Experimental and numerical investigation of coaxial pressure swirl injectors

Baran, Onur.
Experimental and numerical investigations were carried out for determining spray characteristics of a liquid-liquid coaxial injector in this work. As a baseline injector, the RD-0110 rocket engine injector was chosen which consists of two coaxial atomizers. The inner atomizer is an open-end type pressure swirl atomizer which supplies oxidizer, whereas the outer one is a closed-end type pressure swirl atomizer which supplies fuel. Tests were carried out for two different recess lengths and various mass flow rates. A high-speed camera was used to determine the spray cone angles, while a phase Doppler particle analyzer (PDPA) was employed to characterize the distributions of various parameters. More specifically two-dimensional velocity profiles and Sauter mean diameters (SMD) were obtained for both inner atomizer and the coaxial injector, but PDPA measurements could not be performed for the outer one due to the high spray cone angle. Also, 2D axisymmetric swirl and 3D CFD analyses were carried out for the inner and outer atomizers at different mass flow rates. Experimental and numerical results are compared in detail. Results show that big spray droplets move with the same velocity as that of the liquid film, whereas small droplets move with the air. When the inner and outer atomizers operate together, their spray cone angles change from those observed from standalone operations. Spray cone angle of the outer atomizer decreases, while that for the inner one increases, but they later merge at some point and forms a single spray. It was observed that the inner atomizer has more effect on this spray than the outer atomizer. Comparing the two different recess length reveals that recess length is significant parameter which affects spray properties. Lastly, comparing the experimental and numerical results proved that numerical analyses match well with test results. Therefore, numerical analyses can be used to find the velocity profile of the spray prior to detailed measurements.