超临界燃料喷射过程大涡模拟:状态方程的影响

Effect of equations of state on numerical simulation of supercritical fuel spray

中文关键词: 大涡模拟  超临界  燃料喷雾  数值模拟  状态方程  密度梯度

英文关键词: LES  supercritical  fuel spray  numerical simulation  equation of state

中文摘要:

      针对Sandia实验室关于正庚烷喷雾的实验数据，基于CONVERGE软件采用大涡模拟方法对以正庚烷为燃料喷入超临界环境中的雾化过程进行了数值模拟。以实际气体状态方程Soave-Redlich-Kwong (SRK)和Peng-Robinson(PR)两个方程为基础，重点研究了两状态方程对超临界状态下燃料喷雾的发展过程、射流密度变化、燃料喷雾的质量分数随温度变化的影响，并用模拟所得与实验结果进行对比。结果表明，同一时间下PR方程模拟的燃料喷雾的贯穿度更大；两实际气体状态方程下射流表面都有大的密度梯度，并与实验所得的密度值相吻合；PR方程对于超临界工况的计算可能更优于SRK方程。燃料质量分数随温度的变化符合实际的情况，密度值的急剧变化验证了射流表面是一个介于液体与超临界流体之间的混合层，并可以通过密度梯度来推测混合层位置。

英文摘要:

      Large eddy simulations of injection and atomization of n-heptane under supercritical conditions were performed using the commercial CFD software CONVERGE. The predictions were compared to experimental data provided by Sandia National Laboratories. Based on two cubic equations of state, i,e, SRK and PR equations, the effect of equations of state on dynamics of fuel spray、flue jet density、the variation of mass fraction of fuel spray with temperature was studied and compared with the experimental data. The simulated results show that the fuel spray penetration predicted by SRK state equation is deeper, and there exits a significant density gradient on the jet flow interface for both equations,.The predictions agree well with the experimental results, but the PR equation behaves better than the SRK equation under supercritical conditions. The variation of mass fraction of fuel spray with temperature is well predicted. The sharp change in density verifies that the jet flow interface is a mixing layer between the liquid and its surrounding supercritical fluid.The density gradient can be used to identify the mixed layer position.