| In the context of energy crisis and energy saving and emission reduction,the application of numerical simulation technology in the concept development stage of gasoline engine can effectively improve the efficiency of performance optimization of gasoline engine.But there are still some problems such as unclear boundary conditions,low simulation accuracy and lack of guidance for optimization direction when performance is not up to standard.The main performance indexes of gasoline engine are economic performance and dynamic performance.Their optimization process needs to summarize the common rules and internal relations of many control parameters of gasoline engines,and quantitatively analyze the influencing factors of performance parameters.This paper is based on the performance benchmarking data of three turbocharged direct injection gasoline engines.First,this paper studies the main influencing factors of the indicated average pressure of the dynamic performance index of the gasoline engine,and at the same time derives the control equation of the quantitative relationship between the indicated average pressure and the influencing factors.Then this paper studies and analyzes the indicated thermal efficiency of economic performance index of gasoline engine,and decomposes the indicated thermal efficiency into three parts: combustion efficiency,adiabatic efficiency and expansion efficiency.At the same time,the control equations between the above parameters and other control operating parameters are established respectively.Finally,bring the experimental data into the above equations and verify its reliability,establish the GT-Power simulation digital model,guide the input of the boundary conditions of the digital model according to the derived quantitative relationship,and find the cause of error based on the quantitative relationship when the performance does not meet the standard.The model is optimized and the results are verified.The research work is as follows: the indicated average pressure is mainly related to the parameters such as intake air density,indicated thermal efficiency and volumetric efficiency,and volumetric efficiency is a function of the cylinder volume ratio at the time of intake valve closing and the residual gas fraction,while the residual gas fraction is related to parameters such as valve timing,intake and exhaust pressure,etc.The indicated thermal efficiency can be decomposed into three parts: combustion efficiency,adiabatic efficiency,and expansion efficiency.The combustion efficiency is a linear function of excess air coefficient.The adiabatic efficiency is related to load,speed,cylinder pressure and other parameters.The main factors affecting the expansion efficiency are the instantaneous heat release rate,the effective expansion ratio,and the ignition advance angle.The instantaneous heat release rate can be calculated by parameters such as combustion quality parameters,combustion duration,and 50% combustion position points;The quantitative relationship can be successfully applied to the simulation development of gasoline engines,and it has a guiding role in the input of boundary conditions and optimization directions during modeling. |
