The Prediction And Control Of Combustion Noise In Diesel

In the twenty-first century,the internal combustion engine industry has a better development,new technologies,new methods,new materials and other aspects have made great progress,the engine power performance,economic performance,reliability and automation levels continue to improve.At the same time,the vibration and noise problems of internal combustion engine are catching the eyes of many institutions and scholars at home and abroad.As the main noise source of diesel engine combustion noise,Cylinder pressure effects the diesel engine performance much,same to the vibration and noise characteristics.In this paper,I will search the factors influencing the internal pressure of diesel engine,such as operating conditions and fuel injection strategy and explore the influence of various factors on diesel engine performance and cylinder pressure,at the same time,put forward regular conclusions.Take use of the dynamics calculation of internal combustion engine to get the main sources of combustion noise:head load,cylinder load and main bearing load.The vibration characteristics of the diesel engine structure caused by the excitation and resultant load are calculated by using the finite element method respectively.The noise characteristics of the surface of the diesel engine are calculated by using the boundary element method.The results show that in the three excitation sources which cause the combustion noise,the cylinder load influence the vibration of the whole machine most,followed by the main bearing,and finally the cylinder head load.The average sound pressure level at 0.5m from the machine boundary is 103.9dB.From the results of vibration and noise,it is found that the change of vibration and noise response and the change of excitation force show a consistent law.Therefore,the level of excitation force can reflect the level of overall vibration and noise response.And the optimized vibration of the whole machine can be understood by the optimization effect of excitation force.Based on the study of the influence of diesel engine operating conditions and fuel injection timing on the pressure in the cylinder and the calculation of the vibration and radiation noise characteristics of the original machine,the combustion noise of the diesel engine is optimized.Starting from the source,select the appropriate compression ratio and fuel injection strategy to recalculate the cylinder pressure curve and use it as the excitation force to calculate the vibration and radiation noise characteristics of the whole machine.Five cases are provided.The results show that the vibration and radiation noise characteristics of the whole machine under secondary injection are better,but the fuel consumption rate is higher;Decreasing the compression ratio or advancing the injection time will also optimize the vibration and noise and decrease the fuel consumption rate at the same time.