Session: 01-02 Conceptual Design and Optimization I

Paper Number: 123977

123977 - Step-by-Step Evaluation of the Fuel Switch From Kerosene to Hydrogen on the Thermodynamic Cycle in Gas Turbine Engines 

The main challenge for aviation in this century is to reduce absolute emissions and climate impact while the demand for air transportation will increase steadily. While evolutionary component development is a feasible way forward, additional revolutionary changes are necessary to face these challenges. The use of hydrogen as a fuel for aviation is considered as a revolutionary development for future aircraft engines. In the scientific and political world propulsion with hydrogen is a major research field where the use itself varies; e.g. powering a fuel cell or direct combustion.

While various authors in the literature agree on a general reduction of thrust-specific energy consumption in hydrogen combustion engines, the effects on the entire engine and aircraft system are currently not yet fully understood. The density of hydrogen compared to kerosene is much lower and this alone has a major implication on the aircraft. The combustion will take place in a completely different way and the exhaust gas properties differ as well. Hydrogen is stored in its liquid for at 20 K but will be burned at much higher temperature. Therefore, an additional heat exchanger is required for heating the fuel to a feasible combustion temperature. This heat exchanger is a heat sink which will impact the thermodynamic cycle and the overall geometry considerable. This leads to three main effects impacting the engine design:

- Different combustion results in additional water in the exhaust gas and the potential to extract more power from the flow

- Impact of the higher mass flow quality and the heat exchanger on the engine design and the overall thermodynamics

- Different thrust requirements for the engine because the aircraft also receives major changes

While there is many information about the engine performance of hydrogen combustion engines it is not clear to which extend each property of the fuel switch effects the engines thermodynamic cycle and component behavior. Many effects play a crucial role but it is difficult to look at this in a differentiated way and it is necessary to understand each step while switching from kerosene to hydrogen. The basic architecture is identical for both fuels but it is not known to which extend already existing and fully designed components can be used for the new application.

The hydrogen fueled turbofan shows benefits in thrust specific energy consumption compared to a design for kerosene but to accurately assess where the changes are coming from, a step-by-step approach is taken. A high value is placed on consistency for each step, so that sound results are produced. How to archive this consistency will be explained fully in the paper but will be based on a knowledge-based approach for turbomachinery efficiency and geometry, turbine cooling air requirements, basic turbofan design methods and more. Furthermore, emerging effects from the use of hydrogen are addressed to create understanding of the new technology. The engines presented during this approach will be design for a short-range application similar to the Airbus A320 with EIS2040 and the steps are as follows:

1. Design of a reference turbofan engine on performance level with kerosene combustion

2. Reference engine but fueled with hydrogen without other changes. This means that the geometry and turbo components remain identical

3. New designed engine but withput changes to the thrust requirements

4. Fully new designed engine with hydrogen specific thrust requiements

The advantage of this small step approach is the possibility to study each effect independently and to increase the knowledge of the new technology.

Presenting Author: Alexander Görtz German Aerospace Center

Presenting Author Biography: B.Sc. Mechanical Engineering at Technical University Dortmund
M.Sc. Mechanical Engineering - Aero Engines at Technical University Berlin

2020 - now: Researcher at German Aerospace Center - Institute of Propulsion Technology - Engine Department

Authors:

Alexander Görtz German Aerospace Center
Björn Schneider German Aerospace Center