Numerical and Experimental Results From a Common-Source High-G Ultra-Compact Combustor

Abstract

Ultra-Compact combustion presents a novel solution to address the demand for increasingly compact, efficient, and low weight aircraft gas turbine engine propulsion systems. An Ultra-Compact Combustor (UCC) operates by diverting a portion of the compressor exit flow into a cavity about the engine outer diameter. Injection into the cavity can be done at an angle in order to induce bulk circumferential swirl. Swirl velocities in the cavity then impart a centrifugal load of approximately 1000g0. This high-g UCC concept has been investigated by The Air Force Institute of Technology with the goal of incorporating a common upstream flow source to distribute the simulated compressor exit flow into separate core and combustion cavity flow paths. Experimental results from this test rig are presented, with particular emphasis on establishing the design flow split through the diffuser into the circumferential cavity. The implementation of a core channel plate was instrumental in control of the mass flow splits. Computational Fluid Dynamics (CFD) supplement the experiments and enable a more detailed understanding of the interactions within the diffuser and the interactions between the air injection jets and the fuel jets. A range of cavity equivalence ratios was studied and combustion within the cavity was shown to be a strong function of cavity loading, which was in turn a function of the total mass flow. Varying the orientation of the channel plate with respect to guide-vane leading edges caused a change in the core flow development which then had a secondary effect of aiding the combustion process within the cavity.