Experimental Studies of a High-g Ultra-Compact Combustor at Elevated Pressures and Temperatures

Abstract

Volatile fuel costs have initiated a global sprint for technologies that will increase fuel efficiency in gas turbine engines, which continue to be a primary propulsion system for commercial and military aircraft. The Ultra-Compact Combustor (UCC) is an advanced gas turbine combustor which integrates the high pressure turbine inlet guide vanes into the combustor. In comparison to conventional combustor systems, the UCC has the potential to shorten engine length, decrease engine weight, and reduce pressure losses entering the high pressure turbine rotor, all of which contribute subtantially to improving engine efficiency. The UCC has been studied in two forms in the literature – the Trapped-Vortex concept (TV) and the High-g concept (HG); the current study focuses on the latter. The HG-UCC utilizes a rectangular cavity wrapped around the outside circumference of the combustor where fuel and air are injected in a manner that generates a highly swirling flow within the circumferential cavity. The flow within the cavity experiences a centripetal acceleration (“g-load”) which varies with tangential velocity and radius from the combustor axis. This “high-g” effect has the potential to increase flame speeds and volumetric heating rates, as well as enhance fuel air mixing and spreading providing the potential to reduce fuel injector count without compromising performance. Experiments were performed on the HG-UCC combustor at higher operating pressures, temperatures, and equivalence ratios than previous high-g experiments conducted in a similar uncooled inter-turbine burner (ITB). Results show that the HG-UCC has high combustion efficiencies for the entire range of data considered. The effects of pressure and temperature, cavity driver angle, centripetal acceleration (g-load), and equivalence ratio are studied for their impacts on combustion efficiency and nitrogen oxide (NOx) emissions. An important result of this work is the construction of NOx correlations for the HG-UCC. Test data performance results and correlations are compared to previous trapped vortex and high-g UCC experiments.