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The Jet Set

When it comes to building jet engines, Pratt & Whitney has discovered the best way to stay on top: forging a partnership with WPI.

By Carol Cambo

If a Pratt & Whitney PW4000 jet engine powered up in your front yard, it would suck the oxygen out of your house in half a second. Inside the engine's turbine amid a blur of precisely machined blades and expanding gases, temperatures can top 2000°C. That's twice the temperature of the hottest fires that felled the World Trade Center and three times that of the sunlit side of Mercury, the planet closest to the sun.

A turbine blade, or airfoil, is not much bigger than your fist. Each is cast from a nickel-based superalloy that melts at about 1400°C. Theoretically, the blades should turn to mush inside the engine's inferno—not a comforting thought when you're cruising at 30,000 feet in a Boeing 747.

The fact that the blades survive has to do with a bit of alchemy performed by Pratt's engineers and technicians. They coat the blade with vaporized zirconia, a thermally insulating ceramic highly resistant to heat, then perforate each airfoil with tiny laser-drilled holes to pump cooling air. By the time it's finished, a blade is ready to withstand extraordinary temperatures—at a cost of between $1,000 and $5,000 a piece.

In the cutthroat business of building jet engines, every dollar and every degree of temperature counts. Through a cooperative program called the Learning Factory, WPI students tackled projects at Pratt & Whitney that have helped the company solve the cooling problem and other manufacturing issues. It's a relationship that gives students real work experience, with a company whose products power more than half of the world's commercial aviation fleet. For Pratt, the payoffs are unleashing agile minds on its challenges and, often, giving potential employees a test flight.

Illuminating the Problem

"Fly this girl as high as you can into the wild blue...", The Dixie Chicks

Twangy country vocals fill the hallway outside Washburn 252. Inside the closet-sized lab, seniors Susie Mendenhall and Beka Fowler attach coated wires to light-emitting diodes. Beka instant messages a friend as she calls up LabView on her computer. The women are preparing for a test run of their system this afternoon.

Susie and Beka are the latest WPI students to work on thermal barrier coating systems for PW4000 Pratt & Whitney turbine blades, which are used in a variety of gas turbine engines for both military and commercial aircraft. Using beams of light to simulate the application of zirconia vapor during the manufacturing process, the students have developed a computer model that can predict exactly how the coating will be applied.

The zirconia coating is the key to running a hotter, more efficient engine, but sometimes it's not enough to apply a simple, uniform barrier. Specific parts of the blade may need varying thicknesses, depending on the blade's position inside a working turbine.

Beka attaches sensors to a wax cast of the blade. (WPI students do not work with actual airfoils because their precise shape and size are proprietary, the kind of information a competitor would like to get its hands on.) Using photocells to measure the intensity of light that falls on each sensor, the women can calibrate the intensity of light with a blade's position in the coating cell (and by association, the thickness of the thermal barrier coating) to achieve the desired thickness.

Girls Just Wanna Build Stuff: To simulate Pratt & Whitney's turbine thermal barrier coating process using light, WPI senoirs Beka Fowler, left, and Susie Mendenhall hand-machine dozens of sensors that can measure varying degrees of light intensity and feed the data into a computer program.

These experiments are the culmination of much detail-oriented work, the students say. They set up a scrap blade with cooling holes, configured a light box, customized the software, and hooked up all the emitters and sensors.

Despite all of the hard work—or maybe because of it—they say the project is meaningful. "I know it is a cliché," says Beka. "But the greatest thing about WPI is getting to apply what we've learned to a real problem."

Their work is meaningful, at many levels, for many reasons. Pratt engines may literally fly these women high into the wild blue. After graduation, both ROTC students sign on with the Navy. In May Susie ships off to Jacksonville to join a jet squadron while Beka heads for San Diego to fly helicopters.

Above—And Beyond

Every few seconds—more than 20,000 times a day—a Pratt & Whitney-powered airliner takes flight somewhere in the world. Since 1925, the company's engines have broken the barriers of time and distance, conquering gravity along the way. United Technologies (UTC), Pratt's parent company, is a $27.9 billion entity that includes Otis elevators and escalators, Carrier heating and air-conditioning systems, Sikorsky helicopters, and Hamilton Sundstrand aerospace systems.

The relationship between WPI and UTC reaches back to the 1940s. Arthur Smith '33, an early graduate of the Institute's aero option, spent most of his career at United Aircraft (which later became UTC). He ascended to president in 1968 and chairman in 1972. As an engineer, he pioneered the use of water injection to increase aircraft engine power, which contributed to the success of American aircraft during WWII.

Over the years, UTC has funded numerous research projects and initiatives at WPI. The company's largest gift to the school—$500,000 over five years, ending in 1995—enabled WPI to establish the Office of Minority Affairs and to launch Strive, a summer outreach program for minority students. The gift enacted a vision shared by the company and the school, that promoting diversity is the key to ensuring a next generation of highly skilled scientists and engineers.

The relationship took a more integrated turn in 1996 with the founding of the Learning Factory, a project center located at the East Hartford plant where UTC makes commercial jet engines. WPI professor Rick Sisson, head of the Materials Science and Engineering Program, developed cooperative research projects between students and UTC. The inaugural project looked at improving the way blades are held during grinding. Since then, projects have run the gamut from devising better methods for holding the blade to improving management databases. And Sisson is still at it; he has advised the thermal barrier coating project for over three years.

WPI professor Rick Sisson, head of the Materials Science and Engineering Program

The project of "intelligently" applying thermal coating to airfoils was a brainchild of Mark Zelesky, manager at Pratt's Power Systems, and Sudhangshu Bose, a Pratt & Whitney fellow in materials and manager of the hot section alloys group. "Over 30 undergrads have worked on this," says Sisson, "including Bill Weir, who completed his Ph.D. in manufacturing engineering on the project last May." Weir now teaches ME1800, an introduction to manufacturing processes (affectionately known as "grunge lab") at WPI. Members of the team had a major breakthrough when they realized they could use light to simulate the low-pressure, high-temperature coating process. "With a little more work we will be close to implementing some of their findings," says Bose. "If the intelligent thermal barrier coating modeling had been done in-house, it would have taken longer and cost more money. So the company benefits." And so do the students. "They are exposed to a real manufacturing environment, in a leading aerospace industry," he says. "They contribute to technical problems and help us be more competitive while we are able to watch for potential employees."

The Hunt for Red X

Ryan Walsh '99 was one such student. He and his roommate, Jason Astle '99, worked at the Learning Factory during their senior year. They were charged with finding the cause of excessive airfoil scrapping—unusable "factory seconds."

"We had to understand the entire process first," remembers Walsh. "The scrap problem was occurring during laser drilling. We ran experiments, collected data. We looked at every reaction and interaction. It took us two months—and a bit of luck—but we finally figured out what was happening."

The students' research showed that scrapping spiked after a particular laser drilling machine was "homed out." Inside the machine is an arm to which the blades are affixed; whenever the machine get serviced, the arm gets homed out—sent to its farthest possible coordinates. Walsh and Astle pored over the maintenance logs. They found that the scrapping problem began six months earlier, following a maintenance overhaul of the machine in question.

That led to a talk with the technician who performed the overhaul. During the checkup he had changed the arrangement in the machine's wiring to make it more ergonomic for the worker. "In doing so, a rerouted wire was pulled taut every time the machine was homed out, thus disrupting the flow of information from the machine's positioning arm to its controller. That's what caused the drilling errors."

Pratt officials were impressed. It was the first time students claimed a "red x kill," company jargon for solving a thorny problem through statistical analysis. Walsh and Astle received an award from Pratt. Walsh signed on with the company as an employee in January 2000. Now he works developing software for the procurement end of the business.

[It's an exciting time to be in the e-business department; Pratt & Whitney is in the throes of a facility-wide software changeover that WPI's Department of Management is studying (see sidebar). "It's a monster," says Walsh of the process. Ed.]

"The best part about doing my project at Pratt was being part of the company. Except for the different color of our badges, we were real employees working on a real project—and we produced real results. That's better than any textbook you can get in any class. Plus we got to deal with real people."

Bose says the students' fresh perspective is a productive addition in the workplace. "They see the bureaucracy, but they don't get involved so much. They focus on the work." He is sold on the WPI difference; his son Krish '94 works at Pratt and son Jay graduated from WPI's electrical engineering program in 2001.

Dick Fair '74, Pratt's vice president of sales and customer service for the Americas, serves as liaison between the company and WPI. He marks his 25th year with UTC in 2003. "The relationship makes the company strong," says Fair. "The Learning Factory is a great recruiting tool. People are attracted to a company for many reasons, but they stay because of the culture. If they feel comfortable here, we're more likely to retain them."

Walsh says that it was the network, especially on a social level, that made Pratt the right fit for him, and probably for most of the other 100 or so WPI alums who work at Pratt. "You step right into a company of friends," he says. He and Fair have formed a WPI Focus Team to look at ways to foster the relationship. "We'll look at how we can support recruiting and diversity efforts and co-op programs," says Fair, "as well as work to steer grants and funding WPI's way."

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