Research on the Influence of Bench Installation Conditions on Simulation of Engine Main Bearing Load

The simulation of main bearing load plays an important role in engine multi-body dynamics simulation, seemingly influencing the simulation of strength, vibration and acoustics. It is necessary to conduct engine bench test to validate the result of simulation. More attention has been paid to the flexibility of engine blocks and crankshafts, but not on the installing conditions of engine test bench, such as the stiffness of mounts, the presence of the connecting flange and the elasticity of shaft coupling, which are easy to ignore. The work presented here focuses on the influence of bench installation conditions on the multi-body dynamics simulation of an engine. A flexible multi-body dynamics model of a 4100QB diesel engine is built by employing the modal synthesis technique in the software ADAMS. By comparing the simulation results of different models, the effects of the connecting flange, the stiffness of mounts and the elasticity of shaft coupling are discussed. The result show that: Firstly, the inclusion of the connecting flange is important in the main bearing load calculations, when the engine is flexibly installed on the bench. Secondly, the difference of main bearing load caused by the changing of mounting stiffness is limited and can be neglected when the accuracy is not strictly demanded. Thirdly, the influence of elastic shaft coupling is negligible in main bearing load simulation. At the end of this paper, the simulation is validated by the measurement of vibration acceleration.