Research On Diagnosis Analysis And Simulation Optimization Of Combustion Noise Of Direct Injection Internal Combustion Engine

The combustion noise problem of direct injection engine is an important part of the whole noise problem of direct injection engine.This article has launched a series of researches on the test diagnosis analysis and simulation optimization method of direct injection engine combustion noise.The specific work content and results are as follows:First of all,a combustion noise optimization test was carried out on a certain type of direct injection diesel engine,and the combustion parameters that meet the emission and performance indicators were selected for adjustment,and the test process design was carried out.The optimization results of single-variable rail pressure,main injection angle,pre-injection interval,and pre-injection volume are obtained.On this basis,an improved version of the orthogonal test multi-variable optimization design and implementation was carried out.The combustion noise of the whole machine was optimized in the low-to-medium speed region,and the exhaust and performance indicators of the whole machine were ensured.Secondly,the combustion noise diagnosis test and regression analysis of this type of direct injection diesel engine were carried out.The cylinder pressure was decomposed according to the test phenomenon and empirical formula of the whole engine,and the cylinder pressure was divided into three frequency bands of low,medium and high.Three indicators of pressure,pressure rise rate and high-frequency oscillation energy are used to perform regression analysis on the sound pressure level of the whole machine.The cylinder pressure curve and the attenuation curve were used to predict the combustion noise of the whole machine,and the relationship between the combustion noise in the low,middle and high frequency bands and the various combustion noise indicators was established.Two types of combustion noise are analyzed.The medium-frequency rumble and high-frequency oscillating combustion noise changes with the combustion noise index,rail pressure,main injection angle,preinjection interval,and pre-injection volume.Cylinder pressure related parameters are directly related to mechanical noise and two types of combustion noise.Subsequently,for the direct injection diesel engine,the mechanism of high-frequency oscillation combustion noise was studied,and the high-frequency component separation and influencing factors of the cylinder pressure of the direct-injection diesel engine were tested.The adaptive TVF-EMD method was used to control the high frequency in the cylinder.Oscillations are separated and three indicators are defined,which are center frequency,normalized energy and average center frequency for research.The influence of engine speed,load,rail pressure,and other parameters on high-frequency oscillation is analyzed,and an improved method is proposed.This signal processing method is also applicable to other engines.Furthermore,the research results on combustion noise of direct injection diesel engines are extended by analogy.For a certain type of four-cylinder direct injection gasoline engine,combustion noise test optimization,combustion noise source diagnosis,and cylinder pressure high frequency oscillation separation are studied.The noise frequency peaks(which can be considered as combustion noise changes)at a fixed speed and load are compared with the combustion chamber acoustic oscillation frequency model.Then,taking the previous test direct injection diesel engine and direct injection gasoline engine as examples,a one-dimensional thermodynamic simulation model of the whole machine was established separately,which was verified with the test cylinder pressure,and the flame propagation parameters based on the one-dimensional simulation test were established.The combustion noise can be predicted more effectively by the multiple regression prediction model.On this basis,a threedimensional fluid dynamics in-cylinder combustion simulation model was established,which verified with the cylinder pressure,and a combustion noise optimization method based on the combination of combustion noise test and three-dimensional in-cylinder flow field simulation was established.At the same time,the in-depth mechanism of combustion noise source optimization is discussed.Finally,a complete set of research methods for combustion noise experiment diagnosis,signal separation,simulated prediction and optimization of direct injection engine are established...