Research On The Prediction Of Diesel Engine Vibration And Noise Based On Combustion Process And Optimization Of Combustion Chamber Structure

The vibration and noise problem of diesel engine brings hidden danger to its reliability and safety,so the vibration and noise of diesel engine becomes the key concern of researchers.The vibration noise generated during the combustion process accounts for a relatively high proportion of the overall vibration noise of diesel engines,while the research on the shape of the combustion chamber is mainly focused on the optimization of emission performance and the control of the heat release law.Based on the above reasons,this paper will consider the influence of combustion process on the vibration noise of diesel engine,calculate the vibration noise characteristics of diesel engine and optimize the structure of diesel engine combustion chamber.The research in this paper is divided into three main parts as follows:(1)summarize the in-cylinder averages that affect the combustion noise in the combustion process and can be used to evaluate the combustion noise,and refine four quantitative evaluation parameters of combustion noise,such as cylinder pressure,pressure rise rate,pressure rise rate derivative and heat release rate.The one-dimensional combustion simulation model of the whole engine was established by GT Power and verified by the cylinder pressure and the performance of the whole engine,and then the runnability parameters of the whole engine were obtained as the initial and boundary conditions of the three-dimensional combustion simulation model;the three-dimensional combustion simulation model was established and verified,and the quantitative evaluation parameters of the combustion noise such as cylinder pressure and the distribution of the in-cylinder temperature field and equivalent ratio concentration field were obtained by the simulation model calculation;(2)Using the equivalent nodal load method,the cylinder head and cylinder liner forces were calculated based on the cylinder pressure calculation results,and the main bearing forces were calculated using the internal combustion engine dynamics principle as the excitation for the transient dynamic response calculation.A finite element and boundary element model of diesel engine whole engine vibration and noise calculation was established for transient dynamics and sound field calculation,and the vibration and noise characteristics of the studied diesel engine under the original combustion chamber structure were obtained by analyzing the vibration displacement and average effective velocity of the diesel engine surface vibration monitoring points and the sound pressure level of radiated noise.(3)Eight different combustion chamber structures were designed by changing three parameters such as width,crater radius and opening form of ω-type combustion chamber,and the three-dimensional combustion simulation models under different combustion chamber shapes were established by using CONVERGE,and the effects of different combustion chamber structures on the quantitative evaluation parameters of combustion noise and physical field distribution in the cylinder were compared and analyzed;the higher power and smaller burst pressure and pressure rise rate were selected The three combustion chamber structures with high power and low burst pressure and pressure rise rate were selected,and the vibration and noise characteristics of the diesel engine under the three combustion chamber structures were calculated by using the finite element method and boundary element method.By comparing and analyzing the combustion process of diesel engine and the vibration and noise characteristics of the engine,we know that the appropriate increase of combustion chamber width is beneficial to reduce the vibration and radiation noise of the engine,and the indentation design of the combustion chamber can also reduce the vibration and noise of the engine,but the power reduction is large and the performance of the diesel engine is reduced.