Evaluation of Local Mixture and Flow Rate Ratio for Liquid-Liquid Type Pintle Injector

To determine key parameters and achieve high thrust performance across a wide range of thrust levels, it is essential to investigate the distributions of the local mixture and flow rate ratio under various conditions. However, the experimental knowledge on them for a liquid-liquid type pintle injector has been limited, while the mixing state governs the thrust performance of bipropellant thrusters. In this study, therefore, the cold-flow tests, in which water/dyed water was used as simulants of real propellants, were conducted to evaluate the mixing state and distribution of the spray formed by the liquid-liquid type pintle injector. A two-dimensional patternator made by a three-dimensional printer was used to understand the whole aspect of the spray. It was found that the mixing loss in the radial direction was more distinct than that in the circumferential direction. A one-dimensional patternator with fine spatial resolution for radial direction was also applied in the cold-flow tests to evaluate the radial distribution of the spray in detail, and the non-dimensional injection condition, which uniformly organized the spray distribution, was considered. As a result, the non-dimensional injection condition based on the total momentum ratio could characterize the center of gravity of the spray in the radial direction.