Spray combustion characteristics of a gas-liquid pintle injector with variable swirl intensities

The present paper experimentally verified and computationally explained an improved design concept of the spray combustion of a gas-liquid pintle injector with variable swirl intensities. By pintle injector, we mean a promising injector for the throttleable engines with variable thrust capacities, which features the moveable pintle continuously controlling the mass flow rates of fuel and oxidizer where the radial and axial flows encounter to form a spray cone and spray atomization. First, the cold flow test was conducted to study the swirl effects on the spray angle, followed by the combustion test to study the total pressure and the specific impulse under different swirl intensities. The results show that the swirl enhances the combustion performance by increasing the total pressure and specific impulse. Second, the swirl-assisted spray was numerically simulated based on a validated volume-of-fluid method to explain the experimental findings. The diameter distribution and spatial distribution of dispersed droplets were analyzed by the Sauter mean diameter (SMD) and the Voronoi tessellation, respectively. The results show that the swirl significantly promotes the breakup of liquid jet or film, producing smaller SMDs and a more uniform spatial distribution of dispersed droplets. The consolidated correlation between the non-reacting spray characteristics and the combustion performance suggests that the proposed methodology can be used to fast prescreen pintle injector designs.