Study On Magnetorheological Fluid Torsional Vibration Damper Based On Engine Crankshaft System

One of the main reasons for the damage of the engine crankshaft system is the torsional vibration of crankshaft.The practical way to reduce the torsional vibration of crankshaft is to install a torsional vibration damper at the free end of crankshaft.The constant damping torsional vibration damper is only used to reduce the torsional vibration of a single order vibration.Damping ratio is one of the decisive factors in the damping effect of the torsional vibration damper.Therefore,the study of the adjustable damping ratio of the magnetorheological fluid torsional vibration damper,is necessary for achieving several orders reduction of torsional vibration of the crankshaft system.The main contents include:1.The engine crankshaft system is simplified as a lumped parameter model,and the torsional vibration characteristics(including natural frequency and vibration mode etc.)of the crankshaft system are calculated,which are theoretical basis of crankshaft torsional vibration research.2.The Catia,HyperMesh and Adams are used to establish engine crankshaft system of rigid-flexible coupled model for the analysis of torsional vibration characteristics;the torsional damper damping mechanism and the factors of damper inertia ratio,tuning ratio and damping ratio of vibration damping effect are researched;the relationship between damping fluid viscosity and damping ratio of vibration damper is studied,the constant damping torsional vibration damper for the maximum vibration amplitude of the crankshaft system is designed.3.The magnetorheological properties,working mode and damping force of magnetorheological fluid is studied,the working characteristic curves of selected MRF-250 type magnetorheological fluid by experiment is obtained;the designs of the magnetorheological fluid torsional vibration damper which aims at the main orders resonance according to the crankshaft torsional vibration characteristics and the design principle of the damping torsional vibration damper are carried out;simulation and analysis of the original engine crankshaft system,coupled system with constant damping torsionalvibration damper,coupled system with magnetorheological fluid torsional vibration damper are carried out to get the curves of their torsional vibration characteristic by Adams.The simulation results of different multibody system dynamics show that compared to the original crankshaft system,constant damping torsional vibration damper only can reduce a single order(6 order)of the crankshaft torsional vibration amplitude from 0.3809 °to 0.2561°(reduced by 32.76%).But for the 7.5 and 9 order of damping effect is not obvious(only reduced 15.44% and 14.37%);on the other hand,the magnetorheological fluid torsional vibration damper not only reduce the 6 order amplitude of crankshaft torsional vibration from 0.3809° to 0.2561°(reduced by 32.76%),but also reduce vibration amplitude from 0.1885° to 0.1192 °(reduced by 36.76%,7.5 order)and another amplitude from 0.1232° to 0.08627°(reduced by 29.98%,9 order).The results indicate that the magnetorheological fluid torsional vibration damper has good damping effect on the main orders torsional vibration of the crankshaft system,it is better for improving the torsional vibration characteristics of engine crankshaft system.