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Internal Flow Field Simulation of Passenger Car Exhaust System Cold End and Prediction of Muffler Airflow Regenerated Noise

Author: GuoXueMin
Tutor: HouXianJun；LiuZhiEn
School: Wuhan University of Technology
Course: Power Machinery and Engineering
Keywords: Exhaust System Backpressure CFD Flow noise
CLC: U464.134.4
Type: Master's thesis
Year: 2011
Downloads: 130
Quote: 2
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Abstract


With the surge in the number of city cars, worsening air pollution and noise pollution caused by the attention. Governments has developed increasingly stringent emissions regulations, various car manufacturers are also committed to reducing vehicle emissions and noise, and the consumers are more and more inclined to choose good comfort, good economy, less pollution car. The exhaust system is to reduce vehicle noise and reduce vehicle exhaust pollution generally means good design performance exhaust system to reduce air pollution and noise pollution caused by vehicles is of great significance. Automobile exhaust system designed to focus on considering its performance muffler, aerodynamic performance and flow noise performance. In this paper, computational fluid dynamics software FLUENT the cold side of a passenger car exhaust system design, three-dimensional flow field simulation, based on its pressure loss and velocity field, pressure field, turbulent kinetic energy field analysis, combined with the muffler related theory proposed structural improvements for reduced backpressure and improved program flow field simulation, the simulation results show that effectively reduce the back pressure of improvement programs. Experiments show improved programs to meet the premise of performance muffler backpressure real machine test effectively reduce the original programs and improvement program, in good agreement with the backpressure experimental results and simulation results, also proved this article in FLUENT The software used in the calculation method has a better calculation accuracy. Air flow in the muffler, on the one hand, due to the influence of the local resistance and friction will generate a series of turbulence, and thus the radiated noise, on the other hand, the pressure pulsation of the fluid excitation the muffler inner member vibration also radiated noise, these two noise muffler flow noise. When the flow noise reaches a certain level, it will reduce the actual muffler muffler, and even the muffler sound amplifier design muffler flow noise sufficient attention. The turbulent flow caused by the air flow within the muffler noise is the main ingredient of the flow noise, air noise muffler This article attempts to predict. FLUENT software provides three aeroacoustics calculation model, this paper is the use of FLUENT software provides broadband noise model C the from direct acoustic calculation model, as well as the FW-H acoustic calculation model to try to predict the airflow noise muffler. The study found three methods can predict airflow within the muffler noise to some extent, but the three methods have limitations. This article also three acoustic calculation method in the prediction of air noise muffler applicability and advantages and disadvantages of doing discussed to provide some reference flow noise prediction muffler.

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CLC: > Transportation > Road transport > Automotive Engineering > Automotive engine > Reciprocating engine > Components, parts > Valve > Intake and exhaust systems
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