外文翻译-V8发动机排气管内震动与排气噪声特性的分析与研究—关于排气歧管最优化连接的研究.doc

1、Analysis of pulsation inside pipe and study on exhaust soundCharacterstics of V type 8 cylinder engine-study onOptimized front pipe junction structureABSTRACTThe research of pulsation wave propagation inside exhaust pipe in V8 engine shows that pulsation from engine was changed by joining two front

2、pipes in entire exhaust pipe. In short ,frequency of pulsation inside the pipe is not always equal to engine explosion fitst order frequency or its harmonics.Accordingly,structure of junction has been studied,which indicated that having volume at junction add edgine revolution first order component

3、pressure fluctuation to blow-down wave component and makes exhaust sound worse.This phenomena is caused by irregular explosion interval on each bank of V8 engine and phase delay of propagation at junction.INTRODUCTIONRecently,V type engines meeting the LEV and ULEV emission regulations are equippen

4、with a large capacity catalytic converter for each of the left and right banks,and the front pipes ten to be long and join in the middle of overall length of the exhaust sustem(Fig.1)and substantial changes have been made in the exhaust pipe structure.An optimum exhaust system superior in quietness

5、and engine performance should be considered.Irregular exploslon intervals among cylinders on each bank of the V8 engine produce pulsation with complex characteristics inside the left and right front pipes,which is different from pulsation inside front pipes in the other type of engines,for instance

6、,in-line 4 cylinder engine and so on.There has been no studies of the mutual effect between pulsation inside right front pipe and that inside left front pipe and no studies of propagation of pulsation at junction of the front pipes.While analysis of junction has been studied regarding flow,there has

7、 been no irregular explosion intervals among cylinders on each bank of the V8 engine.While attenuation technique with muffler has been widely studied,there has been few studies with junction.Moreover,it is necessary to optimize the junction for exhaust sound quality recently focused on.In this paper

8、,propagation of pulsation at junction was investigated to optimize the front pipe junction of V8 engine with experiments and numerical calculation.Linear frequency response calculation of exhaust noise using finite element method or the likeis not suitable for boundary condition and variety of frequ

9、ency inside entire pipe of V8 engine.On the other hand,acoustic calculation using fluid dynamics model has studied to predict sound pressure and recently improved to apply to full size model with good results in modified one dimensional calculation,In hybrid linear/three-dimensional calculationand i

10、n hybrid one-dimensional/three-dimensional calculation.On the other hand there has been no application to analyzing mechanism of phenomena.In this paper,the mechanism of engine revolution first order component pressure fluctuation caused at the front pipe junction of V8 engine exhaust pipes was anal

11、yzed by measuring pressure inside pipe and calculation with fluid dynamics model from intake to exhaust with comparison between measured and calculated results.PULSATION WAVE PROPAGATION INSIDE EXHUAT PIPE WITH LONG FRONT PIPE INSTALLED IN V TYPE 8 CYLINDER ENGINETo meet requirements of the emission

12、 regulations,the exhaust pipe tends to be of a shape shown in Fig.1. The pipes of exhaust manifold join near the exhaust port at each of the left and right banks and then forms left and right front pipes,each of which is equipped with a large capacity catalytic converter,and resultant long front pip

13、es join in the middle of the entire exhaust pipe.Fig.2 shows the pulsation inside the pipe at each part of the exhaust pipe during steady operation at a constant engine speed.Seven major peaks were observed at the outlet of exhaust port during engines second rotation,while there were eight peaks at

14、the junction having a uniform interval between peaks and an equal peak level.That is,the frequency of the pulsation wave propagated inside the pipe was changed by joining two front pipes.In the case of the most genersl in-line 4 cylinder engine,the frequency of the pulsation wave inside the pipe is

15、almost equal to engine explosion first order frequency or its harmonic frequencies at each of the exhaust pipe. There is an essential difference in the pulsation propagating process inside the pipe between the V type 8 cylinder engine and in-line 4 cylinder engine.Fig.3 shows the order of explosion

16、in each cylinder of the V type 8 cylinder engine,where explosion does not occur alternately but at irregular intervals of crank angles of 180,90,180 and 270 degrees on each bank. Next,results of measurement of the pulsation wave at each part inside the front pipe are shown in Fig.4.Considering exhaust requirements,the pulsation wave at the exhaust port outlet was detemined by the length from exhaust port toexhaust maniflod junction and the volume of the j