軸対称超音速衝突噴流のノイズ特性におけるNPRの影響

抄録

This study was focused on the noise characteristics of axisymmetric supersonic impinging jet. The diameter of the jet is D= 5.2 mm. The jet was issued from Laval nozzle with designed Mach number M_j = 2.0. The impinging plate was inserted into the jet and the impinging distance between nozzle exit and the center on the plate surface was varied 15≦ L ≦40. Moreover the plate was inclined for three angle conditions, α=0, 15, 30 deg. and NPR, which was pressure ratio of chamber pressure P_c to atmospheric pressure P_a, was changed from 3.0 to 4.0. As a result SPL is increased with impinging distance for NPR ≧ 3.5. The static pressure on the plate is decreased with increasing the impinging distance. For NPR = 4.0, the both of SPL and the pressure varies cyclically and some peaks and valleys are observed. Especially impinging distances where show peaks of SPL, dominant frequency was observed in frequency analysis results, and these tendencies vary with impinging distance and inclined angle of the plate.