Atomization of gelled kerosene by multi-hole pintle injector for rocket engines

Abstract

Gelled propellants for rocket propulsion present various advantages, such as storability with regard to liquid rocket propellants and a high specific impulse with regard to solid rocket propellants. However, one of the main limitations of gelled propellants in rocket propulsion is their low mixing performance resulting from their high viscosity. For these reasons, conventional injectors such as coaxial and pintle injectors are not suitable for spraying gelled propellants. To address this issue, we have herein devised new methods to increase the mixing performance. For the gelled propellant, liquid kerosene was compounded with 5 wt% of Thixatrol ST, a gelling agent, and shear viscosity data according to the shear rate were measured to confirm viscosity. Two types of injectors—flat type and deflector—were used to confirm the spray characteristics, such as spray angle, via the backlight image technique. The spray angle was formulated according to the total momentum ratio for comparison with the measured experimental data, and the result regarding the measured spray angle in the deflector type injector satisfies the expected spray angle. The dominant difference in spray characteristics between the flat type and deflector type injectors is in terms of a liquid jet stream, related to the breakup and atomization processes. In the case of the flat type injector, the liquid jet stream was detected even for a high total momentum ratio. However, in the case of the deflector type injector, the liquid jet stream disappeared with an increase in the total momentum ratio.