Detailed Investigation of the Combustion Efficiency of the DLR API Injector for LOX/H2 Rocket Engine Applications

Abstract

Since a few years DLR Lampoldshausen has been engaged in the development of a new injection concept for cryogenic liquid propellant rocket engines. This concept bases on the injection of the liquid oxygen through a large number of simple tubes while the entire hydrogen is injected through the porous face plate. The experimental results reported here show results from two different sets of test campaigns, one with 50 mm diameter (API50) and one with 80 mm diameter (API80) combustion chamber, respectively. The API50 part of the paper summarizes test campaigns using gaseous hydrogen at 105 K with two different combustion chamber lengths, which result in L* = 0.46 m and 0.66 m, respectively. It is worthwhile noticing that the combustion efficiency for L* = 0.46 m which is well below any recommendation from the literature is similar to the one measured for L* = 0.66 m. The API80 part of the paper reports results from a test campaigns of an 80 mm diameter subscale chamber having a contraction ratio of 2.56 and a L* of 0.87 m with hydrogen at 45 K. The measured combustion efficiencies are almost pressure independent for the entire combustion chamber pressure range between 5 and 9 MPa.