Recognition The Cylinder Pressure Based On The Vibration Signal

Measuring and analyzing the cylinder pressure of internal combustion engine is important in engine design, performance improvement, and condition monitoring and fault diagnosis. The acquisition of the cylinder pressure is generally obtained through the cylinder head processing manometers channel, measure directly using the pressure sensor. But it is inconvenient to diagnose or monitor combustion due to installation difficulties of cylinder pressure sensor. While the surface vibration of cylinder head contains a wealth of information which related to the combustion process, so the indirect method by measuring the internal combustion engine surface vibration signal to identify the cylinder pressure has important theoretical significance and practical value.Reconstruction the cylinder pressure is usually use vibration acceleration signal. Cylinder pressure signal is mainly concentrated in the low frequency; however, the vibration acceleration signal contains low frequency components rarely. It’s difficult to reconstruct the low frequency signal with high frequency. Earlier simulation results shows that there is a linear relationship between vibration displacement and cylinder pressure before the peak pressure. Experimentally results shows that measured combustion vibration displacement signal are overwhelmed by the vibration displacement that induced by non-combustion excitations. Therefore, the methods of how to use the measured vibration velocity and acceleration signal to obtain the vibration displacement is talked about, and use the vibration displacement signal to identify the cylinder pressure. Also the methods of how using different vibration signals to monitor the combustion process is talked about, the influence of non-combustion excitations on combustion vibration responses is studied. The main works of this paper are described in the following sections. The main research efforts and conclusions are as follows.Experiments are conducted on the195diesel engine, and the cylinder pressure signal and the cylinder head surface vibration signal are measured. The characteristics of the cylinder pressure signal and the measured surface vibration signal are analyzed on the time domain and frequency domain. The result shows that vibration velocity signal is a combination of the vibration excited by cylinder pressure and reciprocating inertia force incentive response, and the two forces are overlap in time-frequency domain. What’s more, the low-frequency component in the cylinder head vibration velocity signal is mainly caused by the second order reciprocating inertia force.The reciprocating inertia force has a great impact on the acquisition of the vibration displacement signal. The article use filtering method to process the vibration velocity and vibration acceleration signal, then the vibration displacement signal is reconstructed by the method of integral. Results show that the integral of the vibration displacement signal can reflect the changes of cylinder pressure after remove the influence of the reciprocating.The correlation between the integral of the vibration displacement signal and the cylinder pressure signal are analyzed. Compared the two signals, the result shows that there is a approximate linear relationship between the vibration displacement signal and the cylinder pressure signal, and the location of the maximum cylinder pressure can be identified by the location of the maximum vibration displacement. Based on the approximate linear relationship between the vibration displacement signal and the cylinder pressure signal, he cylinder pressure can be identified by the the vibration displacement signal.