Secondary fluid heat exchangers for improvement of aero engine efficiency

Purpose and goal

In the project Second-To-None, GKN Aerospace and Chalmers have investigated how fluids and gases can be used as a secondary flow to transfer heat in aircraft turbine engines to increase their efficiency and safety. The study focused on how hydrogen, fed to the engine in liquid form can be preheated before combustion by intercooling the compressor, and recuperating heat from the exhaust flow. The results indicate that high-pressure helium can transfer sufficient heat to reduce the fuel consumption by 5%.

Expected results and effects

The goal to reduce the fuel consumption for an aircraft by 5% is supported by the calculated net decrease of the specific fuel consumption by 3% by recuperation of exhaust heat and additional effects of intercooling. This leads to reduced weight and volume of fuel and tanks, which also reduces the aircraft drag. The project has developed critical models and input to other projects regarding hydrogen fueled aircraft engines, such as ENABLEH2 and H2JET supported by the EU and the Swedish Energy Agency and the planning of new activities in the EC’s Horizon Europe, including Clean Aviation.

Planned approach and implementation

The project team’s experience of primary flow heat management was extended to heat transfer using secondary fluids with a literature study followed by concept generation to reach TRL 1. In a second step, models of heat exchangers and the fluid properties of transfer media and liquid hydrogen were added to the simulation code GESTPAN. An analytic basis for heat exchanger design was established from which three tubular heat exchanger geometries were generated and modelled in GESTPAN to reach TRL 2. The performance impact of the concepts installed in an aircraft was estimated.