| With the rapid development of construction machinery, agricultural machinery and other non-road mobile machinery industry, non-road diesel engine market space is becoming increasingly broad. For the reason that the Non-road diesel engines working at harsh conditions, high load, changing dramatically operating conditions, a large power range, the reliability of the diesel engine, acceleration and economy have higher requirements. With the high noise emission regulations and improvement of users, there are higher requirements to reduce the diesel engine vibration and noise. To research the engine vibration and noise characteristics, a common-rail diesel engine is takn as the research object。The research has guiding significance on the reducing vibration and noise.In this paper, A diesel engine finite model is established by the Hypermesh finite software. The engine block finite model is proved to be accurate by comparing the modal test result and the computing modal result. The vibration character of the diesel engine is analyzed by under different mechanical load. By carrying on a diesel engine vibration bed test, the multibody dynamics model is confirm to be correct. Based on the diesel engine multibody dynamics model, the influence factors of vibration and noise character such as different mechanical load level, different crankshaft counterbalance, different piston pin-off, different valve clearance and different main bearing clearance is researched. In order to reduce the diesel engine vibration and noise, the structure of oil pan end engine block is optimized.The main research results show as below:1) the modal analysis of the block and crankshaftBased on the Modaview modal test software, the modal of the diesel engine block is tested. The finite modal created by finite software is prove to be correct by comparing the modal test result and the computing modal result.2) The engine vibiration and noise analysisBy establishing the valve train dynamics model, piston dynamic model and total engine dynamic modal, the valve train load, piston slap load and main bearing load is calculated. The vibration velocity level of cylinder head cover and oil pan is bigger than other component’s in different 1/3 octave frequency bands. With the frequency which the range is 500Hz to 3000Hz increased, the vibration velocity level of the total model present a decreased tendency.The sound power level of the engine is increase with the speed. The sound power of the oil pan is biggest among the components. The sound power of the cylinder head cover is second biggest. When the engine is working on rate condition, the sound power ratio of the oil pan is 43.1%, the sound power ratio of the flywheel cover and cylinder head cover are 23.1% and 18.6%. Based on the WBT theory, a sound field analysis model is created. When the sound frequency is 523Hz, the sound pressure level of the engine appeared a peak valve. The peak value is 85.23dB. The sound pressure level minimum value is 46dB at 1911Hz. As the frequency increases, the sound pressure level increases first, then decreases.By adding reinforcing rib on the bottom of the oil pan, the constrain modal of the oil pan increase. The mean velocity level decrease more than 4dB.3) The vibiration and noise factor analysisAfter the valve train load applied on the model, the velocity level at high frequency range increase. When the piston slap load on the liner, the velocity level increase much more. The piston slap have much more effect at the upper area of the engine.The vibration velocity level of the engine is smaller at low-medium frequency when the crankshaft is four-counterweight structure model. But at medium-high frequency, the vibration velocity level of the engine is smaller at low-medium frequency when the crankshaft is eight-counterweight structure model.When the pin-off value is-1.2mm, clearance value is 0.15mm, main bearing clearance is 0.15mm, the vibration acceleration level and sound power level is smallest. |
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