Prediction Of Combustion Noise And Experimental Investigation Of Gasoline Engine

With the development of our society, technology and the people’s standard ofliving, the requirement of mobile quality has been higher and higher, and more peoplefocus on the quality of engines’ noise. The intense vibration would not only do harmto the engine itself, but also radiates noise to the outside environment through thevibration surface which would greatly weaken driving comfort, and people’s health.Consequently, it’s an important and urgent task for the engine research&developmentand manufacturing enterprise to investigate the method of reducing the noise ofengine. For the total noise of engine, the combustion noise contributes more part of it,so it’s a very meaningful thing to research how to reduce the combustion noise.This paper was composed by two main parts. The first part is in the design stageof the engine, predictive analysis the combustion noise. Used the professionalsoftware GT-Power to simulate the cylinder pressure when the engine works, whichincluded the normal pressure when combustion and the motoring condition, and usedthe simulated cylinder pressure through filtering and subtracting to get the in-cylindercombustion pressure, then changed to noise level, the next step is to use Fouriertime-frequency transform method to do spectral analysis with the in-cylindercombustion noise, then draw a conclusion about how the different workingcondition(different rotate speed and torque) had effects on internal combustion noise.The second part of the paper is based on the engine test bench experiments.Calculated the radiated noise from the surface of engine through using experimentalcylinder pressure and total noise. The chosen method is multiple regression analysismethod, this method was chosen by assuming that the total engine noise was onlyconsisted by combustion noise and mechanical noise. Used MATLAB software toprogram for the separation calculation, finally draw the conclusion of combustionnoise and mechanical noise changing discipline.After the analysis of the in-cylinder combustion spectrum, we can draw aconclusion that during the500~4KkHz in the frequency domain, the combustionpressure play more part in it, but in the frequency band which higher than4kHz, thecompression pseudo-motored pressure contribute more than combustion pressure.Through the separation of the combustion noise, we can draw a conclusion that during the working process of gasoline engine, both the engine load and speed have stronginfluence on combustion noise, but the influence of engine load is the key factor.