MRI Imaging Accelerates Jet Engine Efficiency Research

Magnetic resonance imaging (MRI), a medical imaging technology that captures detailed 3‑dimensional data of moving fluids, is poised to transform jet engine design, says Lt. Colonel Michael Benson, a Ph.D. candidate in Mechanical Engineering at Stanford University.

In a single MRI scan, researchers can acquire the same volumetric flow and mixing data that traditionally takes two or more years of on‑ground experiments—drastically shortening development cycles and enabling rapid optimization of turbine performance.

Benson first introduced the concept at the American Physical Society Division of Fluid Dynamics meeting in Long Beach, Calif., on November 17. He explains that MRI can provide insights into a wide range of fluid‑mixing challenges, from combustion chemistry to oil transport through porous rock.

His work builds on pioneering studies by Stanford researchers Christopher Elkins and John Eaton, who used MRI to examine coral colonies and turbine blades. Eaton suggested that Benson apply the technique to the mixing of hot combustion gases and cooler bypass air inside jet turbines.

Jet engines operate most efficiently at the highest temperatures possible, but this pushes turbine blades—especially those just downstream of the combustor—near their melting points. To keep them from melting, the trailing edges of these blades are manufactured extremely thin.

“If you don’t actively cool them, they melt,” Benson explains. “Turbine engines divert some incoming air into snake‑like passages that run through each blade, providing cooling. When the blades become too thin, they shed a thin skin at the tip and let the air flow over the trailing edge.”

When the cooler air exits the blade, it mixes with the hot combustor air, raising the blade surface temperature above the coolant temperature. By mapping this mixing process, Benson hopes to refine bypass design and reduce the amount of coolant required, thereby boosting engine performance and fuel efficiency.

Traditionally, researchers measure temperature and velocity of the hot and bypass air streams by seeding the flow with fluorescent dyes or oil droplets, illuminating them with a laser, and recording their motion with high‑speed cameras. The limited field of view and shallow depth of field mean that many image tiles must be stitched together to form a single plane, and dozens of planes are needed to reconstruct a three‑dimensional experiment—a time‑consuming process.

“I know one Ph.D. student who spent three years collecting this type of data,” Benson says. “MRI can capture the same volume of data in four to eight hours.”

MRI achieves this by perturbing protons in hydrogen molecules with an electromagnetic pulse and measuring their rapid realignment with the magnetic field, providing volumetric imaging of the flow field.

For his experiments, Benson uses a research‑grade MRI imager and images water mixed with copper sulfate—a low‑cost chemical that reacts quickly to the MRI pulses. Medical MRIs often rely on gadolinium as a contrast agent, but that is expensive for scans that run for hours.

Although still refining blade trailing‑edge designs, Benson reports an early success: a 10 percent increase in surface cooling, translating to a 100‑150 °F reduction in blade temperature.