音速喷嘴内水蒸气自发凝结流动自激振荡和分歧现象

Spontaneous Condensation Steam Flow with Self-Excited Oscillation and Bifurcation Phenomenon in Sonic Nozzles

气体在喷嘴中流动伴有很大的温降,会使其中的水蒸气发生凝结,并对其计量产生影响.针对音速喷嘴中过热水蒸气自发凝结流动产生的非稳态自激振荡和流动分歧现象,建立了考虑黏性的水蒸气自发凝结数值模型;根据凝结诱导的气动激波的振荡幅度将自激振荡分为3种不同的模式,其中模式Ⅲ的压力波动会波及喉部上方,且会出现非对称流动分歧现象,而模式Ⅰ中气动激波仅在平衡位置附近小幅度振荡;最后研究了自激振荡对喷嘴的质量流量的影响,并给出了相应的修正系数,最小值为0.988,需要加以重视.

The gas temperature will drop greatly when the gas flows through the nozzle,which leads to the condensa-tion of the vapor. To investigate the phenomenon of self-excited oscillation and bifurcation induced by spontaneous condensation of the pure superheated steam flow,a numerical viscous model of supersonic nozzle flow was established. Three self-excited periodic oscillation modes were classified according to the oscillation amplitude of aerodynamic shock. It is found that the pressure fluctuations spread to the upstream of the nozzle throat in mode Ⅲ,while the shock in modeⅠoscillates with small amplitude. Moreover,the effect of self-excited oscillation on the mass flowrate of nozzle was studied in detail. Correction factor for condensation effect was obtained and the minimum value was 0.988,which calls for pay more attention.