Research On Numerical Method Of Crankshaft Torsional Vibration Of Multi-Cylinder Engine Based On Transfer Function

Torsional vibration is one of the main factors causing the vibration and noise of engine, serious resonance will have negative influence on engine performance and do damage to the engine itself. Testing and calculation analysis are two main methods to study the torsional vibration of crankshaft, in this thesis a new method based on the transfer function between excitation torque and response of the crankshaft has been discussed. As a supplement to currently used method, it can be utilized for the calculation under transient condition and the research on fault diagnosis. The work of the thesis has been carried out as the following:(1) Methods and essential process of torsional vibration testing and calculation analysis has been introduced with practical work, the limits of calculation and the importance of transient condition as well. The mold calibrated with testing results was the object mainly studied in the thesis.(2) Relationship between the torsional vibration and the excitation has been defined in the forms of impulse response and frequency response calculated with TVCA.(3) Impulse-response-method has been introduced to the calculation of torsional vibration by trying to calculate the vibration response with convolution integral of impulse response and excitation torque. Programs have been compiled and calculating results of vibration response on steady condition obtained, comparisons with the results of TVCA proved the feasibility and accuracy of the impulse response method. Application range and main influence factors of the impulse- response-method have been investigated.(4) Frequency-response-method has been introduced to the calculation of torsional vibration, calculating programs have been compiled on the basic theory of this method. The feasibility and calculation accuracy of this method have been proved by comparing the calculation results under steady condition with the results of TVCA. Frequency response method was used to calculate the vibration response under transient condition and the correctness of the algorithm has been analyzed.The above work and results have proved that torsional vibration response can be calculated with the transfer function and excitation torque. Both impulse-response-method and frequency-response-method can be feasible under steady condition while the latter can be applied in a wider range and be feasible under transient condition.