非均匀当量比对旋转爆震燃烧室性能影响的三维数值模拟研究

Three-dimensional numerical study on influences of uneven equivalence ratio on performances of a rotating detonation combustor

为研究入口当量比的不均匀分布对旋转爆震燃烧室性能的影响,建立了当量比在入口环缝的径向或周向的函数模型,将模型公式代入组分质量分数与当量比的关系式,得到组分质量分数在径向或周向的分布函数。通过Fluent软件中的自定义函数工具,构造入口边界组分的分布函数,利用三维瞬态欧拉方程模拟了C_(10)H_(22)/air旋转爆震燃烧室中爆震波的传播过程及流场特性,对比了不同当量比分布下爆震波及旋转爆震燃烧室性能参数的变化特征。结果表明:入口当量比的不均匀分布会影响爆震波的传播特性;当量比为0.4~1.6且沿径向非均匀分布时,随着入口面中线位置当量比的增大,爆震波的高度减小;当量比为0.4~1.6且沿周向非均匀分布时,随着变化周期数的增加,爆震波的高度几乎不受影响;当量比的不均匀分布会削弱旋转爆震燃烧室的增压效果和温升效果,沿径向不均匀分布的情况相较于沿周向不均匀分布的情况,影响更明显;旋转爆震燃烧室内,爆震波的诱导和反应区并非严格位于前导激波的正后方,而是位于前导激波的斜后方,且在曲率的影响下,在靠近燃烧室外壁面的区域,前导激波沿中径圆柱面的圆周线传播。

To investigate the effects of the inlet equivalence ratio distribution on the performance of a rotating detonation combustor(RDC),the radial or circumferential function model of equivalence ratio at the entrance of the RDC was established.The distribution function of component mass fraction in radial or circumferential direction was obtained by substituting the function model of equivalence ratio into the function of component mass fraction and equivalence ratio.The distribution function of entry boundary components was constructed by the user-defined function tool in the Fluent code.A three-dimensional transient Euler equation was employed to simulate the propagation process and flow field characteristics of detonation waves in a C_(10)H_(22)/air RDC, and the characteristics parameters of the detonation waves and RDC were compared under different equivalence-ratio distributions. The results show that the uneven distribution of the inlet equivalence ratio will affect the characteristics of the detonation waves. When the equivalence ratio ranges from 0.4 to 1.6 and is not uniformly distributed along the radial direction, the height of the detonation wave decreases with the increase of equivalence ratio at the midline of the inlet surface. When the equivalence ratio ranges from 0.4 to 1.6 and the distribution is non-uniform in the circumferential direction, the height of the detonation wave is almost not affected with the increase of the number of changing periods. The uneven distribution of equivalence ratio will weaken the pressure-gain effect and temperature rise effect of the RDC, and the influence of the uneven distribution of equivalence ratio along the radial direction is more obvious than that along the circumferential direction. In the RDC, the induction and reactant region of detonation wave is not strictly behind the leading shock wave, but is located at the oblique rear of the leading shock wave, and under the influence of curvature, the leading shock wave propagates along the circumference of the middle diameter cylinder near the outer wall of the RDC.