An engine cyclic variation model has been built by using the residual gas temperature for the n th cycle as the input of the model, through constant pressure intake process, adiabatic compression process, constan...An engine cyclic variation model has been built by using the residual gas temperature for the n th cycle as the input of the model, through constant pressure intake process, adiabatic compression process, constant volume combustion process, adiabatic expansion process, adiabatic blow down process and constant pressure exhaust process to approximate the thermodynamic processes in the cylinder, finally the residual gas temperature for the ( n+1) th cycle can be estimated. Because of the adding of engine operating parameters such as engine speed, spark advance, equivalence ratio, intake air pressure, intake air temperature to the model, effects of these parameters on cyclic variation can be estimated quantitatively. Since residual gas temperature fluctuation between cycles reflects the circumstances of engine cyclic variation, parameters to which residual gas temperature is sensitive are most likely used as the means to control cyclic variation. Model simulation shows that for the nearly stiochiometric mixture, cyclic variation is not obvious or even quite stable, but for the lean mixture, under the circumstances of partial load and larger spark advances, engine cyclic variations occur chaotically or with bifurcation.展开更多
Aviation heavy-fuel spark ignition(SI)piston engines have been paid more and more attention in the area of small aviation.Aviation heavy-fuel refers to aviation kerosene or light diesel fuel,which is safer to use and ...Aviation heavy-fuel spark ignition(SI)piston engines have been paid more and more attention in the area of small aviation.Aviation heavy-fuel refers to aviation kerosene or light diesel fuel,which is safer to use and store compared to gasoline fuel.And diesel fuel is more suitable for small aviation application on land.In this study,numerical simulation was performed to evaluate the possibility of switching from gasoline direct injection spark ignition(DISI)to diesel DISI combustion.Diesel was injected into the cylinder by original DI system and ignited by spark.In the simulation,computational models were calibrated by test data from a DI engine.Based on the calibrated models,furthermore,the behavior of diesel DISI combustion was investigated.The results indicate that diesel DISI combustion is slower compared to gasoline,and the knock tendency of diesel in SI combustion is higher.For a diesel/air mixture with an equivalence ratio of 0.6 to 1.4,higher combustion pressure and faster burning rate occur when the equivalence ratios are 1.2 and 1.0,but the latter has a higher possibility of knock.In summary,the SI combustion of diesel fuel with a rich mixture can achieve better combustion performance in the engine.展开更多
To ensure the control of the precision of air-fuel ratio(AFR)of port fuel injection(PFI)spark ignition(SI)engines,a chaos radial basis function(RBF)neural network is used to predict the air intake flow of the engine.T...To ensure the control of the precision of air-fuel ratio(AFR)of port fuel injection(PFI)spark ignition(SI)engines,a chaos radial basis function(RBF)neural network is used to predict the air intake flow of the engine.The data of air intake flow is proved to be multidimensionally nonlinear and chaotic.The RBF neural network is used to train the reconstructed phase space of the data.The chaos algorithm is employed to optimize the weights of output layer connection and the radial basis center of Gaussian function in hidden layer.The simulation results obtained from Matlab/Simulink illustrate that the model has higher accuracy compared to the conventional RBF model.The mean absolute error and the mean relative error of the chaos RBF model can reach 0.0017 and 0.48,respectively.展开更多
The performance of microwave-assisted spark ignition(MAI)under exhaust gas recirculation conditions was explored with CO_(2)-diluted CH-air premixed spherical flames in a constant volume combustion chamber.The flame k...The performance of microwave-assisted spark ignition(MAI)under exhaust gas recirculation conditions was explored with CO_(2)-diluted CH-air premixed spherical flames in a constant volume combustion chamber.The flame kernel radius at 5 ms after spark started was selected to evaluate the property of MAI for CO_(2)dilution ratio of 0-20%and equivalence ratio of 0.6-1.4 with 1 kHz microwave pulse repetition frequency under 0.2 MPa ambient pressure.The results showed that the addition of microwave induced some wrinkles on the flame surface and strongly deformed the flame.MAI expanded the limit of CO_(2)dilution ratio to 16%with an equivalence ratio of 0.75,in which case the spark only(SI)failed to ignite the mixture.With the CO_(2)dilution ratio increasing,the wrinkles induced by microwave pulses decreased apparently,and the enhancement value of MAI peaked at 4%CO_(2)dilution ratio.The effect of microwave was considered in two aspects,namely,reaction kinetics and thermal effect,which shows a“trade-off”as CO_(2)dilution ratio rose.With 8%volume of CO_(2)added,the flammable interval(equivalence ratio 0.6-1.2)of mixture in SI mode shrunk,and MAI can maintain a flammable interval consistency with the case that no CO_(2)was added.展开更多
An experimental investigation was conducted on combustion characteristics of a single cylinder spark ignition engine fueled with coal-mine methane （CMM）.The CMM was simulated by the compressed nature gas （CNG）/nit...An experimental investigation was conducted on combustion characteristics of a single cylinder spark ignition engine fueled with coal-mine methane （CMM）.The CMM was simulated by the compressed nature gas （CNG）/nitrogen blend fuels.The cylinder pressure was measured.The maximum heat release ratio,the flame development duration and the main combustion duration were analyzed with the nitrogen volume fraction in the blends changing from 0% to 35%.The results indicate that the maximum cylinder pressure,the maximum rate of pressure,the flame development duration and the main combustion duration increase and the maximum rate of heat release decreases with increasing nitrogen fraction.When the level of nitrogen volume fraction in coalmine methane is lower than 20%,the combustion process of engine is stable.But with the level of nitrogen volume fraction over 30%,the cycle to cycle combustion variation is large,especially under low load condition.展开更多
<span style="font-family:Verdana;">The objective of this study was to investigate performance characteristics of a spark ignition engine, particularly, the correlation between performance, exhaust gas ...<span style="font-family:Verdana;">The objective of this study was to investigate performance characteristics of a spark ignition engine, particularly, the correlation between performance, exhaust gas temperature and speed, using Kiva4. Test data to validate kiva4 si</span><span style="font-family:Verdana;">mulation</span><span style="font-family:Verdana;"> results were conducted on a 3-cylinder, four-stroke Volkswagen (</span><span style="font-family:Verdana;">VW) Polo 6 TSI 1.2 gasoline engine. Three different tests were, therefore, carried out. In one set, variations in exhaust gas temperature were studied by varying the engine load, while keeping the engine speed constant. In another test, exhaust gas temperature variations were studied by keeping the engine at idling whilst varying the speeds. A third test involved studying variations in exhaust gas temperature under a constant load with variable engine speeds. To study </span><span style="font-family:Verdana;">variations in exhaust gas temperatures under test conditions, a basic grid/</span><span style="font-family:Verdana;">mesh generator, K3PREP, was employed to write an itape17 file comprising of a 45</span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">°</span><span> <span style="font-family:Verdana;">asymmetrical mesh. This was based on the symmetry of the combustion ch</span><span style="font-family:Verdana;">amber of </span><span style="font-family:Verdana;">the engine used in carrying out experimental tests. Simulati</span><span style="font-family:Verdana;">ons were therefore p</span><span style="font-family:Verdana;">erformed based on the input parameters established in</span><span style="font-family:Verdana;"> the conducted tests. Simulations with the kiva4 code showed a significant predictability of the performance characteristics of the engine. This was evident in the appreciable agreement obtained in the simulation results when compared </span><span style="font-family:Verdana;">with the test data, under the considered test conditions. A percentage error, be</span><span style="font-family:Verdana;">tween experimental results and results from simulations with the kiva4 code of only between 2% to 3% was observed.</span></span></span></span></span>展开更多
In the present paper, the effect of the combustion chamber design parameters on the improvement of combustion efficiency (the heat generated inside the combustion chamber) and the enhancement in the pollution rates (h...In the present paper, the effect of the combustion chamber design parameters on the improvement of combustion efficiency (the heat generated inside the combustion chamber) and the enhancement in the pollution rates (heat emissions) from a four-stroke, spark-ignition engine has been studied experimentally and theoretically. Two different programs, Gaseq and Ansys, were used to simulate the effect of the combustion chamber shape, turbulent kinetic energy, intake temperature, intake pressure, parity ratio, compression ratio, and engine speed on reducing specific fuel consumption in the engine, reducing carbon dioxide emissions, and increasing overall engine efficiency. The results showed increasing the intake temperature increased the amount of heat produced in the combustion chamber. This leads to increases in the overall efficiency of the engine, but leads to increasing the carbon dioxide and nitrogen oxide emissions. Increasing the intake pressure has a positive effect on the combustion temperature and pressure, but it has a negative effect on carbon dioxide and nitrogen oxides. Raising the pressure ratio improved the overall efficiency of the engine by increasing the combustion heat, but increasing specific fuel consumption and emissions. Also, increasing the engine speed above the permissible limit has an adverse effect on the spraying speed due to the piston speed being higher than the flame speed, which leads to a reduction in the engine brake torque. An increase in the compression ratio leads to higher fluid pressure and output capacity, but combustion methods occur. An increase in the kinetic energy of the turbulence leads to good combustion. A bowl in a piston has the highest rate of rotation and rotation compared to flat and hemispherical pistons. That is, the design of the cylinder head of this type leads to an improvement in the combustion efficiency and thus the efficiency of the engine.展开更多
This paper deals with the application of two different injection strategies in a natural gas direct injection spark ignition single-cylinder engine model. The analysis includes the air flow characterization during com...This paper deals with the application of two different injection strategies in a natural gas direct injection spark ignition single-cylinder engine model. The analysis includes the air flow characterization during compression stroke and also the charge stratification. Two different swirl ratios are applied and piston bowl effects are analyzed during the gas jet deflection towards the spark plug. Achieving wall-guided effect, consequently, the charge stratification in spark plug region is obtained. The goal is to study the mixture formation differences for a single and a bi pulsed CNG （compressed natural gas） injection profiles and check the evolution of the methane concentration at the spark plug at the start of combustion.展开更多
In this study,an artificial neural network(ANN)is developed to predict the performance of a spark-ignition engine using waste pomegranate ethanol blends.A series of experiments on a single-cylinder,four-stroke spark-i...In this study,an artificial neural network(ANN)is developed to predict the performance of a spark-ignition engine using waste pomegranate ethanol blends.A series of experiments on a single-cylinder,four-stroke spark-ignition engine yielded the data needed for neural network training and validation.70 percent of the experimental data was used to train the network using the feed-forward back propagation(FFBP)algorithm.The developed network model’s performance was evaluated by contrasting its output with experimental results.Input parameters included engine speed,ethanol blends,and output parameters included indicated and brake power,thermal,volumetric,and mechanical efficiencies.Training and testing data had regression coefficients that were almost identical to one.The research revealed that the ANN model can be a better option for predicting engine performance with a higher level of accuracy.展开更多
The leaks of pressurized hydrogen can be ignited if an ignition source is within a certain distance from the source of the leaks, and jet ftres or explosions may take place. In this paper, a high speed camera was used...The leaks of pressurized hydrogen can be ignited if an ignition source is within a certain distance from the source of the leaks, and jet ftres or explosions may take place. In this paper, a high speed camera was used to investigate the ignition kernel development, ignition probability and flame propagation along the axis of hydrogen jets, which leaked from a 3-ram-internal-diameter nozzle and were ignited by an electric spark. Experimental results indicate that for successful ignition events, the ignition delay time increases with an increase of the distance between the nozzle and the electrode. Ignitable zone of the hydrogen jets is underestimated if using the predicted hydrogen concentration along the jets centerline. The average rate of downstream flame decreases but that of the upstream flame increases with the electrode going far from the nozzle.展开更多
Consideration of the chemical reaction activity of the end gas in a spark ignition and operating conditions are combined to predict the onset of knock and associated performance in an engine fuelled with methane.A two...Consideration of the chemical reaction activity of the end gas in a spark ignition and operating conditions are combined to predict the onset of knock and associated performance in an engine fuelled with methane.A two-zone predictive combustion model was developed based on an estimate of the efiFective duration of the combustion period and the mass burning rate for any set of operating conditions.The unburned end gas preignition chemical reaction activity is described by a detailed chemical reaction kinetic scheme for methane and air.The variation with time of the value of a formulated dimensionless knock parameter(k)is calculated.It is shown that whenever knocking is encountered,the value of'k' builds up to a sufficiently high value that exceeds a critical value.Under normal operating conditions, the value of'k'remains throughout the whole combustion period at comparatively very low levels. It is shown that the model and the use of this knock criterion'k'produce results that are in good agreement with experiment.展开更多
The fuel dynamic transfer process,including fuel injection,fuel film deposition and evaporation in the intake port,was analyzed for spark ignition(SI) engines with port fuel injection(PFI).The influence of wall-wettin...The fuel dynamic transfer process,including fuel injection,fuel film deposition and evaporation in the intake port,was analyzed for spark ignition(SI) engines with port fuel injection(PFI).The influence of wall-wetting fuel film,especially its evaporation rate,upon the air-fuel ratio of in-cylinder mixtures was also discussed.According to the similarity principle,Fick's law,the ideal gas equation and the Gilliland correlation,an evaporate prediction model of wall-wetting fuel film was set up and an evaporate prediction based dynamic fuel film compensator was designed.Through engine cold start tests,the wall-wetting temperature,which is the key input of the fuel film evaporate prediction model,was also modeled and predicted.Combined with the experimental data of the evaporation characteristics of ethanol-gasoline blends and engine calibration tests,all the parameters of the wall-wetting fuel film evaporate prediction model used in the fuel film compensator were identified.Square-wave disturbance tests of fuel injection showed that with the help of the fuel film compensator the response of the in-cylinder air-fuel ratio was significantly improved and the real air-fuel ratio always closely matched the expected ratio.The fuel film compensator was then integrated into the final air-fuel ratio controller,and the engine tests showed that the air-fuel ratio control error was less than 2% in steady-state conditions,and less than 4% in transient conditions.The fuel film compensator also showed good adaptability to different ethanol-gasoline blends.展开更多
A two-tracer PLIF system was developed to measure fuel stratification in cylinder of a spark ignition engine which is achieved by producing a strong tumbling flow and introducing two fuels through two separate intake ...A two-tracer PLIF system was developed to measure fuel stratification in cylinder of a spark ignition engine which is achieved by producing a strong tumbling flow and introducing two fuels through two separate intake ports.Two tracers,3-pentanone and N,N-dimethylaniline(DMA),were doped in two fuels,hexane and iso-octane,respectively.A spectroscopic test result showed that when subject to irradiation by a XeCl Excimer laser(308 nm),3-pentanone and DMA emit fluorescence within different wavelength regions.Their fluorescence can be separated by two band-pass optical filters and recorded into a single intensified CCD camera through a specially designed image doubling system.The advantage of the measurement method is that both fuel distributions in cylinder can be visualized by one shot.Measurement results showed that two fuels were well stratified in the cylinder.展开更多
A numerical program is built to simulate the performance of a spark ignited two-stroke free-piston engine coupled with a linear generator. The computational model combines a series of dynamic and thermodynamic equatio...A numerical program is built to simulate the performance of a spark ignited two-stroke free-piston engine coupled with a linear generator. The computational model combines a series of dynamic and thermodynamic equations that are solved simultaneously to predict the performances of the engines. The dynamic analysis performed consists of an evaluation of the frictional force and load force introduced by the generator. The thermodynamic analysis used a single zone model to describe the engine＇ s working cycle which includes intake, scavenging, compression, combustion and expansion, and to evaluate the effect of heat transfer based on the first law of thermodynamics and the ideal gas state equation. Because there is no crankshaft, a time based Wiebe equation was used to express the fraction of fuel burned in the combustion. The calculated results were validated by using the experimental data from another research group. The results indicate that the free-piston generator has some advantages over conventional engines.展开更多
In this paper,the characteristics of detonation combustion ignited by AC-driven non-thermal plasma and spark plug in air/acetylene mixture have been compared in a doubletube experiment system.The two tubes had the sam...In this paper,the characteristics of detonation combustion ignited by AC-driven non-thermal plasma and spark plug in air/acetylene mixture have been compared in a doubletube experiment system.The two tubes had the same structure,and their closed ends were installed with a plasma generator and a spark plug,respectively.The propagation characteristics of the flame were measured by pressure sensors and ion probes.The experiment results show that,compared with a spark plug,the non-thermal plasma obviously broadened the range of equivalence ratio when the detonation wave could develop successfully,it also heightened the pressure value of detonation wave.Meanwhile,the detonation wave development time and the entire flame propagation time were reduced by half.All of these advantages benefited from the larger ignition volume when a non-thermal plasma was applied.展开更多
An evaluation method of engine cyclic variation is proposed based on fuzzy mathematics concept. The degree of engine cyclic variation is divided into 4 levels: stable, slight variation, moderate variation and serious ...An evaluation method of engine cyclic variation is proposed based on fuzzy mathematics concept. The degree of engine cyclic variation is divided into 4 levels: stable, slight variation, moderate variation and serious variation based on the statistic standard deviation of residual gas temperatures within the specified simulation cycles and the function of cyclic variation is also inducted for the cyclic variation control. Because the degree of engine cyclic variation can be estimated qualitatively, the effective control means can be applied to appease the undesired cyclic variation. Simulation result shows that for a very serious cyclic variation through the proper adjustment of the spark angle and the cyclic variation will disappear.展开更多
High-power precise delay trigger/ignition system is a programmable pulse generator developed for experiment controlling in explosively driven magnetic flux compression generators. Precise delay pulses are generated by...High-power precise delay trigger/ignition system is a programmable pulse generator developed for experiment controlling in explosively driven magnetic flux compression generators. Precise delay pulses are generated by the digital circuit, after being magnified and sharpened through multistage isolated amplifiers and rising edge sharpening device, high-voltage steep delay pulses with precision less than μs level are obtained. This system has been used in our compact magnetic flux compression generator experiments in place of the traditional primaeord delay device.展开更多
Volumetric efficiency and air charge estimation is one of the most demanding tasks in control of today's internal combustion engines.Specifically,using three-way catalytic converter involves strict control of the ...Volumetric efficiency and air charge estimation is one of the most demanding tasks in control of today's internal combustion engines.Specifically,using three-way catalytic converter involves strict control of the air/fuel ratio around the stoichiometric point and hence requires an accurate model for air charge estimation.However,high degrees of complexity and nonlinearity of the gas flow in the internal combustion engine make air charge estimation a challenging task.This is more obvious in engines with variable valve timing systems in which gas flow is more complex and depends on more functional variables.This results in models that are either quite empirical(such as look-up tables),not having interpretability and extrapolation capability,or physically based models which are not appropriate for onboard applications.Solving these problems,a novel semi-empirical model was proposed in this work which only needed engine speed,load,and valves timings for volumetric efficiency prediction.The accuracy and generalizability of the model is shown by its test on numerical and experimental data from three distinct engines.Normalized test errors are 0.0316,0.0152 and 0.24 for the three engines,respectively.Also the performance and complexity of the model were compared with neural networks as typical black box models.While the complexity of the model is less than half of the complexity of neural networks,and its computational cost is approximately 0.12 of that of neural networks and its prediction capability in the considered case studies is usually more.These results show the superiority of the proposed model over conventional black box models such as neural networks in terms of accuracy,generalizability and computational cost.展开更多
Concerns about environmental pollution and energy shortages have increased worldwide. One approach to reduce CO2 emissions from gasoline engines is to achieve stratified charge combustion with various injection ratios...Concerns about environmental pollution and energy shortages have increased worldwide. One approach to reduce CO2 emissions from gasoline engines is to achieve stratified charge combustion with various injection ratios using port fuel injection （PFI） and direct injection. The combustion and emission characteristics of a 4-valve direct injection spark ignition （DISI） engine equipped with a dual injection system were investigated while the injection ratio was varied. When the direct injection ratio increased, the lean limit A/F was extended. This suggests that the dual injection gasoline engine with both PFI and direct injection can meet severe vehicle emission and fuel economy requirements. The dual injection system had higher combustion pressure than that of either a conventional or direct injection systems. Therefore, the engine power of a dual injection DISI engine would be higher than that of a single injection DISI engine. However, NOx emissions increased compared with the emission levels in both PFI and DISI systems.展开更多
Turbochargers have been known in compression ignition engines for power generation.Recent trends in power generation through gas cycles have recorded successes via turbochargers application in spark ignition engines a...Turbochargers have been known in compression ignition engines for power generation.Recent trends in power generation through gas cycles have recorded successes via turbochargers application in spark ignition engines as well.When power cycles are turbocharged,there is a general expectation of a higher power and performance output from the cycle as compared to when they are naturally aspirated.This research was conducted to estimate the thermodynamic properties of a spark ignition engine power generating system when it is both naturally aspirated and when the same system is turbocharged to 2.5 times the amount of air in natural aspiration.Octane fuel was employed for petrol approximation during this study.The system process was broken down into stages of charging between natural aspiration and turbocharged;thus MATLAB program was applied to model the system for the case of natural aspiration and turbocharging with no increase in fuel supply.The results were used for both analyses and comparison which showed that the system generates slightly more power with turbocharging at 0%increase in fuel consumption.The natural aspiration achieved values are 2.8232 kJ/mol and 55.26%for output and efficiency respectively,while the turbocharged engine produced optimal values of 2.8833 kJ/mol and 56.51%for output and efficiency.The air fuel ratio by mole for the turbocharged engine was 145.18:1,which shows a greater fuel economy of 59%as compared to the 59.5:1 A/F(air/fuel)ratio of the naturally aspirated engine.展开更多
文摘An engine cyclic variation model has been built by using the residual gas temperature for the n th cycle as the input of the model, through constant pressure intake process, adiabatic compression process, constant volume combustion process, adiabatic expansion process, adiabatic blow down process and constant pressure exhaust process to approximate the thermodynamic processes in the cylinder, finally the residual gas temperature for the ( n+1) th cycle can be estimated. Because of the adding of engine operating parameters such as engine speed, spark advance, equivalence ratio, intake air pressure, intake air temperature to the model, effects of these parameters on cyclic variation can be estimated quantitatively. Since residual gas temperature fluctuation between cycles reflects the circumstances of engine cyclic variation, parameters to which residual gas temperature is sensitive are most likely used as the means to control cyclic variation. Model simulation shows that for the nearly stiochiometric mixture, cyclic variation is not obvious or even quite stable, but for the lean mixture, under the circumstances of partial load and larger spark advances, engine cyclic variations occur chaotically or with bifurcation.
基金Project(2018JJ2041)supported by the Science and Technology Project in Hunan Province,ChinaProject(szjj2019-008)supported by the Open Research Subject of Key Laboratory of Fluid and Power Machinery,Ministry of Education,China。
文摘Aviation heavy-fuel spark ignition(SI)piston engines have been paid more and more attention in the area of small aviation.Aviation heavy-fuel refers to aviation kerosene or light diesel fuel,which is safer to use and store compared to gasoline fuel.And diesel fuel is more suitable for small aviation application on land.In this study,numerical simulation was performed to evaluate the possibility of switching from gasoline direct injection spark ignition(DISI)to diesel DISI combustion.Diesel was injected into the cylinder by original DI system and ignited by spark.In the simulation,computational models were calibrated by test data from a DI engine.Based on the calibrated models,furthermore,the behavior of diesel DISI combustion was investigated.The results indicate that diesel DISI combustion is slower compared to gasoline,and the knock tendency of diesel in SI combustion is higher.For a diesel/air mixture with an equivalence ratio of 0.6 to 1.4,higher combustion pressure and faster burning rate occur when the equivalence ratios are 1.2 and 1.0,but the latter has a higher possibility of knock.In summary,the SI combustion of diesel fuel with a rich mixture can achieve better combustion performance in the engine.
基金Project(51176014)supported by the National Natural Science Foundation of ChinaProject(2016JJ2003)supported by Natural Scienceof Hunan Province,ChinaProject(KF1605)supported by Key Laboratory of Safety Design and Reliability Technology of Engineering Vehicle in Hunan Province,China。
文摘To ensure the control of the precision of air-fuel ratio(AFR)of port fuel injection(PFI)spark ignition(SI)engines,a chaos radial basis function(RBF)neural network is used to predict the air intake flow of the engine.The data of air intake flow is proved to be multidimensionally nonlinear and chaotic.The RBF neural network is used to train the reconstructed phase space of the data.The chaos algorithm is employed to optimize the weights of output layer connection and the radial basis center of Gaussian function in hidden layer.The simulation results obtained from Matlab/Simulink illustrate that the model has higher accuracy compared to the conventional RBF model.The mean absolute error and the mean relative error of the chaos RBF model can reach 0.0017 and 0.48,respectively.
基金Project(KF2028)supported by the State key Laboratory of Automotive Safety and Energy,ChinaProject(KF2028)supported by the State Key Laboratory of Automotive Safety and Energy,China。
文摘The performance of microwave-assisted spark ignition(MAI)under exhaust gas recirculation conditions was explored with CO_(2)-diluted CH-air premixed spherical flames in a constant volume combustion chamber.The flame kernel radius at 5 ms after spark started was selected to evaluate the property of MAI for CO_(2)dilution ratio of 0-20%and equivalence ratio of 0.6-1.4 with 1 kHz microwave pulse repetition frequency under 0.2 MPa ambient pressure.The results showed that the addition of microwave induced some wrinkles on the flame surface and strongly deformed the flame.MAI expanded the limit of CO_(2)dilution ratio to 16%with an equivalence ratio of 0.75,in which case the spark only(SI)failed to ignite the mixture.With the CO_(2)dilution ratio increasing,the wrinkles induced by microwave pulses decreased apparently,and the enhancement value of MAI peaked at 4%CO_(2)dilution ratio.The effect of microwave was considered in two aspects,namely,reaction kinetics and thermal effect,which shows a“trade-off”as CO_(2)dilution ratio rose.With 8%volume of CO_(2)added,the flammable interval(equivalence ratio 0.6-1.2)of mixture in SI mode shrunk,and MAI can maintain a flammable interval consistency with the case that no CO_(2)was added.
基金Sponsored by the National Natural Science Foundation of China (50976012)
文摘An experimental investigation was conducted on combustion characteristics of a single cylinder spark ignition engine fueled with coal-mine methane （CMM）.The CMM was simulated by the compressed nature gas （CNG）/nitrogen blend fuels.The cylinder pressure was measured.The maximum heat release ratio,the flame development duration and the main combustion duration were analyzed with the nitrogen volume fraction in the blends changing from 0% to 35%.The results indicate that the maximum cylinder pressure,the maximum rate of pressure,the flame development duration and the main combustion duration increase and the maximum rate of heat release decreases with increasing nitrogen fraction.When the level of nitrogen volume fraction in coalmine methane is lower than 20%,the combustion process of engine is stable.But with the level of nitrogen volume fraction over 30%,the cycle to cycle combustion variation is large,especially under low load condition.
文摘<span style="font-family:Verdana;">The objective of this study was to investigate performance characteristics of a spark ignition engine, particularly, the correlation between performance, exhaust gas temperature and speed, using Kiva4. Test data to validate kiva4 si</span><span style="font-family:Verdana;">mulation</span><span style="font-family:Verdana;"> results were conducted on a 3-cylinder, four-stroke Volkswagen (</span><span style="font-family:Verdana;">VW) Polo 6 TSI 1.2 gasoline engine. Three different tests were, therefore, carried out. In one set, variations in exhaust gas temperature were studied by varying the engine load, while keeping the engine speed constant. In another test, exhaust gas temperature variations were studied by keeping the engine at idling whilst varying the speeds. A third test involved studying variations in exhaust gas temperature under a constant load with variable engine speeds. To study </span><span style="font-family:Verdana;">variations in exhaust gas temperatures under test conditions, a basic grid/</span><span style="font-family:Verdana;">mesh generator, K3PREP, was employed to write an itape17 file comprising of a 45</span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">°</span><span> <span style="font-family:Verdana;">asymmetrical mesh. This was based on the symmetry of the combustion ch</span><span style="font-family:Verdana;">amber of </span><span style="font-family:Verdana;">the engine used in carrying out experimental tests. Simulati</span><span style="font-family:Verdana;">ons were therefore p</span><span style="font-family:Verdana;">erformed based on the input parameters established in</span><span style="font-family:Verdana;"> the conducted tests. Simulations with the kiva4 code showed a significant predictability of the performance characteristics of the engine. This was evident in the appreciable agreement obtained in the simulation results when compared </span><span style="font-family:Verdana;">with the test data, under the considered test conditions. A percentage error, be</span><span style="font-family:Verdana;">tween experimental results and results from simulations with the kiva4 code of only between 2% to 3% was observed.</span></span></span></span></span>
文摘In the present paper, the effect of the combustion chamber design parameters on the improvement of combustion efficiency (the heat generated inside the combustion chamber) and the enhancement in the pollution rates (heat emissions) from a four-stroke, spark-ignition engine has been studied experimentally and theoretically. Two different programs, Gaseq and Ansys, were used to simulate the effect of the combustion chamber shape, turbulent kinetic energy, intake temperature, intake pressure, parity ratio, compression ratio, and engine speed on reducing specific fuel consumption in the engine, reducing carbon dioxide emissions, and increasing overall engine efficiency. The results showed increasing the intake temperature increased the amount of heat produced in the combustion chamber. This leads to increases in the overall efficiency of the engine, but leads to increasing the carbon dioxide and nitrogen oxide emissions. Increasing the intake pressure has a positive effect on the combustion temperature and pressure, but it has a negative effect on carbon dioxide and nitrogen oxides. Raising the pressure ratio improved the overall efficiency of the engine by increasing the combustion heat, but increasing specific fuel consumption and emissions. Also, increasing the engine speed above the permissible limit has an adverse effect on the spraying speed due to the piston speed being higher than the flame speed, which leads to a reduction in the engine brake torque. An increase in the compression ratio leads to higher fluid pressure and output capacity, but combustion methods occur. An increase in the kinetic energy of the turbulence leads to good combustion. A bowl in a piston has the highest rate of rotation and rotation compared to flat and hemispherical pistons. That is, the design of the cylinder head of this type leads to an improvement in the combustion efficiency and thus the efficiency of the engine.
文摘This paper deals with the application of two different injection strategies in a natural gas direct injection spark ignition single-cylinder engine model. The analysis includes the air flow characterization during compression stroke and also the charge stratification. Two different swirl ratios are applied and piston bowl effects are analyzed during the gas jet deflection towards the spark plug. Achieving wall-guided effect, consequently, the charge stratification in spark plug region is obtained. The goal is to study the mixture formation differences for a single and a bi pulsed CNG （compressed natural gas） injection profiles and check the evolution of the methane concentration at the spark plug at the start of combustion.
文摘In this study,an artificial neural network(ANN)is developed to predict the performance of a spark-ignition engine using waste pomegranate ethanol blends.A series of experiments on a single-cylinder,four-stroke spark-ignition engine yielded the data needed for neural network training and validation.70 percent of the experimental data was used to train the network using the feed-forward back propagation(FFBP)algorithm.The developed network model’s performance was evaluated by contrasting its output with experimental results.Input parameters included engine speed,ethanol blends,and output parameters included indicated and brake power,thermal,volumetric,and mechanical efficiencies.Training and testing data had regression coefficients that were almost identical to one.The research revealed that the ANN model can be a better option for predicting engine performance with a higher level of accuracy.
基金Supported by the Fundamental Research Funds for the Central UniversitiesNational Natural Science Foundation of China(No.50806071)and(No.51276177)
文摘The leaks of pressurized hydrogen can be ignited if an ignition source is within a certain distance from the source of the leaks, and jet ftres or explosions may take place. In this paper, a high speed camera was used to investigate the ignition kernel development, ignition probability and flame propagation along the axis of hydrogen jets, which leaked from a 3-ram-internal-diameter nozzle and were ignited by an electric spark. Experimental results indicate that for successful ignition events, the ignition delay time increases with an increase of the distance between the nozzle and the electrode. Ignitable zone of the hydrogen jets is underestimated if using the predicted hydrogen concentration along the jets centerline. The average rate of downstream flame decreases but that of the upstream flame increases with the electrode going far from the nozzle.
基金support of the Natural Sciences and Engineering Research Council of Canada(NSERC)
文摘Consideration of the chemical reaction activity of the end gas in a spark ignition and operating conditions are combined to predict the onset of knock and associated performance in an engine fuelled with methane.A two-zone predictive combustion model was developed based on an estimate of the efiFective duration of the combustion period and the mass burning rate for any set of operating conditions.The unburned end gas preignition chemical reaction activity is described by a detailed chemical reaction kinetic scheme for methane and air.The variation with time of the value of a formulated dimensionless knock parameter(k)is calculated.It is shown that whenever knocking is encountered,the value of'k' builds up to a sufficiently high value that exceeds a critical value.Under normal operating conditions, the value of'k'remains throughout the whole combustion period at comparatively very low levels. It is shown that the model and the use of this knock criterion'k'produce results that are in good agreement with experiment.
基金Project (Nos. 51106136 and 50776078) supported by the National Natural Science Foundation of China
文摘The fuel dynamic transfer process,including fuel injection,fuel film deposition and evaporation in the intake port,was analyzed for spark ignition(SI) engines with port fuel injection(PFI).The influence of wall-wetting fuel film,especially its evaporation rate,upon the air-fuel ratio of in-cylinder mixtures was also discussed.According to the similarity principle,Fick's law,the ideal gas equation and the Gilliland correlation,an evaporate prediction model of wall-wetting fuel film was set up and an evaporate prediction based dynamic fuel film compensator was designed.Through engine cold start tests,the wall-wetting temperature,which is the key input of the fuel film evaporate prediction model,was also modeled and predicted.Combined with the experimental data of the evaporation characteristics of ethanol-gasoline blends and engine calibration tests,all the parameters of the wall-wetting fuel film evaporate prediction model used in the fuel film compensator were identified.Square-wave disturbance tests of fuel injection showed that with the help of the fuel film compensator the response of the in-cylinder air-fuel ratio was significantly improved and the real air-fuel ratio always closely matched the expected ratio.The fuel film compensator was then integrated into the final air-fuel ratio controller,and the engine tests showed that the air-fuel ratio control error was less than 2% in steady-state conditions,and less than 4% in transient conditions.The fuel film compensator also showed good adaptability to different ethanol-gasoline blends.
基金Engineering and Physical Sciences Research Council(EPSRC) in the UK(Grant No.GR/M97909/01(P))
文摘A two-tracer PLIF system was developed to measure fuel stratification in cylinder of a spark ignition engine which is achieved by producing a strong tumbling flow and introducing two fuels through two separate intake ports.Two tracers,3-pentanone and N,N-dimethylaniline(DMA),were doped in two fuels,hexane and iso-octane,respectively.A spectroscopic test result showed that when subject to irradiation by a XeCl Excimer laser(308 nm),3-pentanone and DMA emit fluorescence within different wavelength regions.Their fluorescence can be separated by two band-pass optical filters and recorded into a single intensified CCD camera through a specially designed image doubling system.The advantage of the measurement method is that both fuel distributions in cylinder can be visualized by one shot.Measurement results showed that two fuels were well stratified in the cylinder.
文摘A numerical program is built to simulate the performance of a spark ignited two-stroke free-piston engine coupled with a linear generator. The computational model combines a series of dynamic and thermodynamic equations that are solved simultaneously to predict the performances of the engines. The dynamic analysis performed consists of an evaluation of the frictional force and load force introduced by the generator. The thermodynamic analysis used a single zone model to describe the engine＇ s working cycle which includes intake, scavenging, compression, combustion and expansion, and to evaluate the effect of heat transfer based on the first law of thermodynamics and the ideal gas state equation. Because there is no crankshaft, a time based Wiebe equation was used to express the fraction of fuel burned in the combustion. The calculated results were validated by using the experimental data from another research group. The results indicate that the free-piston generator has some advantages over conventional engines.
基金supported by National Natural Science Foundation of China(No.51176001)
文摘In this paper,the characteristics of detonation combustion ignited by AC-driven non-thermal plasma and spark plug in air/acetylene mixture have been compared in a doubletube experiment system.The two tubes had the same structure,and their closed ends were installed with a plasma generator and a spark plug,respectively.The propagation characteristics of the flame were measured by pressure sensors and ion probes.The experiment results show that,compared with a spark plug,the non-thermal plasma obviously broadened the range of equivalence ratio when the detonation wave could develop successfully,it also heightened the pressure value of detonation wave.Meanwhile,the detonation wave development time and the entire flame propagation time were reduced by half.All of these advantages benefited from the larger ignition volume when a non-thermal plasma was applied.
文摘An evaluation method of engine cyclic variation is proposed based on fuzzy mathematics concept. The degree of engine cyclic variation is divided into 4 levels: stable, slight variation, moderate variation and serious variation based on the statistic standard deviation of residual gas temperatures within the specified simulation cycles and the function of cyclic variation is also inducted for the cyclic variation control. Because the degree of engine cyclic variation can be estimated qualitatively, the effective control means can be applied to appease the undesired cyclic variation. Simulation result shows that for a very serious cyclic variation through the proper adjustment of the spark angle and the cyclic variation will disappear.
基金the Ministerial Level Advanced Research Foundation(40407010305)
文摘High-power precise delay trigger/ignition system is a programmable pulse generator developed for experiment controlling in explosively driven magnetic flux compression generators. Precise delay pulses are generated by the digital circuit, after being magnified and sharpened through multistage isolated amplifiers and rising edge sharpening device, high-voltage steep delay pulses with precision less than μs level are obtained. This system has been used in our compact magnetic flux compression generator experiments in place of the traditional primaeord delay device.
文摘Volumetric efficiency and air charge estimation is one of the most demanding tasks in control of today's internal combustion engines.Specifically,using three-way catalytic converter involves strict control of the air/fuel ratio around the stoichiometric point and hence requires an accurate model for air charge estimation.However,high degrees of complexity and nonlinearity of the gas flow in the internal combustion engine make air charge estimation a challenging task.This is more obvious in engines with variable valve timing systems in which gas flow is more complex and depends on more functional variables.This results in models that are either quite empirical(such as look-up tables),not having interpretability and extrapolation capability,or physically based models which are not appropriate for onboard applications.Solving these problems,a novel semi-empirical model was proposed in this work which only needed engine speed,load,and valves timings for volumetric efficiency prediction.The accuracy and generalizability of the model is shown by its test on numerical and experimental data from three distinct engines.Normalized test errors are 0.0316,0.0152 and 0.24 for the three engines,respectively.Also the performance and complexity of the model were compared with neural networks as typical black box models.While the complexity of the model is less than half of the complexity of neural networks,and its computational cost is approximately 0.12 of that of neural networks and its prediction capability in the considered case studies is usually more.These results show the superiority of the proposed model over conventional black box models such as neural networks in terms of accuracy,generalizability and computational cost.
基金supported by the Industrial Strategic Technology Development Program, 10042559‘Development of fuel injector for 200 bar gasoline direct injection system’ funded by the Ministry of Trade, Industry & Energy (MI, Korea)
文摘Concerns about environmental pollution and energy shortages have increased worldwide. One approach to reduce CO2 emissions from gasoline engines is to achieve stratified charge combustion with various injection ratios using port fuel injection （PFI） and direct injection. The combustion and emission characteristics of a 4-valve direct injection spark ignition （DISI） engine equipped with a dual injection system were investigated while the injection ratio was varied. When the direct injection ratio increased, the lean limit A/F was extended. This suggests that the dual injection gasoline engine with both PFI and direct injection can meet severe vehicle emission and fuel economy requirements. The dual injection system had higher combustion pressure than that of either a conventional or direct injection systems. Therefore, the engine power of a dual injection DISI engine would be higher than that of a single injection DISI engine. However, NOx emissions increased compared with the emission levels in both PFI and DISI systems.
文摘Turbochargers have been known in compression ignition engines for power generation.Recent trends in power generation through gas cycles have recorded successes via turbochargers application in spark ignition engines as well.When power cycles are turbocharged,there is a general expectation of a higher power and performance output from the cycle as compared to when they are naturally aspirated.This research was conducted to estimate the thermodynamic properties of a spark ignition engine power generating system when it is both naturally aspirated and when the same system is turbocharged to 2.5 times the amount of air in natural aspiration.Octane fuel was employed for petrol approximation during this study.The system process was broken down into stages of charging between natural aspiration and turbocharged;thus MATLAB program was applied to model the system for the case of natural aspiration and turbocharging with no increase in fuel supply.The results were used for both analyses and comparison which showed that the system generates slightly more power with turbocharging at 0%increase in fuel consumption.The natural aspiration achieved values are 2.8232 kJ/mol and 55.26%for output and efficiency respectively,while the turbocharged engine produced optimal values of 2.8833 kJ/mol and 56.51%for output and efficiency.The air fuel ratio by mole for the turbocharged engine was 145.18:1,which shows a greater fuel economy of 59%as compared to the 59.5:1 A/F(air/fuel)ratio of the naturally aspirated engine.
