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Impact of Fuel Heating on Combustion and Emissions

Project Number: 067
Category: Alternative Fuels, Aircraft Technology Innovation

Fuel heating has been identified as one of the key advancements to increase the cycle efficiency of advanced gas turbines operating at very high pressure ratios. However, heating the fuel will affect the performance of the combustor, principally by changing the penetration, atomization, and vaporization characteristics of the fuel spray. These effects may also vary with fuel composition.

Stored fuel is a convenient working fluid on aviation platforms, where stringent weight and system reliability requirements drive innovation in the design of ancillary airframe and engine systems. When fuel is used as a heat sink, the enthalpy transferred to the fuel from the heat exchange process still contributes to thrust generation, rather than being dissipated (and lost) by other means. The temperature of the air entering an engine core increases as a function of the flight Mach number squared and rapidly increases the cooling requirements throughout the propulsion system at supersonic flight speeds. Fuel can be used to support the increased thermal management load, enabling higher flight speeds. However, small changes in the fuel supply temperature can have strong effects on the structure and dynamics of fuel-air injection, mixing, and ignition in high-pressure, swirl flames. The performance of modern, low-emissions combustors is particularly sensitive to these changes due to the tight coupling of physical and chemical processes within the heat release zone. The goal of this task is to investigate the effects of hot fuel on combustion performance and the level of emissions for a lean burn combustor. Laser-based measurements of these physical and chemical processes performed at engine flow conditions will provide key insight to the effects of fuel temperature on gas turbine combustion devices.

Outcomes

This project will characterize the global and local impact of hot fuel injection on the performance of combustion systems in modern aircraft engines. Extractive exhaust sampling will provide valuable information on global metrics such as combustion efficiency and pollutant emission production. Advanced diagnostics will provide crucial insight into the physics of hot fuel injection and mixing within the flow as well as the coupled chemical processes that manifest the global trends. The impact of this project will be to advance lean-burn, low emissions gas turbines to the next level of cycle efficiency by providing the key insights needed to design combustion devices for operation with hot fuels.

Last Updated 7/7/2020

Participants

Program Managers