Internal rotating plasma spraying (IRPS) plays an important role in improving the properties and prolonging the service life of internal parts and components of mechanical systems. IRPS is conducted in the confined and semi-enclosed spaces at a spraying distance of 30–70 mm to coat the engine cylinders of automobiles or heavy equipment. Occasionally, particles cannot be appropriately treated in the plasma flow, and owing to several factors, the particles remain suspended in the air rather than being deposited onto the substrate. Consequently, the suspended particles are difficult to remove efficiently within the confined space, and can thus have severe effects on the properties of coatings, including porosities and inclusions. It is therefore essential to develop appropriate methods to avoid defects in the coating by removing suspended particles inside the cylinder. In this study, numerical simulations were conducted to investigate the flow-velocity field and particle-mass-concentration distribution within the cylinder. The flow-velocity and particle mass concentration in the cylinder space were analyzed under different working conditions that can induce different suction pressures driven by a three-phase asynchronous motor connected to the bottom of the cylinder by a suction tube. The results showed that the flow-velocity field is symmetrical along the axis of the cylinder and the mass concentration of particle is concentrated on the region from middle to bottom of the cylinder, under the effect of the suction pressure. In addition, the low-velocity and high-particle-mass-concentration regions are mainly located in the vicinity of the internal wall. Furthermore, the flow velocity was measured using a hot-wire-anemometer and the coating microstructure was observed using scanning electron microscope (SEM). We compared numerical simulation results and experimental measurements, which validated the flow-velocity field directly and the distribution of particle mass concentration indirectly. Based on the numerical results that consider the removal degree of suspending particles and the stability of the plasma jet, it can be determined that the optimal suction pressure is −100 Pa for decreasing dust pollution during the spraying process.

内部旋转等离子喷涂（IRPS）在改善机械系统内部零件的性能并延长其使用寿命方面起着重要作用。IRPS在狭窄和半封闭的空间中进行，喷洒距离为30-70 mm，以覆盖汽车或重型设备的发动机气缸。有时，无法在等离子流中对粒子进行适当的处​​理，并且由于多种因素，粒子仍然悬浮在空气中，而不是沉积在基板上。因此，难以在有限的空间内有效地去除悬浮颗粒，从而可能对涂层的性能（包括孔隙和夹杂物）产生严重影响。因此，必须开发出适当的方法，通过去除圆柱体内的悬浮颗粒来避免涂层缺陷。在这项研究中，进行了数值模拟，以研究圆柱体内的流速场和颗粒质量浓度分布。在不同的工作条件下分析了气缸空间中的流速和颗粒质量浓度，这些条件可以通过由吸管连接到气缸底部的三相异步电动机产生不同的吸力。结果表明，在吸气压力的作用下，流速场沿圆柱轴对称，颗粒的质量浓度集中在圆柱的中下部。此外，低速高颗粒质量浓度区主要位于内壁附近。此外，使用热线式流速计测量流速，并使用扫描电子显微镜（SEM）观察涂层的微观结构。我们比较了数值模拟结果和实验测量结果，直接验证了流速场，间接验证了颗粒质量浓度的分布。根据考虑了悬浮颗粒的去除程度和等离子流稳定性的数值结果，可以确定为减少喷涂过程中粉尘污染的最佳吸入压力为-100 Pa。用热线式流速仪测量流速，并用扫描电子显微镜（SEM）观察涂层的微观结构。我们比较了数值模拟结果和实验测量结果，直接验证了流速场，间接验证了颗粒质量浓度的分布。根据考虑了悬浮颗粒的去除程度和等离子流稳定性的数值结果，可以确定为减少喷涂过程中粉尘污染的最佳吸入压力为-100 Pa。用热线式流速仪测量流速，并用扫描电子显微镜（SEM）观察涂层的微观结构。我们比较了数值模拟结果和实验测量结果，直接验证了流速场，间接验证了颗粒质量浓度的分布。根据考虑了悬浮颗粒的去除程度和等离子流稳定性的数值结果，可以确定为减少喷涂过程中粉尘污染的最佳吸入压力为-100 Pa。