This paper discusses the concept of MTU Aero Engines’ high-speed low-pressure turbine for the geared turbofan, which is based on the European Union research program ‘Clean’. Under the program, MTU developed the high-speed low-pressure turbine, the turbine centre frame, and an integrated heat exchanger. The paper also highlights that Pratt & Whitney, launched its geared turbofan (GTF) demonstrator project and asked MTU to be a partner. MTU has secured a 15 percent stake in either GTF version, which brings its high-speed low-pressure turbine, plus the first four stages of the high-pressure compressor.

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Want to frustrate engineers? Then go and lock the results of their research away in a drawer, safely preventing them from ever meeting with an application. Happily, nothing of the sort happened to the findings of the Clean (Component validator for environmentally friendly aero engine) program, a research project sponsored by the European Union (EU). Those results soon went to testify to MTU Aero Engines’ variously demonstrated knack for successfully transitioning technology into product lines.

In 2000, MTU partnered with France’s Snecma and others under the Clean program to explore a joint technology demonstrator conceived to validate components for future engine concepts. Under the program, MTU developed the high-speed lowpressure turbine, the turbine center frame and an integrated heat exchanger.

"The demonstrator engine was successful in the altitude test facility in Stuttgart," recalls Dr. Giinter Wilfert, senior manager, technical program management, new programs; who headed up the Clean program at MTU. "The test runs concluded in 2004 and that wrapped up the Clean program. We figured our turbine would sit around for a few years waiting for a geared turbofan to turn up." But much to the surprise of all involved, Pratt & Whitney (P&W) a year later, launched its geared turbofan (GTF) demonstrator project and asked MTU to be a partner.

"Our components didn’t even have time yet to catch dust on the racks; we rebuilt them right away," enthuses Wilfert. "Good thing we designed the highspeed low-pressure turbine so it could be paired also with a PW6000 core engine. The Clean experience has been invaluable in the design of the PurePower™ PW1000G and appreciably mitigates our development risk."

Technology leaps are a thing of the past, unless someone comes up with a breakthrough concept. Pratt & Whitney, in concert with MTU Aero Engines and other partners, did just that with its PW1000G two-shaft geared turbofan engine, a leader in terms of economy, environmental compatibility and noise reduction.

"Rather than a common shaft, the geared turbofan uses a reduction gear between the fan and low-pressure turbine, decoupling them," explains Wilfert. With its large diameter, the fan revolves once while the smaller turbine makes three revolutions in the same period of time. "That lets both compo"nents operate at their respective optimum speed and efficiency, making them considerably more efficient overall."

The engine burns 15 percent less fuel because the larger fan diameter raises the bypass ratio, and reduces noise by 24 decibels. Additionally, lower stage and blade counts save weight and reduce maintenance costs.

Mitsubishi and Bombardier have ordered the GTF which is expected to enter service in 2013. MTU has secured a 15 percent stake in either GTF version, which brings its highspeed low-pressure turbine, plus the first four stages of the high-pressure compressor.

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