| Mostly,the developments of vehicle engine are based on steady state when engine speed and load are fixed.However,the operation condition of it is variable(the engine speed and load are changing all the time)due to its application in carrier machinery.Thus,the actual operation condition and the development condition do not match so as to make the actual performance much lower than the steady-state test level on the development platform.Therefore,the detection,analysis and evaluation of engine performance parameters,the identification of key influencing factors(control parameters)and the proposal of performance improvement schemes are significant to realize energy saving and emission reduction in the actual operation conditions.The dynamic performance of engine and the inner link between gasoline engine performance and its control,operation parameters under vehicle operating conditions were studied.The performance parameters of gasoline engine are gradually analyzed and decomposed into a clear mathematical relationship between control and operation parameters.Then,the obtained laws are used to analyze the energy flow variation of engine and powertrain during the startup process of vehicle at cold and warm-up conditions as well as the standard WLTC operating conditions.Meanwhile,they are also used to determine boundary conditions and guide performance optimization direction of simulation based on standard mathematical model.The main research work and results of this paper are as follows:(1)The quantitative equations between gasoline engine performance and control parameters were established and improved,and the quantitative relationships of equivalent effective expansion ratio with CA50,combustion duration and combustion quality parameters were derived.The coupling equations of combustion duration,CA50 and other relevant operation parameters for engine design and control were derived.And a closed loop was built up to quantify the relationships between in-cylinder indicated thermal efficiency,average indicated pressure and main operation and control parameters of gasoline engine.A simplified calculation method of residual exhaust gas coefficient in cylinder was presented,which reduce the cost of testing equipment setting and data processing.(2)The quantitative relationships between engine performance,control and operation parameters were verified systematically and comprehensively in steady states and dynamic road test conditions.Compared with the measured results,it was shown that the quantized equations can predict the parameters more accurately in both steady and transient conditions.The proposed effective expansion ratio extends the relationship between thermal power conversion efficiency and combustion phase from "qualitative" to "quantitative",realizing the closed-loop prediction of thermal power conversion performance parameters.(3)Based on the WLTC condition,the vehicle energy flow evaluation analysis and quantitative research were carried out to explore the energy transfe r and loss efficiency,the systems and the components that loss energy and the energy consumption form in the energy transfer path.The influence mechanism of various operation and control parameters on the energy flow under transient conditions and the adjustment mechanism of various energy losses in the actual thermal cycle were found,which provides theoretical guidance and data support for improving the vehicle power matching and optimizing the transient performance.(4)Based on the experimental data,a vehicle energy flow model was constructed and validated,and a real-time updating method of the boundary conditions in the engine performance simulation model was proposed.The energy saving potential of various improvement schemes was compared and analyzed,and the quantitative relationship of the influence of various factors on fuel consumption was obtained.The results showed that when the sliding curve is simulated with the announcement value of sample vehicle B,it has the greatest influence on the fuel consumption,which can be reduced by164.07 g and the fuel consumption improvement rate is as high as 10.24%.On this basis,the influence mechanism of various improvement schemes on the energy consumption of the whole vehicle were expounded,and the guidance for improving energy consumption of the whole vehicle were put forward.Through the research of this paper,the quantization equation of gasoline engine performance under dynamic conditions was established and it was also verified in the energy flow testing of the vehicle.The research results not only extend the quantitative analysis theory of vehicle engine from steady-state to transient,improve the basic theory of internal combustion engine,but also provide a strong support fo r engine performance optimization and energy consumption improvement of vehicle under dynamic conditions. |
