超临界碳氢燃料的射流特性研究

Investigation on Jet Characteristics of Supercritical Hydrocarbon Fuel

针对未来先进航空发动机的超临界燃油喷射混合问题,采用纹影法对超临界正十烷(n-decane)/正戊烷(n-pent ane)混合物在静止环境中的射流激波结构进行试验,同时采用理论分析的方法研究了射流的相变途径和流量特性。纹影照片显示,在试验工况下射流在喷口附近呈现出马赫波等激波结构,燃料的压力是激波结构的主要影响因素。理论分析表明:在混合物的临界点附近,燃料压力较高时更有可能导致相变。由于物性的不同,大分子与小分子碳氢燃料的相变途径存在一定的差异,小分子燃料在喷射过程中更容易发生冷凝。采用1维等熵计算方法可以较精确地计算高温高压碳氢燃料的流量。

The shock structures of supercritical n-decane/n-pentane mixtures into atmospheric environment was experimentally investigated by Schlieren method,and the phase transition path and mass flow rate characteristics of fuel jets were theoretically studied. Flow visualization showed that internal shock structures are observed near the nozzle exit for the test conditions and the fuel pressure has the primary influence on shock structures. Theoretical analysis revealed that fuel condensation phenomenon occurs more possibly at higher fuel pressures near the critical point and the condensation of small hydrocarbon fuel is more likely to occur than large hydrocarbon fuel because of the different thermodynamic properties. The mass flow rate of hydrocarbon fuel at high temperature and high pressure conditions can be calculated accurately using one-dimensional isentropic calculation method.