The Research Of Jet Mixing Based On The Pulsed Mini-jet At The Different Reynolds Numbers

Based on the efficiency improvement of fossil fuel combustion,the jet control under different Reynolds number is carried out through experiments,and the mixing mechanism of jet is explored.In this experiment,a single high frequency valve periodically pulsed mini-jet is used for active control.The experiment uses the hot wire measurement technology to measure the axial and radial distributions of the mean velocity and turbulence intensity at different positions of the whole flow field,and then change the mass flow ratio Cm,and frequency fe for seeking optimal parameters of jet mixing.The mini-jet is located at the upstream of the nozzle exit at the position of x=0.85 D.The experiment parameters are mass flow ratio Cm=0~13%,the duty ratio dc=15%,excitation frequency fe=17~420 Hz,the jet exit Reynolds number Re=4×10~3~2.4×10~4.In general,for the free jet,the physical statistics of the free jet or controlled jet show that the critical Reynolds number is existed.When the Reynolds number is higher than the critical Reynolds number,the sensitivity of the flow is weaker than that of the Reynolds number below the critical Reynolds number.the main jet controlled by the pulsed micro jet promotes the mixing characteristics in the downstream flow field,further enhances the velocity decay,propagation,diffusion and entrainment,and each Reynolds number has the best Cm and the best fe.This effect is due to the incomplete vortex ring structure and turbulence.