The objective of this project was to study and manufacture a Wasted Heat Regeneration System (WHRS).

The WHRS is composed of :

• a heat exchanger, to be tested within the exhaust gas nozzle of a turbo shaft engine
• a hot air piston engine, to be tested with an artificial electric hot source

The heat exchanger is an air / air type directly installed in the gas turbine exhaust nozzle.

In the final application, it withdrew the heat from the exhaust gases and heated up the “hot loop” pressurised air flow coming from and going to the piston engine.

During this prototype phase, the air flow was supplied to the heat exchanger by an artificial air compressor in order to evaluate the heat transfer obtained by this heat exchanger.

The heat exchanger had to respect strong environment constraints due to its integration in a turbine exhaust nozzle. It should not have a major impact on the architecture of the turbine or on the exhaust gas flow.

The hot air piston engine was a mono-cylinder reciprocating piston engine rotating up to 7.500 rpm if necessary at the end of test (6000 rpm max speed during the main part of the tests), fed by external air through classical admission and exhaust system, and getting its power from the artificial electric hot loop.

The design of the engine was optimised in terms of internal frictions in order to maximize the work produced by the WHRS.

This was achieved by using the correct materials and surface treatments, and by the design of an engine equipped with unconventional valves.

The hot temperatures provided by the hot source required the use of low thermal expansion coefficient materials for the components in order to ensure the correct fitting of components and avoid seizure of the system.

Our consortium realised the following tasks:

• Detailed study and manufacturing of 2 heat exchangers
• Study of the base engine components (piston / rod / crankshaft / cylinder block)
• Performance test on partial cylinder head components in terms of permeability and friction-sealing compromise
• Partial redesign of cylinder head depending on partial tests results + process/material integration
• Manufacturing of one hot air piston engine
• Study and manufacturing of a bench (adaptation of an existing engine test rig) for the piston engine with the electric artificial hot source
• First verification of the piston engine performance and mini-endurance test (approx. 50h).