Experimental Study on Torsional Vibration of Engine Crankshaft and Cylinder Block

Abstract

Abstract Engine cylinder block vibration usually does not consider the influence of torsional vibration of crankshaft. Because cylinder block and crankshaft vibrate separately, crankshaft torsional vibration may have a coupling effect on the vibration of the cylinder block, especially when the crankshaft torsional vibration is very large when engine is idling. In order to evaluate the coupling effect, a pilot test program was designed and developed under idle no-load condition. The torsional vibration of the crankshaft comes from the encoder sensor, and the torsional vibration of the cylinder block comes from the calculation of two acceleration sensors arranged on the cylinder block. This paper derives the formula for extracting the torsional vibration signal of the cylinder from two acceleration signals. Data analysis of spectrum and coherence reveal that the torsional of the crankshaft is greater than the cylinder block at the engine 3rd order frequency 35Hz, and the torsional vibration signals of the two have strong coupling at integer multiples of the 0.5th order frequency of the engine in the range of 100Hz that is prone to vibration problems. Through the above tests and data analysis, it is more accurate to consider the influence of crankshaft torsional vibration when studying engine vibration.