连续旋转爆轰燃烧室增压特性的热力学分析

Thermodynamic Analysis on Pressurization Characteristics of Continuously Rotating Detonation Combustor

关键词:  旋转爆轰  数值模拟  增压比  熵  吉布斯自由能

Key words:  Rotating detonation  Numerical simulation  Pressurization ratio  Entropy  Gibbs free energy

摘要:

为了探究连续旋转爆轰燃烧室(CRDC)增压特性产生的根本原因，利用二维可压缩欧拉方程对正庚烷-空气CRDC进行了数值研究，从熵和自由能变化的角度对比了燃气轮机燃烧过程、等压燃烧过程、旋转爆轰燃烧过程和等容燃烧过程的差异，并分析了轴向尺寸对CRDC增压特性的影响。研究表明:对比等压燃烧过程，旋转爆轰燃烧过程熵增更小，吉布斯自由能损失更小，出口工质做功能力更强；但旋转爆轰燃烧过程增压能力远小于等容燃烧过程。轴向尺寸越小，旋转爆轰燃烧过程中经斜激波作用的工质比例越小，吉布斯自由能损失越小，CRDC的增压能力越大。当轴向尺寸由200mm逐渐减小至100mm，CRDC的热效率始终保持在99%以上，增压比由1.8279提高至2.2167，吉布斯自由能减小量由5067.1kJ/kg降低至4914.6kJ/kg，然而等容燃烧过程增压比为6.1467，吉布斯自由能减小量为4192.2 kJ/kg，两者仍有较大差距。

Abstract:

Based on compressible Euler equation， two-dimensional numerical study was conducted to investigate the basic reason of pressurization characteristics in continuously rotating detonation combustor (CRDC) using heptane-air mixture. The difference from gas turbine combustion， isobaric combustion， rotating detonation combustion and constant-volume combustion was discovered by studying the entropy and Gibbs free energy. And the effects of axial length on pressurization characteristics were analyzed. It can be concluded that compared with that in isobaric combustion， the smaller entropy increase in rotating detonation combustion contributes to a smaller loss of Gibbs free energy and a stronger potential power. But the pressurization ratio in rotating detonation combustion is still much smaller than that in constant-volume combustion. With the decrease of axial length， the ratio of the working fluid passing through the oblique shock in CRDC decreases， so the loss of Gibbs free energy decreases， and the pressurization characteristics of CRDC strengthens. When the axial length decreases from 200mm to 100mm gradually， the thermal efficiency is always greater than 99%， the pressurization ratio increases from 1.8279 to 2.2167， and the loss of Gibbs free energy decreases from 5067.1kJ/kg to 4914.6kJ/kg， but there are also great gaps as the pressurization ratio is 6.1467 and the loss of Gibbs free energy is 4192.2kJ/kg in constant-volume combustion.