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The designed system for the monitoring of the fouling of the furnace and superheaters/ reheaters, presented in the paper, will make it possible to operate the boiler with high efficiency. Measurements of temperatures, pressures, flows, and gas analysis data are used to perform heat transfer analysis in the boiler furnace and evaporator. Power boiler efficiency is calculated by an indirect method. The local and average degree of the combustion chamber slagging is determined in an "on-line" mode. In the case of superheaters, the fouling coefficient is determined for each superheater stage, due to big differences in ash-related fouling of individual stages. Fouling processes deteriorate the boiler capacity and efficiency and increase the rate of corrosion of the boiler heating surfaces. The energy consumption of flue gas fans rises as well because the accumulation of slag and ash involves higher pressure losses at individual superheater stages. In addition, examples of ash fouling of individual boiler heating surfaces are presented and discussed in the paper. [ABSTRACT FROM AUTHOR]

In order to shorten the deflagration-to-detonation transition (DDT) distance of the pulse detonation combustion chamber, an experimental study of the effect of pneumatic atomization injector modification on atomization particle size amd gas-liquid two-phase U-bend pulse detonation combustion (U-PDC) chamber was carried out. Gasoline and air were used as fuel and oxidizer, and the atomization particle size was tested and the detonation characteristics of the U-PDC were obtained using the pneumatic atomization injector before and after the modification. The results show that the atomization size range of the injector before the modification is 111.6~152.9 µm, after the modification of the injector atomization size range of 76.4~107.2 µm, atomization size than before the modification is significantly reduced. The U-PDC using the injector before and after the modification can achieve stable operation in the range of 10~30 Hz, and the DDT distance shortened with the increase in frequency. At an operating frequency of 30 Hz, the DDT distance of U-PDC with the injector before modification is about 676 mm, and the DDT distance of U-PDC with injector after modification is shortened by 8.9% to about 616 mm. In addition, under the same operating conditions, due to the better atomization effect of the injector after modification, The fuel flow rate of U-PDC with the injector after modification is 5~10% smaller than that with the injector before modification when the average detonation pressure reaches its maximum value during the adjustment of fuel-flow. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study on the combustion process of methane mixed with NH3 in flameless mode. At a time of striving for CO2-free power, NH3 became a potential energy storage carrier fuel from renewable sources. Flameless combustion features low emissions and is a very efficient technology used in the power sector, as well as steel production, ceramics, etc. Industrial furnaces were tested in the context of pure methane combustion with an addition of NH3, up to 5%. Flameless combustion conditions were achieved with a regenerative gas burner system (high regenerative system). The burner consists of four ceramic regenerators allowing for continuous preheating of air, even up to 50 K lower than the temperature of the combustion chamber wall. Constant power of the introduced fuel was kept at 150 kW and the fuel-air equivalence ratio ranged from 0.75 to 0.95. The results have shown a growth of molar fraction of NO in flue gases when NH3 content in the fuel rose. The increase is more significant for the tests with a higher amount of oxygen in the combustion chamber (a lower fuel-air equivalence ratio). An addition of 5% of NH3 into the fuel caused an emission of NO at the levels of 113 ppmv and 462 ppmv (calculated to O2 = 0%), respectively for low and high fuel-air equivalence ratios. The calculated conversion factor of NH3 to fuel NO has shown extremely low values, equal to 2% (ø = 0.95) and 8.4% (ø = 0.75), which indeed confirmed that NH3 can be burned with low emissions in flameless combustion technology. [ABSTRACT FROM AUTHOR]

This paper investigates the temperature control of the heat air-flow wind tunnel for sensor temperature-calibration and heat strength experiment. Firstly, a mathematical model was established to describe the dynamic characteristics of the fuel sup-plying system based on a variable frequency driving pump. Then, based on the classical cascade control, an improved control law with the Smith predictive estimate and the fuzzy proportional-integral-derivative was proposed. The simulation result shows that the control effect of the proposed control strategy is better than the ordinary proportional-integral-derivative cascade control strategy. [ABSTRACT FROM AUTHOR]

In this study, the combustion chamber geometry for spray-guided, wall-guided, and air-guided combustion strategies were fabricated. The piston crown shape and the cylinder head in each combustion chamber geometry was machined by fixing the fuel injector and spark plug at proper positions to obtain swirl, turbulence, and squish effects for better mixing of fuel with air and superior combustion of the mixture. Conducted tests on all the three modified gasoline direct injection engines with optimized exhaust gas recirculation and electronic control towards fuel injection timing, the fuel injection pressure, and the ignition timing for better the performance and emissions control. It is clear from the results that NOx emissions from all three combustion modes were reduced by 4.9% up to 50% of loads and it increase for higher loads due to increase of in-cylinder pressure. The fuel consumption and emissions showed better at 150 bar fuel injection pressure for wall-guided combustion chamber geometry. Reduced HC emissions by 3.7% and 4.7%, reduced CO emissions by 2% and 3.3%, reduced soot emissions by 6.12% and 10.6%. Reduces specific fuel consumption by about 10.3% and 13.3% in wall-guided combustion strategy compare with spray-guided and airguided combustion modes respectively. [ABSTRACT FROM AUTHOR]

This paper presents results of experimental investigation on elimination of combustion oscillations caused by new low pollution burner which was integrated in a gas heater. The method is known as a passive method, based on introducing the air in the combustion chamber. Since efficiency of the passive method is highly dependent of the way the air is injected, several different methods were investigated and compared. The paper also presents effects on pollution characteristics during its operation in the unstable regime. [ABSTRACT FROM AUTHOR]

Upcoming stringent Euro-6 emission regulations for passenger vehicle with better fuel economy, low cost are the key challenges for engine development. In this paper, 2.2L, multi cylinder diesel engine have been tested for four different piston bowls designed for compression ratio of CR 15.5 to improve in-cylinder performance and reduce emissions. These combustion chambers were verified in CFD at twofull load points. 14 mode points have been derived using vehicle model run in AVL CRUISE software as per NEDC cycle based on time weightage factor. Base engine with compression ratio CR16.5 for full load performance and 14 mode points on engine test bench was taken as reference for comparison. The bowl with flat face on bottom corner has shown NOx emission reduction by 25% and 12 % NOx at 1500 and 3750 rpm full load points at same level of Soot emissions. Three piston bowls were tested for full load performance and 14 mode points on engine test bench and combustion chamber C has shown improvement in thermal efficiency by 0.8 %. Combinations of cooled exhaust gas re-circulation and combustion chamber C with geometrical changes in engine have reduced exhaust NOx, soot and CO emissions by 22 %, 9% and 64%as compared to base engine at 14 mode points on engine test bench. [ABSTRACT FROM AUTHOR]

In recent years, the gas turbine power plant has been increasingly used in various industries in Kazakhstan. The reasons for this are: thermal efficiency, simplicity of the thermal scheme and design, small mass per power unit, high maneuverability, low toxicity, and relatively simple automation of operation. This paper presents the experimental study results of a two-tier air burner as the part of the gas turbine engine combustion chamber at burning liquid fuel. A new design of a microflame device was developed. Two-tier burner makes possible the combustion process in a number of discrete zones, i.e. microflame combustion. During the experiment, the installation angles of the blades of the external and internal registers, as well as the ratio of the coefficients of excess air in the tiers, were changed. The experimental studies of a two-tier burner confirmed the possibility to increase fuel combustion efficiency, a low degree of temperature field unevenness and to decrease NOx emission. [ABSTRACT FROM AUTHOR]

This paper describes a numerical analysis of a heat transfer enhancement technique that introduces fractal-shaped design for impingement cooling. Based on the gas turbine combustion chamber cooling, a fractal-shaped nozzle is designed for the constant flow area in a single impingement cooling model. The incompressible Reynolds-averaged Navier-Stokes equations are applied to the system using CFD software. The numerical results are compared with the experiment results for array impingement cooling [ABSTRACT FROM AUTHOR]

Modern and advanced control systems for internal combustion engines require accurate feedback information from the combustion chamber. Whereas the in-cylinder pressure sensor provides this information through its close thermodynamic ties with the combustion process, drawbacks in its implementation push research towards other non-intrusive sensing methods. This paper suggests alternative methods of combustion phasing detection relying on measured angular crankshaft speed. Method developed, achieves sensing of angular position of the 50% of mass fraction burned (MFB50) through two steps: calculation of, so called, synthetic torque and its non-linear transformation to a combustion feature estimator through localmodel. In order to calibrate both parts of this virtual combustion sensor, parameters of a high-fidelity crankshaft dynamic model are identified, and the linear neuro-fuzzy based model is trained with extensive experimentally collected data set. Created virtual MFB50 sensor, demonstrated its performance, on a large test data set comprised of 70% of gathered data. [ABSTRACT FROM AUTHOR]

Micro-combustors are a key component in combustion-driven micropower generators, and their performance is significantly affected by their structure. For the application of micro-thermophotovoltaic system, a high and uniform temperature distribution along the walls of the micro-combustor is desired. In this paper, a 3-D numerical simulation has been conducted on a new-designed parallel plate micro- combustor with two nozzles. The flow field and the combustion process in the micro-combustor, and the temperature distribution on the wall as well as the combustion efficiency were obtained. The effects of various parameters such as the inlet angle and the fuel volumetric flow rate on the performance of the micro-combustor were studied. It was observed that a swirl formed in the center of the combustor and the radius of the swirl increased with the increase of the inlet rate, and the best working condition was achieved at the inlet angle, θ = 20°. The results indicated that the two-nozzle combustion chamber had a higher and more uniform mean temperature than the conventional combustor under the same condition. [ABSTRACT FROM AUTHOR]

The aim of this paper is to examine whether the use of baffles in a combustion chamber, one of the well-known low-cost methods for the boiler performance improvement, can be enhanced. Modern day tools like computational fluid dynamics were not present at the time when these measures were invented, developed, and successfully applied. The objective of this study is to determine the influence of location and length of a baffle in a furnace, for different mass flows, on gas residence time. The numerical simulations have been performed of a simple Scandinavian stove like furnace. The isothermal model is used, while air is used as a medium and turbulence is modeled by realizable k-e model. The Lagrange particle tracking is used for the residence time distribution determination. The statistical analysis yielded the average residence time. The results of the computational fluid dynamics studies show that influence of baffle positions, dimension, and flow rates can decrease residence time even 17% but also increase it up to 13%. Vertical position of the baffle is the most important factor, followed by the length of the baffle, while the least important showed to be the mass flow. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive thermodynamic modeling and multi-objective optimization of a micro turbine cycle in combined heat and power generation are presented, which provides 100 kW of electric power. This combined heat and power system is composed of air compressor, combustion chamber, air preheater, gas turbine, and a heat recovery heat exchanger. At the first stage, the each part of the micro turbine cycle is modeled using thermodynamic laws. Next, with using the energetic and exergetic concepts and applying economic and environmental functions, the multi-objectives optimization of micro turbine in combined heat and power generation is performed. The design parameters of this cycle are compressor pressure ratio (rAC), compressor isentropic efficiency, gas turbine isentropic efficiency, com-bustion chamber inlet temperature, and turbine inlet temperature. In the multi-objective optimization three objective functions, including the combined heat and power exergy efficiency, total cost rate of the system products, and CO2 emission of the whole plant, are considered. The exergo-environmental objective function is minimized whereas power plant exergy efficiency is maximized usinga Genetic algorithm. To have a good insight into this study, a sensitivity analysis of the result to the fuel cost is performed. The results show that at the lower exergetic efficiency, in which the weight of exergo-environmental objective is higher, the sensitivity of the optimal solutions to the fuel cost is much higher than the location of the Pareto frontier with the lower weight of exergo-environmental objective. In addition, with increasing exergy efficiency, the purchase cost of equipment in the plant is increased as the cost rate of the plant increases. [ABSTRACT FROM AUTHOR]

This article presents the improvement of operation characteristics and emissions reduction by means of creating an air-cell inside the piston body, exhaust gases re-circulating and insulating combustion chamber in a direct injection diesel engine simultaneously. The engine considered is a caterpillar 3401 which is modeled with an air-cell included as part of the piston geometry. This air-cell demonstrates that air injection in late combustion period can be effective in a significant reduction of soot emission while cold exhaust gas re-circulation can be effective in reduction of NOx emission. Also for increasing of performance parameters, combustion chamber with air-cell is insulated. The analyses are carried out at part (75% of full load) and full load conditions at the same engine speed 1600 rpm. The obtained results indicate that creating the air-cell has a slight effect on improvement of performance parameters and it has significantly effect on soot reduction. The air-cell decreases the soot pollutant as a factor of two at both part and full load conditions. Also, the adding 5% of cold exhaust gas re-circulation in inlet air decreases NOx by about half and insulating the engine increases the power and indicated mean effective pressure by about 7.7% and 8.5% and decreases the indicated specific fuel consumption by about 7.5% at part load and increases power and indicated specific fuel consumption by 8.5%, and decreases indicated specific fuel consumption by 8% at full load condition, respectively. Using this method, it was possible to control emissions formation and increase performance parameters simultaneously. The predicted results for mean in-cylinder pressure and emissions are compared to the corresponding experimental results and show good agreements. [ABSTRACT FROM AUTHOR]

In this paper we simulate a turbulent premixed V-shape flame stabilized on a hot wire. The device used is composed of a vertical combustion chamber where the methane-air mixture is convected upwards with a mean velocity of 4 m/s. The flow was simulated running Fluent 6.3, which numerically solved the stationary Favre-averaged mass balance; Navier-Stokes equations; combustion progress variable, and k-ϵ equations on a two-dimensional numerical mesh. We model gaseous mixture, ignoring Soret and Dufour effects and radiation heat transfer. The progress variable balance equation was closed using eddy break up model. The results of our simulations allow us to analyze the influence of equivalence ratio and the turbulent intensity on the properties of the flame (velocity, fluctuation, progress variable, thickness of flame).This work gives us an idea on the part which turbulence can play to decrease the risks of extinction and instabilities caused by the lean premixed combustion. [ABSTRACT FROM AUTHOR]

The study of a novel two-tier micro-flame combustor for gas turbines involved comprehensive modelling using SolidWorks and ANSYS FLUENT software packages, alongside physical experiments. Analysis of air-flow velocities, pressures, temperatures within the combustion chamber, and NOx emissions led to several key findings. The SolidWorks modelling confirmed stabilized air-flow and uniform pressure distribution, enhancing fuel combustion. Optimal air-flow velocities (15 m/s and 30 m/s) for different operating modes were determined, highlighting the importance of air-flow regulation. The ANSYS FLUENT analysis revealed efficient mixing of the fuel-air mixture through the device's two tiers. The analysis of NOx emissions confirmed compliance with regulatory standards, up to 15 ppm. These results underscore the efficiency and stability of the combustor, making a significant contribution the advancement of gas turbines while meeting requirements for efficiency and environmental safety. [ABSTRACT FROM AUTHOR]

The laminar burning velocity and NO formation process of ammonia-hydrogen combustion within a two-stage combustion chamber were investigated numerically in the present study. A chemical reactor network method involving perfectly stirred reactor, plug flow reactor, and partially stirred reactor configurations with the 24-species Xiao mechanism was implemented to simulate the premixed ammonia-hydrogen-air combustion process. The effects of inlet temperature and pressure conditions on the laminar burning velocity were investigated. Results proved that elevated pressure condition decreased primary flame thickness leading to lower laminar burning velocity while inlet temperature increased flame temperature which in turn increased the laminar burning velocity. Investigation of the effect of humidification on the laminar burning velocity showed that humidification can counteract the effect of high inlet temperature. The NO emission studies indicated a twofold impact of pressure on NO formation processes: preventing NO formation in the primary combustion zone, and promoting thermal NO formation in the lean combustion zone. The minimum amounts of NO emission were obtained at total equivalence ratios of 0.4. Humidification prevented the NO formation in the lean combustion through the competitive effect of H2O on O, whilst temperature effect was comparatively small. Humidity and pressure were optimized in the two-stage configuration achieve both low emission and high efficiency. [ABSTRACT FROM AUTHOR]

Adding methane to methanol can solve the problem of difficult cold starts of methanol engines. Therefore, it is important to understand the combustion of methane and methanol fuel blends. Because of this, this study explores the effect of methane addition on the laminar burning velocity and Markstein length of methanol/methane premixed flames under stoichiometric conditions at the initial temperatures of 353 K, 373 K, and 393 K, initial pressures of 1 bar, 2 bar, and 4 bar, using methane addition ratios of 0%, 25%, 50%, 75%, and 100% in a constant volume combustion chamber. The results show that the laminar burning velocity decreases linearly with the increase of methane addition ratio due to the linear decrease of the Arrhenius factor. The sensitivity analysis revealed that the kinetic effect is the main reason for the inhibition of laminar burning velocity, which is insensitive to initial temperature but enhanced at a high initial pressure. The Markstein length decreases with the addition of methane and the increase of initial pressure, which is mainly caused by the high mass diffusivity of methane and the decrease of flame thickness due to the increase of initial pressure. [ABSTRACT FROM AUTHOR]

Small-scale power generation using heat energy from hydrocarbon fuels is a proven technology. In this study, we analyzed 2-D flame development in mesoscale Swiss roll combustor. A mixture of 60% butane and 40% propane was used (0.25–0.55 L per minute). During all the analyses, equivalence ratio (1.1) was kept constant by adjusting air quantity against fuel quantity. The effect of increase in the mixture velocity on the development of flame shapes/patterns was monitored. We found different patterns of flame, e. g., planar, concave, and conical, with the increase in mixture velocity. Increase in combustion chamber temperature was also noted. No flashback was observed and blowout was observed with very high mixture velocity. Combustion chamber temperatures were found to be increasing with the increase in mixture velocity at the same equivalence ratio. Elongation of the flame was observed because of the increased flow velocity. Heat re-circulation to the reactants enhances flame characteristics. [ABSTRACT FROM AUTHOR]

In-cylinder gas motion is the essential parameter that enhances fuel-air mixing and increases the combustion rate and governs the performance and emission of the engine. It also has significant impact on heat transfer. Angling the intake port into various angles is the one of the method to enhance swirl motion inside the combustion chamber. In this project, direct port is converted into helical port to analyze the air motion inside the engine cylinder. In order to analyze the effect of helical port design the various flow parameters such as swirl ratio, flow coefficient, and turbulent kinetic energy are calculated. By angling the intake port, swirl generation during suction stroke is comparatively larger than direct port. A commercial CFD software STAR-CCM is used to analyze the in-cylinder air motion. [ABSTRACT FROM AUTHOR]

The purpose of the present work is the analysis of the fluid dynamic behaviour of a high performance internal combustion engine during the intake phase. In particular, a four-valve spark-ignition engine has been characterised at the steady flow rig. Dimensionless discharge coefficients have been used to define the global fluid dynamic efficiency of the intake system, while the laser-Doppler anemometry technique has been employed to evaluate the mean flow in the valve curtain area and to characterise the interference phenomena between the two intake valves. The investigation has shown the significant influence of the valve lift on the volumetric efficiency of the intake apparatus. Moreover, the experimental analysis has highlighted that the valve-valve interference phenomena have a relevant impact on the head breathability, on the flow development within the combustion chamber and on the velocity standard deviations. [ABSTRACT FROM AUTHOR]

The compression ratio strongly affects the working process and provides an exceptional degree of control over engine performance. In conventional internal combustion engines, the compression ratio is fixed and their performance is therefore a compromise between conflicting requirements. One fundamental problem is that drive units in the vehicles must successfully operate at variable speeds and loads and in different ambient conditions. If a diesel engine has a fixed compression ratio, a minimal value must be chosen that can achieve a reliable self-ignition when starting the engine in cold start conditions. In diesel engines, variable compression ratio provides control of peak cylinder pressure, improves cold start ability and low load operation, enabling the multi-fuel capability, increase of fuel economy and reduction of emissions. This paper contains both theoretical and experimental investigation of the impact that automatic variable compression ratios has on working process parameters in experimental diesel engine. Alternative methods of implementing variable compression ratio are illustrated and critically examined. [ABSTRACT FROM AUTHOR]

In modern research, simulation has become a powerful tool as it saves time and also economical when compared to experimental study. This paper deals with a comprehensive model of a spark ignition hydrogen fueled engine. Woschni's heat transfer co-relation is used by this model for predicting the heat transfer in the engine. Two zone combustion model has been opted for simulating the combustion process. Two zone models account for the combustion chamber geometry and for the presence of burnt and unburnt gases. The results are compared with the experimental data and it is found that there was a good convergence of results. The engine efficiency and power has been slightly over predicted because dissociation has not been included in the model. [ABSTRACT FROM AUTHOR]

A numerical investigation of combustion of propane-hydrogen mixture in a swirl premixed micro gas turbine combustor is presented. The effects of hydrogen addition into propane on temperature distribution in the combustor, reaction rates of propane and hydrogen and NOx emissions for different equivalence ratios and swirl numbers are given. The propane-hydrogen mixture of 90/10% by volume was assumed. The numerical results and measurements of NOx emissions for pure propane are compared. Excellent agreements are found for all equivalence ratios and swirl numbers, except for the highest swirl number (1.13). It is found that the addition of hydrogen into propane increases NOx emission. On the other hand, the increase of swirl number and the decrease of equivalence ratio decrease the NOx emissions. [ABSTRACT FROM AUTHOR]

The study of micro flame characteristics is an essential basis for developing micro combustors. Therefore, the non-premixed C3H8-air micro flame characteristics were experimentally studied. Flame length, flame shape, and blow-out limit were studied by varying the equivalence ratio, Φ, the inlet velocity of C3H8-air, v, and angles of the burner. The results showed ignited non-premixed C3H8-air had three combustion states: no flame, a stable flame, and a blow-out flame. Whether ignited non-premixed C3H8-air could form a stable flame mainly depended on Φ and v. In addition, total flame lengths increased with the increase of Φ and v firstly. However, when Φ increased to a certain value, total flame lengths were independent of Φ and only affected by v. Moreover, flame length and shape were affected by the angle of the burner. Instead, the blow-out limit was found to be associated solely with Φ, but not the burner angle. The findings of this study provided fundamental data for the development of high-efficiency micro combustors. [ABSTRACT FROM AUTHOR]

Piston performance has an important on vehicle reliability, efficiency, and exhaust emissions. Application of the thermal barrier coating is an effective method for preventing heat transfer from combustion chamber to the substrate. The numerical model of thermal barrier coating piston is established by using finite element method, and a comprehensive thermal-mechanical result is given to determine the influence of ceramic thickness on ceramic layer and substrate. Compared with uncoated piston, the maximum temperature of substrate decreased by 3.34%, 4.09%, 5.19%, 5.95%, and 6.69%, corresponding to ceramic thicknesses of 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, and 0.35 mm. The maximum thermal stress decreases from 78 MPa to 73 MPa. For ceramic layer of the thermal barrier coating piston, the maximum temperature appears at the top surface of the ceramic layer, while the maximum thermal stress occurs at the bottom of the ceramic layer. As the ceramics thickness increases from 0.15 mm to 0.35 mm, the maximum temperature of the ceramic layer increases from 322 °C to 377 °C, while the maximum thermal stress decreases from 95 MPa to 89 MPa. Thermal-mechanical coupled stress analysis shows that the maximum coupling stress occurs at the pinhole and its value does not change significantly. The thickness of the ceramic layer has little effect on the pinhole, but has a great influence on the ceramic layer. [ABSTRACT FROM AUTHOR]

An integrated solar combined cycle system based on parabolic trough solar collector and combined cycle power plant is proposed. The advanced system is socio-economic significance compared to traditional combined cycle power system. Plainly, the exergetic analyses (exergy destruction and efficiency) via conventional and advanced methods are used for thermodynamic properties of the integrated solar combined cycle system components. In addition, the exergy destruction is divided into endogenous, exogenous, avoidable, and unavoidable. The results show that the combustion chamber has the largest fuel exergy and the highest endogenous exergy destruction rate of 1001.60 MW and 213.87 MW, respectively. Additionally, the combustion chamber has the highest exergy destruction rate of 235.60 MW (60.29%), followed by the parabolic trough solar collector of 54.20 MW (13.87%). For overall system, the endogenous exergy destruction rate of 320.83 MW (82.10%) and exogenous exergy destruction rate of 69.97 MW (17.90%) are resulted via the advanced exergy analysis method. Besides, Several methods to reduce the exergy destruction and improve the components' efficiency are put forward. [ABSTRACT FROM AUTHOR]

A thermal calculation based on a table of thermal properties of gas was carried out for a micro gas turbine system without a recuperator. The performance parameters of the micro gas turbine system were obtained. The results of the thermal calculations were verified using ASPEN PLUS, and it shows that the thermal calculations fit well with the ASPEN simulation results. Based on this thermal calculation method, the variation of the performance parameters of the micro gas turbine system under different pressure and temperature ratios was analyzed. The results show that there is no optimum pressure ratio within the general design parameters of micro gas turbines, which leads to extreme values of thermal efficiency. The NOx generation in the combustion chamber of the micro gas turbine based on the Zeldovich mechanism was modeled and analyzed by coupling the 1-D thermal calculation model with the NOx emission model. The relationship between NOx generation rate, molar fuel factor, the characteristic pressure, and the characteristic temperature was obtained. The results of the analysis show that, in terms of controlling NOx emissions from a gas turbine, the use of an increased pressure ratio has a significant advantage over an increased temperature ratio to improve the thermal efficiency of the micro gas turbine. [ABSTRACT FROM AUTHOR]

By using exhaust gas as heating source, a combined cycle power plant with inlet fuel heating is investigated experimentally. Energy analysis and exergy analysis are carried out under different power load and ambient temperature. The results reveal that the thermal efficiency of the power plant system increases as power load increases. The thermal efficiency and power output at 5 °C are 54.15% and 412 MW, respectively, while when the ambient temperature is 35 °C, the thermal efficiency and power output are 52.3% and 330 MW, respectively. Under the same conditions, the combustion chamber has the highest irreversibility rate, while the air compressor has the lowest. The irreversibility rate of the power plant system increases in line with power load. The second-law efficiency increases from 37.0-50.12% when the power load changes from 30-100%. [ABSTRACT FROM AUTHOR]

Thermal devices with porous structures, intended for the combustion chambers of gas turbine units, as well as for cutting and boring of the turbine housings of electric power plants have been developed and studied. Photographs of combustion chambers and nozzles, studied in terms of their geometry and thickening of the nozzle walls, excess oxidant (0.3-0.8) and the operating conditions until the limit state of the metal is reached (1 · 106 W/m²) have been presented. The optimal geometry of the chambers and nozzles, as well as the type of porous structure have been determined. Coolant consumption has been reduced dozens of times, which has environmental significance. The appraisal of the structures studied showed the advantages to the flow cooling system. An analytical model of the heat exchange crisis is proposed. The system of differential equations for 1-D flow of one-phase liquid is solved. A physical picture of the heat exchange process is presented. In the equation of motion, the coefficient which determines the viscosity in the general pressure gradient is introduced. The actual velocity of the fluid is accounted for by the coefficient of moisture content in the porous structure. [ABSTRACT FROM AUTHOR]

Combustion instability and NOx emission are crucial factors for modern gas turbine combustors, which seriously hampers the research and development of advanced combustors. To eliminate combustion instability and NOx emissions simultaneously, effects of the oxy (CO2/O2, N2/O2, Ar/O2, and He/O2) jet in cross-flow on combustion instability and NOx emissions are experimentally studied. In this research, the flow rate and oxygen ratio of the combustor are varied to evaluate the control effectiveness. Results denotes that all the four oxyfuel gas: CO2/O2, N2/O2, Ar/O2, and He/O2, could suppress combustion instability and NOx emissions. The CO2/O2 dilution can achieve a better damping results than the other three cases. There are peak values or lowest points of sound pressure amplitude as the parameter of oxy jet in cross-flow changes. Mode transition appears in both acoustic signal and CH* chemiluminescence of the flame. But the turning point of mode transition is different. Under the CO2/O2 cases, the NOx emission decreases from 22.3 ppm to 15.2 ppm, the damping ratio of NOx is 40.39%. The flame shape and length were changed under different jet in cross-flow dilutions. This research could promote the application of jet in cross-flow methods on combustion instability or pollutant emissions in gas turbines. [ABSTRACT FROM AUTHOR]

The spatial structure of a swirling turbulent flow has been investigated based on the three-component laser Doppler anemometry method in an isothermal laboratory model of a four-vortex furnace. The structure of the vortex cores of the flow with the shape of a deformed vertical elliptical cylinder is visualized using the "minimum total pressure" criterion. The spectrum of velocity pulsations indicates the absence of unsteady periodic vortex structures, which means the occurrence of a stable vortex flow in the volume of the combustion chamber. [ABSTRACT FROM AUTHOR]

Experimental and numerical modelling studies on optimized design of micro-modular air driven combustion nozzle have been developed. Moreover, optimal angle of outlet swirler (vortex generator) connected in series with the nozzle has been analyzed in the context of minimization of NOx in the flue gases. Numerical modelling by ANSYS verifying the experimental data has been carried out. It has been established that an angle of about 20° of the outlet vortex generator has been able to assure optimal flame length and combustion efficiency. [ABSTRACT FROM AUTHOR]

The article presents the research results related to the influence of turbulence on the efficiency of the combustion chamber of gas turbine. An artificial increase in the intensity of turbulence is considered as a way to improve the formation of a fuel-air mixture. Turbulent flow is formed due to the installation of guide swirlers at the entrance to the device for creating a fuel-air mixture – a micro module. The angle of rotation of the swirler blades is selected. Theoretical research, mathematical software modelling, as well as an aerodynamic experiment have been carried out. As a result, design solutions are provided that significantly increase the efficiency and reliability of the gas turbine combustion chamber. In the course of the study, guide vanes were selected, and their design was established. The recommended swing angle of the swirler guide vanes is 40°. The recommended depth of the fuel injector inside the chamber is 1.0 gauge. [ABSTRACT FROM AUTHOR]

Precise control of needle lift provides one possibility to control the diesel spray and combustion process actively. However, most studies of needle lift focus on internal flow or near nozzle spray. Little work has been performed on its effects on reacting spray. In this work, one way to change the needle lift profile of a solenoid injector has been developed and the relationship between needle lift and reacting spray has been investigated. The needle movement was detected with an optical nozzle. In addition, the visualization of reacting sprays of the same injector equipped with a single hole nozzle was conducted in a combustion chamber. Some simulations were also performed to assist the analysis. The results show that the needle lift profile can be regulated by changing the thickness of an adjusting pad. It seems the different needle lift profiles do not bring in significant influences on reacting spray characteristics. The CFD results indicate that it is mainly caused by the similar internal flow characteristics which do not show strong variation when needle lift is higher than 0.1 mm. However, the discharge coefficient and velocity coefficient decrease sharply when needle lift is smaller than 0.05 mm because of the "throttle" effect. [ABSTRACT FROM AUTHOR]

A correction to the article "Effect of Combustion Chamber Geometry on Performance, Combustion and Emission of Direct Injection Diesel Engine with Ethanol-Diesel Blend" that was published in the year 2016 issue of the journal is presented.

Bottom ash samples were collected from four lignite power plants of Greece. Granulometric analysis was executed and after homogenization four distinct fractions (>1.25, 0.63-1.25, 0.18-0.63, <0.18 mm) were obtained. The samples were analysed by X-ray diffraction and energy dispersive system, while thermogravimetric and stereomicroscope viewing were applied for the coarse fractions. Furthermore, proximate analysis (moisture, ash, volatiles, fixed carbon) was undertaken and loss on ignition and calorific values were determined. The particle size distribution revealed that bottom ash satisfies the gradation criteria for concrete and geotechnical applications. The mineral composition included mainly amorphous matter, quartz, plagioclase, calcite and gehlenite and minor amounts of pyroxene, portlandite, hematite, micas, etc. The chemical analysis showed Si, Ca, Al, Mg, Fe, S as major and Ti and K as minor chemical elements, indicating high slagging, and fouling potential within the thermal chambers. Based on the chemistry and mineralogy of the bottom ash samples, a potential utilization in concrete manufacturing is discussed, taking into account certain limitations. Based on loss on ignition, proximate analysis, calorific values and thermogravimetric profiles of the coarse fractions (>1.25 mm), certain differences in the characteristics of the bottom ash of the younger and the three older power plants were observed. High amounts of unburnt carbon were determined in the coarse fraction (>1.25 mm) of all plants except the younger one, indicating a problematic combustion within the chambers and a potential of reburning these coarse material in a waste to energy application. [ABSTRACT FROM AUTHOR]

An experimental study was carried out to investigate the effect of intake air preheating, exhaust gas re-circulation, and hydrogen enrichment on performance, combustion, and emission characteristics of CH4/waste cooking oil biodiesel fuelled compression ignition engine in dual fuel mode. Methyl ester derived from waste cooking oil was used as a pilot fuel which was directly injected into the combustion chamber at the end of the compression stroke. The CH4/hydrogenenriched methane was injected as the main fuel in the intake port during the suction stroke using a low pressure electronic port fuel injector which is controlled by an electronic control unit. The experiments were conducted at a constant speed and at the maximum load. Experimental results indicated that the increase in energy share of gaseous fuel extends the ignition delay. With air preheating the thermal efficiency increased to 49% and 55% of CH4 and hydrogen-enriched CH4 energy share, respectively. The CO and HC emissions were higher in CH4 combustion with biodiesel when compared to the conventional diesel operation at full load and a reduction in CO and HC was observed with air preheating. Lower NOx were observed with gaseous fuel combustion and it further reduced with exhaust gas re-circulation but NOx increased by preheating the intake air. Improvement in thermal efficiency with a reduction in HC and CO was observed with hydrogen-enriched CH4. [ABSTRACT FROM AUTHOR]

Crude oil is an attractive fuel for energy production, since its use does not require additional processing costs. Existing technologies for burning liquid fuel do not always ensure the achievement of the modern ecological and energy performance when using highly viscous and substandard fuels. This relates to unstable ignition and combustion of such fuels in the combustion chamber, relatively fast coking of the burner surfaces, etc. The work deals with investigation of crude oil burning in a flow of superheated steam as a promising way to reduce NOx and increase the completeness of fuel combustion. The experiments were carried out using an original burner where liquid fuel is sprayed due to interaction with a high-velocity flow of superheated steam. This method of spraying allows the creation of a highly dispersed two-phase flow and prevents nozzle chocking and coking when using substandard fuel and waste. At the same time, steam gasification of products of fuel thermal decomposition allows the reduction of toxic emissions, increasing carbon burnout. The regimes of crude oil burning in a modernized burner that provide high completeness of fuel combustion (~44 MJ/kg) with a low content of NOx and CO in the combustion products have been determined. The amount of these toxic components corresponds to class 1 of EN 267. The results obtained confirm the effectiveness of the investigated method of fuel spraying by a superheated steam jet for environmentally friendly crude oil burning, including this process in the low-power burners (~15 kW). Such devices can be used for the cleaner elimination of liquid hydrocarbon waste with the receipt of thermal energy. [ABSTRACT FROM AUTHOR]

This work numerically investigates the effects of turbulators at the air and fuel (methane) inlets on the thermal behavior of a combustion chamber. Conservation equations for mass, momentum, energy, gaseous chemical species, soot, and temperature fluctuation variance in cylindrical axysimmetric co-ordinates were solved using the finite volume method. Chemical reaction rates were computed through the Arrhenius-Magnussen model, with two-step combustion reaction. The turbulence closure model, to compute the turbulent viscosity, was the standard k-ε. The modelling of turbulence-radiation interactions considered the absorption coefficient-temperature correlation and the temperature self-correlation. The radiative heat source was calculated using the discrete ordinates method, considering the weighted-sum-of-gray-gases model with the superposition method to compute the radiation from the gaseous species and soot. The effect of inlet turbulators was studied by varying the turbulence intensity (TI) of both inlet streams (air and fuel), encompassing mild to severe turbulators (TI = 3%, 6%, 15%, and 20%). The results showed that temperature and radiative heat source fields, and heat transfer rates on the chamber wall and radiative fraction were importantly affected by the different turbulators intensities (e. g. radiative fraction was increased from 20.6% to 32.8% when the TI was varied from 3% to 20%). Comparisons of results obtained when turbulence-radiation interactions modelling was neglected in relation to results obtained when turbulence-radiation interactions modelling was computed showed that turbulence-radiation interactions influenced the thermal field (temperature and radiative exchange) in a similar way independently of the turbulator intensity (e. g. radiative fraction decreased 20% when turbulence-radiation interactions modelling was neglected, for both turbulators intensities). [ABSTRACT FROM AUTHOR]

In order to study a new clean and efficient combustion mode, which can relieve the pressure of traditional energy and ensure low emissions, in this study, a diesel/natural gas dual fuel engine is designed by non-dominant sorting genetic algorithm (NSGA-II), and its thermodynamic characteristics are studied. The WP10.290 Diesel engine is modified into a diesel/natural gas dual fuel engine. The emissions of harmful substances and thermal efficiency of the modified engine under different working conditions are compared. The combustion chamber structure and adaptability between combustion chamber and injection parameters are optimized by using NSGA-II algorithm and CFD software. The results show that the emission of NOx and CH4 and the fuel consumption rate can be reduced simultaneously by using the composite combustion model compared with the original engine. When the CH4 emission is close to zero, the fuel consumption rate decreases obviously, and NOx slightly increases. When the angle between the injection holes is 141.57°, the amount of NOx in the cylinder is large. When the injection advance angle is 21.91 °CA, the pressure in the cylinder is the highest, the CH4 production is the lowest, the NOx production is higher, and the oxygen content in the combustion mixture is less. The NOx production is the lowest. diesel/natural gas dual fuel engine can ensure efficient combustion while reducing emissions. In this study, the performance of the dual fuel engine at various speeds can be further studied, which can provide theoretical support for the design of diesel/natural gas dual fuel engine. [ABSTRACT FROM AUTHOR]

Gas turbine combustor performance was explored by utilizing a 1-D flow network model. To obtain the preliminary performance of combustion chamber, three different flow network solvers were coupled with a chemical reactor network scheme. These flow solvers were developed via simplified, segregated and direct solutions of the nodal equations. Flow models were utilized to predict the flow field, pressure, density and temperature distribution inside the chamber network. The network model followed a segregated flow and chemical network scheme, and could supply information about the pressure drop, nodal pressure, average temperature, species distribution, and flow split. For the verification of the model's results, analyses were performed using CFD on a seven-stage annular test combustor from TUSAS Engine Industries, and the results were then compared with actual performance tests of the combustor. The results showed that the preliminary performance predictor code accurately estimated the flow distribution. Pressure distribution was also consistent with the CFD results, but with varying levels of conformity. The same was true for the average temperature predictions of the inner combustor at the dilution and exit zones. However, the reactor network predicted higher elemental temperatures at the entry zones. [ABSTRACT FROM AUTHOR]

Experiments on fuel effects flame stabilization processes, NOx generation and temperature at combustion chamber outlet when using a group of three V-gutter flame holders have been reported. Fuel supply directly to the re-circulation zone on the inside of the V-gutter (type A fuel supply), and alternatively in the second type, fuel was supplied to the V-gutter symmetry axis on the outside (type B fuel supply have been carried out. [ABSTRACT FROM AUTHOR]

Blow-off performance and NOx emissions of the propane and air mixture in a rectangular combustion chamber with bluff bodies were investigated experimentally and numerically. The effects of distance between bluff bodies on NOx emissions, the blow-off limit, and exhaust gas temperature were examined. It was observed that NOx emissions are highly dependent on distance between V-gutters. The re-circulation zone behind the bluff body expands in width based on the decrease of distance between V-gutters, and expands in length with the increase of inlet velocity. The temperature fields behind the bluff body show a similar change, the temperature behind the bluff body reaches its highest when the distance between V-gutters reaches 20 mm, meaning it has better flame stability. The blow-off limit is significantly improved with the decrease of distance between V-gutters. The blow-off limit is greatly improved by reducing the distance between the V-gutters. Maximum blow-off limit of 0.11 is reached in the case of 20 mm, compared with 0.16 at 50 mm at a speed of 10 m/s. [ABSTRACT FROM AUTHOR]

Fluid-solid coupling simulation is conducted to investigate the performance of effusion cooling in the real combustion chamber condition of strong rotation and primary holes. The wall temperature and film cooling effectiveness of different deflection angle is analyzed. From the results, it is concluded that the performance of effusion is better than conventional film cooling. The wall temperature and gradient is lower, the cooling efficiency is higher and the coolant is reduced by 20%, but pressure loss is slightly increased. The cooling effectiveness decreases behind primary holes because of local combustion. Comparison with the effect of deflection angle, the cooling performance of 60 deg deflection angle is best. The coolant is better attached to the wall downstream when the deflection angle is same as the rotating mainstream. In addition, the effect of deflection angle is not so significant on the coolant flow rate, but a large negative impact on the pressure loss. Although the cooling effectiveness of 60 deg deflection angle is highest, the total pressure recovery coefficient is lower. The maximum temperature drops about 70 K and the outlet temperature distribution trends more consistent. So various factors should be taken into consideration when designing of deflection angle. [ABSTRACT FROM AUTHOR]

The interactions between flame and vortex in a 2-D trapped vortex combustor are investigated by simulating the Reynolds averaged Navier-Stokes equations, for the following five cases: (1) non-reacting (base) case, (2) post-vortex ignition without premixing, (3) post-vortex ignition with premixing, (4) pre-vortex ignition without premixing, and (5) pre-vortex ignition with premixing. For the post-vortex ignition without premixing case, the reactants are mixed well in the cavity resulting in a stable C shaped flame along the vortex edge. Further, there is insignificant change in the vorticity due to chemical reactions. In contrast, for the pre-vortex ignition case (no premixing); the flame gets stabilized at the interface of two counter rotating vortices resulting in reduced reaction rates. There is a noticeable change in the location and size of the primary vortex as compared to case (2). When the mainstream air is premixed with fuel, there is a further reduction in the reaction rates and thus structure of cavity flame gets altered significantly for case (5). Pilot flame established for cases (2) and (3) are well shielded from main flow and hence the flame structure and reaction rates do not change appreciably. Hence, it is expected that cases (2) and (3) can perform well over a wide range of operating conditions. [ABSTRACT FROM AUTHOR]

In diffusion combustion systems, fuel and oxidizer (usually air) are admitted into the combustion chamber separately in the form of turbulent jets. Most often, fuel enters the furnace from a round nozzle and air is admitted through an annulus surrounding the central fuel nozzle. Momentum of the fuel and air jets is utilized for directing the flame and controlling the mixture formation which is typically the rate-limiting step of the combustion process. Hence the behavior of turbulent coaxial jets must be well understood prior to any detailed analysis of these systems. In this study, a set of relations is proposed to predict the behavior of turbulent coaxial gaseous jets using curve-fits to the computational fluid dynamics solutions and the fluid flow governing equations as well as the ideal gas equation of state. A computer program is developed to implement the presented model. Results are compared with existing data and reasonable agreement is observed. According to the results, the presented model makes sufficiently accurate estimates of the flow and concentration fields in a very short time. [ABSTRACT FROM AUTHOR]

Increased environmental awareness and depletion of resources are driving the industries to develop viable alternative fuels like vegetable oils, compresed natural gas, liquid petroleum gas, producer gas, and biogas in order to provide suitable substitute to diesel for compression ignition engine. In this investigation, a single cylinder, vertical, air-cooled diesel engine was modified to use liquid petroleum gas in dual fuel mode. The liquefied petroleum gas, was mixed with air and supplied through intake manifold. The liquid fuel neem oil or diesel was injected into the combustion chamber. The performance, emission, and combustion characteristics were studied and compared for neat fuel and dual fuel mode. The experimental results on dual fuel engine show a reduction in oxides of nitrogen up to 70% of the rated power and smoke in the entire power range. However the brake thermal efficiency was found decreased in low power range due to lower calorific value of liquid petroleum gas, and increase in higher power range due to the complete burning of liquid petroleum gas. Hydrocarbon and carbon monoxide emissions were increased significantly at lower power range and marginal variation in higher power range. [ABSTRACT FROM AUTHOR]

The effect of the three injection rate modes on fuel spray-wall impingement and combustion process in a direct injection diesel engine is investigated in present work. A three-dimensional computational fluid dynamics model for flow field, spray, spray-wall interactions, combustion, and emission formation processes have been used to carry out the computations. The optimized omega combustion chamber geometry was used in the diesel engine model instead of baseline cylindrical geometry and the results were verified for this improved combustion chamber geometry. Results for different injection modes indicate that using the ramp injection rate curve, the spray-wall impinging is increased due to higher injection rate at the end of injection duration. Also the increased in-cylinder temperature, piston surface temperature and higher turbulence intensity leads to enhanced wall-film evaporation. Soot mass fraction also decreases due to improved air-fuel mixing and evaporation of wall-film by reduction of the fuel rich zones especially in the impingement regions. Results for different injection modes indicate that using the ramp injection rate shape slightly retards the combustion process and improves combustion characteristics while maintaining lower NOx and considerably lower soot emissions compared to the boot and rectangle injection modes. Also, in this injection mode, because of the high pressure injection, higher spray droplet velocities (higher Weber number) and increased wall spray height than the other modes, it could be said that the dominant impingement regime may be the splashing regime. The results of model for baseline diesel engine are compared with the corresponding experimental data and show good levels of agreement. [ABSTRACT FROM AUTHOR]