Session: 01-17 Modelling, Simulation and Validation IV

Paper Number: 121342

121342 - Toward Net Zero: an Engine Electrification Strategy Approach of Fuel Cell and Steam Injection 

The turbofan engine electrification is a promising element in the global effort to achieve the 2050 net-zero emission target. This transformative shift embraces the utilization of alternative energy sources and amplifies system efficiency. Power injection, using the electric motor to provide power assistance for the gas turbine, is a promising concept. Batteries and fuel cells are emerging as prime candidates for the direct replacement of traditional fossil fuel power requirements, offering compelling advantages, particularly with electric powertrains offering superior efficiency when compared to traditional gas turbines. This direct power injection assistance reduces the power requirement from the combustion, thus reducing the fuel flow and Turbine Entry Temperature (TET). As an outcome, this alteration yields favourable consequences, notably in the form of diminished Carbon Dioxide (CO₂) and Nitrogen Oxide (NOx) emissions and lower engine fuel consumption. However, this transition comes at the cost of a potential thermal efficiency penalty, impacts engine stability, and adds extra weight. These drawbacks compromise the power injection's benefit, highlighting the necessity for introducing electrification strategies in future engine designs.

This paper presents an innovative electrification strategy using fuel cells as the power source for engine electrification. The strategy highlights the collection of water as a by-product, followed by treatment processes involving condensation, pressurization, and superheating. The fuel cell in this configuration, is designed to provide power to the electric motor, which injects power into the low-pressure shaft of the engine. This power injection reduces the peak power demand from the gas turbine, and the resultant peak power shaving capability opens up opportunities to resize the engine for enhanced cruise efficiency. This strategy of core-resizing aims at sizing and designing the gas turbine for a superior efficient cruise segment and using electric power to provide extra assistance during the take-off and climb. Additionally, steam injection, leveraging the by-product water, enhances the benefits derived from electrification by recovering and redirecting the waste heat from exhaust gases into the combustor.

To evaluate the potential impact of this electrification strategy, this research selected and modeled three representative engines, each representative of typical thermodynamic cycles. Two different approaches to steam management were considered, including instantaneous injection with production and storage of steam during production for release during specific flight segments. Different degree of hybridization has been considered, and a typical mission profile has been chosen.

This research established the synergy between steam injection and different engine thermodynamic cycles and provided a visualized method of evaluation. The impact of fuel cell electrification has been quantified in terms of fuel consumption, energy utilization, CO₂ emission, engine efficiency, and engine creep lifing consumption. An estimation of the weight penalty, including fuel cells, hydrogen storage, and heat exchanger, is also provided. Furthermore, the sizing of the superheating heat exchanger is analysed to assess its influence on the electrification strategy.

The research indicates that the fuel cell electrification strategy holds substantial promise, delivering benefits in terms of fuel consumption reduction and emission mitigation. This research has also captured the physics of recovering the waste heat from exhaust pipe could lead to a compromise of fuel consumption benefit, which imposes a penalty on electrification.

The results and assessments reach to conclusion that the electrification strategy of fuel cell and steam injection is preferable for high-temperature, low specific thrust engines. The temperature of the steam is the dominant factor in bringing fuel consumption benefits, thus the preferable steam management approach is to inject during T/O and climb.

Presenting Author: Zhengfei He Cranfield University

Presenting Author Biography: Zhengfei He is a PhD researcher focused on hybrid-electric aircraft propulsion and engine electrification. He has worked on aircraft propulsion since his bachelor’s study. Zhengfei is currently working on a design space exploration for the future hybrid-electric aircraft propulsion, aiming for net-zero emissions in 2050. His research is looking at exploring aircraft propulsion electrification strategies, improving the propulsion system's efficiency and performance, as well as reducing emissions and fuel usage.

Authors:

Zhengfei He Cranfield University
Evangelia Pontika Cranfield University
Panagiotis Laskaridis Cranfield University