Effect of dilution in an inter-turbine Flameless combustor

Alternatives to combustion in aircraft engines are not expected to become feasible in the decades to come. As the aviation traffic increases and regulations become more stringent, reduction in pollutant emissions are needed. The Flameless Combustion (FC) regime has been one of the promising candidates to achieve lower emissions in gas turbine engines. This combustion regime is characterized by welldistributed reactions, with low peak temperatures, resulting in lower emissions and acoustic oscillations. However, the attainment of the FC regime is not straight forward considering the conditions and requirements of gas turbines. Most of the previous combustor design attempts failed to provide broad operational range, high combustion efficiency, or were difficult to integrate in an engine. Along with a novel aircraft concept, the European project AHEAD (Advanced Hybrid Engines for Aircraft Development) resulted in the conceptual design of a gas turbine engine with two sequential combustion chambers1. As the aircraft concept allows the use of cryogenic fuels, the first combustion chamber was designed to operate with hydrogen or natural gas. The second is the inter-turbine combustor herein studied, which would operate under the FC regime burning conventional fuels.