A Study on the Spray Characteristics of a Liquid-Propellant Thruster Injector by PIV/PDA Optical Measurements

Spray characteristics of an injector employed in liquid-propellant thrusters are investigated by optical measurement techniques such as Particle Image Velocimetry (PIV) and Dual-mode Phase Doppler Anemometry (DPDA). The injector adopted in this experiment has 8 holes each of which has 30° cant angle from the center-axis with 16/1000 inches of hole diameter. Instantaneous plane images captured by PIV technique are examined in order to judge a pass-fail criterion of spray injection performance according to the specific pressures supplied. DPDA through which two-dimensional velocity components can be acquired is also applied in order to measure the velocity and size of spray droplets which were not obtainable from the PIV measurement. The non-dimensional parameters (e.g., Reynolds, Weber, and Ohnesorge numbers) based on the velocity data measured by DPDA are used to characterize the spray behavior in terms of the atomization and turbulence nature. Objectives of this experiment are to establish a non-intrusive evaluation technique for the injector performance and to utilize the clear understanding of spray characteristics for the design of brand-new thrust chamber as well.