Muffler Conceptual Research On Jet Noise Of Rocket Engine Ground Test

The rocket engine will generate strong jet noise, which is the tremendous pollution source. It has great sense to study the noise countermeasure of the jet noise created by the rocket engine.This paper analyzed the characteristics of the three kinds of basic sound source and carried on the comparison. The turbulent current noise source sprayed by the rocket engine belong to the four-pole source of the three kinds, its sound power level direct proportion to the high power of the airstream speeds. Concentrate on reducing the velocity of the exhaust, the paper carried on the research of the mechanism that engender the deceleration and noise reduction by shock wave and got the connection of the wedge semiapex angle, shock wave angle, Mach number of the wave front with sound power level. Analyzed by Matlab, it can obtained that the decrease of sound power lever followed by the magnification of shock wave angle and the decline of Mach number of the wave front. If the airstream is supersonic through the first wedge, then it needs the second wedge until it declined to subsonic, after that the deceleration and noise reduction can continue through diffusion part. The sound power lever reduced followed by enlarging the wedge semiapex angle. By setting tube in the muffler, it can get the effect of the deceleration and noise reduction is better than setting wedge in the muffler. Carried on an analysis towards the deadening program which showed the same result with programming analyse. Concentrate on reducing the velocity of the exhaust as the same, the paper advanced that using the convergent-divergent channel as muffler. Through programming analyzed by Matlab, it obtained the connection of the export speed coefficient, Mach number, temperature with the export arearatio. The result of example analysis indicated that the sound power lever diminished along with the diminution of the throat diameter, but it was not apparent. The sound power lever was reduced greatly by enlarging the export area ratio.Carried on analysis of silencing of noise by minipore ejecting, which make use of the minipore to change the low-frequency noise to high frequency. It was proved that this kind of muffler have a nice result in reducing the sound power lever regardless at subjective or objective by design a muffler for a pressure relief valve. The result of example analysis indicated that the pressure loss was less enough to guarantee the airstream was lucid.The paper made emulate analysis to the interior flow field and got the free frequency and mode through modal analysis. It can avoid the free frequency of muffler be closed to noise source by thickening the shell and changing the stiffness of the muffler.