Characterisation of Cryogenic Jets at Supercritical Conditions

Abstract

Diesel engines, gas turbines, rocket engines and many others rely on high pressure combustion to produce high power energy conversion and thrust. Increasing performance of these engines requires high pressure injection often above propellant critical pressures. Understanding how the propellants react and perform under these conditions allows the designer to employ time and cost saving modelling tools to design a higher performing, lower cost device. Much work has been accomplished in this area as can be seen in references (1,2 and 3 and 4), but a strong understanding of the injection process and the development of reliable modelling tools still requires much research. This investigation takes a step in this direction using liquid nitrogen as a liquid oxygen simulant (5). The investigation considers test conditions at 4.0, 5,0 and 6.0 MP at two different nominal injection velocities (2 and 5 m/s) and temperatures (120 K and 130 K). Experimental density measurements taken by Raman imaging are compared to computational models. The measured results compare fairly well with the computational results specifically in the density profiles. The supercritical jet is extremely sensitive to temperature variations and injection temperature.