Numerical Study On The Film Cooling Characteristics For The Longitudinal Ripple Heat Shield In The Afterburner

This paper performed experimental and numerical studies on the film cooling characteristics of the longitudinal ripple heat shield of the afterburner to provide some references for the advanced aero-engine heat shield design. The main contents and conclusions are as follows:1) The experimental system was designed and built to investigate the wall surface temperature of the longitudinal ripple heat shield, channel pressure distribution for some typical heat shield at different blowing ratios, opening ratios and amplitudes. Experiment data show that longitudinal ripple heat shield exhibits the different temperature distribution characteristics of high temperature area at peaks and the low temperature area at valleys comparing to the ordinary flat heat shield. On the same secondary flow rate, the film cooling efficiency of the ripple heat shield is greater than that of the plate heat shield. The improvement of the blowing ratio and increase of the opening rate can reduce the wall temperature and improve the film cooling efficiency of the heat shield. Film cooling efficiency firstly increases, and then decrease with the increase of heat shield amplitude. The change of the flow coefficient for heat shield with different structure has the similarity. With the increase of Reynolds number of secondary flow, the flow coefficient increases slightly. The flow coefficient increases firstly, and then tends to be constant with the increase of blowing ratio. For the same Reynolds number of secondary flow, the flow coefficient decreases gradually with the increases of opening ratio. However, with the increase of the amplitude, the flow coefficient increases firstly and then decreases.2) Based on the experimental models, numerical simulations of the longitudinal ripple heat shield were carried out. The comprehensive analysis shows that the numerical simulation results were similar with the experimental data. The difference between numerical data and experimental data is about 3%- 8% for the film cooling efficiency, and is about 6% for the flow coefficient.3) For the longitudinal sinusoidal corrugated heat shield, the effects of blowing ratio, hole spacing and corrugated plate structure on the flow and heat transfer of heat shield were revealed by computational analysis. The film cooling efficiency can be improved with the increase of blowing ratio M, the decrease of span-wise spacing ratio p/L and the stream-wise spacing ratio s/L. The film cooling efficiency increases slightly with the increase of the cooling channel height ratio H/L. The film cooling efficiency of the heat shield at the first sinusoidal area and the downstream windward side valley area can be improved by increasing the amplitude ratio A/L. The bigger heat shield wave numbers get, the higher film cooling efficiency at the windward side valley area of secondary flow downstream becomes. On the condition of M=0.5, H/L=0.158 and A/L=0.126, it appears the overflow phenomenon at the valley area of the first and second sinusoidal zones of the heat shield, which is detrimental for cooling the heat shield. With the increase of the blowing ratio, the channel height and the heat shield amplitude, the overflow phenomenon was suppressed. For the non-uniform holes structure, with the decrease of the row numbers of cooling holes in the windward side of the secondary flow, the film cooling efficiency is more and more uniform.4) For the non-sinusoidal longitudinal corrugated heat shield, the effects of three kinds of corrugated plate structure on the flow and heat transfer were analyzed. On the condition of Q_f?5.4kg/(m~2.s), with the increase of the shift distance of the wave peak for the non-sinusoidal longitudinal corrugated heat shield, the film cooling efficiency increases at the windward side of secondary flow, and decreases at the backward side. The phenomenon gets more obvious when the shift distance becomes longer. On the condition of Q_f>5.4kg/(m~2.s), the film cooling efficiency has not distinct for the three kinds of non-sinusoidal structures. At the downstream of heat shield, the film cooling efficiency tends to a certain value. The time reaching to the certain value becomes shorter when the Q_f is improved.