The Frontiers of Engine Technology — The Energy Efficient Engine

In the early 1980s. the aircraft industry had endured numerous difficulties, including reduced profitability, increasing fuel costs, higher worker wages, political pressures with deregulation, and increasing worldwide competi­tion. Many once-dominant airlines were fighting for their survival, includ­ing Pan Am. Pratt & Whitney and General Electric, two of the leading U. S. engine manufacturers, were “cutting each others’ throats, and prices,” and experiencing increasing difficulties competing in the world market against the British government-owned Rolls-Royce.30 But according to one 1983 report, despite these problems, the “airline industry in the years ahead

Model of the E* technology improvements. These included improved component aerodynamics, improved compressor loading, active clearance control, low emissions combustor, and higher-temperature materials. (NASA Glenn Research Center |NASAGRC].)

looks a bit rosier.” One major reason cited for this optimism was a “less noticed effort” that involved the redesign of the aircraft engine itself.[223] [224] This was another ACEE project managed by Lewis Research Center, known as the Energy Efficient Engine. As Forbes magazine reported, EJ was a "NASA success story.. . thoroughly overshadowed by the glamor­ous space programs.”’2

Given their intense competition. Pratt & Whitney and General Electric were strange bedfellows, but they continued this relationship in the Ei project. Each organization had ideas about how to improve fuel efficiency for aircraft engines, but neither was willing to accept the risk, in both time and money, to develop these ideas on its own. NASA stepped in to assume the majority of the risk, providing $90 million to each company, with a promise that each would invest $10 million of its own. This program had

GE Energy Efficient Engine (June 16.1983). (NASA Glenn Research Center |NASAGRC|.)

several main goals: to reduce fuel consumption by 12 percent, decrease operating costs by 5 percent, meet FAA noise regulations, and conform to proposed EPA emission standards. Additional goals included guidelines for minimum takeoff thrust and a safe and rugged engine with a 10-percent weight reduction.5′ The engines used for benchmarking fuel efficiency were the same ones used for the ECI studies—the Pratt & Whitney JT9D and the General Electric CF6. Also as in the ECI program, these two prime contractors worked with the airlines to discuss engine design options. These included Boeing. Douglas, and Lockheed. Eastern Airlines and Pan American served as additional advisers and contributed opera­tional experience.

The program was managed by Carl Ciepluch at Lewis (as well as Raymond Colladay for a time), Ray Bucy at General Electric, and W. B. Gardner at Pratt & Whitney. Bucy was extremely enthusiastic about this program, saying that the E’ program was “guiding the future of aircraft engines.”[225] [226] Fuel-efficient aircraft were very complex technological sys­tems that required extensive and costly research, he believed, but the rewards would be well worth the investment. Bucy hoped the resulting engine would save 1-million gallons of fuel per year for each aircraft fly­ing commercially. Gardner even thought that the program would surpass its expectations “beyond the program goal.”[227] [228]

That goal was to have a new turbofan engine ready for commercial use by the late 1980s or early 1990s. A turbojet derived its power and thrust entirely from the combustion and exhaust of its burning fuel.5* A turbofan is also a turbojet, but it has an extra set of rotating, propeller-like blades, positioned ahead of the engine core. The air from the fan goes partly through the engine core, and the remainder flows around the out­side the engine. The “bypass ratio” is the ratio of air flowing around the engine to the air flow ing through it. When this ratio is either 4 or 5 to 1. the engine is referred to as a “high-bypass engine.” The high-bypass turbofans were more efficient than were either the turbojets or the earlier low-bypass engines developed in the 1950s and 1960s. However, by the 1970s. the high-bypass engines promised greater potential for application to wide – body commercial aircraft, although one of their main problems was their environmental impact, in terms of noise and emissions.” The potential of the high-bypass turbofan engine was the Ei program’s main goal.

The idea for incorporating high-bypass engines into the existing com­mercial airline fleet began in 1974. Two investigations—the “Study of Turbofan Engines Designed for Low Energy Consumption." led by General Electric, and the “Study of Unconventional Aircraft Engines Designed for Low Energy Consumption," led by Pratt & Whitney—demonstrated a great deal of promise. Both studies suggested to NASA the importance of new high-bypass engines. But, as was so often the case, “the cost of such pro­grams. . . [was] enormous,” and the time required to accomplish it was at least a decade.5*1 To make the development more feasible for industry’, the report suggested a continued joint effort led by NASA, with the results made available to all airlines and engine manufacturers. Without governmental support, such an open research atmosphere would have been impossible. “Results from these studies.” wrote Colladay and Neil Saunders, “indicated enough promise to initiate the EEE project.”[229] [230] [231]

In the E‘ program, both General Electric and Pratt & Whitney were given the task of building a new turbofan engine. But the idea was not for them to build a commercial-ready engine. The E; engine was to be used primarily for testing and proof of fuel-efficient concepts. The new technological components included a compressor, fan, turbine-gas-path improvements, structural advances, and improved blading and clearance control. Although the contractors had the same goal, they approached their work within Ел differently.[232] Pratt & Whitney engineers took a

Energy Efficient High Pressure Compressor Rig (April 10. 1984). (NASA Glenn Research Center [NASA GRC|.)

“component” strategy and concentrated on developing a high-pressure turbine that could be operated with a lower temperature of hot gas to improve efficiency. General Electric proceeded with a more compre­hensive approach, researching the best way to integrate a new fan. high – pressure compressor, and low-pressure turbine. According to Jeffrey Ethell. the freedom that the contractors had was important: “The ‘clean sheet’ opportunity. .. gave both companies the chance to leave their nor­mal line of evolutionary development and leap forward into high-risk. .. areas to research and aggressively push the frontiers of technology.”[233] Along with these two prime contractors, there were subcontracts with major commercial airframe manufacturers. Boeing, Douglas, and Lockheed provided expertise in areas related to airplane mission defini­tions and engine and airframe integration. Just as in the ECI program. Eastern Airlines and Pan American also provided ongoing evaluation of the results from the perspective of the airlines. NASA also planned to use its own in-house technological advances and other contractors to support specific program needs. NASA never intended to develop a new engine as a product. This was a project for the engine manufactur­ers to achieve after NASA assisted with the proof of concepts. Elements of the ECI program such as improved fans, seals, and mixers were incorporated into the E‘program, and the E‘engineers were also able to apply results from the ECI Engine Diagnostic program to improve engine performance.[234]

A first step in the E’ program was to identify risk factors that might potentially cause the new engine to fail. In an April 1976 letter from James Kramer. Director of the ACEE office, to Donald Nored. the chief of the Energy Conservative Engines Office at Lewis, Kramer asked that the Center perform a “risk assessment of the total E‘ program.”[235] With a list of potential failures in hand, the Center could better under­stand the implication on schedules, cost, and program success. A separate action plan could then be put in place to reduce these risks. Two months later, Nored and Lewis completed the risk assessment. “By nature," wrote Nored, “this is a high risk program, as is true of most advanced technology programs, and there is no way to make it a safe bet.”[236] The best way to minimize risk, according to Nored. was to use multiple con­tractors who were supplied with adequate funds. Both General Electric and Pratt & Whitney took on separate areas of risk that were unique challenges to their approaches and engines. With both companies involved. Nored believed “at least one-half or greater of the stated goal” would be achieved.

As the program got underway, one important advance was a com­puter control system known as a full authority digital electronics control (FADEC). It could monitor and control 10 engine parameters at the same time and communicate information to a pilot. Sensors were known to be one of the least reliable of all engine components. The FADEC system was able to compensate for this problem in case of failure by modeling what the engine should be doing at any given time during a flight. If the sensor failed, then the FADEC. based on its model, could tell the various engine components what they should be doing.[237]

In 1982, budget reductions caused “program redirection” for the EJ project. According to Cecil C. Rosen, the manager of the Lewis propulsion office, this meant changes for both General Electric and Pratt & Whitney in how they planned to complete the project. General Electric proceeded with its core engine test and suspended work on emissions testing and an update for a flight propulsion system. For Pratt & Whitney, the redirection meant a continued focus on component technology as opposed to an over­all engine system evaluation. The main concern with this plan was that it provided more funding for Pratt & Whitney than General Electric because it had “much farther to go in its component technology efforts.” Rosen hoped this “unequal funding,” which went against the original spirit of the E’ program, would be acceptable.[238] [239] [240] [241]

General Electric completed the program with a great deal of success and as early as 1983 was being called the “world’s most fuel-efficient and best-performing turbofan engine.”6′ Bucy, the Program Manager at General Electric, called it “one of the most successful programs on an all-new engine in yearsWhile the low-pressure turbine was a diffi­cult challenge from an aerodynamic perspective, it achieved the desired parameters laid out by NASA at the start of the program to define success. There is a 13-percent improvement in fuel efficiency over the CF6-style engine, which was 1 percent better than required. GE immediately began to incorporate the new technology into its latest engine designs, including the CF6-80E, the latest engine for the Airbus A330, and the GE90 engine for the Boeing 777.M The GE90 first made headlines in 1991 because it “pushed the edge of technology ” not only because it was more efficient, but also because it used another ACEE project. It became the only engine to use composite fan blades, making it 800 pounds lighter, with a 3.5-per­cent fuel savings. It also had a cleaner burn, producing 60 percent less nitrous oxide, and was quieter. Though it was a larger engine, its engineers believed that the wind whistling over the landing gear would produce more noise than the engine. As Christopher D. Clayton, the manager of the GE90 technical programs said,‘’It will give us a much more efficient engine. That’s the real purpose of it."[242] [243] The 777 now Hies with an engine based directly upon the one developed through the efforts of the E’ ACEE program.

Pratt & Whitney also had success with its energy efficient engine technology, though at a slower pace. In 1988, it reported that the “effi­ciency trends show a steady increase”’1 with the E3 technology. But the company still had research to perform to enable it to realize the gains for “tomorrow’s engine." These successes were finally realized in 2007, when it launched the new energy-efficient Geared Turbofan as the engine for the Mitsubishi Regional Jet. This was a 70- to 90-seat passenger aircraft, and Mitsubishi planned to purchase 5,000 of them over the coming 20 years. The technology for this engine could be directly traced back to Pratt & Whitney’s participation in the ACEE program.[244]*

These favorable results of the E* program, as well as the achievements of the EC1 program, resulted in enthusiasm for ACEE. In 1979, Colladay said, “This early success in the first of the ACEE Program elements to near completion is certain to continue as more of the advanced concepts are put into production.”[245] However, this “continued certainty” was seri­ously threatened in 1980 with a new presidency on the horizon. Unlike ECI, which returned such fast and positive results, the other ACEE pro­grams required a longer window to develop and prove their technologies, and their engineers required a commitment of time and money from the United States Government to ensure that their research continued. Just 3 years after the entire program began, there were serious concerns not only for the future of ACEE. but for the future of all aeronautics activi­ties at NASA. For the ACEE participants, the question was: Would the Government terminate such a vital fuel-efficiency program to the Nation early, when it had already had such success with its shorter-term projects like the Engine Component Improvement? For NASA, the question was even more dire: Would the Agency be allowed to continue its work in aeronautics?