Analysis And Improvement Strategy On Efficacy Loss Of Diesel Engine Valve

Valve as an executing element of valve train mechanism of diesel engine, itplays an important part in ensuring power performance, economic performance,reliability and durability of diesel engine. At present, in order to improve thepower performance, economic performance and emission index of diesel engine,many diesel engine manufacturers adopt the technology of increasingdisplacement, increasing speed, using TC and TCI. With diesel engine beingfurther strengthened unceasingly, the problem of losing efficacy of valve is moreand more outstanding. It has become vicious failure in the field of vehicle dieselengine, which has caused highly concerns from diesel engine manufacture.This paper describes the significance and complexity of losing efficacy ofvalve in present vehicle diesel engine. And it points out that some of the reason iscaused by the defects of valve itself, some is correlation losing efficacy caused byinterrelated factors;some is caused by single factor, and some is resulted frommultiple factors.By statistically classifying of valve losing efficacy of diesel engine and byanalyzing the reasons of losing efficacy, this paper puts forward the major modesof valve losing efficacy are falling head of neck, falling piece of disk, burningerosion, bend upwards, worn of cone face, broken in stem, crumbling of stem endas well as falling off of welding sheet, etc. Through the analysis on typical case,the paper points out that main reason of losing efficacy is mechanical fatiguewhich causes falling piece from the disk, head off not from the second hot pointand stem broken. The key to solve efficacy loss of the valve should focus onimproving the mechanical performance of the valve at high temperature, especiallyimproving mechanical stress.This paper detailedly analyzes the reasons of valve losing efficacy in design,manufacture and operation of valve and offers some suggestion to improve valveperformance. In addition, it also simply discusses about the issue of intake valvewearing when TC,TCI and diesel engine are changed to use LPG and CNG. It isvery significant in theory and valuable in practical use to guide the design,manufacture and operation of diesel engine valve.