The gas-particle two-phase flow in a convergent-divergent nozzle is encountered in many applications like solid-propellant rocket motors (SRMs). The “Particle-free Zone” adjacent to the nozzle wall is crucial for the nozzle performance which is closely related to the specific impulse of the motor. Though it has been usually observed by many investigators, the existence of the particle-free zone in different nozzles and its effect on nozzle performance are still ambiguous. In this research, we investigated the two-phase flow with monodispersed micron particles in a nozzle using a two-way coupled Eulerian-Lagrangian model and found that the particle-free zone does not exist for smallest particles (d_p = 1.0 μm). Moreover, we built a theoretical model for predicting the extent of the particle-free zone by calculating the trajectory of the particle closest to the nozzle wall. The effects of the particle size, total pressure, total temperature and nozzle geometry on the particle-free zone were studied. Finally, we analyzed the nozzle performance and found that the gas velocity at the outlet and the thrust do not change with particle size monotonously, and the medium-sized particles cause the largest thrust loss.

在固体推进剂火箭发动机 (SRM) 等许多应用中都会遇到会聚-发散喷嘴中的气体-颗粒两相流。喷嘴壁附近的“无颗粒区”对喷嘴性能至关重要，它与电机的比冲密切相关。虽然很多研究者经常观察到，但不同喷嘴中无颗粒区的存在及其对喷嘴性能的影响仍然不明确。在这项研究中，我们使用双向耦合欧拉-拉格朗日模型研究了喷嘴中具有单分散微米颗粒的两相流，发现最小颗粒 (d _p = 1.0 微米）。此外，我们建立了一个理论模型，通过计算最接近喷嘴壁的颗粒的轨迹来预测无颗粒区的范围。研究了粒径、总压力、总温度和喷嘴几何形状对无颗粒区的影响。最后，我们分析了喷管性能，发现出口处的气体速度和推力不随颗粒尺寸单调变化，而中等尺寸颗粒造成的推力损失最大。