Product category:
Stepper and Servo Drives, Motors, Controls
News Release from: Motor Technology | Subject: Servo systems
Edited by the Engineeringtalk Editorial
Team on 24 March 2008
Customised servo answers jet test
demands
Servo system is designed to drive a rotating drum at high speed in the exhaust of a test rig designed to replicate a jet engine combustor.
Motor Technology has designed a servo system to drive a rotating drum at high speed in the exhaust of a test rig designed to replicate a jet engine combustor The rig, which was project managed and built by Howco Oilfield Services based on a design by the Frazer Nash Consultancy, replicates the combustor of a jet engine found on modern passenger aircraft
This article was originally published on Engineeringtalk on 29 Aug 2001 at 8.00am (UK)
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The rotating drum, positioned in the exhaust of the combustor, generates acoustic excitations, which can affect the flame inside the combustor in different ways.
Research and development engineers, working for a major aero engine manufacturer, wanted to test the responsiveness of the flame to a range of acoustic excitations.
The servo system had to provide precise control of the drum's speed and tolerate the hot exhaust gases of the combustor.
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The rotating hexagonal drum changes the size of the exhaust area and creates a pressure wave that reacts with the flame inside the combustor.
Probes then measure the amplitudes of pressure fluctuations and the results can be used to improve the technology of future engine design.
The drum had to rotate at speeds up to 8000rev/min and generate frequencies up to 800Hz.
To meet specifications Motor Technology customised a 16.9kW servomotor with a maximum speed of 13,400rev/min that would drive the drum through a metal bellows coupling.
The customisation of the motor involved using a Kevlar wrap to bond the magnets to the rotor providing added protection against the high centrifugal forces exerted on the magnets at high speed.
As the motor would be located only 300mm from the 700-800C exhaust emissions, special care had to be taken when specifying the coupling, feedback device and cables.
Furthermore, fitting cold plates on three sides of the motor was necessary so that it could be water cooled.
Motor Technology also supplied bespoke, PC-based operator software to enable the operators to set-up and store a number of different test-cycle recipes, comprising frequency range, number of step points and dwell time, which meant that a 2-3h test run could be carried out without user intervention.
During a test cycle the drum would increase its frequency over a period of time from zero to 800Hz.
In addition, test engineers would alter the exhaust pressure by as much as 21bar.
Due to the very high costs involved in running the tests - the rental for the test facility based at the German Institute for Air and Space Travel alone ran to tens of thousands of euros per day - the drive system had to be designed for high reliability.
The final system, which was designed and built in-house by Motor Technology's engineering department, provides full manual control in case of computer failure.
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