| Hydrodynamic instabilities within injector passages can couple to chamber acoustic modes and lead to unacceptable levels of combustion instabilities inside liquid rocket engines. The instability of vena-contracta regions and mixing between fuel and oxidizer can serve as a fundamental source of unsteadiness produced by the injector, even in the absence of upstream or downstream pressure perturbations. This natural or "unforced" response can provide valuable information regarding frequencies where the element could conceivably couple to chamber modes. In particular, during throttled conditions the changes in the injector response may lead to an alignment of the injector and chamber modes. For these reasons, the basic unforced response of the injector element is of particular interest when developing a new engine. The Loci/Chem code was used to perform single-element, 2-D unsteady CFD computations on the Hydrogen/Oxygen Multi-Element Experiment (HOMEE) injector which was hot-fire tested at Purdue University. The Loci/Chem code was used to evaluate the effects of O/F ratio, LOX post thickness, recess length and LOX tube length on the hydrodynamics of shear co-axial rocket injectors. |
