MTU Aero Engines: Award-Winning Technology

In view of increasingly scarce resources, rising fuel prices, and the growth in air traffic – which continues unabated at an average rate of 5 percent per year – passengers, people living in the vicinity of airports, authorities, organizations, and other players in the aviation industry are calling for more fuel-thrifty and cleaner aircraft and engines. MTU Aero Engines has been working on innovative technologies for decades to further improve the environmental compatibility of future engines.

The target: Each new engine is to burn less fuel and be cleaner and quieter than its predecessor model. The key to success: With the PurePower® PW1000G Geared Turbofan™ (GTF), MTU and its US partner Pratt & Whitney have developed a solution for meeting the exacting requirements of the future. They are building a highly advanced engine that burns 15 percent less fuel, emits 15 percent less CO2, and cuts the perceived noise level in half. It marks the debut of a new family of environmentally friendly engines.

An indispensable, key component of the GTF is MTU’s high-speed, low-pressure turbine. Germany’s leading engine builder has been specializing in low-pressure turbines (LPT) for aircraft engines for decades and has become the world’s technology leader in this field. The company’s masterpiece is the high-speed turbine for the GTF, which beats conventional models by a wide margin. MTU is the leading manufacturer of this engine component worldwide. In March and April 2013, the company won two German Industry Innovation Awards for the novel technology.

The geared turbofan is based on an entirely new engine architecture: What sets this innovative propulsion system apart is that it features a reduction gearbox between the fan – that is, the large rotor at the engine inlet – and the low-pressure turbine, which drives the fan. With today’s engines, the two are seated on a common shaft. Uncoupling the two components allows the fan with its large diameter to rotate more slowly and the turbine to rotate much faster. This lets the individual components achieve their respective optimum speeds, greatly boosting the geared turbofan’s efficiency. The result is a significant reduction in fuel consumption, emissions of CO2, and noise; moreover, the propulsion system is much lighter than a conventional engine, as it has fewer stages, and hence a lower parts count.

Apart from the high-speed, low-pressure turbine, MTU also contributes the forward four stages of the high-pressure compressor to the GTF. This new transonic compressor is characterized by a markedly increased efficiency, which gives it a clear edge over most existing commercial models. It comes as an all-blisk design – blisks (blade-integrated disks) are high-tech rotors in which the disk and blades are produced as a single piece, eliminating the need for blade roots and disk slots. This increases strength and lowers weight. The GTF is a textbook example of successful technology development funding: Two of its key components – the high-speed, low-pressure turbine and the high-pressure compressor – are based on technologies developed under national and European research programs. With both components, MTU is setting new standards worldwide.

The GTF concept is catching on: The engine has meanwhile developed into a bestseller. Some 3,500 orders have been received to date. First applications include the Bombardier CSeries and Mitsubishi MRJ regional jets, the Airbus A320neo short- and medium-haul aircraft, and the Irkut MS-21. Last but not least, Embraer, too, has selected the clean engine as the powerplant for its second-generation E-Jets.

The geared turbofan offers even more savings potential, and work on its optimization has already commenced. Jointly with Bauhaus Luftfahrt, MTU has defined an ambitious program to further reduce the CO2 emissions of aircraft engines: With its Clean Air Engine (Claire) technology initiative, the company aims to reduce its CO2 emissions by 30 percent by the year 2035 in staged goals. The GTF engine alone already provides a reduction in CO2 emissions of around 15 percent. The second stage is aimed at reducing emissions by at least 20 percent by the year 2025. This can be achieved by making thrust generation even more efficient, for instance through the further development of individual components or through the use of a shrouded, counter-rotating propfan. The necessary technologies were developed by MTU already back in the 1980s. The company expects to achieve the 30 percent target in 2035. In the third and last stage, the efficiency of the core engine will be further enhanced, for example through the use of a heat exchanger.