Research On Acoustic Performance Of Intake And Exhaust Systems Of Engine

With the continuous increase in environment improvement requirement, the noiseof engine has attracted more attention. Intake and exhaust system noise of engine arethe main sources of inside and outside noise of vehicle. In order to reduce the noise ofintake and exhaust system, the acoustic characteristics of intake and exhaust system ofa2.0L gasoline engine are simulated in GT-POWER, and an experiment of the intakenoise has been conducted to verify the simulation results. Comparison between theexperiment results of the intake noise and the simulation results shows that theacoustic characteristics simulated in GT-POWER have a good agreement with that inexperiment at low speeds. Because GT-POWER can only be used to calculate theaerodynamic noise and the noise reduction elements are designed primarily forreducing the aerodynamic noise, the simulated noise characteristics of the noisereduction elements in GT-POWER is very suitable. According to the simulated totalnoise and order noise of the intake and exhaust system, and the noise limits proposedby the company, the speed and order which are in excess of the limits can be found.And the noise frequency which is in excess of the limits can be calculated. Thisfrequency is determined as the center frequency of the noise reduction elements. Thenthe Helmholtz resonator or quarter wave tube is chosen according to thecharacteristics of the center frequency, and the size of the Helmholtz resonator orquarter wave tube is calculated.In addition to the size of the noise reduction elements, the reduction effect of thenoise reduction elements are associated with the location in the intake system. Inorder to optimize the location of the noise reduction elements in the intake system, theacoustic mode of the intake system is analyzed in SYSNOISE, and the top ten modalfrequencies and the corresponding modal formation are calculated. Then the modalfrequency which is the most closed to the center frequency of the noise reductionelements is found, and the corresponding antinodes locations of modal formation inthis modal frequency are the best position of the noise reduction elements located.The influence of the location of the noise reduction elements on the reduction of theorder noise is implemented by changing the corresponding modal formation which isclosed to the center frequency. The calculation results show that2dB order noise reduction and1dB total noise reduction are obtained at the acoustic modal frequencywhen the noise reduction elements are located at the antinodes of the acoustic modecomparing to that at the nodes.