Monday, 25 April 2011

Small-Scale Gas Turbine Engines

Dr. Jürg Schiffmann
Advisor: Prof. Spakovszky
Small-scale gas turbine engines can provide much higher power densities than conventional batteries, and show promise as a portable and enduring power source. A 1kW class small-scale gas turbine generator is being developed for this purpose. Experimentally identified key issues for making the engine work are thermal management and rotordynamic stability.
The heat generated by the engine through windage losses in the bearings and in the generator needs to be removed and the rotor has to be effectively shielded from high temperature sources to ensure the mechanical integrity of the generator. The challenge is set by the small-scale architecture. The goal is to establish an appropriate thermal management scheme. The technical approach is based on a parametric thermal resistance network that is calibrated with experimental data.
The high rotational speeds required to reach acceptable aerodynamic efficiency call for gas lubricated bearings, which are known to have a low threshold of stability and are prone to large amplitude sub-synchronous vibration. Hence, another goal is to investigate these phenomena and develop design guidelines for high-speed gas bearings. Our approach is based on high level modelling of the bearings and to perform a sensitivity analysis to identify significant scaling effects.
Due to the small scale of these engines, the effect of the interactions between the different components on the efficiency is significant. Hence a future goal is to apply an integrated design and optimization approach to investigate alternative engine configurations.

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