Experimental research on the spray characteristics of pintle injector

Abstract

The spray characteristics of an oxidizer-centered liquid-liquid pintle injector at different momentum ratios are experimentally investigated. Water is used as the simulation fluid of both the fuel and the oxidizer and injected into the axial annular gap and radial orifices, respectively. The radial-to-axial local momentum ratio (LMR) is varied from 0.16 to 0.93 by adjusting the mass flow rate of the oxidizer under constant mass flow rate of the fuel. A high-speed camera and Phase Doppler Anemometry (PDA) system are used to investigate the spray pattern, spray angle, droplet size and velocity distribution. The results indicate that the spray generated by the pintle injector is shaped as a hollow-to-solid cone with a rough boundary. A hollow structure appears in the spray center in the near field and disappears in the far field. With the increase of the momentum ratio, the outer boundary of the spray field is enlarged and the range of the hollow field also increases. The spray angle varies from 34° to 122° for the LMR in the range of 0.16–0.93. Furthermore, the spray angle is deduced as a monotonically increasing function of the local momentum ratio of the pintle injector with discrete radial orifices. The diameter-velocity distribution indicates that SMD (Sauter Mean Diameter) increases slightly and the axial velocity decreases mildly with the increase in the momentum ratio. The SMD curve exhibits an “N” shape in the radial direction, whereas the axial velocity and radial velocity curves exhibit inverted “V” shapes in general. The spray distribution and spray development are mainly controlled by the interaction of the radial flow of the jet and the axial flow of the film, and also to some degree by the impingement of the liquid droplets in the spray center. From the spray center to the edge, the spray of the pintle injector is divided into three regions: the spray core, the mainstream, and the outer boundary.