發(fā)布時間：2018-07-06 12:47

  本文選題：排氣系統(tǒng) + 消聲器��； 參考：《吉林大學》2014年碩士論文

【摘要】：排氣系統(tǒng)的設計直接關系到整車的動力性、舒適性和經濟性，隨著國家對機動車噪聲限制的日趨嚴格，使排氣系統(tǒng)的優(yōu)化設計成為車輛設計的重點之一，越來越受到人們的重視�，F階段我國排氣系統(tǒng)的設計還處于被動降噪階段，存在一定局限性。本文結合國家科技支撐計劃課題“面向節(jié)能與安全的集成智能化工程機械裝備研發(fā)”（課題編號：2013BAF07B04），以某車排氣系統(tǒng)消聲器為研究對象，通過計算機模擬技術，結合被動與主動控制設計方式，對該車排氣系統(tǒng)消聲器的傳遞損失、壓力損失進行分析研究及優(yōu)化設計。 根據消聲器結構參數，建立前、后消聲器的數值模型，分別利用Virtual LabAcoustics軟件進行了聲學性能分析，利用Fluent軟件進行了流體特性分析，得到了前、后消聲器的傳遞損失和壓力損失，詳細評價了各消聲器內的聲壓分布、流場的速度和壓力分布等情況，指出了相關結構不足之處。對排氣系統(tǒng)的消聲效果進行試驗測量，測量結果與仿真結果均顯示在某些頻率消聲效果較差，從而驗證了仿真方法的正確性。還就氣體溫度和氣體流速等因素對消聲器聲學性能的影響進行了分析。 在對消聲器聲學及氣體動力性能分析的基礎上，根據消聲器的基本消聲原理針對消聲器結構存在的不足之處，對前消聲器進行了四處改進設計，對后消聲器進行了兩處改進設計，將改進前后的傳遞損失進行仿真對比，結果表明改進后的消聲器消聲量增大、消聲頻帶拓寬并且流體特性有所改善。另外還對安裝有改進后的前、后消聲器的排氣系統(tǒng)進行了傳遞損失分析，分析表明該排氣系統(tǒng)具有較好的消聲效果，為實際工程設計提供了技術指導。 為更好的對發(fā)動機排氣噪聲進行降噪處理，本文除了對消聲器結構進行改進，還從有源消聲器的主動控制方面對排氣噪聲進行降噪分析。在Matlab軟件平臺上建立了排氣噪聲主動控制模型，在發(fā)動機轉速一定時，對收斂因子和濾波器長度對系統(tǒng)的影響進行了分析，，在此基礎上設計了基于變收斂因子自適應算法的排氣噪聲主動控制模型，并對發(fā)動機不同轉速下的排氣噪聲進行控制分析，計算結果表明設計的可變步長的自適應噪聲主動控制系統(tǒng)設計合理，具有較好的魯棒性，達到了控制要求，為工程中實現排氣系統(tǒng)噪聲的主動控制奠定了理論基礎。
[Abstract]:The design of exhaust system is directly related to the power, comfort and economy of the whole vehicle. With the increasingly strict restrictions on vehicle noise in the country, the optimization design of the exhaust system becomes one of the key points of vehicle design. People are paying more and more attention to it. At present, the design of exhaust system in China is still in the stage of passive noise reduction, which has some limitations. In this paper, combining with the national science and technology support project "Integrated Intelligent Construction Machinery equipment Research and Development for Energy Saving and Safety" (subject No.: 2013BAF07B04), the muffler of a vehicle exhaust system is taken as the research object, and the computer simulation technology is adopted. Combined with the passive and active control design, the transmission loss and pressure loss of the muffler in the exhaust system of the vehicle are analyzed and optimized. According to the structural parameters of the muffler and the numerical model of the muffler before and after, the acoustic performance analysis is carried out by using Virtual LabAcoustics software, and the fluid characteristics are analyzed by fluent software. The transmission loss and pressure loss of the front and rear mufflers are obtained. The sound pressure distribution, the velocity and pressure distribution of the flow field in each muffler are evaluated in detail, and the shortcomings of the related structures are pointed out. The noise suppression effect of the exhaust system is measured experimentally. Both the measurement results and the simulation results show that the noise suppression effect of the exhaust system is poor at some frequencies, which verifies the correctness of the simulation method. The influence of gas temperature and gas velocity on acoustic performance of muffler is also analyzed. Based on the analysis of acoustics and aerodynamic performance of muffler, according to the principle of muffler, aiming at the deficiency of muffler structure, the design of front muffler is improved. Two improvements were made to the rear muffler, and the transmission loss before and after the improvement was simulated and compared. The results showed that the noise quantity of the improved muffler was increased, the frequency band of the muffler was widened, and the fluid characteristics were improved. In addition, the transmission loss analysis of the exhaust system with the improved front and rear silencers is carried out. The analysis shows that the exhaust system has a better silencing effect and provides technical guidance for the practical engineering design. In order to deal with the engine exhaust noise better, this paper not only improves the structure of the muffler, but also analyzes the exhaust noise from the active control of the active muffler. The active control model of exhaust noise is established on Matlab software platform. The influence of convergence factor and filter length on the system is analyzed when the engine speed is constant. On this basis, an active exhaust noise control model based on variable convergence factor adaptive algorithm is designed, and the exhaust noise at different engine speeds is analyzed. The calculation results show that the design of adaptive noise active control system with variable step size is reasonable and robust, which can meet the control requirements and lay a theoretical foundation for the active control of exhaust system noise in engineering.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：U464.134.4;TB535.2

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