外文翻譯--內(nèi)燃機(jī)主動(dòng)衰減排氣閥門設(shè)計(jì)（英文 ）

1、Design of an active exhaust attenuating valve for internal combustion engines.R. Boonen, P. Sas KULeuven, Department of Mechanical Engineering, Celestijnenlaan 300 B, B-3001, Heverlee, Belgium e-mail: rene.boonen@mech.ku

2、leuven.ac.beAbstract An active silencer to attenuate internal combustion engine exhaust noise is developed. The silencer consists of an electrically controlled valve connected to a buffer volume. The pulsating flow from

3、the engine is buffered in the volume and the valve resistance is continuously controlled such that only the mean flow passes to the atmosphere. This flow is free of fluctuations and consequently free of sound. The design

4、 of the active silencer is carried out using electrical analog circuits. First, the interaction between the active silencer and the engine will be studied using an analog circuit including the combustion engine and a lin

5、earized active silencer. Then, a detailed valve model is built in a separate electrical analog circuit. It includes the electrical, the mechanical and the flow-dynamic properties of the actuator valve. The actuator valve

6、 concept is then simulated, from which a prototype can be constructed. The active silencer has been tested on a cold engine simulator. This device generates realistic exhaust noise with the associated gas flow using comp

7、ressed air. The silencer can attenuate pulsations from engines at very low revolution speed, without passive elements preconnected between the engine and the active silencer. This is not possible using loudspeaker based

8、active silencers.1 IntroductionThe internal combustion engine has found its way into a broad spectrum of applications, wherein transporta- tion has far the largest share. The success of the in- ternal combustion engine h

9、as also created problems associated with it, such as air pollution and environ- mental noise.During the past decades, legislation has come for- ward which stringently reduces air pollutants, green- house gases and noise

10、emission. Today, the noise emission limits are set to 74 dBA for cars and 80 dBA for heavy vehicles [1]. For cars, the emission of CO2 is limited to 190 g/km (EU III-directive), and will be further reduced to 170 g/km (E

11、U IV) in 2003 and 140 g/km (EU V) in 2008. Although these directives are not related at first sight, they do have their impli- cations on the exhaust system development. It will be necessary to develop exhaust systems wi

12、th minimum back pressure to the engine, to maximize engine effi- ciency and this without loss of noise attenuation per- formance. A way out to this problem is to develop active exhaust systems.Much research on active noi

13、se cancellation in ducts is carried out in the recent years and numer- ous patents have been generated. Loudspeaker sys-tems are successfully applied and commercial avail- able in ventilation channels [2]. Loudspeaker sy

14、stems are also developed for stationary diesel engines, for example by Detroit Diesel Corporation [3] and the KEBA AISTM-system. For cars, active loudspeaker systems are developed for six or more cylinder en- gines [4].

15、For four-cylinder engines, loudspeaker sys- tems suffer from problems as the low sound generat- ing efficiency and reliability in the extreme conditions of an engine exhaust. Applying a controllable valve in the exhaust

16、duct is a more robust concept. The restricting element of the valve can be small and rigidly constructed. It can be exposed to the exhaust gas directly. The resistance of the valve is continuously vari- able by applying

17、an external signal. It is assumed that the valve is purely resistive, it isn’t capable to store energy from the gas flow. As consequence of the gas flow, the valve generates a pressure drop over it. Ac- tive noise cancel

18、lation is achieved, when the volume velocity behind the valve is kept constant. In figure 1, the first graph demonstrates how the sound pressure influences the fluid flow via the valve resistance characteristic. The seco

19、nd graph demon- strates how the opposite fluctuating flow is generated from the mean pressure drop over the valve by vary-33wherein R0 is the initial valve resistance. The same result can be achieved by a controller whic

20、h mini- mizes the pressure UZ after the valve:d UZ d t = Z d IRd t = 0 (5)This simple consideration has two important conse- quences. First, by balancing the volume-valve com- bination, it is always possible to control t

21、he flow of any volume velocity source. Second, the resistance R0 can be chosen freely with the only restriction that the resistance R(t) remains always positive. The re- sistance R0 can be optimized to obtain minimum bac

22、k pressure to the engine, resulting in a higher engine ef- ficiency.2.2 Electrical equivalent model for the engine and the silencerThe simple model, presented in figure 2, looks not very realistic for an engine exhaust s

23、ystem, therefore the model will be expanded. The volume velocity source will be replaced by an engine model, and a duct is connected between the engine and the active silencer. A tail pipe is connected behind the silence

24、r. The resulting circuit is presented in figure 3.The left part of the circuit is the engine model. The four variable capacitors represent the four en- gine cylinders, who’s volume varies sinusoidal be- tween maximum and

25、 dead volume. The upper set of switch-resistors represent the intake valves, the lower set the exhaust valves. The switches are actuated in the same sequence as the cam shaft operates the en- gine valves. The four short

26、transmission lines behind the exhaust valve resistors represent the four exhaust conduits between the cylinder ports and the exhaust manifold junction. The intake side is connected to a voltage source UB representing the

27、 atmospheric pres- sure and equals 100 kV. The combustion is simulated by charging the cylinder capacitor by a pulsing cur- rent source parallel over the capacitor. The charge time point corresponds to the ignition time

28、point.The right part represents the active exhaust sys- tem. The silencer is connected to the engine via the duct represented by the transmission line T. The ca- pacitor C represents the buffer volume and the vari- able

29、resistor R(t) the control valve. The transmis- sion line Tt represents the tail pipe and the resistor- inductor combination Ra and La corresponds to the spherical radiator impedance. In simulation, a collo- cated feedbac

30、k controller conducts the control valveFigure 3: Electrical analog circuit for an internal combustion engine equipped with an active noise con- trol valve.resistance. This controller is only needed to deter- mine the act

31、ive silencer properties. In practice, other control strategies must be applied to handle the time delay between the valve action and its effect in the error sensor. In principle, the back pressure to the engine can be se

32、t to any desired value by choosing the appropriate buffer volume capacitor C. In practice, it will result in a compromise between available space for the active silencer and acceptable back pressure.Figure 4: Simulated i

33、ndicator diagram from the cir- cuit presented in figure 3.2.3 Simulation resultsIn the electrical circuit of figure 3, the engine param- eters of a 2000 cm3 engine are introduced. The ducts have a diameter of 60 mm. The

34、duct between the en- gine and the silencer is 500 mm long, the tail pipe 700 mm long. The back pressure is set to 10 kPa, resulting in a buffer volume of 12 dm3. The initial actuator valve resistance is set to 200 k? (1