MRI may hold key to improved jet engine performance

Monday, November 22, 2010

WASHINGTON - Apart from the usual task of imaging organs and soft tissues, Magnetic Resonance Imaging (MRI) could prove useful in improving the efficiency of jet engines, says researcher.

Lt. Colonel Michael Benson of the Stanford University is using MRI to improve jet engine. The technique could also provide insights into other fluid mixing problems, ranging from combustion to the flow of oil through porous rock in a well.

Jet engines are more efficient when they run hotter. In fact, the blades just downstream of the engine’s combustor run very close to their melting point. To maximize efficiency, the trailing edges of these blades are razor thin.

“If you don’t actively cool them, they melt,” said Benson.

Turbine engines cool blades by diverting some incoming air into a series of snake-like passages that run through each blade.

“At some point, the blades become too thin to do that, so they peel off some skin at the end of the blade and let the air run over the trailing edge,” said Benson.

When that cooler air exits the blade, it mixes with the hot air from the combustor, increasing the temperature of the blade surface above the coolant temperature.

This type of analysis starts by measuring the temperature and velocity of the hot and bypass air streams as they mix.

Researchers do this by releasing small particles, such as fluorescent dyes or oil droplets and hitting them with a laser. This illuminates the particles, whose positions are caught on a high-speed camera.

Unfortunately, the cameras capture only a small area, or tile, at a time. It also takes a lot of time doing so.

However, the MRI captures the same amount of data in four to eight hours, as they are designed to image three-dimensional objects.

Benson used a research grade MRI imager to run his experiments. The MRI images water mixed with copper sulfate, a low cost chemical often used to kill algae in ponds, which provides a rapid response to the pulses.

“Medical MRIs often use gadolinium as a contrast agent, but that’s really expensive, especially if you’re feeding fluid for a scan that runs for hours,” said Benson.

The findings were describes at the American Physical Society Division of Fluid Dynamics (DFD) meeting in Long Beach. (ANI)

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