3000中英文翻譯.doc

汽車消聲器的研究汽車消聲器的研究背景隨著汽車工業(yè)的迅速發(fā)展，人們對于汽車的舒適性和振動噪聲控制的要求越來越嚴格。據(jù)國外有關資料表明，城市噪聲的百分之七十來源于交通噪聲，而交通噪聲主要是汽車噪聲。它嚴重的污染者城市環(huán)境，影響著人們的生活、工作和健康。所以噪聲的控制，不僅關系到乘坐舒適性，而且還關系到環(huán)境的保護。然而一切噪聲又源于振動，振動能夠引起某些部件的早期疲勞損壞，從而降低汽車的使用壽命；過高的噪聲技能損害駕駛員的聽力，還會使駕駛員迅速疲勞，從而對汽車行駛安全性構成了極大的威脅。所以噪聲控制，也關系到汽車的耐久性和安全性。因此振動、噪聲和舒適性這三者是密切相關的，既要減小振動，降低噪聲，又要提高乘坐舒適性，保證產(chǎn)品的經(jīng)濟性，使汽車噪聲控制在標準范圍之內。噪聲評價指標主要是指車內、外的噪聲值和振動適應性。評價方法可分為主觀評價和客觀評價。影響汽車噪聲主觀評價的主要因素是舒適性、響度和確定性，例如可以利用語義微分法進行主觀評價。在客觀評價時，可以采用PCNM噪聲裝置測量試驗進行分析；此外模擬技術中的有限元法（FEM）和邊界元法（BEM）也被廣泛應用。降低發(fā)動機噪聲是汽車噪聲控制的重點。發(fā)動機是產(chǎn)生振動和噪聲的根源。發(fā)動機的噪聲是由燃料燃燒，配氣機構，正時齒輪及活塞的敲擊噪聲等合成的。降低發(fā)動機本體的噪聲就要改造振源和聲源，包括用有限元等方法分析設計發(fā)動機，選用柔和的燃燒工作過程，提高機體的結構剛度，采用嚴密的配合間隙，降低汽缸蓋噪聲。例如在油底殼上增設加強筋和橫隔板，以提高油底殼的剛度，減少振動噪聲。另外，給發(fā)動機涂阻尼材料也是一個有效的辦法。阻尼材料能把動能轉變成熱能。進行阻尼處理的原理就是將一種阻尼材料與零件結合成一體來消耗振動能量。它有以下幾種結構：自由阻尼結構、間隔自由阻尼層結構、約束阻尼層結構。它的采用明顯的減少了共振的幅度，加快了自由振動的衰減，降低各個零件的傳振能力，增加了零件在臨界頻率以上的隔振能力。目前，已有一些國家的專家設計了一種發(fā)動機主動隔振系統(tǒng)，用于減少發(fā)動機振動，以達到降低噪聲的目的。 對于汽車噪聲的控制，除了在設計上使用優(yōu)化方法和零件的優(yōu)化選用以外，還可以對噪聲進行主動控制。這就是以聲消聲技術，原理是：利用電子消聲系統(tǒng)產(chǎn)生與噪聲相位相反的聲波，使兩者的振動相互抵消，以降低噪聲。這種消音裝置采用極其先進的電子元件，具有優(yōu)異的消聲效果，可以用于降低車內噪聲、發(fā)動機噪聲，還可以用于主發(fā)動機支撐系統(tǒng)，以抵消發(fā)動機振動噪聲。汽車消音器的原理就是其排氣管是由兩個長度不同的管道構成，這兩個管道先分 開再交匯。由于兩個管道的的長度差值等于汽車所發(fā)出的聲波的波長的一半，使得兩列聲波在疊加時發(fā)生干涉時相互抵消而減弱聲強，使聲音減小，從而起到消音的效果。 阻性消聲器主要是利用多孔吸聲材料來降低噪聲的。把吸聲材料固定在氣流通道的內壁上或按照一定方式在管道中排列，就構成了阻性消聲器。當聲波進入阻性消聲器時，一部分聲能在多孔材料的孔隙中摩擦而轉化成熱能耗散掉，使通過消聲器的聲波減弱。阻性消聲器就好象電學上的純電阻電路，吸聲材料類似于電阻。因此，人們就把這種消聲器稱為阻性消聲器。阻性消聲器對中高頻消聲效果好、對低頻消聲效果較差。 抗性消聲器是由突變界面的管和室組合而成的，好象是一個聲學濾波器，與電學濾波器相似，每一個帶管的小室是濾波器的一個網(wǎng)孔，管中的空氣質量相當于電學上的電感和電阻，稱為聲質量和聲阻。小室中的空氣體積相當于電學上的電容，稱為聲順。與電學濾波器類似，每一個帶管的小室都有自己的固有頻率。當包含有各種頻率成分的聲波進入第一個短管時，只有在第一個網(wǎng)孔固有頻率附近的某些頻率的聲波才能通過網(wǎng)孔到達第二個短管口，而另外一些頻率的聲波則不可能通過網(wǎng)孔只能在小室中來回反射，因此，我們稱這種對聲波有濾波功能的結構為聲學濾波器。選取適當?shù)墓芎褪疫M行組合就可以濾掉某些頻率成分的噪聲，從而達到消聲的目的。抗性消聲器適用于消除中、低頻噪聲。 把阻性結構和抗性結構按照一定的方式組合起來，就構成了阻抗復合式消聲器。微穿孔板消聲器一般是用厚度小于1mm的純金屬薄板制作，在薄板上用孔徑小于1mm的鉆頭穿孔，穿孔率為1%一3%。選擇不同的穿孔率和板厚不同的腔深，就可以控制消聲器的頻譜性能，使其在需要的頻率范圍內獲得良好的消聲效果。小孔消聲器的結構是一根末端封閉的直管，管壁上鉆有很多小孔。小孔消聲器的原理是以噴氣噪聲的頻譜為依據(jù)的，如果保持噴口的總面積不變而用很多小噴口來代替，當氣流經(jīng)過小孔時、噴氣噪聲的頻譜就會移向高頻或超高頻，使頻譜中的可聽聲成分明顯降低，從而減少對人的干擾和傷害。 有源消聲器的基本原理是在原來的聲場中，利用電子設備再產(chǎn)生一個與原來的聲壓大小相等、相位相反的聲波，使其在一定范圍內與原來的聲場相抵消。這種消聲器是一套儀器裝置，主要由傳聲器、放大器、相移裝置、功率放大器和揚聲器等組成。 消聲器的主要結構形式汽車消聲器按消聲原理與結構可分為抗性消聲器、阻性消聲器和阻抗復合型消聲器三類 1. 抗性消聲器 抗性消聲器是在內部通過管道、隔板等部件組成擴張室、共振室等各種消聲單元時，聲波在傳播時發(fā)生反射和干涉，降低聲能量達到消聲目的?？剐韵暺飨曨l帶有限，通常對低、中頻帶消聲效果好，高頻消聲效果差，貨車多采用抗性消聲器。2. 阻性消聲器 E是在內部排氣通過的管道周圍填充吸聲材料來吸收聲能量達到消聲目的的消聲器。對中、高頻消聲效果好，單純用作汽車排氣消聲器較少，通常與抗性消聲器組合起來使用。- 3 阻抗復合型消聲器 是分別用抗性消聲單元和吸聲材料組合構成的消聲器，它具有抗性、阻性消聲器的共同特點。對低、中、高頻噪聲都有很好的消聲效果。消聲器的主要作用降低發(fā)動機的排氣噪聲，并使高溫廢氣能安全有效地排出。消聲器作為排氣管道的一部分，應保證其排氣暢通、阻力小及足夠強度。消聲器要經(jīng)受500700高溫排氣，保證在汽車規(guī)定的行駛里程內，不損壞、不失去消聲效果汽車消音器在現(xiàn)實中的作用汽車噪聲主要來自汽車排氣噪聲。若不加消聲器，在一定速度下，噪聲可達100分貝以上。其次為引擎噪聲和輪胎噪聲，引擎噪聲在汽車正常運轉時，可達90分貝以上，而輪胎噪聲在車速為90公里/時以上時，可達95分貝左右。因此，在排氣系統(tǒng)中加上消聲器，可使汽車排氣噪聲降低20-30分貝。在引擎方面，以汽油引擎代替柴油引擎，可以降低引擎噪聲6-8分貝。常見故障及排除故障現(xiàn)象：一輛東風EQ1090D型汽車在行駛中消聲器出現(xiàn)放炮現(xiàn)象，停車檢查中，當把點火線圈高壓總火線拔下，在距離缸體34mm處試火，扳動分電器斷電觸點或搖轉曲軸時，跳火均正常，但發(fā)現(xiàn)分電器斷電觸點有燒蝕現(xiàn)象。用砂條修磨觸點并調整間隙至0.35-0.45mm后，發(fā)動機啟動后運轉正常，但是當汽車行駛約40公里后，消聲器又出現(xiàn)放炮現(xiàn)象。故障檢查與排除：根據(jù)上述現(xiàn)象對消聲器放炮原因進行了仔細分析，為找出故障癥結，檢查了點火次序、分電器斷電觸點臂彈簧力、點火正時、火花塞等均未發(fā)現(xiàn)問題。繼續(xù)檢查化油器空氣濾清器、氣門間隙也沒結果。再次啟動發(fā)動機又運轉正常，但是沒有多久舊病又復發(fā)了。 停車再次檢查分電器部分。通過拆卸和仔細檢查，終于發(fā)現(xiàn)斷電器觸點臂至低壓接線柱的銅膠線在拐彎處折裂，只剩下幾根細銅絲相連。更換斷裂的銅膠線后，故障現(xiàn)象消失。故障分析：當分電器低壓導線部分銅絲折斷后，導線橫截面積減小，從而使初級電路電阻增大，電路中電流減小，造成點火線圈產(chǎn)生的高壓不足。當發(fā)動機溫低時，雖然啟動困難一些，但啟動后發(fā)動機能正常運轉。待發(fā)動機溫度升高后，點火線圈溫度隨之升高，電阻又隨溫度上升而增大，所以點火線圈產(chǎn)生的高壓電會更加不足，高壓火花更弱，甚至斷火。由于不時斷火，氣缸里未被點燃的可燃混合氣排入消聲，在消聲器中膨脹時，遇到廢氣中的火星即發(fā)生爆燃，表現(xiàn)為消聲器放炮。The research of car mufferThe research background of car mufflerWith the rapid development of industry, people for the car comfort and vibration noise control requirements more and more strictly. According to foreign relevant data show that seventy percent of noise from the city traffic noise, and the traffic noise is mainly automobile noise. It serious polluters of the urban environment, affecting peoples life, work and health. So the noise control, is not only related to the ride comfort, but also related to the protection of the environment. But all the noise and vibration from, can cause some parts of vibration early fatigue damage, so as to reduce the car service life; The noise of the high skill damage the drivers hearing, still can make drivers quickly fatigue, thus vehicle driving safety constitute a great threat. So noise control, but also related to the cars durability and safety. So the vibration and noise and comfort that are closely related, not only reducing the vibration, lower noise, and to improve the ride comfort, and ensure that the products economy, make the vehicle noise control in the standard range.Noise evaluation index is mainly refers to the car, the noise and vibration value adaptability. Evaluation method can be divided into subjective evaluation and objective evaluation. Impact noise subjective evaluation car is the main factor comfort, loudness and certainty, for example can use semantic differential method on subjective evaluation. In an objective evaluation, can use PCNM noise device to measure test analysis; In addition simulation technology of finite element method (FEM) and the boundary element method (BEM) is also widely used. Reduce engine noise is the focus of automobile noise control. The engine is the source of vibration and noise. The noise of the engine by fuel burning, with gas institutions, timing gears and piston percussive noise of synthesis.Reduce engine noise will transform the body vibration source and sound sources, including the use of finite element analysis and design methods of engine, choose soft combustion process and improve the body structure stiffness, the tight fitting clearance, reduce the cylinder cover noise. For example in the oil pan is adding reinforcement and horizontal clapboard, in order to improve the stiffness of the oil pan, reduce vibration noise. In addition, for engine with damping materials is also an effective way. Damping materials can put the kinetic energy into heat. On the principle of damping processing is a kind of damping materials and components combined into one to vibration energy consumption. It has the following structure: free damped structure, interval free damping layer structure, constrained damping layer structure. Its the obvious reduced the resonance of the amplitude, speed up the free vibration of attenuation, and reduce vibration of the various parts of the ability to increase the parts in the critical frequency of vibration isolation above ability.Currently, there are some countries of experts design a kind of engine active vibration isolation system, used to reduce engine vibration, in order to achieve the purpose of reducing the noise.For the car noise control, except on the design optimization method and use of the optimization of the parts choose beyond, still can active control of noise. This is the sound attenuation technology, principle is: use electronic sound system with opposite phase noise produced the sound waves, make the vibration offset each other, in order to reduce the noise. The device USES extremely advanced deadened the electronic components, with excellent silencing effect, can be used to reduce the interior noise, engine noise, can also be used for the main engine support system, in order to offset the engine vibration noise.Car muffler principle is the exhaust pipe is made from two different length of pipe form, the two pipe first points again open intersection. Since the two pipe length difference is equal to the car out of the wavelength of the sound waves half, make two columns of sound in a superposition interference occurs when each other when they weaken offset sound intensity to make the voice decrease, and play a sound effect.Resistance is the main sexual muffler porous absorption material to reduce noise. The absorption material in air passages of the fixed on the wall or according to certain in the pipe arrangement in the way, constitutes the resistance of the muffler. When sound waves into resistance when sexual muffler, part of the sound energy in porous materials of pores in the friction and into heat energy dissipation off, make the sound waves through the muffler weakened. Sex is like electrical resistance on the muffler pure resistance circuit, and the absorption material similar to the resistance. So, people took the muffler called resistance sex muffler. Resistance to high frequency of sexual muffler attenuation effect is good, the low frequency sound effect is poorer. Resistance is the interface by mutation muffler tubes and a combination of room, and it seemed to be an acoustic filter, and electrical filter similar, each with a tube of a cell is a web filter hole, pipe to the air quality in electrical inductance and equivalent resistance, called the sound quality and resistance. The small room of air volume is equivalent to the electrical capacitance, called the sound. And electrical filter similar, each with a tube of small room has its own natural frequency. When contains various frequency component of the sound into the first short tube, only in the first natural frequency of the near net mesh some of the frequency of sound waves to through the nets hole reached the second short tube mouth, but some of the frequency of sound waves is not possible through the nets hole. Only in a small room in reflected back and forth, and, therefore, we call this a sound wave filter function for the structure of a acoustic filter. Selecting proper tube and room for combination. Can filter out some frequency components of the noise, so as to achieve the purpose of the dead. Resistance is applicable to eliminate the muffler, low frequency noise. The resistance of structure and resistance structure according to certain way together, they form a complex impedance muffler.Micro-perforated panel with thickness is generally muffler 1 mm of pure metal plate making, thin plate with less than 1 mm in diameter drill perforation, perforation rate for a 3% to 1%. Choose different perforation rate and the thickness different cavity deep, can control the spectrum of the muffler performance, in the need of the frequency range for good silencing effect. The muffler structure is a small holes in the closed end roots straight pipe, tube wall drilling has many small holes through them. The principle of the holes in the jet noise muffler for the spectrum of the basis, if the total area of the same but keep spout with many small vent to replace, when air holes, jet noise when after the spectrum will move to the high frequency or uhf, make of the spectrum can listen to sound composition reduced significantly, and thus reduce the interference and damage to people. The basic principle of active muffler is in the original field using electronic equipment to produce a with the original sound pressure equal and opposite phase of sound waves, make it within a certain range and the original sound field phase offset. The muffler is a set of instruments device, mainly by microphones, amplifiers, phase shift device, power amplifier and speaker etc.The main structure form mufflerAccording to the car muffler attenuation principle and structure can be divided into resistance the silencer, sex and impedance muffler compound muffler three categories1. The resistance in internal resistance muffler muffler is through pipes, clapboard components and other parts expansion chamber, resonant chamber, etc. Various kinds of silencing unit, sound in reflection and transmission occurs when interference, reduce the energy to sound attenuation purpose. Resistance muffler attenuation band limited, usually to low, medium frequency band sound effect is good, high frequency sound effect is poor, van used more resistance muffler.2. The resistance of the internal exhaust muffler E is through around the pipeline of filling the sound-absorbing material sound absorption energy to the muffler attenuation purpose. On the high frequency, silencing effect is good, as a simple car exhaust muffler less, often combined with resistance muffler use. -3 impedance muffler is compound respectively with resistance silencing unit and absorption material that constitute the muffler, it has resistance, resistance of the common characteristics of the muffler. For low, medium and high frequency noise all have good silencing effect.The main function of the mufflerReduce engine exhaust noise, and make the hot flue gas can safely and effectively eduction. As part of the exhaust muffler pipeline, should guarantee its exhaust expedite, and small resistance and enough strength. Be subjected to 500 muffler 700 high temperature exhaust, ensure the provisions in the car trip mileage inside, do not damage, dont lose silencing effectCar muffler in real in the roleCar noise from the car exhaust noise mainly. If be not added, muffler, in a certain speed, the noise of up to 100 decibels. Next is the engine noise and tyre noise, the engine noise in the car when the normal operation, up to 90 decibels, while tyre noise in the speed of 90 miles an hour or more, can reach 95 decibel. Therefore, in the exhaust system with muffler, can make the automobile exhaust noise reducing 20-30 decibels. In the engine, to gasoline engines instead of diesel engine, can reduce engine noise 6-8 decibelsCommon fault and ruled outFault phenomenon: a car EQ1090D type dongfeng automobile in motion appear muffler while phenomenon, stop the inspection, the ignition coil when high pressure total fleet pulled from 34 mm place in cylinder try fire, wind power distributor contacts or wave turned the crankshaft, jump fire all normal, but found distributor contacts have power ablation phenomenon. Article with sand the grinding contacts and adjust the clearance to 0.35-0.45 mm, after the engine starts operation, but when the automobile driving after about 40 km, muffler appeared adopting phenomenon.Fault inspection and exclude: according to the above phenomenon of muffl