Study Of Intake And Exhaust Valve Diameter Ratio's Influence On Gas Exchange Process Of Diesel Engine

The movement of gas in an engine's cylinder depends on the gas exchange process which also affects the combustion process and the economic and dynamic performance of the engine.Therefore,it is of great significance to study the gas exchange process of the engine.This paper uses a simulation software GT-POWER to study the influence of intake and exhaust valves' diameter ratio on gas exchange process in a four-valve diesel engine under different conditions.Firstly,this paper introduces a single-cylinder engine's experiment system based on which a one-dimensional simulation model is established.And then selects the right combustion model,heat transfer model,friction model and so on.After setting up some necessary parameters,calibrates the established model with the experimental data.By comparing cylinder pressure curve,heat release rate curve and power which are from the experiment and the corresponding simulation result,the accuracy of the simulation model is verified.Secondly,with regard to different intake and exhaust pressure i.e.different intensity,different exhaust condition and different engine speed,the paper chooses various diameters of intake and exhaust valves and then optimizes the valve timing.This paper mainly focuses on the optimizing of intake valve close timing and exhaust valve open timing which affect the engine's performance most.Finally obtains the optimized valve timing.Based on previous text,by analyzing the change and their laws of brake power,volumetric efficiency and pumping loss under the different conditions that mentioned before,this paper studies the influence of intake and exhaust valves' diameter ratio on gas exchange process with the optimized valve timing and the various alternative intake and exhaust valves' diameters.On the basis of the simulation result,this paper finds that the valves' diameter ratio under different intensity,exhaust condition and engine speed have an influence on gas exchange process,but the degree is various.Considering the simulation result of brake power,volumetric efficiency and pumping loss,the optimized valves' diameter ratio is higher than before.This paper provides a very important basis for designing the intake and exhaust valves of the engine.