The Research On Cylinder Pressure Reconstruction By Impulse And Response Signals In Diesel Engine

Cylinder pressure measurement and analysis has played a very important role in diesel engine monitoring and diagnosis to improve its performance, optimal injection and emission control. For large and medium sized diesel engine is generally available measured through direct measurement of cylinder pressure indicator valve, but for small sized diesel engine was measured by pressure measurement sensor fixed on the body punching. The diesel engine cylinder working conditions is quite poor, the cylinder pressure sensor directly affected by the impact of high temperature and high pressure gas, the sensor was easily caused by thermal ablation and damage, and pressure sensor is so expensive, costs are relatively high of pressure measurement. Therefore, it has actually value engineering application through other easy to identified signal from the external measurement of cylinder to reconstruct the cylinder pressure This article author has carried on the recognition method research based on the diesel engine cylinder cover surface vibration signals to reconstruct the cylinder pressure, has obtained the following research results:Take 4120SG diesel engine as the research object, has analyzed the cylinder cover system drive source and the vibration response signals characteristics, through add the window and the signal processing technology to the acquisition time domain signals, have removed other stimulating the force effect; have carried out the signal-to-noise ratio outcome raised by many times averagely on the acquisition signals. Identify the engine cylinder pressure and the vibration signal on the cylinder cover surface relationship finally.Then simplified the diesel engine cylinder cover system as a multi-input and single-output linear system (MISO), Measured the diesel engine instantaneous speed, the top dead center, 3, 4-cylinder pressure, vibration signals of the diesel engine cylinder cover; design a low-pass finite impulse response filter design (FIR), then build a transfer function model by transfer function method with the cestrum technology, and use this function model to reconstruct the cylinder pressure. Point out the applicability and the prospects of the transfer function method and application by comparing the measured pressure and the pressure reconstruct by inversion.Because of the uses in the cylinder pressure inversion construction method mostly based on the cylinder pressure are measured and prophet before the construction, In order to determine the directly diesel engine cylinder transfer function model under the pressure unknown condition, and construct the cylinder pressure directly, the author also carried on the exploration to determine the cylinder cover function model by static rap the cylinder cover and discussed this kind of inversion reconstruction method feasibility.