New manu­facturing processes made by MTU

For decades now, compressors and turbines made by MTU Aero Engines have been among the finest to be found in the marketplace. The masterpieces of Germany’s leading engine manufacturer in these technology fields are the high-pressure compressor and the high-speed low-pressure turbine for the Geared Turbofan™ engine. Both components incorporate leading-edge technologies and have been manufactured using highly advanced processes—likewise developed by MTU.

11.2014 | Text: Martina Vollmuth

Aircraft engines are high-tech products that must meet ever more stringent re­quire­ments: Each new generation of propulsion systems must be more efficient, cleaner and less noisy than its predecessor generation. In their Strategic Research and Innovation Agenda (SRIA), the European aviation industry and the research community have defined the ambitious targets for future air traffic: By the year 2050, they aim to reduce fuel consumption and CO2 emissions by 75 percent each and cut noise levels by 65 percent as compared with typical new aircraft in 2000. MTU Aero Engines has for years been developing innovative engine technologies that will now contribute greatly towards achieving these goals.

Progress in engine construction essentially depends on whether manufacturers suc­ceed in improving two physical key parameters: propulsion efficiency and thermal efficiency. MTU’s development efforts are targeted at optimizing both parameters, because each efficiency enhancement reduces pollutant and noise emissions. But the increased efficiency comes at a price: “As a result of the higher stresses acting on the engine components, both the materials and manufacturing techniques have to satisfy more exacting requirements,” explains Dr. Stefan Weber, Senior Vice President, Tech­nology and Engineering, Advanced Programs at MTU. New materials, such as cer­am­ics, call for new manufacturing processes, while existing technologies are being pushed to their physical limits. MTU’s experts have for decades been busy exploring all aspects of manufacturing, refining existing techniques and developing new ones. “Our technological capabilities are top-notch,” says Richard Maier, Senior Vice President, Production Development and Support at MTU in Munich. “In some manufacturing technology areas, the company has become a world leader.”

A textbook example of MTU’s expertise is Pratt & Whitney’s PurePower® PW1000G Geared Turbofan™ engine family: The Munich-based engine manufacturer not only contributes highly engineered components to this game-changing propulsion system, such as parts of the high-pressure compressor, the high-speed low-pressure turbine and innovative brush seals, it also produces these parts using its high-tech processes.

Blisk manufacture

Blisks (blade integrated disks) are high-tech components manufactured in one piece, a design that eliminates the need to fix separately manufactured blades to the disk. They are used in low-pressure and high-pressure compressors for military and com­mer­cial applications. MTU is one of the leading manufacturers of these blade in­te­grated disks worldwide. To remain at the forefront of this technology and to further expand its production capacities, MTU last year set up a center of excellence for blisks at its premises in Munich. “Our new production for blisks is surely leading-edge manu­fac­turing for engine components of this kind,” according to MTU Chief Operating Officer Dr. Rainer Martens. The production concept is based on optimized, automated process workflows and the latest in machinery and equipment.

The Munich headquarters is where the center of excellence for blisk production is located.

PECM

Ever more complex compressor airfoil geometries, more sophisticated materials and tighter manufacturing tolerances are pushing conventional production techniques to the limits of their functional capacities. This is why MTU has developed precise elec­trochemical machining, or PECM for short, and is now using this technique to process compliance hardware for the PurePower® PW1100G-JM Geared Turbofan™, the en­gine powering the A320neo—blisks with an extremely complex airfoil geometry—on the two new machines commissioned this year.

PECM is a further development of the ECM process. Production specialist Maier ex­plains: “Electrochemical machining is a standard technique that has long been part of our portfolio of manufacturing capabilities. PECM allows us to work even more pre­cise­ly and effectively, as only two steps are needed to produce a nickel blisk airfoil.” The advantages the technique affords over conventional machining: The tools do not actually touch the workpiece, so they do not suffer wear in the process. Moreover, PECM allows an unprecedented level of precision to be achieved. Says Dr. Martens: “In the field of this highly complex technology we are well ahead of the field—and likely to remain so for quite some time. After all, we possess the relevant patents.”

Production components manufactured using selective laser melting. Hover over the image for a bigger view

Production components manufactured using selective laser melting.

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Production components manufactured using selective laser melting.

Additive Verfahren

3D-Printing, Rapid Manufacturing oder auch Additive Verfahren sind Oberbegriffe für Fertigungs­techno­logien, die derzeit eine Wirtschafts­branche nach der anderen erobern. In der Luftfahrt­branche ist die MTU eines der ersten Unternehmen, das bereits Bauteile für die Serie herstellt. Der Durchbruch gelang mit dem selektiven Laser­schmelz­verfahren (Selective Laser Melting = SLM), das Bauteile Schicht für Schicht entstehen lässt. Damit fertigt die MTU in München Boroskop­augen für das A320neo-Triebwerk, das PurePower® PW1100G-JM. Boroskop­augen sind Teil des Gehäuses der schnell­laufenden Nieder­druck­turbine und werden benötigt, um die Beschaufelung auf mögliche Abnutzungen hin zu überprüfen. Additive Verfahren eignen sich vor allem für die Fertigung von Kleinserien oder individuell aufgebauten Bauteilen. Bei der MTU ist die Übertragung des SLM-Verfahrens auf andere Bauteile und Triebwerks­typen bereits in Vorbereitung, denn die Vorteile sind bestechend: Komplexe Bauteile können mit geringerem Material- und Werkzeug­einsatz hergestellt, neue Designs realisiert, Entwicklungs-, Fertigungs- und Lieferzeiten verkürzt und die Herstellkosten deutlich gesenkt werden.

Brush seals

A small but superb production area at MTU in Munich is brush seal manufacture. The company has been working on brush seal technology for more than 30 years and has meanwhile established itself as a global leader in this field. The innovative components have proved their worth in steam and gas turbines, pumps and a variety of other mech­an­ic­al engineering applications and now also in aviation. The breakthrough came with the GTF, which will feature MTU brush seals at up to four different locations.

“The construction typically includes thousands of thin bristles forming a very flexible seal which continuously adapts to the moving surface to be sealed,” explains Benjamin Großkurth, who heads up brush seal production at MTU. This way, brush seals clearly outperform conventional labyrinth seals, as they reduce leakages by up to 90 percent, which boosts the performance of the engine or gas turbine. They are suitable for a wide variety of applications and are capable of withstanding extreme service con­di­tions. They are easy to install, have a long life and a compact design. On top of that, they are easy to maintain and to replace. All of these benefits help appreciably reduce operating costs. For the manufacture of these seals, MTU has developed and patented a unique winding and clamping method. Großkurth expects the innovative sealing sys­tem to play an increasingly important role in engine construction down the road. In prep­ar­ation for growing demand MTU is already stepping up its efforts to further op­ti­mize the seal: New materials and more flexible designs are being tested. In addition, innovative manufacturing processes are used. The first seal housing prototypes have already been produced using additive techniques.

A world-class product: MTU first started to manufacture brush seals 30 years ago. Hover over the image for a bigger view

A world-class product: MTU first started to manufacture brush seals 30 years ago.

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A world-class product: MTU first started to manufacture brush seals 30 years ago.

Over the last decades MTU has built up unique manufacturing know-how and ex­pert­ise. The company has made a name for itself in the fields of advanced coatings and hardfacing of blade tips as well as laser-caving to produce cooling air holes in high-pressure turbine airfoils. To secure its technological edge, MTU is investing in a variety of technological activities, remaining committed to its tradition as a company that drives progress in aviation.

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Additive manu­facturing in engine production

05.2014 | Additive manufacturing is rapidly spreading from one industry sector to the next and playing an increasingly important role in aviation too. In engine construction, MTU Aero Engines has achieved a breakthrough: As one of the first manufacturers in the world it makes production parts using these processes.