Power Conversion Group
School of Electrical and Electronic Engineering
The University of Manchester
Electro-Mechanical Interaction in
Aero Gas Turbines
For details contact: Tom Feehally;
E-Mail: [email protected]
Supervisor: Dr J Apsley; Tel.: +44 (0)161 306 4732;
E-Mail: [email protected]
Acknowledgements: University of Manchester Alumni Fund,
EPSRC, Rolls-Royce Plc
• Develop methods for predicting electro-mechanical interaction in
aero gas turbines
• Assess functionality of DFIGs for aero applications
• Develop schemes to reduce the impact of interaction between
electrical and mechanical domains
Today’s aircraft require high levels of electrical power. Typical loads
can include: flight control systems, wing anti-icing, actuation and air-
conditioning.
Electrical generators are mounted on the outer casing of the gas
turbine alongside other auxiliary loads such as hydraulic pumps, fuel
pumps and oil scavengers. These are driven from a common, parallel
axis, gearbox which is coupled mechanically to a rotating spool of the
engine via a complex transmission system. This electro-mechanical
network is shown in Figure 1.
Project Background
Project Objectives
Electro-Mechanical Interaction
Double Fed Induction Generator
Electrical loading is transferred through the generator as torque
loading on the mechanical drivetrain. Hence, variable electrical loads
can excite resonances within the mechanical network, increasing the
likelihood of mechanical component failure.
Extensive MATLAB/Simulink simulation has been carried out which
includes the mechanical transmission and electrical generator. This is
used to demonstrate the ability of pulsed electrical loads to induce
sustained mechanical oscillation within the gearbox, see Figure 2.
Electro-Mechanical Test Rig
The electrical generator and its control dictates the extent to which
mechanical resonances can be excited by electrical systems. The fast
dynamics of a Double Fed Induction Generator (DFIG) offer the
potential for a control system to partially decouple the electrical and
mechanical domains.
The DFIG is also able to provide a constant frequency electrical
output across the mechanical speed range of the gas turbine. This
offers the benefit of a constant frequency system without the
traditional requirement for a Constant Speed Drive hydraulic coupling,
The test rig, shown in Figure 3, provides a scaled representation of an aero gas turbine electro-mechanical system. A DC drive machine and high
inertia flywheel are controlled to replicate spool behaviour. The transmission system is represented by a long driveshaft, with low torsional
stiffness, which powers the gearbox. Three loads are driven from the gearbox, two flywheel loads and a DFIG with coupled electrical load bank.
Generator control is implemented to produce constant frequency electrical supply and to develop active damping between electrical and
mechanical networks.
Figure 3: Electro-mechanical test rig (CAD)
Figure 1: Gas turbine cross section showing mechanical drivetrain (CAD)
[image courtesy of Rolls-Royce plc]
Key features of the test rig:
• Based on Trent1000 architecture
(matching frequency response)
• Variable gearbox drive configuration
• Software based emulation of gas turbine
spool behaviour
• Adaptable architecture (e.g. alternate
generator configurations, use of hydraulic
loads)
• Control scheme to reproduce aircraft
mission profile
• High bandwidth torque and position
sensing
Figure 2: Simulated pulsed electrical loading and resultant gearbox torque
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