YN30CR Diesel Engine Crankshaft Torsional Vibration Measurement And Analysis And Research

It is necessary to detect the rationality of the crankshaft design and its shock absorber match relying on the test due to the importance of crankshaft in the engine design. And the crankshaft torsion vibration testing is an important step. In this paper, the crankshaft torsion vibration is analyzed when the engine works in the steady-state and unsteady-state condition. The influence of engine load and working uneven on engine crankshaft torsion vibration is explored based on this.On the basis of YN30diesel produced by YunNeiDongLi Company, the information of the crankshaft vibration type and the critical speed is got by using the AVL Excite Designer software to simulate and analyze the crankshaft vibration mode. Then a test and analysis system of crankshaft torsion vibration is developed using the Lab View programming software and PXI-6259multifunction DAQ (data acquisition) board of NI Company. The system uses non-contact measurement method. Then synchronous acquisition module is used to sample the magnetoelectric sensor simulation signal of the flywheel end and the photoelectric encoder digital signal of the free end in high-frequency and the DAQ of the crankshaft torsional vibration test is achieved. In the data analysis module, the data is analyzed in the time domain and frequency domain. The analysis of the amplitude value and phase of each harmonic of the angular displacement of the torsion vibration can distinguish the rolling vibration mixed in the torsion vibration angular displacement. Test results and the crankshaft torsion vibration simulation results are cross-checked to verify the accuracy of the simulation and experimental results.The amplitude value and the phase of the main harmonic of angular displacement of vibration are analyzed combined with the simulating results. The critical speeds of rotation of torsion vibration of crankshaft of YN30engine are2200r/min and2750r/min, and the intrinsic frequency is367Hz, the amplitude value of the free ends’ torsion vibration is much bigger than that of the flywheel end, vibration node is near the flywheel end. At the same time, the rationality of the design of crankshaft of this engine and corresponding damping solutions are tested and verified too.During the study of the influence of engine load and working uneven on engine crankshaft torsion vibration, the torsion vibration is tested when the loads are different and one of the cylinders is not supplied. The results show that the amplitude value of the torsion vibration in every harmonic is increased with the load increasing, and the influence on the torsion vibration is little when the engine works in the unsteady-state condition, for example the vibration type and the critical speed are almost the same with that in the stable condition while the larger amplitude value of the rolling vibration in low harmonic occurs when the harmonics of the vibration displacement are0.5,1,1.5in turn. Though the damage of the rolling vibration harmonic is not serious, but affects the noise of the engine and the affiliated organ to the crankshaft severely. So the designer should pay attention to the rolling vibration harmonic.