Research On The Transient Speed Signal Of Internal Combustion Engine

The transient speed contains information related to combustions and working status, and the type of speed senor has the characteristic of simple installment, strong suitability and high reliability. The diagnosis of engine status by using the transient speed has been the most practical and valuable technology in the engine fault diagnosis technology.The transient speed was influenced by pressure and other factors. In order to diagnose the working status of internal combustion engine (ICE) by the transient speed, factors affected on the transient speed of ICE were analyzed, and the influence rule was studied. The main research efforts and conclusions are as follows.Based on ICE dynamics and kinematics, the D495QB diesel was simplified to obtain the mathematical model. The crankshaft dynamic model was built using MATLAB/SIMULINK. In the assumption of flexible and rigid crankshaft, the transient speed was calculated by using the crankshaft dynamic model, and compared with testing result to verify the accuracy of the crankshaft dynamic model. The simulation result of the flexible and rigid model was analyzed by using time domain, frequency domain and time-frequency domain. Results indicate that the influence of reciprocating force of inertia and cylinder pressure on the transient speed was different in time domain and the same at frequency domain. The transient speed fluctuation induced by torsion vibration was more complex, and it is difficult to be separated on time domain and frequency domain. Therefore, it is necessary to choose a suitable method to separate the transient speed fluctuation induced by the torsion vibration.After analyzing the characteristics and shortcomings of different methods of transient speed measurement, the appropriate program of measuring transient speed was selected, and the digital filter and wavelet de-noising were designed to realize the data processing. The transient speed was measured under different speeds and different loads on the 495T diesel by designing test platform. According to transient speeds obtaining from crankshaft flywheel end and free-end, the working capability and the torsion angle were calculated. Results show that the amplitude fluctuations in the transient speed reduced with speeds rising, and the transient speed obtaining from free-end was more irregular and more complex on frequency domain.Transient speed fluctuations induced by cylinder pressure, reciprocating force of inertia and torsion vibration were separated. The transient speed fluctuations induced by reciprocating force of inertia can be separated from measured results when the whole of moment of inertia was got. The blind source separation was used on simulation results and measurement results, and the separation results of measurement results were verified by measured cylinder pressure. The separation results can better reflect the operating conditions of engine.