煤油液滴高压蒸发特性

摘要

The transient droplet evaporation model including both sub-and super-critical mechanisms under high-pressure conditions was established on the basis of accurate prediction of the non-ideality of thermo-physical properties of the fluid using real-fluid models,as well as the high-pressure vapor liquid phase equilibrium of multi-components and the solubility of ambient gas into liquid phase using Equation of State (EoS) method.The evaporation characteristics of the kerosene droplet and the effect mechanisms of various factors on which under supercritical environments related to high-pressure staged-combustion liquid oxygen/kerosene rocket engine were studied.The results indicate that the subcritical evaporation state controlled by phase equilibrium was still behaved under weakly supercritical environment although the rise rate of droplet temperature was clearly enhanced under high-pressure conditions,whereas supercritical evaporation state controlled by diffusion appeared only under highly supercritical environment.The evaporation rate would be underestimated with ignoring the solubility of ambient gas under high-pressure and high-temperature conditions.Under the weakly supercritical environments,the rising ambient temperature would accelerate monotonically evaporation rate;the rising ambient pressure would suppress the evaporation rate under lower ambient temperature,whereas accelerate it under higher ambient temperature.In contrast,under the highly supercritical environments,the rising ambient temperature would accelerate the evaporation rate of the initial subcritical evaporation stage,whereas not affect the evaporation rate of the supercritical evaporation stage;the rising ambient pressure would also accelerate the evaporation rate of the initial subcritical evaporation stage,whereas suppress the evaporation rate of the supercritical evaporation stage,and the total lifetime of droplet would decrease slightly with the increase of ambient pressure.%采用真实流体模型描述高压下流体热物理性质的非理想性,并采用状态方程(EoS)法计算多组分高压气液相平衡及环境气体溶解性,在此基础上建立包含亚临界和超临界两种不同机制的瞬态液滴高压蒸发模型.针对中国新一代高压补燃液氧/煤油发动机,详细研究了煤油液滴在超临界环境下的高压蒸发特性及各因素影响机理.结果表明:高压环境会显著加快液滴温升速率,但弱超临界环境下仍然为相平衡控制的亚临界蒸发状态;只有强超临界环境下才较容易发生扩散控制的超临界蒸发状态.在高压、高温环境下,忽略气相溶解性将导致液滴蒸发速率明显偏小.针对弱超临界环境,温度升高会使液滴蒸发速率单调增加;压力升高则在低温下降低蒸发速率,而在高温下加快蒸发速率.针对强超临界环境,温度升高只提升初始亚临界蒸发阶段的蒸发速率,而超临界蒸发阶段的蒸发速率与环境温度无关;压力升高则同样会提升初始亚临界蒸发阶段的蒸发速率,但会降低超临界蒸发阶段的蒸发速率,此时的总蒸发寿命随压力升高小幅下降.