Session: 01-05 Engine Performance and Cycle Design III

Paper Number: 151182

Implementation of Inter Compressor Cooling in the Cycle Analysis of Hydrogen Powered Gas Turbine Engines Using Scalable Heat Exchanger Maps 

From a scientific and policy point of view, hydrogen propulsion is an important area of research where the use itself varies, e.g. powering a fuel cell or direct combustion. Several authors in the literature agree that climate-neutral aircraft will fly with liquid hydrogen as fuel in the future. In its liquid form, hydrogen is stored in the aircraft fuselage at 20 K, but combustion requires a much higher temperature. Conditioning of the hydrogen needs a large amount of thermal energy, which can come from a variety of sources. There are smart ways of achieving this heating within the core engine, which can even have a positive impact on the thermodynamic cycle. The most common concepts of heat exchanger integration in the engine are cooled cooling air, waste heat recovery and inter compressor cooling.

Although inter compressor cooling has been investigated in the past, this is a completely new way of transferring energy to the fuel at this point. High temperature differences from 20 K on the coolant side to more than 300 K after the booster compressor allow for smaller heat exchangers. Comparatively low Mach numbers lead to low pressure losses on the core flow. However, modeling methods for this type of heat exchanger vary widely, from simple energy balance methods to 3D-CFD. For performance calculations, 3D-CFD is not feasible and simpler methods such as the Number of Transfer Units (NTU) suffer from uncertainties, especially for during off-design calculations.

This paper suggests a scalable performance map for hydrogen conditioners to be used as "inter compressor cooling" heat exchangers during cycle analysis.

To tackle this approach, a reference engine for a short to medium range application is first designed at a thermodynamic cycle level. In addition, the 2D flow path is sized using a knowledge-based sketching method to estimate the available installation space for a heat exchanger. A tool for the calculation of heat exchangers in aviation with a higher lever of detail is used to design the hydrogen conditioning system. For this application, a tube bundle heat exchanger is selected and the calculation is performed with a cell based NTU approach. The main influencing variables are identified through parameter studies in the engine relevant operating range. This study is the basis for creating a scalable map, similar to those used for turbo components. The map is validated with two further generic engines and corresponding heat exchanger designs. Using the heat exchanger map in the cycle analysis, this paper will answer the following research questions:

-          - What is the impact of LH2 inter compressor cooling on the overall engine design?

-          - What are feasible integration concepts of the novel heat exchanger on cycle level?

-          - What are the operating conditions of the LH2 heating system within the flight envelope?

Since the direct use of hydrogen as a coolant can lead to icing problems and there are additional challenges with the safety of such a system, two other options for hydrogen conditioning are presented. These are the use of an intermediate fluid and full electrical conditioning.

Presenting Author: Alexander Görtz German Aerospace Center

Presenting Author Biography: - 2020: M.Sc. Mechanical Engineering - Technical University Berlin
- 2024: Guest Researcher at Mälardalens University, Västerås, Sweden
- 2020 - present: Researcher at the German Aerospace Center, Institute of Propulsion Technology

Authors:

Alexander Görtz German Aerospace Center
Konstantinos Kyprianidis Mälardalens University
Dimitrios Bermperis Mälardalens University