Abstract In the suspension high velocity oxy fuel (SHVOF) thermal spray, a suspension is injected into the combustion chamber where the jet undergoes primary and secondary breakup. Current knowledge of the primary breakup within the combustion chamber is very limited as experimental investigations are impeded due to direct observational inaccessibility. Numerical methods are also limited due to the computational costs associated with resolving the entire range of multiphase structures within SHVOF thermal spray. This paper employs a coupled volume of fluid and discrete phase model, combined with a combustion model, to simulate primary breakup at a fraction of the cost of a fully resolved simulation. A high-fidelity model is employed within this study to model the combustion chamber; the model shows a backflow region that will contribute to clogging within the nozzle. This study modifies the injector type for SHVOF thermal spray by introducing a co-flow around the liquid injection to reduce clogging within the combustion chamber. This study shows that introducing a co-flow of gas at a velocity of 200 m/s around the liquid injection reduces the backflow region by 40% within the combustion chamber. The addition of a gas co-flow results in a smaller region of backflow. Small suspension droplets with insufficient momentum are unable to overcome the backflow and will likely deposit themselves onto the wall of the combustion chamber. The deposition of the particles on the walls causes clogging of nozzles often seen in SHVOF thermal spray. The addition of a gas co-flow results in an increase in the velocity of droplets formed during primary breakup. The greater droplet velocity allows for small droplets to overcome the small backflow region near the liquid injection. The Sauter mean diameters predicted from the numerical model are compared to experimental measurements available within the literature and shows good agreement.

中文翻译：

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使用耦合体积的流体和离散相模型对悬浮高速氧燃料热喷涂中的初级破裂进行高保真模拟

摘要 在悬浮高速氧燃料 (SHVOF) 热喷涂中，悬浮液被喷入燃烧室，在那里射流经历一次和二次分裂。目前对燃烧室内初级破裂的了解非常有限，因为由于无法直接观测而阻碍了实验研究。由于与解析 SHVOF 热喷涂内的整个多相结构范围相关的计算成本，数值方法也受到限制。本文采用耦合体积的流体和离散相模型，结合燃烧模型，以完全解析模拟成本的一小部分来模拟一次破裂。本研究采用高保真模型对燃烧室进行建模；该模型显示了会导致喷嘴内堵塞的回流区域。该研究通过在液体喷射周围引入协流来减少燃烧室内的堵塞，从而修改了 SHVOF 热喷涂的喷射器类型。该研究表明，在液体喷射周围以 200 m/s 的速度引入气体协流可将燃烧室内的回流区域减少 40%。添加气体协流导致较小的回流区域。动量不足的小悬浮液滴无法克服回流，很可能会沉积在燃烧室壁上。颗粒在壁上的沉积导致在 SHVOF 热喷涂中常见的喷嘴堵塞。添加气体协流导致初级破碎期间形成的液滴速度增加。较大的液滴速度允许小液滴克服液体注射附近的小回流区域。从数值模型预测的 Sauter 平均直径与文献中可用的实验测量值进行比较，并显示出良好的一致性。