超临界燃料在喷嘴附近的相变和流动过程

Phase Transition and Flow Process of Supercritical Fuel near Injector Nozzle

关键词:  超临界燃料  实验研究  一维分析  相变和冷凝  流动参数分布

Key words:  Supercritical fuel  Experimental research  One-dimensional analysis  Phase transition and condensation  Flow parameters distribution

摘要:

为了研究超临界碳氢燃料喷射特性，采用实验结合一维分析的方法，对超临界正十烷/正庚烷/正戊烷混合物喷射到静止大气环境中的相变和流动过程进行了研究，揭示了燃料在喷口附近发生相变的途径，获得了相变分界线和喷嘴内部一维流动参数分布。研究结果表明:当喷射温度接近临界温度时，超临界正十烷/正庚烷/正戊烷混合物喷射过程中，会在喷嘴内部及喷口下游发生相变而产生冷凝；相变冷凝的转化过程发生在一定的温度范围内，在超临界压力下，射流发生完全冷凝的喷射温度为510K；喷射过程的相变分界线与相态之间的界面线并不重合；超临界正十烷/正庚烷/正戊烷混合物喷射到静止大气环境中时，在喷口处达到了当地声速，此时当地静压与喷射压力的比值约为0.64，静温与喷射温度的比值在0.97以上；不同喷射工况下，喷嘴内部的一维流动参数变化规律基本一致，比热比和压缩因子是影响无量纲流动参数分布规律的重要影响因素。

Abstract:

To explore the supercritical hydrocarbon fuel injection characteristics，the phase transition and flow process of supercritical n-decane/n-heptane/n-pentane mixtures injected into stationary atmospheric environment were studied by experimental and one-dimensional analysis method，and fuel phase transition path near the injector exit，phase transition boundary and one-dimensional flow parameters distribution inside the injector were obtained. The results revealed that phase transition and fuel condensation phenomenon occur when supercritical n-decane/n-heptane/n-pentane mixtures injected near the critical temperature. The condensation processes of fuel mixture occur within a certain temperature range and complete condensation occurs at the injection temperature of 510K under the supercritical injection pressure. The phase transition boundary line does not coincide with the phase boundary line. When the supercritical n-decane/n-heptane/n-pentane mixtures injected into stationary atmospheric environment，the velocity of the mixtures reaches the local sound speed at the injector exit，the ratio of local static pressure to injection pressure is about 0.64 and the ratio of local static temperature to injection temperature is above 0.97 in present test conditions. The one-dimensional flow parameter distributions are roughly coincident at different injection conditions，and the analysis results showed that the specific heat ratio and compressibility factor have significant influences on the distribution of one-dimensional flow parameters.