Low Nox Hydrogen Combustion Testing In High Steam Environment For Future Aeroengine Concept

Abstract

This paper reports high-pressure tests of hydrogen combustion in a steam-air mixture representing the hot-section working fluid of a Hydrogen Steam-Injected Intercooled Turbine Engine (HySIITE). The HySIITE concept targets 35% efficiency improvement in comparison with today's kerosene-powered turbofan engines, making the concept a promising candidate to defray the cost of expensive zero-carbon fuels. The efficiency improvement is primarily achieved by recovering water from the engine exhaust. A key component in the cycle is a combustor that maintains stable hydrogen combustion at high Steam-to-Air Ratios (SAR), virtually eliminating NOX emissions and enabling high combustor-liner longevity. To validate this concept, an Advanced Rich-Quench-Lean combustor was selected as a burner architecture due to low flashback risk and good turndown performance. A fuel injector was designed for good mixing and secure flame anchoring with high steam content, but without having flame attachment. Throughout the tests, the combustor was operated at scaled pressure (1035 kPa) and steam/air mixture temperature (620 K – 730 K) with variable high-pressure saturated steam quantities mixed into the air. NOX emissions were measured at rig-scaled Cruise and Max-Takeoff conditions, including with sweeps across equivalence ratio and SAR. The resulting NOX emission levels were lower than 2.5 ppm for all conditions investigated as a result of low combustion temperature at high steam content. Combustor pressure fluctuations and wall temperatures were continuously monitored, and no significant fluctuations or excessive temperatures were observed at any conditions tested.