Effect of Injector Design on the Combustion of Ethanol and Hydrogen-Peroxide Sprays

This paper describes the injection and combustion behavior of liquid reactants—ethanol and hydrogen peroxide—in relevant conditions for storable bi-propellant space thrusters. Particularly, this study points out the comparison between two fundamental injector designs based on impinging-jet atomization. First, like-doublet injection generates separate sprays of oxidizer and fuel that need to undergo vaporization, mixing, and chemical reaction. Second, unlike-triplet injection generates a unique spray of bipropellant mixture that only has to vaporize before burning. The effect of these two injection processes is compared in terms of spray pattern, drop size and velocity, as well as combustion efficiency. For this purpose, direct and OH*-filtered visualizations of the reacting flow are performed, and the characteristic velocity is computed from experiments at combustion pressure 0.6 MPa and overall equivalence ratio in the range 0.5–2.2.