Research On The Influence Law Of Performance Consistency Of Diesel Engine Used In Agricultural Machine

With the increasingly serious environmental problems,emission pollution has also increasingly attracted people's attention.On the one hand,engine manufacturers adopt a series of technological innovations to reduce engine emissions;on the other hand,the emission standards are also getting more stringent.For agricultural machinery which mainly use diesel engines as power source,the emission standards have also been continuously increased.The consultation draft of Emissions control technical requirements of non-road mobile machinery and diesel engine(phase 4)has been released recently.This impels each engine manufacturer adopt more advanced emission control technology one after another to make the prototype meet the requirements of the national four emission standards However,to make the products competitive,the manufacturers must ensure the consistency in engine performance.This involves the effective control of engine manufacturing accuracy,and the requirements of the system need to be taken into account at the engine design stage.The dimensional tolerance is closely related to the assembly and manufacturing processes of the engine,which affects engine performance as well as the emissions.Therefore,control of the engine dimensional tolerance has become one of the most important procedures during the engine design stage.In this paper,a diesel engine installed on agricultural machinery is taken as the research object.First,according to the product drawing and technical standards,the dimension parameters of the engine's key components are obtained,and the geometric model is constructed.Then the three-dimensional CFD software CONVERGE is used to simulate the combustion process and the formation process of emissions.Then the in-cylinder pressure curve obtained is compared with the one-dimensional calculated indicator diagram to verify the validity of the model.Next,the key dimensions of the engine are selected.The orthogonal test design is used to analyze the sensitivity relationship between the key dimensions and performance indicators as well as the significance.Then the single factor test method is used to analyze the effects of fluctuations in key dimensions on the performance of the engine.On this basis,the limit working conditions of the engine due to the variation of key dimensions are found out.Then the effect of changes in injection advance angle on engine performance is analyzed,and the feasibility of improving the consistency of diesel engine performance by correcting the injection advance angle is verified.The simulation results show that the fluctuation of the typical critical dimensions has a certain influence on the consistency of the engine performance.In the case of critical values of all critical dimensions,engine performance fluctuations are already very obvious.By adjusting the injection advance angle,the consistency of diesel engine performance can be improved to a certain extent.However,this method has certain limitations and cannot solve the problem of diesel engine performance fluctuation caused by dimensional tolerance fundamentally,thus other technical methods should be considered.