mechanism. The approaches to modeling of apparatus performance, with experimental validation of the models used, as well as resulting design are presented. The new cyclone type separator, with vertical baffles along with improved separation efficiency, by 37.8%, allows for external flue gas recycle, which results in emissions of NO x reduced by 20.3% as well as energy efficiency improved by 2.3%. The measurement results of an industrial case study are presented and discussed. [ABSTRACT FROM AUTHOR]

The firebricks in gasifier combustion chamber are the vital parts for gasification. They are gradually degraded with service time due to the harsh conditions. This paper focuses on the recognition of degradation of firebricks and analysis of their residual life, which are of great significance for ensuring the safe operation of a gasifier. In this paper, the Hidden Semi-Markov Model (HSMM) was employed and the degradation recognition and residual life analysis of the firebricks in a gasifier combustor of a company under actual working conditions were carried out. The results show that the degradations of firebricks in the jet area of cylinder part are faster than that in the arch crown and the pipe area. In the early and middle stages of firebrick life, the transformation of its degradation state takes longer time than in the later stage of firebrick life. And the residual life of each layer firebrick is short in the later stage of the firebrick life. The residual life of firebricks in the jet area of cylinder part is shorter than that in the jet area of arch crown and pipe area. HSMM method is a suitable method that provides new solutions for firebrick maintenance strategies. • HSMM was used for degradation and residual life analysis of firebricks in gasifier. • The degradation rate of firebricks in the jet area of the cylinder is the fastest. • The residual life of firebricks in the jet area of the cylinder is the shortest. • The HSMM method provides a new solution for firebrick maintenance strategies. [ABSTRACT FROM AUTHOR]

The objective of the paper is a proposal of a quick start of the steam boiler from the cold state. Fuel consumption rate necessary for heating the evaporator from initial temperature to a predetermined temperature was determined using a transient mathematical model of the boiler evaporator developed in the paper. The model takes into account that at the beginning of the evaporator water is heated without steam generation and then after reaching the saturation temperature the boiling process is started and steam is produced. The mathematical model of the evaporator was verified experimentally. Heating of the evaporator is carried out with a maximum temperature change rate due to the maximum circumferential stress occurring at the edge of the drum–downcomer junction. After determining the optimum fluid temperature the pressure can easily be determined because the pressure of the saturated steam is a function of temperature. Using mathematical models of the evaporator and the combustion chamber the mass flow rate of the fuel ensuring optimum drum heating was calculated. The mass of heavy oil consumed during optimum warm-up of the drum was also calculated. [ABSTRACT FROM AUTHOR]

This paper proposes a combined cooling, heating and power (CCHP), and multi-effect desalination system to supply cooling, heating, power and freshwater. The proposed system mainly includes a gas turbine (GT), a multi-effect desalination unit with a thermal vapor compressor (MED-TVC), an organic Rankine cycle (ORC) integrated with a steam ejector refrigerator (SER), and heat exchangers. The mathematical model is developed to thermodynamically conduct energy-exergy analysis, and a parametric study is performed to explore the effects of key design parameters such as air compressor pressure ratio, inlet air temperature of air compressor, pinch point temperature difference of waste heat boiler, motive steam pressure of MED-TVC unit, TVC compression ratio and working medium flow rate of ORC on the system performance. The proposed system can provide power, heating, cooling and freshwater at loads of 31.25 MW, 1.108 MW, 4.203 MW and 85.89 kg/s under the design conditions. The electrical, the exergy, and the overall energy efficiencies of the present system are 36.44%, 41.26% and 46.70%, respectively. The results indicate that the power output of GT can be increased by precooling the inlet air of air compressor, and the integration of GT with MED-TVC unit, ORC and heat exchangers can efficiently recover the waste heat from exhaust gas based on the principle of "energy cascade utilization". In addition, the largest exergy destruction occurs in the combustion chamber followed by regenerator 1 and the MED-TVC unit. • Energy and exergy analysis of a poly-generation system is presented. • Waste heat is recovered based on the principle of "energy cascade utilization". • Organic Rankine cycle is integrated with a steam ejector refrigerator. • The inlet air of GT is precooled to improve the power output. [ABSTRACT FROM AUTHOR]

The biomass-based systems have considerable feasibility to design a co-generation with different subsystems. This paper presents a novel biomass-based gas turbine with a modified Kalina cycle, supercritical-CO 2 cycle, and LNG regasifying subsystems. A turbine is installed in the LNG regasifying subsystems to produce more power. Energy, advanced exergy, including thermal and mechanical exergies, and economic analyses are applied to assess the system's performance. Three double-objective and two triple-objective optimizations are carried out to obtain the system's operation mode at the optimum state. The results reveal that the combustion chamber and supercritical-CO 2 cycle's condenser have the highest exergy destruction. Also, the compressors and turbines have the main portion of the investment cost rate of about 79.91%. The design system provides 7560 kW net power, 41.75% exergy efficiency, and 6.2 years payback period. Regarding the parametric study, the system's performance indexes are mainly affected by the air compressor's pressure ratio. Furthermore, considering the net power-sum unit cost of production as the optimization goal represents the best performance of 7830 kW net power, 42.97% exergy efficiency, and 7.262 $/GJ sum unit cost of products. • A novel Power generation system driven by biomass gasification and LNG regasification is proposed. • Thermodynamic, exergoeconomic, and economic analyses are implemented. • Advanced exergy analysis based on mechanical and thermal exergies is performed. • A multi-objective optimization is applied using the MOPSO algorithm is applied. • The system's exergy efficiency and net output power are 41.75 % and 7.56 M W , respectively. [ABSTRACT FROM AUTHOR]

Using hydrocarbon fuel as cooling film is one of the most promising ways to thermally protect supersonic combustors and it can also be considered as a special combustion process. Parametric analysis is very important for increasing combustion efficiency of this special combustion process which is a parallel fuel wall-jet, and it is numerically investigated in this paper. It is found that, for parallel wall-jet combustion lacking near-field mixing enhancement because of the thermal protection purpose, decreasing equivalence ratio can lead to a significant increase in combustion efficiency since the wall-jet combustion efficiency is only determined by the shear mixing process. Moreover, under the constant equivalence ratio, increasing injection height from 0.67 mm to 2 mm can only slightly increase the combustion efficiency by 1.5% although it can reach a much better cooling performance. It is worth mentioning that, the effects of mainstream parameters on combustion efficiency present a step trend, self-ignition will occur as the mainstream temperature or Mach number reaches a certain value. And afterward, keep increasing mainstream temperature has little effect on the combustion efficiency since the mixing process keeps almost unchanged. Whereas, continuous reduction of mainstream Mach number will improve combustion efficiency by significantly enhancing mixing. • Parallel wall-jet combustion is very sensitive to wall-jet equivalence ratio. • Higher injection height promotes combustion with constant equivalence ratio. • Higher injection height can also promote cooling performance meaning time. • Effects of mainstream parameters on combustion efficiency presents a step trend. [ABSTRACT FROM AUTHOR]

Proposing an effective multi-source plant is a promising approach to achieving higher performance in energy systems. By utilizing multiple energy sources, such as renewable and conventional sources, synergistically, a multi-source plant can enhance system efficiency, reliability, and sustainability. This paper presents a novel combination of a gas turbine cycle and a geothermal system for power and freshwater production, where the gas turbine cycle is an integration of modified methane and biomass-based systems. The proposed plant aims to improve the performance of conventional systems by considering thermodynamic, economic, and multi-objective optimization perspectives. Energy, exergy, and economic analyses are applied to assess the system's performance. Two double-objective optimizations are carried out to obtain the system's operation mode at the optimum state. The results reveal that the combustion chamber has the highest exergy destruction rate by 2967 kW. At the base operation conditions, the design system provides 5601 kW of net power, a freshwater production rate of 10.05 kg/s, and 39.5% of exergy efficiency. Furthermore, considering the net power-freshwater production rate as the optimization scenario, the optimum of 7070.52 kW net power and 41.16% exergy efficiency. While, considering exergy efficiency-exergy destruction as the objective scenario, the best payback period is obtained to be 5.71 years. • Proposal and assessment of a novel multi-source power and freshwater production cycle. • Reporting the highest exergy destruction rate of 2967 kW for the combustion chamber. • Reporting 5601 kW net power and 10.05 kg/s freshwater in the designed system at the base operating conditions. • Achieving 41.16% exergetic efficiency with 5.86 years payback period and 10.85 M$ NPV in the second optimization scenario. • The best payback period is reported for the second optimization scenario by 5.71 years. [ABSTRACT FROM AUTHOR]

The combustion instability has been an ubiquitous problem for more than a century, especially for the first-order tangential modes. In this mode, the heat transfer rates may be greatly enhanced, resulting in the deterioration of the propulsion performance and even severe physical damage of the injector faceplate. In this paper, the effect of the longitudinal baffled blades on the first-order tangential acoustic mode in a cylindrical chamber with the nozzle was theoretically and experimentally investigated. The longitudinal baffled blades were installed on the inner surface of the chamber. The linear analysis method was adopted. The theoretical results were in good agreement with the experimental results. The conclusion was that the longitudinal baffled blades can restrain the first-order acoustic instability of the combustion chamber. With the increase in the height and number of the baffle blade, the amplitude of the first-order tangential acoustic mode gradually decreased, while the amplitude of the other modes gradually increased. With the increase in the diameter of the nozzle outlet, the amplitudes of the first-order tangential oscillation mode and the first-order tangential acoustic mode all decreased. However, they varied in a relatively small range. • Effects of the inner-surface chamber baffled blades on the tangential acoustic mode are studied. • Effects of nozzle diameters on tangential acoustic mode in a cylindrical chamber are considered. • The baffled blades can restrain the first-order acoustic instability of combustion chamber. • Amplitudes of tangential acoustic mode decrease with the increase of baffle blade height and number. [ABSTRACT FROM AUTHOR]

Combustion of hydrogen or hydrogen containing blends in gas turbines and industrial combustors can activate thermoacoustic combustion instabilities. Convective instabilities are an important and yet less investigated class of combustion instability that are caused by the so called "entropy waves". As a major shortcoming, the partial decay of these convective-diffusive waves in the post-flame region of combustors is still largely unexplored. This paper, therefore, presents an investigation of the annihilating effects, due to hydrodynamics, heat transfer and flow stretch upon the nozzle response. The classical compact analysis is first extended to include the decay of entropy waves and heat transfer from the nozzle. Amplitudes and phase shifts of the responding acoustical waves are then calculated for subcritical and supercritical nozzles subject to acoustic and entropic forcing. A relation for the stretch of entropy wave in the nozzle is subsequently developed. It is shown that heat transfer and hydrodynamic decay can impart considerable effects on the entropic response of the nozzle. It is further shown that the flow stretching effects are strongly frequency dependent. The results indicate that dissipation and dispersion of entropy waves can significantly influence their conversion to sound and therefore should be included in the entropy wave models. • Decaying mechanisms of a hot spot can affect indirect noise, depending on nozzle regime. • Only low frequency content of entropy wave can survive the diffusive-dissipative flow. • Stretch of the entropy wave in the nozzle can be a main source of dispersion. [ABSTRACT FROM AUTHOR]

In the continuous quest for increased efficiency and reduced environmental impact in the use of internal combustion engines (ICEs), water injection has historically been one strategy used to achieve these objectives. However, practically all of the investigations carried out in this field are experimental tests in which water is injected into the air or combustible air mixture prior to entering the cylinder. The research presented in this paper demonstrates the results of a thermodynamic model simulation of two zones, which integrates the water injection directly into the combustion chamber. The model allows for prediction of the performance parameters of an ICE that uses water injection, as it adequately interprets the injection process phenomenology during the closed phase and the performances of important operating parameters. The model is validated by comparing its results to those reported by experimental research, using the same proposed water injection methodology and gasoline as fuel. The proposed simulation model offers significant flexibility, as it can be used to simulate different engine geometries, rotation speeds and fuels such as gasoline, ethanol, hydrated ethanol or mixtures thereof, in varying proportions. In addition, it provides a starting point for the implementation of a turbo charge and direct fuel injection model, which would allow the simulation of devices representing the current trend in the use of ECI. The results of the comparison between the experimental and simulated data show maximum error percentages of 11% in the case of BSFC, for different percentages of mass of water injection with respect to the mass of fuel, which shows the promising development of the model. • Simulation of the water injection process directly into the combustion chamber of a spark ignition engine. • Simulation of the water evaporation process to the conditions inside the cylinder during the closed phase. • Influence on engine performance, knock prevention and NOx emission control. [ABSTRACT FROM AUTHOR]

Abstract The diesel engine requirements regarding the reduction of exhaust emissions, especially nitrogen oxide (NO x) and particulate matter (PM) are becoming more stringent year by year. A current method used for NO x control is exhaust gas recirculation (EGR). However, this approach significantly increases the production of soot for medium and high rates. Water addition can also be used for NO x control, achieving 50% NO x reduction rates in relation to EGR with a lower production of soot and without additional carbon monoxide (CO) and hydrocarbons (HC) substantially. This paper analyses the weaknesses and the strengths of adding water into the intake manifold with a flow-blurring injector for NOx reduction on a current technology diesel engine with multiple injection thorough a proprietary tool for heat release rate that considered real gas properties. A reduction of NO x emissions around 60–70% was achieved with water injection at different loads and speeds. Besides, a clear relationship was established between the minimum attainable NO x emission and the thermal capacity of the load (air plus water), this result stablish the hard relationship between NO x formation and combustion chamber temperature and therefore shows the strong dependence of the Zeldovich mechanism. Highlights • Effects of adding water into the intake manifold with a flow-blurring injector. • NOx reduction on a current technology diesel engine with multiple injection. • The NO x emission was reduced by adding water in comparison to the EGR. • A reduction of NOx emissions around 60–70% was achieved with water injection. • The minimum attainable NOx emission and the thermal capacity are related. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the overall performance, emission and combustion characteristics of the engine, when fuelled with biodiesel blends of Calophyllum Inophyllum methyl ester as injected fuel and babul wood chip derived producer gas as inducted fuel at constant injection timing (230bTDC), injection pressure (230 bar) and speed (1500 rpm). To improve overall performance, combustion and reduced emission characteristics of the engine, the combustion chamber was varied with 5 different geometries. Experimental results revealed that Toroidal re-entrant combustion chamber had higher Exhaust Gas Temperature and Brake Thermal Efficiency by 20.75% and 6.37% than that of HCC, while Brake Specific Fuel Consumption was reduced by 4.49% at optimal loading condition. However, engine overall performance of TrCC was found to be comparable with Hemi-spherical chamber and other designed combustion chambers. Similarly, comparing exhaust emissions, Oxide of Nitrogen and Carbon dioxide were on its higher side by 19.90% and 27.20% than normal HCC. On the contrary, carbon monoxide, Hydrocarbon and Smoke opacity for TrCC were found to be 76.12%, 33.71% and 38.67% lower than HCC. From the above study, it is finally concluded that converted renewable fuels with TrCC might be utilized as an alternative fuel without any exhaust related problems. Highlights • CIME 20 showed better oil characteristics. • BTE for CIME 20-producer gas with TrCC was 6.37% higher than diesel HCC. • NO x emission for HCC-diesel was 19.9% lower than TrCC CIME20 P. gas. • CIME 20-producer gas with TrCC emits 33.71% and 38.67% less HC and smoke. • Diesel fuel savings of 80.5% for diesel-producer gas at optimal load condition. [ABSTRACT FROM AUTHOR]

Abstract The scavenging process is helpful to suppress the super-knock in a 4-stroke turbocharged gasoline direct injection (GDI) engine because it can strengthen in-cylinder cooling and clear suspending residual particles from previous cycles. This paper investigates the effects of combustion system parameters on scavenging process. The simulation results showed that the piston pit with a shallow depth adjacent to the center of cylinder could intensify the scavenging motion and increase the velocity inside the pit, more residual gas and carbon particles could be therefore cleared. The intake and exhaust valve chamfer angle of 45° was beneficial to the scavenging process because more high-velocity scavenging motion occurred in piston pit and less fresh charge flowed into exhaust port directly. The injector location and ground electrode orientation has little influence on scavenging process because of its tiny volume. Finally, an optimum structural shape of combustion chamber was developed and proposed based on the research results. Highlights • The scavenging had a positive effect on suppressing super-knock in GDI engine. • Shallow piston pit in the middle could strengthen in-cylinder cooling and better clear residual particles. • Decreasing throat cross area and selecting valve chamfer angle of 45° could improve scavenging. • Injector location and spark plug structure had a very small effect on scavenging. • An optimum structural shape of combustion chamber was proposed for improved scavenging. [ABSTRACT FROM AUTHOR]

Abstract Structural weight and flow resistance of the combustor were important parameters affecting the overall performance of gas turbine. The integrated combustion mode and trapped-vortex combustion mode were the means to fulfill these requirements. Components integration of combustor was an important trend in the development of the combustion technology. In this paper, the trapped-vortex combustion mode was combined with integrated combustion mode, and a new type of integrated combustor with various cavities was proposed. By integrating the flameholder with the structural strut, light weight of the structure could be achieved. By adopting trapped vortex combustion mode, high combustion efficiency could be obtained in wide range of inlet velocity and fuel-air ratio. Using the particle image velocimetry and experimental system, the flow field and combustion characteristics, including ignition, combustion efficiency, outlet temperature distribution and wall cooling characteristics, were thoroughly analyzed. Fuel droplets injected by simple nozzles could be evaporated and mixed with mainstream air in a short distance. The feasibility of the novel combustion mode was completely verified. Low flow resistance and high combustion efficiency was achieved, which was difficult for the integrated combustion mode. The results were beneficial to the research of high performance gas turbines with compact structure. Highlights • Two novel integrated combustors with radial and circumferential flameholders were designed. • Various cavities used for forming trapped vortex zone were adopted. • Flow field and combustion characteristics were experimentally studied. • Low flow resistance and high combustion efficiency were achieved. [ABSTRACT FROM AUTHOR]

The paper intends to overcome the difficulties associated with conventional PIV test techniques in measuring the flow fields near curved surfaces. So the paper combines the visual steady flow test and the CFD simulation method, to help observe the law of particle distribution near the cylinder wall directly, and reveal the law of steady/transient flow field movement and airflow evolution. The results show that the distribution of particle density and the gradient boundary lines of the tracer concentration correspond to those of the CFD simulation. Therefore, a visual test can display the characteristics of the movement of air in the cylinder near the wall. The swirl ratio of each radial section in the cylinder and the ω combustion chamber during the intake stroke is influenced by the intake airflow, while the swirl ratio during the compression stroke is determined by the piston movement. At the end of a compression stroke, the location of the highest swirl ratio directly influences the air-fuel mixture. As a result, analyzing the swirl ratio and evolutionary process of the flow fields near the wall of the cylinder and combustion chamber help improve the quality of the air-fuel mixture and the efficiency of combustion. • Establish a visualized test to observe flow fields near the cylinder wall. • Determine characteristics of air movement and distribution from the intake port. • The swirl ratio is dominated by intake air-flow and the piston movements. • Air-fuel mixture is facilitated by the largest swirl ratio. [ABSTRACT FROM AUTHOR]

Due to the growing increase in fuel price, a significant part of costs of power plants is expended on obtaining high-quality fuels. The change of fuel type from the natural gas to the liquid in the winter due to the increase in natural gas consumption is the main reason for this research. The goal is to select the appropriate fuel type from the Energy, Exergy, Exergy-economic, and Environmental (4E) aspects. The topic of this paper is an irreversible comparison of combined cycle power plant (CCPP) components by changing fuel type from natural gas to liquid fuels with different APIs. The costs resulting from the pollution of normalized air with fuel change were compared. The results were validated by the data from the largest CCPP in Iran. Multi-objective optimization of the CCPP was implemented by objective functions of the price of the power produced, exergy efficiency and normalized production amount of CO 2 . The results showed that decrease in API˚ led to proper exergy efficiency and cost but exposed very high environmental impacts compared with gas fuel. Results of changing objective functions demonstrated that propagation rate of CO 2 in gas fuel was much lower than that of liquid fuel. [ABSTRACT FROM AUTHOR]

This paper studied the synergistic behaviors of anthracite and dried sawmill sludge (DSS) in the conversion ratio (CR) of combustible substances, micromorphology variation and constituents' evolutions. The results showed that the blend CRs were the highest, and CRs increased with O 2 and temperature. In ash formation, DSS mainly contributed to the fly ash yield, while anthracite determined the morphology of bottom ash. The carbon proportion of combusted blend decreased to 0, revealing its thorough combustion, thereby proving the synergistic effects between anthracite and DSS. The disappearances of C C, CH 2 and O H determined by FT-IR indicated the burning losses of kinds of hydrocarbons, meanwhile the identified enlarged bands of Si O, Al O and Fe O suggested the formations of inorganic compounds. The XRD results further demonstrated the formations of SiO 2 , Al 2 O 3 , CaSO 4 and Fe 2 O 3 , the rising temperature promoted their melting/conglomeration process, thereby lowering the XRD peaks since the mischcrystals generations. The oxygen-enrich atmosphere inhibited the formations of SiO 2 and Al 2 O 3 but promoted the generation of Fe 2 O 3 , and accelerated the formation of porous-smooth ash. The addition of CaCO 3 assisted the pore formation and integrated the metal-oxides crystals. Urea made the particles welly dispersed, and weakened the XRD peaks since it improved the melting process. [ABSTRACT FROM AUTHOR]

This paper presents two models of fluid heating in waterwall tubes of supercritical steam boilers. The models are named 1D/2D and 1D/3D. The models are formulated and discussed in detail with an industrial application example. For the 1D/2D model, a two-dimensional (2D) transient heat conduction equation is solved for the tube wall with the fin domain, while one-dimensional (1D) mass, momentum, and energy equations are solved for the fluid domain. The 1D/3D model considers a three-dimensional tube wall domain (3D) and one-dimensional fluid domain. At the fluid-solid interface, a conjugate heat transfer model is applied. The model is based on convective flux between the fluid and solid domains. Nonlinear governing balance equations of mass, momentum, and energy for fluid are solved using the forward time backward space (FTBS) scheme. The proposed models allow incorporation of the effect of heat flux nonuniformities along the waterwall tube and on its outer circumference. Transient simulations are carried out to determine the temperature histories for both the fluid and the tube wall in the selected cross sections. The computations are performed using the finite volume method formulation. The results obtained from the 1D/2D model are nearly the same as those from the 1D/3D model; however, the computation time is more than five times shorter. Therefore, an efficient 1D/2D model can be used in power unit simulators. [ABSTRACT FROM AUTHOR]

The paper addresses the production of urea from carbon dioxide and nitrogen in the flue gas of the power plants as an alternative to other proposed and suggested processes. The conventional separation process of CO 2 from flue gases has been so far directed to the methanol synthesis, while nitrogen, as the main part of the combustion product, is ignored. Carelessness about and lack of use of this byproduct is led to the techno-economical failure of the process and cause environmental problems. In this research, to the best of our knowledge, for the first time, the synthesis of urea and ammonia from the combustion of oxy-fuel was investigated and the appropriate and green process was designed and proposed. To enhance economic justification, the process design was carried out using all three main components of the flue gas (CO 2 , N 2, and H 2 O), along with efficiency increment of the combustion units. Considering of 2036 kg/hr oxy-fuel combustion products, direct removal of 1700 kg/hr CO 2 from the carbon cycle and production of 2856 kg/hr molten urea is estimated, which the latter product worth about 3.5 × 10 6 US$/year. [ABSTRACT FROM AUTHOR]

The present paper proposes two energy integration options, Option-1 and Option-2, to compare power generation and preheating scheme in sponge iron process. Option-1 accounts power generation whereas in Option-2 preheating of feed material, slinger coal and kiln air is considered. These options utilize heat of waste gas that exits the after burning chamber of the process, which is available from 994 °C to 250 °C. The process integration principles are applied to conserve energy in Option-1 and Option-2. For Option-1 8.97 MW power is generated using heat of waste gas, which gives payback period as 4.17 years. On the other hand, Option-2 consumes 37.4% and 4.7% less coal and water, respectively, in comparison to the existing system. The payback period for option-2 is 3.22 years. The feasibility analyses of these options are also discussed. Based on payback period preheating is more profitable option in comparison to power generation. However, when net profits of two options are compared, power generation option is more profitable. The results of the present study are compared well with that of published work. [ABSTRACT FROM AUTHOR]

Continuously improving the operational efficiency of aeroengine is an important part to reduce the use of fossil energy and environmental pollution. This makes the combustion chamber hotter and more prone to fault, so fault detection and isolation is even more important. Therefore, a fault detection and isolation method for engine combustion chamber based on the unscented Kalman filter and artificial neural network is proposed. A twin-spool turbofan engine model for combustion chamber fault detection and isolation study is established for the first time. The concept of distributed flame tube health state parameters is proposed, and Kalman filter technique is used to achieve parameter estimation and monitor the health state. Further, in order to address the issue that Kalman filter requires the explicit state and measurement functions to be specified a priori, which are usually rough approximations of reality, this paper proposes to learn rich and dynamic representations of state and measurement models from data by using multilayer perceptron. Besides, it is compared with the method based on exhaust gas temperature dispersion. The experimental results show that the proposed method exhibits excellent performance for both abrupt and ramp faults of the flame tube, and is robust to interference from changes in working conditions. • The concept of "energy distribution coefficient" is first proposed as health state parameters. • A twin-spool turbofan engine model for combustion chamber fault detection is first established. • Fusion of UKF and MLP is first used for combustion chamber fault detection and isolation. • Accurate anomaly detection and isolation of aeroengine combustion chamber are realized. [ABSTRACT FROM AUTHOR]

This paper assesses the influence on techno-economic performance of modularising hybrid Concentrating Solar Power (CSP) systems with fossil fuel backup for both a Hybrid Solar Receiver Combustor (HSRC), which integrates a combustor into a solar cavity receiver, and a Solar Gas Hybrid (SGH) system with a similar cavity receiver and a back-up boiler. It was found that the energy losses in a system of small-sized modules, which employs molten salt as its Heat Transfer Fluid (HTF), are dominated by trace heating owing to the increased piping over their larger receiver counterpart. However, this can be reduced significantly by using alternative HTFs with a lower melting point such as sodium. In addition, for modularisation to be cost effective requires it to also enable access to alternative, lower-cost manufacturing methods. That is, the benefit of standard learning rates is insufficient to lower the Levelized Cost of Electricity (LCOE) on its own. For a plant with 30 units of 1 MW th modules the LCOE is competitive, relative to a single unit of 30 MW th , after ∼10 plants are installed if the modularised components (i.e. heliostats, receivers and towers) can be decreased by >80% and >40% for molten salt and sodium as the HTF, respectively. [ABSTRACT FROM AUTHOR]

The flow input of a variable geometry turbocharger turbine is highly unsteady due to rapid and periodic pressure dynamics in engine combustion chambers. Several VGT control methods have been developed to recover more energy from the highly pulsating exhaust gas flow. To develop a control system for the highly pulsating flow condition, an accurate and valid unsteady model is required. This study focuses on the derivation of governing the unsteady control-oriented model (COM) for a turbine of an actively controlled turbocharger (ACT). The COM has the capability to predict the turbocharger behaviour regarding the instantaneous turbine actual and isentropic powers in different effective throat areas. The COM is a modified version of a conventional mean value model (MVM) with an additional feature to calculate the turbine angular velocity and torque for determining the actual power. The simulation results were further compared with experimental data in two general scenarios. The first scenario was simulations on fixed geometry positions. The second simulation scenario considered the nozzle movement after receiving a signal from the controller in different cases. The comparison between simulation and experimental results showed similarities in the recovered power behaviours the turbine inlet area increases or vice versa. The model also has proved its reliability to replicate general behaviour as in the example of ACT cases presented in this paper. However, the model is incapable to replicate the detailed and complicated phenomena, such as choking effect and hysteresis effect. [ABSTRACT FROM AUTHOR]

A conventional and advanced exergy analysis of an aircraft turboprop engine is presented in this paper. In this framework, the main exergy parameters of the engine components are introduced while the exergy destruction rates within the engine components are split into endogenous/exogenous and avoidable/unavoidable parts. Also, the mutual interdependencies among the components of the engine and realistic improvement potentials depending on operating conditions are acquired through the analysis. As a result of the study, the exergy efficiency values of the engine are determined to be 16.63% at real case and 17.13% at unavoidable case, respectively. The system has low improvement potential because the unavoidable exergy destruction rate is 94%. The relationships between the components are weak since 86% of the exergy destruction is endogenous. Finally, it may be concluded that the air compressor, combustion chamber and power turbine components of the engine should be focused on according to the results obtained. [ABSTRACT FROM AUTHOR]

The aim of the present paper is that of proposing an innovative control strategy based on the FeedBack Linearization (FBL) technique in order to achieve a high performance and decupled control of a gas generating unit. The dynamic performances of a gas generating units are limited by the combustion chamber dynamics where sudden temperature variation may lead to undesired and dangerous phenomena. The FBL application will allow introducing an ideal decupling of the regulated channels so that power variation will have a minimal impact on the combustion chamber temperature obtaining a smoother and quicker response to reference changes in comparison with a tradition, PID based control. The proposed FBL controller will be also tested in presence of model and parameters uncertainties in order to verify the robustness of the proposed control technique. [ABSTRACT FROM AUTHOR]

Energy, Exergy, Exergoeconomic and Environmental (4E) analysis of combined cycle power plant utilizing the method of steam injection into the combustion chamber is performed in the current study. Steam is supplied from low pressure (LP) side of the heat recovery steam generator (HRSG). According to genetic algorithm's results, the steam injection elevates the total combined cycle power by 2 MW while lowers the design costs considerably at optimum state. Some parameters restrict the steam injection usage within combined cycles that could be noted as Gas turbine power decline; Gas turbine loss increase due to pressure loss; HRSG's manufacturing costs growth; opposition between high and low pressure flow rate variations; NO X and CO emission costs dependency on optimum conditions. This paper discusses the above limitations for implementation of such technology in combined cycles. At the optimum point, Exergy and thermal efficiencies values increased from 42% and 47.6% to 47.28% and 48.94% respectively. Optimum pinch and approach temperatures for HP and LP sides were computed to be 35, 20, 17 and 37.5, respectively. Also, the optimum value of X parameter is 23.28%; X is defined as the ratio of steam to the inlet air flow rate divided by the other fraction which is the ratio of fuel to input air flow rate while there is no steam injection into the combustion chamber. [ABSTRACT FROM AUTHOR]

The hot intake air would compromise the power generation performance of a gas turbine (GT). Therefore, GT pre-cooling technologies are studied and applied for GT plants. This paper proposes an improved validated semi-analytical GT model, which can be used to simulate the performance of GT plants under a wide range of intake air conditions. The new model developed is improved, compared to previous models, in the following three aspects: 1) the volumetric flow rate of intake air is no longer assumed to be constant when the temperature of intake air changes; 2) the output temperature of the combustion chamber (CC) is no longer assumed to be a constant either, but depending on air temperature/humidity into the CC and the fuel/air ratio, and 3) the improved model can evaluate the performance of the GT power plant, in terms of power output and thermal efficiency of the plant, directly and explicitly from the intake air conditions of the compressor, which was not possible in the previous models. Deviations between results of the present model and experimental data are less than 3%. In addition, sensitivity analysis of both ambient conditions and GT characteristics is performed as a sample application of the new model which is programed using Engineering Equation Solver (EES) software. • A novel improved semi-analytical model is presented for GT step-by-step. • The model is highly appropriate for (but not limited to) GT pre-cooling technologies. • The model is applicable for all ranges of climate conditions. • The model is programed using EES and validated with experimental data. • Three different types of case studies are provided as various applications of the model. [ABSTRACT FROM AUTHOR]

Interest in circulating fluidized bed (CFB) boilers as a power generation technology has sky-rocketed in recent years because of several advantages this technology offers over conventional boilers, such as increased gas-solid mixing, which results in higher combustion efficiency and the ability to use lower rank fuels. CFB combustors are operated at lower temperatures than conventional thermal power generation combustors, thus reducing NO x emissions, while SO 2 emissions can be conveniently controlled through the addition of Ca-based sulfur sorbents within the combustor. This paper summarizes the modeling effort on a 50 kW th CFB combustor designed, built, and operated at CanmetENERGY in Ottawa, Canada. The numerical model employs the multiphase particle-in-cell (PIC) approach in the open-source Multiphase Flow with Interphase eXchanges (MFiX) Software Suite. The MFiX-PIC model parameters for the simulation are tuned against cold-flow experiments from CanmetENERGY using olivine sand as the inert bed material. It is shown that for the relatively coarse fluid meshes and large parcel sizes necessitated by the scale of the simulation, filter size dependent corrections to the drag law must be incorporated to ensure accuracy of the simulation results. The validated cold flow model is extended to simulate reacting flow with torrefied hardwood as the feedstock and to validate the combustion reaction scheme. The species concentrations at the riser outlet are compared against CanmetENERGY's experiments and show satisfactory agreement. The simulations demonstrate the ability of MFiX-PIC to accurately capture both the physics and chemistry of a CFB combustor at bench scales, which can be further extended to pilot- and industrial-scale systems. • MFiX-PIC is employed to model the 50 kW th circulating fluidized bed at CanmetENERGY. • Calibration of PIC for a large-scale application is discussed in detail. • Filter size dependent corrections are incorporated to the drag law for accuracy. • Combustion reaction scheme is developed and validated against experiment. • MFiX-PIC model accurately captures both physics and chemistry of the CFB combustor. [ABSTRACT FROM AUTHOR]

Thermal steam units cooperating in one power system with wind and photovoltaic farms must have high flexibility, i.e., operate over a wide range of load variations, typically between 40 and 100%. In addition, the start-up and shutdown time of the unit should be short. Thick-walled pressure components that limit the fast start-up of the units are turbines, steam boilers, and pipeline branches due to the occurrence of high thermal stresses in them. This paper determines the allowable heating rates of thick-walled components of a 97.22 kg/s natural circulation steam boiler. The boiler drum is the critical element, with a heating time of about 6000 s from the cold state. Computer simulations of the boiler combustion chamber were also performed at three different loads, i.e., 100, 60 and 40%. The calculations show that the maximum emissions of harmful substances do not exceed the permissible values given in European regulations: CO ≤ 140 mg / m n 3 and NO x ≤ 100 mg / m n 3. The maximum content of CO = 136.8 mg / m n 3 occurs at 60% boiler load. The maximum content of NO x = 217.3 mg / m n 3 in the exhaust gas upstream of the SCR (Selective Catalytic Reduction) system occurs at 40% load, but downstream of the SCR system is reduced below the limit value 100 mg / m n 3. • Measures to improve the flexibility of a steam boiler were investigated. • Allowable heating rates for boiler pressure components were determined. • The boiler drum is a critical component for boiler start-up time. • CFD simulations of the boiler combustion chamber for various loads were conducted. • Pollutant emissions are acceptable with boiler loads from 100% to 40%. [ABSTRACT FROM AUTHOR]

The paper describes numerical simulations of processes occurring in the combustion chamber of a stoker boiler. The main topic of CFD analysis presented in this paper is the process of reducing nitrogen oxides emission using the patented Furnace Jet Boiler System (FJBS) in combination with the selective non-catalytic reduction (SNCR) method (FJBS+). The presented method is characterized by introducing a compressed urea-air mixture into the furnace. The reagent is injected through supersonic nozzles, the operating conditions of which are shown on a separate CFD model. The developed model enabled optimization of the existing NO x reduction system, especially in the case of a boiler operating at maximum load. The overall effect of the operation of FJBS + technology is a significant reduction of NO x emissions, by approximately 57%. The results achieved are comparable to those obtained from measurements. It was also confirmed that the operation of FJBS + has a positive effect on the equalization of temperature distribution in the furnace and the concentration of flue gas components. Finally, a sensitivity analysis on the basis of two parameters, specific heat of the fuel and thermal conductivity is presented. • The process of combustion in a grate boiler and the process of nitrogen oxides reduction using the SNCR method is shown. • The operation of the supersonic nozzles that are used in the FJBS system is presented. • The simulation results are in good agreement with on-site measurements. [ABSTRACT FROM AUTHOR]

This paper deals with artificial neural network (ANN) modelling of a diesel engine using cottonseed methyl-ester (CME) to predict brake specific fuel consumption (BSFC), maximum in-cylinder pressure (CP max) and exhaust emissions (CO, HC, and NO x). To acquire data for training-testing (75%–25%) of the proposed ANN, a single-cylinder diesel engine was fueled with different percentages of CME (B0, B10, B20 and B50) and then operated at different engine loads (2.5, 5, 7.5, and 10 Nm) and injection pressures (175, 190, 205, and 220 bar). Depending on the increase of CME content in the CME-diesel blend, BSFC sharply increased due to the lower heating value of biodiesel. As the engine load increased, HC slightly increased. More oxygen atoms in biodiesel lead to reduce CO emissions owing to more complete combustion. In addition, NO x gradually increased due to high combustion temperature at high engine loads, particularly more for biodiesel-content fuels. Further, the lower cetane number of CME resulted in higher CP max due to rapid combustion of accumulated fuel in the combustion chamber. On the other hand, three metrics of success, namely MEP, RMSE, R2, were discussed for evaluation the success of the developed ANN model in the study. In the result, the developed ANN model is able to predict CO, HC, NO x , CP max , and BSFC quite well with R2 of 0.9902, 0.9990, 0.9999, 0.9979, and 0.9995, respectively. Moreover, each RMSE and MEP values for both training and testing set were less than 0.04 and 9%, respectively. In the conclusion, this paper is clearly reporting that ANN can be applied to accurately predict the engine performance, combustion and emissions of CI engines. • Artificial neural network modelling of BSFC, CP max , NO x , CO and HC. • Injection pressure, engine load and diesel-biodiesel (cottonseed methyl ester) blends were used as input parameters. • The addition of CME biodiesel reduced the CO but increased HC and NO x. • MEP, RMSE and R2 metrics were used as evaluation benchmarks. • A good agreement between experimental data and ANN was noticed. [ABSTRACT FROM AUTHOR]

The DI (Direct Injection) in SI (Spark Ignition) engines is rapidly developing and seems very attractive offering the possibility of multi-mode operation, homogeneous and stratified charge, with valuable benefits respect to conventional PFI (Port Fuel Injection). One of the major drawbacks of the GDI-fueled engine is the impingement of liquid fuel on the combustion chamber walls that generally produces an increasing of HC emissions and detrimental effects on the combustion process, like soot formation in the wall guided engines due to the diffusive combustion of fuel film deposits on the piston head. This paper investigates the structure of gasoline spray-wall interaction generated by a single-hole injector for GDI engines in an optically-accessible quiescent vessel. The axially-disposed hole diameter is 0.200 mm with a L/d ratio of 1.0 while the injection pressure and the wall temperature varied in the range of 10.0–20.0 MPa and ambient to 300 °C, respectively. Injection duration of 1.0 ms was investigated and the nozzle tip-wall distance was 22.5 mm. Optical investigations were carried out at atmospheric backpressure by an in-line schlieren optical setup using a LED source while the cycle-resolved images of the evolving impact were captured by a C-Mos high-speed camera with a time resolution of 80 μs and a window size of 640 × 464 pixels. The optic-geometrical setup realized a spatial resolution of 0.039 mm/pixel. The images were treated by a digital processing software for background subtraction and both liquid and vapor contour extractions. The spatial and temporal evolution of the liquid and vapor phases as a function of the wall temperature is described for the different operative conditions. [ABSTRACT FROM AUTHOR]

This paper proposes a mathematical model with distributed parameters that allows to simulate the heat transfer processes in combustion chamber waterwalls of supercritical steam boilers. The model comprises solving the one-dimensional mass, momentum and energy conservation equations. The Forward Time Backward Space scheme is applied to discretize the governing equations. Two types of computational verification are performed for the proposed model. At first the model is validated with the analytical solution. The computational accuracy of the proposed model was tested for different time steps and grid size. At second, the results produced by the model were compared with those obtained when the Crank-Nicolson scheme is used to discretize the energy equation. In this case of results comparison the fluid flow and heat transfer phenomena were modeled for spirally wounded waterwall tubes of the combustion chamber in a supercritical boiler. A good agreement was found between the results produced by the proposed model and those obtained by using the analytical and Crank-Nicolson approaches. Therefore, the proposed model can be regarded as a useful tool for the design and monitoring of this type of heated surfaces. Moreover, the model can be applied in power units simulators. [ABSTRACT FROM AUTHOR]

Moderate or intense low-oxygen dilution (MILD) combustion is well-known for its high potential of reducing thermal-NO formation during combustion, but its capability of mitigating fuel-NO formation is still elusive. To provide new insights into this aspect, this paper numerically studies the fuel-NO formation characteristics under CH 4 /NH 3 MILD combustion in a lab-scale reversed flow furnace by computational fluid dynamics (CFD) modeling with NH 3 volume fraction varying from 0% to 4%. It is found that, the overall NO emission at the furnace outlet increases as the initial NH 3 concentration rises under both MILD combustion and traditional bluff-body stabilized combustion mode, however, fuel-NO conversion ratio gradually drops. In the present reversed flow furnace, there exists a critical value (1.4%) for the initial NH 3 volume fraction, above which MILD combustion loses the advantage of generating lower NO emission in comparison with the traditional combustion operation. However, this critical value would be case-dependent and should be further re-evaluated for different combustors. In the current combustion system, the lower NO emission under traditional combustion when firing higher NH 3 doping fuels is caused by the enhanced NO reduction via both CH i reburning and NO 2 interconversion routes, which occurs on the outer and inner sides of the flame front, respectively. For MILD combustion, the weakening of CH i reburning in the outer side of reaction zone causes the higher NO emission when initial NH 3 concentration exceeds the critical value. • MILD combustion of CH 4 with doped NH 3 is numerically studied. • NO emission increases with the seeding amount of NH 3 in fuel. • NO emission under MILD combustion surpasses traditional combustion when NH 3 exceeds 1.4%. • NO reburning is stronger under traditional combustion than MILD combustion. • NO reduction by NH i is insignificant under both combustion modes. [ABSTRACT FROM AUTHOR]

The huge amounts of accumulated unclaimed liquid hydrocarbon waste (waste from oil production and oil refining, etc.) determine the prospects for their involvement in energy production. The Waste-to-Energy technology improves economic efficiency through low energy costs. Efficient use of waste for energy production requires the creation of new technologies with high energy efficiency and low emissions. The paper proposes and substantiates a promising new environmentally friendly Waste-to-Energy method of burning liquid fuel with injection of superheated steam (SIM) to the combustion zone. The authors have developed a new burner to combust liquid waste when producing energy (protected by patents of the Russian Federation), in which the fuel is atomized by a jet of superheated steam. This approach provides efficient fuel dispersion, the ability to burn a wide range of waste, high fuel combustion efficiency, long service life due to the absence of fuel injectors, and reduction of toxic combustion products due to steam. The large-scale introduction of new burners based on the SIM combustion technology requires reliable scientific data and pilot test results. First of all, this is the influence of operating parameters (steam flow rate and temperature, fuel and air flow rates) on the combustion performance in the oil-steam burner being developed. The aim of the work is complex laboratory and experimental studies of the characteristics of fuel combustion in a new burner with a controlled excess air ratio. Forced air supply to the combustion chamber of a steam-oil burner is a novelty of the burner under study. Based on the results of laboratory studies, the optimal ratios of operating parameters were found (fuel, steam and air flow rates: 1:0.8:2.75), which provide the best thermal and environmental performance (NOx<35 ppm, CO < 25 ppm). A significant reduction in the content of nitrogen oxides in the flue gases up to 70% was achieved with a high completeness of fuel combustion due to the joint control of steam concentration and excess factor in the gas generation chamber. This claims the proposed burner as a low emission one. To confirm the achieved effect, in this work, for the first time, experimental tests of the burner were carried out under the operating conditions of a low-power boiler plant (10–40 kW). Successful tests prove the efficiency of using the developed burner for solving the problem of efficient and environmentally friendly combustion of fuel (including liquid combustible waste) for the production of thermal energy at small-scale energy facilities. • A new oil-steam burner with a controlled excess air ratio for low-emission Waste-to-Energy combustion has been developed. • The laboratory and experimental tests of this burner have been carried out for the first time. • Optimal operating regimes (fuel-to-steam-to-air ratios of 1:0.8:2.75) have been determined. • NOx emissions reduced by up to 70%, NOx<35 ppm, CO < 25 ppm. • For the first time, stable operation of the burner in a low-power boiler (10–40 kW) has been shown. [ABSTRACT FROM AUTHOR]

Electricity generation from fossil fuels has become a focal point of energy and climate change policies due to its central role in modern economics and its leading contribution to greenhouse gas emissions. Carbon capture and sequestration (CCS) is regarded by the International Energy Agency as an essential part of the technology portfolio for carbon mitigation, as it can significantly reduce CO 2 emissions while ensuring electricity generation from fossil fuel power plants. This paper studies the retrofit of natural gas combined cycles (NGCCs) with an amine-based post-combustion carbon capture system. NGCCs with differently rated capacities were analysed under the assumptions that the heat requirement of the capture system was provided via a steam extraction upstream of the low-pressure steam turbine or by an auxiliary unit that was able to reduce the power plant derating related to the energy needs of the CCS system. Different types of auxiliary units were investigated based on power plant size, including a gas turbine cogeneration plant and a supplementary firing unit or boiler fed by natural gas or biomass. Energy and economic analyses were performed in order to evaluate the impact of type and layout of retrofit option on energy, environmental and economic performance of NGCCs with the CCS system. [ABSTRACT FROM AUTHOR]

Reducing solid particle erosion of blades is one of the most urgent problems for supercritical steam turbine power generation technology. Based on the erosion rate models and the particle rebound models of blade materials obtained through accelerated erosion test under high temperature, systematic numerical simulations of the complex steam-particle flow in high pressure inlet flow channel and governing stage cascade of a supercritical steam turbine with four control valves was performed in this paper. The influence the typical nozzle chamber structure and partial-arc admission on the erosion characteristics of control stage blades was first investigated. Results show that erosion condition of nozzles in the same nozzle segment vary greatly along circumferential direction, while erosion damage to the leading edge of different circumferential rotating blades is uniform. Compared with four-valve opening condition, erosion weight-loss of the whole nozzle segment increases by 14% and 25% under three-valve opening condition and two-valve opening condition, respectively. Besides, under the partial-arc admission conditions, some large particles coming from the steam admission nozzle segment will collide back and forth between vanes and rotating blades in the downstream nozzle segment without steam admission, thus causing certain erosion to the trailing edge of nozzle suction side. [ABSTRACT FROM AUTHOR]

This paper focuses on the multi-objective optimization of the fuel injection parameters, combustion chamber geometry parameters and engine operating parameters of a double-layer combustion chamber. Three optimization objectives have been optimized by combining the NSGA-II genetic algorithm and the KIVA-3V program, including the indicated specific fuel consumption (ISFC) rate, NO x and soot emissions. Meanwhile, 10 engine parameters, including two injection parameters, six combustion bowl geometry parameters, compression ratio, and Exhaust Gas Recirculation (EGR) rate, are optimized simultaneously. The results show that the NO x and soot emissions exhibit an apparent trade-off relationship as well as the NO x emission versus ISFC. In addition, response surface analysis is conducted to investigate the influence of the selected parameters on the optimization objectives. It indicates that the retarded injection timing and EGR are conducive to the reduction of the NO x emission. Moreover, the double-layer combustion chamber with an impingement platform can enhance the fuel-air mixing process, and the air utilization rate of the combustion chamber is henceforth improved. Based on our optimization, the high temperature area is widely distributed throughout the double-layer combustion chamber, and most of the soot can be oxidized sufficiently in the main combustion period. • The genetic algorithm is used for combustion optimization. • The retarded injection timing is conducive to the reduction of NO x emission. • The EGR rate plays a vital role in the reduction of the NO x emission. • The double-layer combustion chamber is beneficial to ISFC and Soot emission. [ABSTRACT FROM AUTHOR]

Stirling machines present a forthcoming potential for substituting the internal combustion engine as an auxiliary power unit in future series hybrid electric powertrains. Different Stirling thermodynamic configurations can be found in the literature. Among them, the recuperative reheat Stirling thermodynamic cycle offers high net specific work and high efficiency, resulting in reduced system's weight, size and integration complexity, as well as reduced vehicle's fuel consumption. This paper presents an experimental investigation of the impact of Stirling combustion reheat process on the system performance and emissions. For that purpose a Stirling combustion chamber was modified and a post combustion chamber was added. The new configuration of the designed combustion chamber was manufactured and tested. The effect of reheating process on pollutant emissions was evaluated by measuring the NO x emissions and compared to the fuel quantity injected in both reheat and no reheat configurations. The test results demonstrate the high importance of reheating process in decreasing the NO x emission. The obtained reduction was more than 50% in comparison to the original construction. Consequently, the recuperative reheat Stirling thermodynamic configuration was selected as the best candidate for replacing the internal combustion engine. • Stirling combustion chamber was modified to enable the reheating process. • Recuperative reheat Stirling machine was tested, NO x emissions were analysed and compared. • This recuperative reheat thermodynamic configuration offers higher efficiency and higher net specific work. • The NO x emissions can be reduced by more than 50% compared to no-reheat thermodynamic configuration. [ABSTRACT FROM AUTHOR]

The purpose of the present investigation is to explore the feasibility of applying the micromix combustion principle (MCP) to design low NO x burners using 100% H 2 as fuel for domestic and industrial boilers. Previous investigations studying the MCP on stationary and aero gas turbine applications, showed low NO x emissions without flashback risk, which represent the two main issues when burning 100% H 2. Since boiler burner operating conditions differ from gas turbine combustors, the present paper studies the MCP through CFD calculations under re-defined conditions for domestic and industrial burners, adapting the energy densities, air-fuel equivalence ratios and pre-heated air temperatures. A reference geometry was built to validate the selected numerical models with experimental results from literature. Afterwards, burners were re-dimensioned following an existing geometry-scaling methodology. The obtained results evidenced that MCP characteristics were still maintained for the defined cases, keeping low NO x values between 4 and 14 ppm. The numerical results were also validated through experimental NO x measurements in a laboratory scale micromix burner prototype. In order to assess the benefits of using hydrogen micromix burners in domestic and industrial boilers, the present work includes a final discussion with practical design considerations. The present study lays the groundwork for complementary experimental research work, which is being carried out in laboratory-scale prototypes. • MCP is a potential technology for domestic and industrial hydrogen burners. • Low NO x and MCP characteristics are preserved for the defined cases. • The lower entropy production in H 2 combustion allows working with higher AFR. • Higher AFR could be beneficial for domestic and industrial low NO x H 2 burners. [ABSTRACT FROM AUTHOR]

In this paper, JT15D turbofan engine and its main subcomponents are assessed with the aviation, energy, exergy, environmental, and sustainability analyses. In the first stage, the system's specific thrust and specific fuel consumption of the engine are found as 315.9 N s/kg and 15.8 g/kN.s, respectively. Then, system's energetic efficiency is estimated as 21.15% and exergetic efficiency is accounted to be 19.919%. The system's exergetic improvement potential rate, productivity lack ratio and fuel exergy waste ratio are determined as 1573.535 kW, 402.024% and 80.081%, respectively. The ecological and environmental effect factors of the turbofan system are computed to be 5.020 and 4.020, respectively, while the sustainable efficiency factor and exergetic sustainability index rates are found as 1.249 and 0.249, respectively. Finally, among the system parts, the Combustion Chamber (CC) has minimum rates of sustainable efficiency factor, exergetic efficiency and sustainability index, while it has utmost rates of ecological and environmental effect factors, fuel exergy waste ratio, irreversibility and productivity lack ratios. As a general conclusion, the combustion chamber and low pressure compressor components should be optimized for better performance of the system. • General aviation and energetic performances of a turbofan engine are assessed. • Thermodynamic inefficiencies are obtained for engine and its components. • Environmental impacts and sustainability levels of turbofan engine are evaluated. • Risky components are determined for enhancing thermodynamic performance. [ABSTRACT FROM AUTHOR]

This paper examines the effect of adding high dosage of copper oxide (CuO) nanomaterials (<77 nm) directly to conventional diesel fuel. The performance of the fuel with CuO added is assessed using a single cylinder, naturally aspirated, direct injection, air-cooled diesel engine. Examined were the characteristics of combustion and emissions for blends of 1000 and 2000 ppm CuO nanoparticles. The CuO blends were tested in the speed range between 2000 and 3000 rpm at intervals of 250 rpm. The CuO nanoparticles have the potential to accelerate the process of combustion by supplying molecules of oxygen and acting as a catalyst. The CuO enhances the thermal conductivity of the test fuels and increases heat dissipation from the combustion chamber. Experimental results show exhaust gas temperature (EGT) is reduced as well as unburnt hydro-carbons (HC) and oxides of carbon and nitrogen (CO and NOx). For CuO additions of 1000 and 2000 ppm, CO emissions fell by 14.6% and 20.8%, HC emissions by 6.2% and 13.4%, and NOx emissions by 4%, and 4.7%. Both blends of CuO increased the heating value of the diesel fuel. Brake-specific fuel consumption (BSFC) dropped by 4.5% and 8% while brake thermal efficiency (BTE) increased by 5.5% and 14.6% for 1000-CuO and 2000-CuO, respectively. On the other hand, nanoparticles accelerated the chemical reactions and the ignition delay (ID) period was shortened by 3.03% and 5.45% for CuO additions of 1000, and 2000 ppm, respectively. It was also observed that CuO nanoparticles up to 2000 ppm can be suspended in diesel fuel without clogging the filter on the injection system. • Impacts of high-dosage CuO nanoparticles-doped diesel fuel on combustion, performance, and emission characteristics. • The simultaneous reduction in CO, NOx, and HC emissions. • Fuel-economy and higher thermal efficiency with oxygen-donating nanoparticles. • Shortened ignition delay with nanoparticle addition by 5.5%. • Lower exhaust gas temperature thanks to the high thermal conductivity and low fuel consumption of nano-CuO. [ABSTRACT FROM AUTHOR]

Premixed gas turbine decreases exhaust emission but is vulnerable to combustion instability. This paper proposes a new method for early detection of combustion instability that damages combustors, thereby helping to operate energy production system in a more stable way. The proposed method is based on analysis of the spectral centroid and the spectral spread of dynamic pressure so that it enables early recognition of periodic waveform generation. To validate this method, transient dynamic pressure data from single and multi-mode instabilities, obtained from the H 2 /CH 4 /CO flames in a model gas turbine combustor, are used. The effectiveness of the method is compared with that of two conventional methods based on a root-mean-square dynamic pressure and a temporal kurtosis. Among these three methods, the method using spectral features shows the best performance in terms of speed, sensitivity, and accuracy in detecting combustion instability. However, the spectral method sometimes misclassifies unstable flames as having a stable status when multi-mode combustion instability occurs. Therefore, spectral features are modified by weighting the amplitude of dynamic pressure oscillation, which shows better performance as a precursor for multi-mode combustion instability detection. • Spectral features of dynamic signals were used to assess combustion instability. • The number of dynamic pressure signal was optimized by sensitivity analysis. • The spectral spread was suitable for single-mode combustion instability assessment. • The advanced spectral spread reflects the weighted amplitude in frequency domain. • The advanced spectral spread can assess multi-mode combustion instabilities. [ABSTRACT FROM AUTHOR]

In this paper, thermodynamic performance of oxy-biogas regenerative gas turbine cycle with CO 2 recirculation is evaluated. The CO 2 stream is split into the primary and dilution zones. In the primary zone, chemical-equilibrium-model is applied for exergy analysis. Influences of relevant parameters—CO 2 -to-O 2 molar ratio (CtO) in the primary zone and primary diluent ratio (PDR)—on the temperature of combustion chamber (CC) and turbine, net produced power, thermal efficiency, specific fuel consumption (SFC) and CO 2 capturing mass flow rate are studied. Decreasing CtO and raising PDR result in high net produced power. Thermal efficiency has a maximum value in the range of CtO (1.5

Micro humid air turbine (mHAT) is a promising distributed generation technology. However, the experiments, especially on the off-design characteristics, are still insufficient to support the theoretical model. In this paper, a detail experimental study is presented on a mHAT converted from a recuperated microturbine by introducing a humidifier, an aftercooler and an economizer. The steady-state thermodynamic performances, and the combustion and emission characteristics are evaluated at rated and part load condition. The off-design performances of the heat exchangers are also evaluated. It is shown that the specific output power and the electrical efficiency are relatively increased by 45% and 18.6% respectively comparing with the recuperated cycle at the rated load, and show a greater relative increment at part load, such as 58.1% and 21% respectively at 62.5% load. Introducing water into the air reduces the risk of NOx formation, but increases dramatically the risk of CO formation and incomplete combustion in the combustion chamber, thus the combustion efficiency deteriorates up to 92.5% at 50% of full load. The introduced heat exchange units display the characteristic of high effectiveness and low pressure loss, which is important for gas turbine system. The recuperator developed for the dry air also displays superior thermodynamic performance for the wet air with humidity ratio up to 0.108 kg·kg da −1. (1) A mHAT facility has been built based on a TG80 microturbine. (2) Experiments are carried out in the output power range of full to 50%. (3) The specific output power and electrical efficiency increase significantly. (4) The NOx emission shows a maximum reduction of 33%, but incomplete combustion risk improves. (5) The humidifier, aftercooler and economizer work well for off-design operation. [ABSTRACT FROM AUTHOR]

CFD-based simulation models of large-scale moving grate combustor for biomass and municipal solid waste are not well established. Although a 3D transient two-fluid model provides dynamic coupling between the fuel bed and the freeboard, simulation of a whole incinerator is extremely computational intensive and difficult for industrial applications. In this paper, an efficient computational method is proposed where a 2D bed model is combined with a 3D steady furnace model. In the new approach, the bed model includes a transient two-fluid simulation using realistic grate geometry cut by the incinerator throat, which includes a dynamic coupling of heat and mass transfers between the fuel bed and the lower combustion chamber. The simulated bedtop profiles are then used as inlet conditions to run a 3D steady simulation of turbulent gas combustion for the whole furnace. The simulation results are validated with our previous 3D transient full-incinerator results (Xia et al., 2020) [1] and on-site measurement data. In addition, effects of particle size, waste throughput, and residence time on the bed incineration performance are investigated. Overall, the current computational method highly promotes the efficiency of modelling industrial moving grate combustors. • An efficient computational method for moving grate incinerators is proposed. • An interactive two-way coupling bed model is realized. • Results are validated by 3D full-incinerator results and on-site measurement data. • Effects of operating parameters on the bed incineration are investigated. • Relative importance to incineration: particle size > residence time > throughout. [ABSTRACT FROM AUTHOR]

In this paper, vortex characteristics and velocity distribution in the chamber region were studied by numerical method. The three-dimensional moving grid and Improved Delayed Detached Eddy Simulation Shear-Stress Transport model which is a hybrid RANS/LES model were used to predict evolution processes of streamlines and velocity change in small rotary engine. The simulation results show that vortex has always existed in intake process and has gone through three stages, including generation, brakedown, regeneration. The generation is mainly due to intake charge. The brakedown and regeneration is because of the shear and friction of the rotor face. Vortex radius in the leading gradually increases and in the trailing decreases in intake stroke from 490 °C BTDC to 390 °C BTDC. And the position of vortex core in the leading has no obvious change and in the trailing moves towards the trailing apex along the rotor wall. In the intake process, the airflow velocity in the middle of chamber is much higher than the one at both sides, even up to hundreds of times. In the compression process, the large velocity gradient in the trailing and high variation frequency in the leading are due to the shear and friction of the rotor face. • IDDES-SST method was used to calculate the flow field in small rotary engine. • The mechanism of vortex generation was investigated in combustion chamber. • The evolution process of vortex at different cross section was studied. • The velocity distribution and change at different cross section was analyzed. [ABSTRACT FROM AUTHOR]

A novel combustor with a flame holder and preheating channels was developed to investigate the synergistic effect of heat and flow recirculation on combustion characteristics. This paper mainly focuses on the thermal condition of flame holder and combustion chamber wall (CCW) and their interaction on flame stabilization. Based on the distribution characteristics of temperature and flow fields, it can be deduced that the interaction between the flame holder and CCW can further increase the incoming fresh mixture temperature and decrease the height of recirculation zone, which subsequently affect the anchoring locations and temperatures of the flame root and top. To be more specific, the flame holder and CCW synergistically improve the preheating temperature of fresh mixture, making it higher than simple linear superposition. Moreover, the anchoring location of the flame root is mainly determined by the heat exchange of flame holder, but CCW matters more significantly for the flame top. Additionally, the anchoring temperature of the flame root is higher than that of the flame top. This study can help us to gain insights into the effect of conjugate heat exchange on flame stability when the effect of heat recirculation and flow recirculation works synergistically in practical combustors (like aero-engine). • Flame dynamics is influenced by synergistic effect of heat and flow recirculation. • Decoupling heat and flow recirculation via controlling thermal condition of walls. • Effects of heat recirculation of solid walls on flame root and top are both studied. • Flame holder and combustion chamber wall cooperatively improve the flame stability. • This study can provide theoretical basis to control the flame structure and behavior. [ABSTRACT FROM AUTHOR]