GE/RR F136, Maximum Thrust 40,000 lb. 달성 소식...

 

현재 General Electric/Rolls-Royce 社가 F-35 JSF 장착용으로 개발하고 있는 F136 엔진이 약 40,000 lb. 이상의 Maxium Thrust

를 달성했다는 AW&ST 의 기사를 소개합니다.

 

美 남부 Tennessee 州에 위치한 美 공군 Arnold 연구소 (AEDC) 에서 최근 실시한 시험에서, GE/RR F136 엔진이 PW F135 엔진

대비 약 15% 이상의 최대 엔진출력을 발휘했다고 합니다. 금년 초 GE/RR 측은 F136 이 F135 대비 약 5% 이상의 높은 출력을 발휘

할 것이라고 주장한 바 있습니다만, 이를 뛰어넘는 15% 선까지 올라갔다는 기사입니다.

 

현재 게이츠 국방장관을 포함한 美 행정부와 백악관은 F-35 JSF 개발 완료에 있어서, F136 과 같은 제2엔진 개발, 즉 추가 개발비

투입은 없을 것이라고 공언을 하고 있습니다만, 美 의회에서는 F-35 JSF 가 Pratt & Whitney F135 단일 엔진으로 개발되는 것에

대한 각종 문제점들을 지적하면서, 지속적으로 GE/RR F136 제2엔진의 (Alternate Engine) 개발 필요성을 강조하고 있습니다.

 

이러한 가운데 이번 F136 엔진의 시험결과는, 향후 F-35 JSF 운용과정에서 발생되는 엔진 정비 및 유지비용과 관련해서 다시한번

제2엔진 필요성에 대한 찬반 논란을 불러올 것으로 예상됩니다.

 

한편 F-35 JSF 의 단일 엔진으로 채용된 F135 엔진 제작社 Pratt & Whitney 역시 향후 기존 F135 대비 최대 20% 이상 엔진출력을

증가시킬 계획이며, Geared Turbofan 을 적용한 가칭 <F135 Plus> 모델의 개발 가능성도 언급하고 있습니다.

 

끝으로 2002년 Farnborough Air Show 당시 Rolls-Royce 관계자는 F136 엔진의 최대 출력을 56,000 lb. 까지 끌어올릴 수 있다고

공언한 바 있습니다. 당초 주장한 40,000 lb. 를 훨씬 뛰어넘는 56,000 lb. 출력 주장으로 인해, 그 가능성에 대해 많은 논란을 불러

온 바 있습니다.

 

이에 이번 40,000 lb. 달성 소식은, 과연 2002년의 발표 자료에서와 같이 GE/RR 의 F136 엔진 최대출력 목표 56,000 lb., 즉 전투기

단일 엔진 최대출력 56,000 lb. 를 달성할 수 있을지 매우 기대되는 그리고 흥미로운 대목이라 생각됩니다.

 

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Alternate JSF Engine Thrust Beats Target

AW&ST, Aug 13, 2010  

By Guy Norris

Los Angeles

 

The intense battle over powering the F-35 Joint Strike Fighter could be heading to new levels following test results that show the General Electric/Rolls-Royce F136 alternate engine has more than 15% thrust margin against specification, significantly exceeding the power of the baseline Pratt & Whitney F135.

 

The tests at the U.S. Air Force’s Arnold Engineering Development Center (AEDC) in Tullahoma, Tenn., are the first to officially calibrate the combat-rated thrust of a production-representative F136 at sea level conditions. Although the test program is only a matter of days old, it already appears to be showing greater performance margin in afterburner than expected, says the General Electric Rolls-Royce Fighter Engine Team.

 

News of the tests reaches Congress as it heads toward a showdown with Defense Secretary Robert Gates, who has made killing the second engine a centerpiece of his crusade to cut unnecessary defense spending. With the Obama administration promising to veto any defense bill that prolongs the F136, the House has defied Gates and passed provisions that fund the engine. The Senate has not weighed in, but key committee chairmen have voiced support for competitive engines. Details of the F136’s test performance could strengthen support and more broadly undermine Gates’s efforts to reform the Pentagon (see p. 20).

 

“Initial results show we have more than 15% margin at sea level combat-rated thrust than the specification. That’s significantly beyond the thrust requirement right out of the chute,” says GE-Rolls. In March this year, following the first maximum afterburner test of a system development and demonstration engine, the team quietly expressed confidence the F136 would exceed the thrust of the baseline F135 by 5%. Actual thrust achieved in the test remains undisclosed, but it is in excess of 40,000 lb.

 

Pratt & Whitney, which derived its F135 from the F-22 Raptor’s F119 engine, remains confident its own growth plans will stave off the challenge from the F136 without getting ahead of the need or increasing development costs. The company, which begins final qualification tests of the short-takeoff-and-vertical-landing (Stovl) engine in Florida this month, plans to start tests of a higher-thrust F135 in January 2011 and begin rig tests of a growth fan later next year.

 

Although the F135’s thrust meets specification for the Lockheed Martin F-35 as currently configured, future growth potential is becoming an important part of the ongoing alternate engine debate. Thrust growth, and the engine life and maintenance cost benefits if traded for lower operating temperatures, are recognized as key factors by both sides. Thrust growth is considered particularly important for the performance of the F-35B Stovl variant, while the ability to use additional temperature margin to cut long-term support costs is applicable to all models, including the conventional-takeoff variants.

 

Given the added margin, GE-Rolls says its baseline F136 will be able to achieve a 5% thrust growth through a simple digital engine control “throttle push,” without eating into what it says could be a 25% maintenance-cost advantage over the F135. Russ Sparks, GE Aviation vice president for military strategy, says the reduced costs are directly related to the lower turbine operating temperatures in the engine, which was resized with a larger core and higher-flow fan in 2005, when Lockheed Martin increased the airflow capacity of the F-35 inlets to 400 lb./sec. The F136 fan was enlarged to pump up to 380 lb./sec., and the AEDC tests are being conducted within the airflow limits of the JSF inlets.

 

Pratt & Whitney Military Engines President Warren Boley says growth testing is part of a medium- to long-term strategy to increase F135 thrust by as much as 20%. “There is no doubt Pratt & Whitney has the suite of technology, and we are dedicated to do that,” he says. Although initial growth is aimed at satisfying F-35 thrust requirements, Boley says more power will also accommodate future applications on other platforms — including unmanned aircraft.

 

The first growth step, starting with tests in January, is based on digital engine control and turbine airfoil changes. These will provide 5-10% thrust growth and could be applicable for F-35s in production Lots 6, 7 and 8, “if needed,” Boley says. The changes could also form the basis of an engine upgrade that would be retrofitable at a depot level, he adds.

 

Beyond this, Pratt & Whitney’s advanced program team is studying more fundamental changes to the basic cycle of the F135 that could enhance performance and provide more growth potential. The initiative would introduce adaptive technology for the core and fan similar to that being developed by Rolls and GE under the U.S. Air Force-led Adaptive Versatile Engine Technology (Advent) research program. Although Pratt & Whitney was not selected to work major elements of Advent, it has continued to refine the technology it originally proposed for the competition.

 

“We are looking at a third fan stream that would take advantage of a gear,” says Boley, adding that this would “bring geared turbofan technology to the front end of the F135.” Studies for the growth engine, dubbed F135 plus, include looking at a “classic bigger fan.” The current focus is on whether it would be better to combine a larger fan with an adaptive core, or make both the core and fan adaptive.

 

GE’s Sparks contends that “maintaining the engine flow path is the key to affordable growth. We don’t need to make it bigger, or make the fan flow more air, to give our engine more thrust. A 5% growth will be achieved with the current F136 hardware, and we’re far enough into performance testing to verify that component efficiency is equal to or better than predicted. That’s the basis for retaining the margin in terms of fan speed and temperature.”

 

To boost thrust by 10%, the team plans to import technology being developed under the Air Force’s Versatile Affordable Advanced Turbine Engine program. “We’re talking things like better cooling and more [ceramic matrix composites], and we’ll do it all without making any airflow changes through the engine,” he says. Ceramic matrix composites are used in the first stage of the F136 low-pressure turbine and would be used for other stages in the higher-thrust version, says the engine team.

 

 

  GE/RR F136 Engine Test at Maximum Thrust Conditions ⓒ USAF

 

  GE/RR F136 Engine Test at Maximum Thrust Conditions ⓒ USAF