Analysis of Flow Migration in an Ultra Compact Combustor

Abstract

The ultracompact combustor (UCC) has the potential to offer improved thrusttoweight and overall efficiency in a turbojet engine. The thrusttoweight improvement is due to a reduction in engine weight by shortening the combustor section through the use of the revolutionary circumferential combustor design. The improved efficiency is achieved by using an increased fueltoair mass ratio and allowing the fuel to fully combust prior to exiting the UCC system. Furthermore, gloaded combustion offers increased flame speeds that can lead to smaller combustion volumes. One of the issues with the UCC is that the circumferential combustion of the fuel results in hot gases present at the outside diameter of the core flow. These hot gases need to migrate radially from the circumferential cavity and blend with the core flow to present a uniform temperature distribution to the highpressure turbine rotor. The current research focused on correlations to control the UCC cavity velocity, control the temperature profile throughout the UCC section, analyze the exhaust species exiting the combustor, and quantify pressure losses in the system. To achieve these goals, a computational fluid dynamics (CFD) analysis was used on a UCC geometry scaled to a representative fighterscale engine. The analysis included a study of cavity to core flow interaction characteristics, a 5and 12species combustion model of liquid and gaseous fuel, and determination of species exiting the combustor. Computational comparisons were also made between an engine realistic condition and an ambient pressure rig environment.