Effect of the Flow Passage Area Ratio on a Double Slit-Type Pintle Injector

Due to the structural characteristics of the pintle injector, a recirculation zone is generated under the pintle, so the pintle tip is directly exposed to a high-temperature environment. Therefore, the cooling technique and protective coating on the pintle tip are essential for improving the reusability and durability of the pintle injector. Although various cooling methods are known, this study applied a forced flow passage cooling method by adding internal structures called inserts to the pintle injector. The characteristics of the insert were analyzed experimentally and numerically based on change of its area ratio. When the internal flow changes, the spray angle, droplet size, and cooling performance also change in accordance with an increase in the insert’s central area. When the insert structure is installed in the pintle post, upward flow may occur, which can worsen the spray angle and droplet distribution characteristics. Nevertheless, owing to the insert structure, the surface temperature of the pintle post is reduced dramatically as intended. Thus, an optimal design technique for cooling by changing the area ratio of the first- and second-row slits of the pintle post can be suggested to overcome the limitations of the insert structure. The results of this study will be helpful in understanding the spray characteristics of the insert structure and optimize the design of cooling channels for reusable pintle injectors in the future.