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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 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 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]

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]

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]

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]

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]