Wireless sensors monitor jet's bearings

Electrical switching & drive systems & components

First Quarter 2008 Electrical switching & drive systems & components

Researchers at Purdue University, working with the US Air Force, have developed tiny wireless sensors resilient enough to survive the harsh conditions inside jet engines, where temperatures are in the order of 300°C, to detect when critical bearings are close to failing and prevent breakdowns.

The devices are an example of an emerging technology known as 'micro electromechanical systems', or MEMS, which are machines that combine electronic and mechanical components on a microscopic scale.

“The MEMS technology is critical because it needs to be small enough that it does not interfere with the performance of the bearing itself,” said Farshid Sadeghi, a professor of mechanical engineering. “And the other issue is that it needs to be able to withstand extreme heat.”

The researchers have shown that the new sensors can detect impending temperature-induced bearing failure significantly earlier than conventional sensors.

“This kind of advance warning is critical so that you can shut down the engine before it fails,” said Dimitrios Peroulis, an assistant professor of electrical and computer engineering.

Dimitrios Peroulis, an assistant professor of electrical and computer engineering at Purdue, holds a new MEMS sensor. (Purdue News Service photo/David Umberger)

The sensors could be in use in a few years in military aircraft such as fighter jets and helicopters. The technology also has potential applications in commercial products, including aircraft and cars.

“Anything that has an engine could benefit through MEMS sensors by keeping track of vital bearings,” Peroulis said. “This is going to be the first time that a MEMS component will be made to work in such a harsh environment. It is high temperature, messy, oil is everywhere, and you have high rotational speeds, which subject hardware to extreme stresses.”

The Purdue researchers received a grant from the US Air Force in 2006 to extend Sadeghi’s previous research (aimed at developing electronic sensors to measure the temperature inside critical bearings in communications satellites) to the high-temperature applications in jet engines.

“Current sensor technology can withstand temperatures of up to about 210°C, and the military wants to extend that to about 300°,” Sadeghi said. “At the same time, we will need to further miniaturise the size.”

The new MEMS sensors provide early detection of impending failure by directly monitoring the temperature of engine bearings, whereas conventional sensors work indirectly by monitoring the temperature of engine oil, yielding less specific data.

The devices will not require batteries and will transmit temperature data wirelessly. Power will be provided using inductive coupling, which uses coils of wire to generate current.

“The major innovation will be the miniaturisation and design of the MEMS device, allowing us to install it without disturbing the bearing itself,” Peroulis said. “Data from the onboard devices will not only indicate whether a bearing is about to fail but also how long it is likely to last before it fails.”

For more information contact Farshid Sadeghi, Purdue University, +91 765 494 5719, [email protected], www.purdue.edu/

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Wireless sensors monitor jet's bearings

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