Study On Combustion Noise Of Diesel Engine Control With Pilot Injection Parameters

This paper research around the impact to combustion noise of diesel engine with pilot injection.It uses the high pressure common rail electronic-control direct injection system to control the pilot injection parameters precisely, which make the pilot injection become a kind of effective method to dominate the combustion noise of engine.First of all, the noise test and the maximum breakout pressure test had been operated in an engine test bench with an A6000diesel engine, and use the Bosch high pressure common rail electronic control system, the noise test equipment and other corresponding test equipment to test1metre average noise, combustion noise, the maximum pressure rise rate, cylinder pressure curve, heat release rate curve, emissions and fuel consumption. From the results of test show that, for the single injection, different loads and speeds have the great influence to the noise of diesel engine. Along with the increase of the engine load the combustion noise increases firstly and then decreases, which reaches maximum in25%load. But in different load the changes of speed to the combustion noise’s law is not uniformity.The rail pressure and injection angle also have effect on the combustion noise. Along with the increase of the rail pressure and injection advanced, the maximum pressure rise rate, the maximum breakout pressure and the noise have been influenced more or less, which is more influenced by the injection angle.For the pilot injection, adding the pilot injection can reduce the combustion noise for lOdB. The changes of combustion noise value by the changes of pilot injection parameters is smaller than the changes in adding pilot injection.After adding pilot injection, the biggest breakout pressure, the maximum pressure rise rate, and the peak of the rate of heat release is decreased obviously. It can get the optimal value of combustion noise by changing the pilot injection parameters in different working conditions.Compared with other performance of the diesel engine before and after pilot injection, the pilot injection not only can cut down obviously combustion noise, but also improve the nitrogen oxide emissions and little influence to fule consumption and FSN.Secondly, it uses the engine simulation analysis software AVL-Boost to simulate the diesel combustion noise. Establish A6000diesel engine mathematic model, and then in single injection and pilot injection, simulate and calculate the influence of the biggest breakout pressure, the maximum pressure rise rate, and the peak of the rate of heat release with the changes of injection parameters and load in different working conditions. The calculation results show that:in single injection, the changes of common rail pressure and injection angle have greatly affected the three targets above. In different conditions, delayed injection, the maximum pressure rise rate, the maximum breakout pressure and the rate of heat release become downtrend. So it can get the best injection angle to make the three targets above have the optimal values. Compared with the single injection, adding pilot injection can greatly reduce the maximum pressure rise rate. It can bring certain effect to the combustion noise by changing the main injection timing, pilot injection timing and pilot injection quality. So it can seek the best injection strategies of pilot injection to improve combustion noise.Also for the same pilot injection parameters, the changes of the load have an impact on the maximum pressure rise rate.The maximum pressure rise rate become rise firstly and then downtrend with the changes of load. Based on the test and simulation results contrast, both have good uniformity in the trend.Finally, the sound quality test had been operated in a engine test bench with a A6000diesel engine, and make the use of the artificial head manufactured by German Head-acoustic corporation and other corresponding test equipment to test and calculate roughness, loudness and sharpness. The test results show that: adding pilot injection, engine sound quality improved obviously. In different working condition it can seek the best injection strategies of pilot injection to make the sound quality get the optimal parameters. In the same condition, contrasting sound quality and1metre average noise, it knows that not the smaller noise value, the sound quality is better. So it must combine the subjective evaluation to evaluate the whole noise of the engine, not just the noise value.