| The thermal protection of high-heat-flux walls is a one of key problems in the advanced aerospace propulsion science and technology.Aiming at the cooling requirement of rotating detonation engines,a combined air-fuel cooling scheme is proposed in the present study.By simplifying the real cooling structure as a semi-confined physical model,a numerical and experimental investigation is conducted.The concerned cooling structures are divided into two catalogues.The first one is based on the air cooling mode,including pure array-jets impingingment,integrated array-jets and pin-fins and integrated array-jets and parallel-ribs.The other one is based on the combined air-fuel cooling mode,including fule-cooled ribs and fule-cooled orifice plate.The main contents in current study are summarized as the follows.Firstly,a numerical study was performed to investigate the flow and heat transfer characteristics of an integrated array-jets and pin-fins cooling structure,on the base of pure air-ccoled scheme,with the main concern on the effects of pin-fins arrangement with respect to the impinging holes,fin-to-hole diameter ratio and pin-fin shape.In order to consider the highly-coupling feature of heat conduction and heat convection in the integrated cooling structure,an equivalent convective heat transfer coefficient on the heated side of target plate was introduced.By using the convective heat transfer coefficient on targeting surface and the equivalent convective heat transfer coefficient on heated side of target plate,an evaluation on the comprehensive performance of integrated cooling structure was made.The results show that the intergration of pin-fins in the array-jets impingement is helpful for enhanceing the heat transfer,with respect to pure array-jets impingement.With the increase of jet Reynolds number,the comprehensive cooling factor decreases.The inline mode of pin fins is more pronounced on enhancing the convective heat transfer when compared to the staggered mode.Simultaneously,the pressure loss in the inline mode is otherwise less than the staggered mode.With regard to the effect of fin-to-hole diameter ratio,it is found that the comprehensive performance evaluation based on the equivalent convective heat transfer coefficient on heated side of target plate is significantly different from that based on the convective heat transfer coefficient on targeting surface.Secondly,a numerical study was performed to investigate the array-jet and fuel-cooling combined structure.By embedding the fule channel in the parallel ribs,a fule-cooled-ribs structure was formed.Some factors were concerned in current study,including the fule flow rate,fule passage diameter,rib width and the passage sectional shape.The results show that the cooling effect of combined array-jet and fuel-cooling structure is better than that of pure air cooling,especially under the situations where the Reynolds number of air jet is small.Increasing the width of the ribs can adjust the heat absorption ratio between the cooling air and fuel and improve the temperature distribution of the wall.But when the width of the diaphragm increases,the air flow area is decreased and consequently increase the air flow resistance greatly.Among the three sections of fuel channel,the target temperature of circular and runway channel is slightly lower than that of rectangular channel,but the flow resistance of the fuel channel is far less than that of the latter.By embedding the fule channel in the orifice plate,a fule-cooled orifice plate structure was formed.With respect to the fule-cooled-ribs structure,the average temperature on the target surface of the fuel-cooling orifice structure is higher and the heat absorption ratio between the fuel and air and the temperature rise of the fuel are lower.At last,the above structures were experimental tested.From the measured temperature on the impact target,the heat transfer coefficient and the relative cooling efficiency of the fuel were obtained,and compared with the results of the numerical simulation.From current study,the influence of the cooling scheme and the working condition on the high-heat-flux wall cooling was preliminarily discussed. |
