Development of an Exhaust Driven Turbine-Generator Integrated Gas Energy Recovery System (TIGERS ^® )

This paper describes the design and development steps taken to realise a functioning Turbo-generator Integrated Gas Energy Recovery System (TIGERS^®).

The main areas covered focus on simulation, machine design, control system development and validation. The mechanical design for this application is particularly challenging for a number of reasons. The turbine is capable of rotating the shaft at speeds greater than its critical rotating limit. Rolling element grease filled bearings are used to allow application flexibility; these have an operating temperature limit of 200°C. The exhaust gas can reach temperatures greater than 900°C in spark ignition applications, whereas the turbine upper functional limit is 850°C. The power electronics are integrally mounted in the machine and have a maximum thermal operating limit of 120°C.

Considering that TIGERS is expected to harvest energy from the exhaust gas it is essential that it not only survives in this harsh environment, but it must also produce work with no adverse impact on vehicle performance or fuel efficiency. The TIGERS device and its control system have been designed to do exactly this through a number of thorough modelling exercises.