| Summary: | Gas turbine design needs of high-speed turbomachinery whose layout is organised in
compressor-turbine pairs mechanically linked by concentric shafts. The mechanical
failure of a shaft leads to compressor-turbine decoupling provoking the acceleration
of the free-running turbine. In view of such scenario, it is of paramount importance
to guaranty the mechanical integrity of the turbine, in terms of high energy
debris release. Certification authorities require proof that any possible failure will be
contained; admitting the reliable simulation capability of the event as certification
strategy.
The objectives of this research activity have aimed at the development of reliable
simulation tools based on analytical and semi-empirical models. The integration
of all the different models/modules together in an “all-in-one” tool provides the
sponsor company with the capability to simulate and assess various shaft over-speed
scenarios during the early stages of an engine's design and development program.
Shaft failure event cannot be understood unless engine components interaction and
fast transient effects are taken into account in a global manner. The high vibration
level consequence of the breakage, or the thermodynamic mismatch due to the rapid
free-running compressor deceleration, trigger the surge of the compression system
which affects to the performance of every engine component. Fully-transient simulation
capability to model compression system post-stall performance and secondary
air system behaviour has been developed. Component map prediction tools have
been created for compressor reverse flow performance and turbines affected by inlet
distorted flows.
The development of the so-called “all-in-one” simulation tool has been completed and
it has been applied to the modelling of a real case of shaft failure. Reliable prediction
of thermodynamic properties evolution and over-speeding turbine terminal speed
have been shown. The robustness and flexibility of the simulation tool have been
demonstrated by its application to different theoretical scenarios.
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