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
The pressure ratio required for a turbocharger centrifugal compressor increases with internal combustion engine power density. High pressure ratio causes a transonic flow field at the impeller inducer. Transonic flow ...The pressure ratio required for a turbocharger centrifugal compressor increases with internal combustion engine power density. High pressure ratio causes a transonic flow field at the impeller inducer. Transonic flow narrows the stable flow range and de-teriorates stage efficiency. In this work, an advanced high pressure ratio transonic compressor was designed. The experimental results show that the maximum pressure ratio of this turbocharger is about 4.2, the maximum efficiency is above 80% and the stable flow range at the designed rotating speed is up to 34%. A turbocharger with this transonic compressor has been applied to some vehicle research actually, and improved power density by 40%.展开更多
In this study,we report an analysis of cylinder head vibration signals at a steady engine speed using short-time Fourier transform(STFT).Three popular time-frequency analysis techniques,i.e.,STFT,analytic wavelet tran...In this study,we report an analysis of cylinder head vibration signals at a steady engine speed using short-time Fourier transform(STFT).Three popular time-frequency analysis techniques,i.e.,STFT,analytic wavelet transform(AWT) and S transform(ST),have been examined.AWT and ST are often applied in engine signal analyses.In particular,an AWT expression in terms of the quality factor Q and an analytical relationship between ST and AWT have been derived.The time-frequency resolution of a Gaussian function windowed STFT was studied via numerical simulation.Based on the simulation,the empirical limits for the lowest distinguishable frequency as well as the time and frequency resolutions were determined.These can provide insights for window width selection,spectrogram interpretation and artifact identification.Gaussian function windowed STFTs were applied to some cylinder head vibration signals.The spectrograms of the same signals from ST and AWT were also determined for comparison.The results indicate that the uniform resolution feature of STFT is not necessarily a disadvantage for time-frequency analysis of vibration signals when the engine is in stationary state because it can more accurately localize the frequency components excited by transient excitations without much loss of time resolution.展开更多
基于进气道燃料喷射(port fuel injection,PFI)氢内燃机试验系统,研究了带热废气再循环(exhaust gas recirculation,EGR)系统氢内燃机的燃烧和排放特性。试验结果表明:采用热EGR能增大氢内燃机的滞燃期和燃烧持续期,显著降低缸内最高压...基于进气道燃料喷射(port fuel injection,PFI)氢内燃机试验系统,研究了带热废气再循环(exhaust gas recirculation,EGR)系统氢内燃机的燃烧和排放特性。试验结果表明:采用热EGR能增大氢内燃机的滞燃期和燃烧持续期,显著降低缸内最高压力和温度;EGR率增大时平均有效指示压力和循环变动的变化并不显著,对整机的功率输出和平顺工作几乎没有影响,中高负荷时需要采用很大的EGR率才能大幅度降低NOx排放,在高负荷时控制排放所需的EGR率不大,高负荷时过大的EGR率可能造成燃料经济性和动力性的大幅度下降。展开更多
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.
基金supported by the National Natural Science Foundation of China (Grant No. 50806040)Specialized Research Fund for the Doc-toral Program of Higher Education) (Grant No. 200800031075)supported by the fund from National Key Laboratory of Diesel Engine Turbocharging Technology
文摘The pressure ratio required for a turbocharger centrifugal compressor increases with internal combustion engine power density. High pressure ratio causes a transonic flow field at the impeller inducer. Transonic flow narrows the stable flow range and de-teriorates stage efficiency. In this work, an advanced high pressure ratio transonic compressor was designed. The experimental results show that the maximum pressure ratio of this turbocharger is about 4.2, the maximum efficiency is above 80% and the stable flow range at the designed rotating speed is up to 34%. A turbocharger with this transonic compressor has been applied to some vehicle research actually, and improved power density by 40%.
基金Project (No. 2011BAE22B05) supported by the National Key Technologies Supporting Program of China during the 12th Five-Year Plan Period
文摘In this study,we report an analysis of cylinder head vibration signals at a steady engine speed using short-time Fourier transform(STFT).Three popular time-frequency analysis techniques,i.e.,STFT,analytic wavelet transform(AWT) and S transform(ST),have been examined.AWT and ST are often applied in engine signal analyses.In particular,an AWT expression in terms of the quality factor Q and an analytical relationship between ST and AWT have been derived.The time-frequency resolution of a Gaussian function windowed STFT was studied via numerical simulation.Based on the simulation,the empirical limits for the lowest distinguishable frequency as well as the time and frequency resolutions were determined.These can provide insights for window width selection,spectrogram interpretation and artifact identification.Gaussian function windowed STFTs were applied to some cylinder head vibration signals.The spectrograms of the same signals from ST and AWT were also determined for comparison.The results indicate that the uniform resolution feature of STFT is not necessarily a disadvantage for time-frequency analysis of vibration signals when the engine is in stationary state because it can more accurately localize the frequency components excited by transient excitations without much loss of time resolution.
文摘基于进气道燃料喷射(port fuel injection,PFI)氢内燃机试验系统,研究了带热废气再循环(exhaust gas recirculation,EGR)系统氢内燃机的燃烧和排放特性。试验结果表明:采用热EGR能增大氢内燃机的滞燃期和燃烧持续期,显著降低缸内最高压力和温度;EGR率增大时平均有效指示压力和循环变动的变化并不显著,对整机的功率输出和平顺工作几乎没有影响,中高负荷时需要采用很大的EGR率才能大幅度降低NOx排放,在高负荷时控制排放所需的EGR率不大,高负荷时过大的EGR率可能造成燃料经济性和动力性的大幅度下降。
