The Study About Improving Efficiency Of Gasoline Engine By Unsteady Flow In The Intake And Exhaust System

This paper states the gas exchange process of four-stroke gasoline engines, and analyzes a variety of elements that affect the charging efficiency. It brings forward a series of measures to improve the quality of gas exchange and charging efficiency. It explains the complicated relationship of effect, moreover coordination, matching, restraint of elements from different aspects. However, it is important to focus on major indexes to increase intake gas, and pay attention to other secondary indexes to optimize functions of the engine.It introduces some advanced technologies which increase the charging efficiency, such as the variable length of the intake duct, the variable valve stroke, the variable valve timing and so on. Based on the experiments, it goes into particularly that unsteady flow in the intake system affects the charging efficiency and how to design the intake and exhaust manifold that may utilize the unsteady flow to improve gas exchange quality s dynamic performance > economy performance^ exhaust index and reach the requirement of users and laws on exhausting.In designing the JT468Q's intake and exhaust system, the effect which unsteady flow has on charging efficiency is thoroughly considered. Test bed results all kinds of engine indexes have achieved the designing targets. It proves that the theory is correct.There are variable intake manifold designed byoverseas auto company which are valuable for designers at home.