Engine Of Local Vibration And Noise Control

With the improvement of working and living conditions, and the implementation of stricter regulations, the reduction of engine vibration and noise has an important significance. In this thesis, the calculations of intensity and flexivity as well as tests are carried out on the crankshaft front-end of a certain engine. The cause of the crankshaft front-end abruption is as follows: The excessive impact of pulley drive causes too much vibration on the front-end, and thus cracks appear on dangerous cross section which finally result in abruption of the crankshaft front-end. To determine the free frequency of the crankshaft front-end, a beam model is used as the simplified model of front-end. The impact factor of pulley drive is acquired through vibration test and analysis on the crankshaft front-end, and measures to reduce the impact factor are introduced.This thesis also carries out vibration test and analysis on high-pressure fuel pipes of a certain engine to determine the causes of pipe abruption and put forward improvement approaches.The noise level of a diesel engine is determined through the measurement of its sound power. The main noise sources of the diesel engine are identified with the sound intensity method, and measures for noise reduction are suggested.As to the excessive vibration of crankshaft front-end, stress analysis shows that safety factor under impact load condition is too low, and as a result the dangerous cross section of the crankshaft should be thickened for reinforcement. The free frequency of crankshaft front-end is calculated, and theoretically resonance vibration is avoided. With the test amplitude of vibration, the actual impact factor of pulley drive is determined. Finally, thickening the dangerous cross section and adding a transition pulley as a buffer settle the problem of excessive impact of pulley drive on the crankshaft front-end. Since test and analysis results show that the root cause of high-pressure fuel pipes abruption lies in the inconsistent vibrations of both ends of fuel pipes, the problem can be solved by changing the resonance speed with the change of pipe bracket stiffness as well as changing the connecting mode between injection pump and transmission gear. The main noisesources of an engine are identified and sorted as cylinder head, exhaust manifold,gearbox and injection pump according to each part's contribution to the overallnoise.