空气流量对煤粉-空气两相旋转爆轰波的影响

Effect of the air mass flow rate on coalair twophase rotating detonation waves

  • 摘要: 理论上旋转爆轰发动机比传统爆燃发动机具有更高的热循环效率,因此被广泛研究。 但目 前关于气固两相旋转爆轰发动机的研究较少,而气固两相旋转爆轰发动机有望用在固体冲压发动 机上。 基于非预混的煤粉-空气旋转爆轰发动机进行二维数值模拟,气相采用具有体积反应的非 定常黏性模型,固相采用离散相模型,煤的表面燃烧反应采用动力学/扩散限制速率模型。 主要研 究空气流量对气固两相旋转爆轰波的影响,分析了不同模态下旋转爆轰发动机的工作特性,并将数 值模拟结果与实验结果进行对比。 结果表明:计算所得旋转爆轰波波速与实验结果吻合较好,旋转 爆轰波流场与实验研究定性一致。 由于入口附近颗粒注射速度低于空气注射速度,颗粒层与空气 层不能完全重合,导致爆轰波前局部当量比大于全局当量比。 空气流量从 38.14 kg/ s 增加到 114.40 kg/ s 时,爆轰波的速度和温度峰值先增大后减小,而压力峰值不断增大。 空气流量为 49.03 kg / s 时,爆轰波速度最大,并且发生模态转换过程。 相对单波模态,双波模态下的爆轰波的 强度和稳定性都有所下降。 根据燃烧室内气固两相的分布情况,爆轰波稳定传播时流场可分为填 充区、爆轰产物区和爆燃产物区 3 个区域。 研究结果对气固两相连续旋转爆轰发动机的实验研究 和工程应用具有一定的指导意义。

     

    Abstract: A lot of studies on rotating detonation engines have been carried out due to the theoretically higher thermal efficiency compared with traditional deflagration engines. However,there are few investigations reported on gassolid twophase rotating detonation engines which may be used as solid ramjets. In this paper,twodimensional numerical simulations based on a nonpremixed coalair rotating detonation engine were carried out. The unsteady viscous model with volumetric reaction was used for the gas phase,the discrete phase model was used for the solid phase,and the kinetics/diffusion limited rate model was used for the surface combustion of coal. The effect of air flow rate on the rotating detonation wave was studied. The working characteristics of the rotating detonation engine under different modes were analyzed and the numerical simulation results were verified by experiments. Results show that the calculated velocity and flow field of the rotating detonation agree well with the experimental results. The layers between air and particles could not completely coincide with each other because the particle injection velocity was lower than air injection velocity,and thus the local equivalence ratio before the detonation wave was higher than the global equivalence ratio. As the air mass flow rate increased from 38.14 kg/s to 114.40 kg/s,the velocity and temperature peak of the detonation wave first increased and then decreased,and pressure peak increased gradually. The detonation velocity reached the maximum and the mode transition process occurred when the air mass flow rate was 49.03 kg/s. Compared with 〖JP〗single wave mode,the strength and stability of double wave mode were decreased. According to the gassolid phase distribution in the combustion chamber,the flow field during the stable propagation of rotating detonation wave can be divided into three zones:filling zone,detonation product zone and deflagration product zone.

     

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