超高速流动中气膜冷却技术的研究综述

Review on Film Cooling Technology in High Supersonic Flow

气膜冷却有长航时、高冷却效率和可重复使用等优点,被认为是天地往返航天器中极有前景的热防护技术。在超声速流动中气膜冷却研究主要集中在切向槽缝射流构型。在超高速流动中,钝头逆向射流气膜冷却研究也已经出现,且相关研究表明该技术有良好的防热减阻效果。在冷却剂物性上,冷却剂分子量、比热、黏度和声速均会影响冷却效率,其中比热的影响较大,模化研究需要注意该因素。在流动条件中,吹风比、激波和边界层状态均会影响气膜冷却效率。对切向气膜冷却来说,激波入射会降低冷却效率,这是因为激波会提高当地绝热壁温,同时加快冷却剂的耗散。然而,激波与交叉射流离散孔气膜冷却相互作用的报道较少,亟须精细化研究探索其作用规律及机理。

Film cooling,characterized by long-lasting duration,high cooling efficiency,and reusability,is considered a highly promising thermal protection technology for spacecraft in Earth-to-orbit missions.In the supersonic flow scenario,the research on film cooling has mainly focused on the configuration of tangential slots.Besides,investigations into the use of film cooling by reverse jet on the blunt nose in high supersonic flow have emerged,with promising results indicating effective thermal protection and drag reduction.Considering coolant properties,molecular weight,specific heat,viscosity,and speed of sound all influence the cooling efficiency,the specific heat playing a significant role requires careful evaluation in scaling studies.In the flow conditions,the blowing ratio,the shock waves,and the boundary layer state also affect the film cooling effectiveness.For tangential film cooling conditions,the presence of impinging shock waves diminishes the cooling efficiency,because these shocks elevate the local adiabatic wall temperature while accelerating the coolant's dissipation.Nevertheless,there are limited studies on the interaction between shock waves and cross-jet film cooling,thus further detailed investigations to explore the underlying principles and mechanisms are necessary.