摘要
我们针对高超声速燃烧加热风洞喷管流动的大扩张比、高马赫数、高低温气体并存和高水蒸气含量的特点,发展了兼顾高温气体效应与水蒸气非平衡凝结过程影响的有限体积计算方法,对伴随水蒸气凝结的喷管流动的机理开展了数值研究.计算中,凝结模型采用Hill矩方法进行模拟.数值分析着重关注喷管进出口气流的参数变化.结果表明,燃烧加热风洞的凝结问题计算中,应考虑高温气体效应的影响,以保证结果的合理性;随总温、水蒸气含量等参数的不同,喷管流动中的凝结现象会呈现明显不同的特征,适量的水蒸气含量和较低的总温会使得凝结后的流场参数发生显著改变.
Water vapor condensation is numerically investigated in hypersonic nozzle flows which are characterized by large expansion ratio, high Mach number, coexistence of high- and low-temperature gases, and high water vapor mass fraction. The numerical method combines the inviscid equilibrium flow model with the extended Hill＇s moment method for describing the water vapor phase transition. The non-equilibrium process of condensation is modeled by a consistently classic nucleation theory and the Gyarmathy droplet growth law. Firstly a typical case of exit Mach number 6 is studied. Different from the conventional supersonic condensing nozzle flows, condensation in the hypersonic nozzle flows mainly takes place far downstream of the nozzle throat, where the flow Mach number is highly supersonic, and, therefore, the unsteadiness due to condensation shock has no importance. It is found that condensation in hypersonic nozzle flow may lead to a significant change of flow state at the nozzle exit and, therefore, a deviation from the designed state. The non-uniform distribution of the liquid droplets and the possible existence of condensation shock greatly deteriorate the flow quality. Then, impacts of different inlet conditions on the outlet parameters are discussed. Results show that the extent of condensation in hypersonic nozzles varies greatly due to the change of initial conditions. The extent of condensation firstly increases with the initial water vapor mass fraction anddecreases after a critical point, which is ascribed to the higher enthalpy of the inlet flow with a higher vapor mass fraction for a given initial temperature. The high vapor mass fraction （after the critical value） leads to a very high static temperature at the nozzle exit （and inside the nozzle） and therefore weak condensation is found.
