Identified Noise Sourse And The Optimized Design Of Shell Components On The Low Noise Structure Of YC6113 Disel Engine

The radiated noise of the dynamical mechanism comes from its surface vibration. It is mechanical engine's aim to decrease the radiated noise through controlling vibration. This paper gives theoretic analyzed and experimental study to the radiated noise on YC6113.The main contents and productions are maintained as follow:This paper takes YC6113 diesel engine as research object. We first measure the pressure level of sound and acoustical power of the engine under the mode external characteristic. The study shows the whole pressure level of sound achieves 97.21 dB (A) at the demarcate point. The noise of gear is higher than other's, so it gives the most contribution to the noise of engine; The order of the noise from high to low are intake side, exhaust side and top side; the noise of flywheel is the lowest, it gives the least contribution to the noise of engine. Then we measure the intake side, exhaust side, gear and top side of the engine in order to identify the source of the noise, using the acoustic holography by electro beam scanning and shield technique, to find out where is the place the noise radiates extrusive. It is showed that the parts of oil pan, gear cover and valve mechanism cover give larger noise radiation.According to the experimentation, the shell components such as oil pan,gear cover and valve mechanism cover give larger noise radiation. Then using finite element method, we put up mode calculation and structure optimization to the shell components above-mentioned to decrease their radiated noise.The mode calculation of the gear cover shows that the fourth mode frequency is sympathetic vibration. On account of the limited space of gear cover, we only use the optimize method of adding rib and convexity, the inherence frequency optimized fore-and-aft increase few, the noise of the whole engine changes few too. After shielding the gear cover, the noise of the front-engine and the whole engine decrease 1.40dB(A) and 1.31 dB(A) respectively at the demarcate point.The mode calculation of the oil pan shows that the mode of oil pan is dense, the whole rigidity is small, vibration of the deep-underside,side face,shallow- underside of the oil pan, and the middle part which joint the deep-underside and the shallow- underside is strong. We use optimize method which adding punch trough to the four sides above-mentioned, the first inherence frequency increases 17.4Hz,other inherence frequency also increase. Considering the lubricating oil level can't fluctuate too intensively, we add a oil baffle-plate on the oil pan, and then optimize it. The inherence frequency increases farther after adding a oil baffle-plate. The experimentation result shows that the pressure level of sound of noise of the whole engine decreases 0.56 dB(A) at the demarcate point.The mode calculation of valve mechanism cover shows that vibration of the top-board of valve mechanism cover is intense, the rigidity is the worst, and the eighth inherence frequency arise sympathetic vibration. Then we take methods as increasing width and number of rib and adding labyrinth-board on the top-board. The inherence frequency increases after increasing width and number of rib, and the inherence frequency decreases after adding labyrinth-board. But vibration centralizes on the labyrinth-board. The noise of top side and the whole engine noise descend 0.5dB (A) and 0.54dB (A) respectively.Thought the amelioration of the scheme upwards, the noise of the whole engine is 95.30dB (A), which is 1.51dB (A) lower relative to the original engine, the effect is salience. It is feasible to control the noise of diesel engine by using structure optimization. It will have the reference meaning in the optimize design of the modern engine and its device.