Analysis Of Torsional Vibration Of Diesel Engine And Design Of Its Magnetic Rheologic Fluid Torsional Vibration Damper

Results from a number of studies show that the torsional vibration of enginecrankshaft is one of the main reasons causing destruction of crankshaft. Usually, thetorsional vibration damper is applied to help suppress the torsional vibration ofcrankshaft. Torsional vibration damper damping damping can be divided into fixedand variable damping torsional vibration damper,Torsional vibration dampers withconstant damping coefficient are widely used, such as silicone oil damper and rubberdamper. However, Magnetic Rheologic Fluid torsional vibration damper belongs tothe torsional vibration damper with variable damping coefficient, which is effective tosuppress the torsional vibration of crankshaft at several different resonance speeds.The present paper is about the investigation on the torsional vibration of crankshaft ofa diesel engine by means of simulation and experiment. We also conduct a furtherinvestigation on the design of Magnetic Rheologic Fluid torsional vibration damper.Firstly, we choose a6cylinder inline diesel engine as the research object. Byusing the classic discrete model and the traditional matrix method, we makecomparison on torsional vibration of the crankshaft system between conditions withand without a torsional vibration damper of constant damping coefficient.Investigations about free vibration and forced vibration of such a systems were carriedout. The results show that both the natural frequency and resonance speed of thesystem change by equipping a torsional vibration damper. The torsional vibrationdamper also plays a role of frequency modulation. Furthermore, torsional vibrationdamper with constant damping coefficient is effective to suppress the torsionalvibration for a resonance speed. However, torsional vibration suppression for otherresonance speed is not ideal. Study on the effects of variation of damping coefficienton the torsional vibration characteristics was also included in this paper. The resultsshow that it is an effective way to reduce the torsional vibration amplitude fordifferent resonance speeds by changing the damping coefficient of damping torsionalvibration damper. Secondly, the paper make analyzes on the MRF torsional vibration damper: basedon its mechanical characteristics, we design the excitation circuit, operation modesand the damping force model of MRF torsional vibration damper, then propose asuitable MRF torsional vibration damper with variable damping coefficient forsuppression of the engine crankshaft system. This paper also includes simulation oftorsional vibration damper of parallel by using the Matlab software, and makescomparisons of variation trend of the torsional vibration characteristics of engine craftsystem among conditions without torsional vibration damper, with a dampingtorsional vibration damper of constant damping coefficient and with a MRF torsionalvibration damper. Results showed that after the engine installed fixed and variabledamping torsional vibration damper which natural frequency and resonance speedsystems have declined. More importantly, with respect to fixed damping torsionalvibration damper, MRF torsional vibration damper of variable damping coefficient,decreased the torsional vibration amplitude of engine draft by44.89%,21.64%and37.23%at1200rpm,1420rpm and1800rpm resonant speeds as changed the dampingfactor of damper, which indicates that MRF torsional vibration damper of variabledamping coefficient has better performance at different resonance speeds.At last, we design and process a MRF damping torsional vibration damper,comparison and analysis of the torsional vibration characteristics of engine shaftingwhen using silicone oil damper and the MRF damping torsional vibration damper.The test results show that compared with silicone oil damper, MRF damping torsionalvibration damper can make a better damping effect on torsional vibration for differentresonance speeds of crankshaft.