Safety and reliability for planes: Researchers explore atmospheric hazards to aircraft engines

A project led by industrial and interdisciplinary academic teams is creating new research on how weather and airborne particulates impact gas turbine engines. This precompetitive work brings together industry leaders Rolls-Royce and Pratt & Whitney along with two colleges within Virginia Tech. The group will look for additional opportunities to expand membership globally to create a wide-reaching set of data.

Gas turbine engines are complex machines with rapidly spinning parts and extreme temperature gradients. They suck in massive amounts of air, compressing it before using it to facilitate combustion and create propulsion. As the engine pulls in air, it also pulls in any particulates that are contained within it. Depending on what those particulates are, they could seriously impact engine function.

In 2010, the eruption of the Eyjafjallajökull volcano in Iceland grounded more than 100,000 flights in Europe. Although the volcano sits as far from most of Europe as California is from Missouri, airlines throughout Europe grounded planes to avoid safety risks. It was the worst peacetime disruption to air travel in history.

This incident followed a dramatic event in 1982 involving British Airways Flight 009, which experienced the failure of all four engines after flying through an unseen ash cloud during a night flight offshore Indonesia. The heroic efforts of that plane’s crew saved the plane and passengers, but the incident shone a light on the dangers of particle matter to flight.

Nonvolcanic threats can be just as dramatic, including well-publicized accidents in which military aircraft kick up clouds of dust upon landing and promptly lose power. Even the seemingly uneventful flights we take every day involve the ingestion of small quantities of dust that can slowly damage engines, shorten intervals between expensive maintenance, and decrease engine efficiency.

The collaborative research team is looking for better solutions than emergency maneuvers and expensive maintenance. By combining researchers' understanding of the properties of airborne particulates with how jet engines function, the team hopes to improve flight safety and engine resilience.

Assembling a team already in place

The ability to navigate constantly changing global air conditions is of great importance to engine manufacturers and their customers. Approaching the problem requires a team with skills in a wide range of areas – a request easily filled by the diverse researchers on Virginia Tech’s Blacksburg campus.

Team member Todd Lowe, professor in the Kevin T. Crofton Department of Aerospace and Ocean Engineering, is excited to apply researchers’ complementary skills to industry.

“We’re trying to create precompetitive knowledge that will let us use learning that we get at the university at the small scale and apply it to big engines on the large scale,” he said.

Prior to the current project, both Pratt & Whitney and Rolls-Royce already had research underway in Virginia Tech labs, working only a few feet away from one another. Lowe directs the Pratt & Whitney Center of Excellence, conducting studies in an ongoing partnership with that company. His colleague, mechanical engineering Professor Changmin Son, heads up the Rolls-Royce University Technology Center, one of only three in the United States.

Research facilities for both centers are contained within the Advanced Power and Propulsion Lab, making the new collaboration a natural fit for Lowe and Son. Virginia Tech is also the only university in America housing such centers for both companies in the same place, thus creating an ideal cooperative space.

To understand the dynamics of airborne particulates, the team also needed a seasoned researcher familiar with the properties of the particles themselves. As luck would have it, Son needed only look across campus to Associate Professor Mark Caddick in the College of Science’s Department of Geosciences. Caddick had conducted previous work at the Advanced Power and Propulsion Lab, so he had established a collaborative relationship with both the research team and the industry partners. His prior research included analyzing how minerals change and react when heated, including how they react with one another when they melt. It turns out that many of the same rules apply equally to a mineral heated in the Earth or in an engine, although key differences represent an exciting new challenge.

According to Caddick, the different minerals in Earth’s atmosphere may each have different effects on the engine. They melt at varying temperatures, have specific strengths, and erode metal surfaces in a multitude of ways. Once melted, however, each mineral has the potential to create clogs within an engine. Caddick’s team will provide input on those material properties, shedding light on how the minerals behave inside engines.

“Engineers have spent a long time trying to understand the effects of the dust and how to mitigate against those effects,” said Caddick. “My contribution here is to improve understanding of how the engine works by improving understanding of how the particles themselves work. Ultimately, we need to know how incomplete our understanding of engine damage might be if the industry only ever considers the simplest of dusts in its test programs.”

Expanding the team

While the team is well-equipped for the current project, Son foresees the scope of its work expanding. Researchers will initially run dust ingestion tests on a Rolls-Royce M250 engine already in place by pushing through a variety of materials. In the future, Son looks to add researchers to tackle the project’s complexities.

“This is a long-term environmental problem that won’t go away,” said Son. “It is a multidisciplinary challenge that includes global weather forecasting, and we need to expand the team. We need to add weather forecasting and modeling, computer scientists to handle big data, and people with expertise in statistics.”

Son has already bolstered the team’s capabilities with several mechanical engineering colleagues, including John Palmore, Rui Qiao, and Wing Ng. Palmore and Qiao have deep expertise in computational simulation and modeling of gas flows and particle collisions, while Ng has his own docket of similar projects at the Advanced Power and Propulsion Lab. This combined knowledge, coupled with the original team’s contributions, creates an unparalleled interdisciplinary approach for tackling the complex problem of atmospheric hazards.