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

Abstract

Although intercompressor cooling has been investigated in the past, it is a completely new way of transferring energy to the hydrogen fuel at this point. High temperature differences from 30 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, the modeling methods for this type of heat exchanger vary a lot from simple energy balance methods to 3D-CFD. During performance calculations a 3D-CFD is not feasible and more simple methods as the number of transfer units suffer from uncertainties especially during off-design calculation. This paper suggests a conditioning system and a scalable performance map for hydrogen conditioners to be used as intercompressor cooling heat exchangers during cycle analysis. A tool for the calculation of heat exchangers in aviation with a higher level of detail is used to design a tube bundle heat exchanger and create the performance map. A concept for the integration of the heat exchanger in the core engine is presented using 8 stacks distributed around the circumference. For a given geometry, errors in transferred heat below 1% are achieved across the entire operating range of the engine. A 15% scaling in effectiveness results in an error of only 3% at the most loaded operating point. First conducted studies indicate to design an engine for the highest possible fuel temperature while using the least amount of air. This achieves the lowers thrust specific fuel consumption. The direct use of hydrogen as a coolant can lead to problems with icing due to wall temperatures in the heat exchanger matrix being below 0 °C. In addition, there are additional challenges with the safety of such a system. A completely different option for hydrogen conditioning is presented. This is the use of a full electrical conditioning.