Engine Technology: Who will win the race?
The systems at work in aviation also need to become more environmentally compatible. Difficult, given that the number of flights globally is increasing each year and yet the total level of emitted pollutants has to be reduced. “A company that makes the wrong decision on the engine issue would lose large amounts of money,” Scott E. Carson warned when he was still head of the commercial business unit at Boeing. There is no doubt: The engine manufacturers must solve the problems soon.
Ten years ago, the European aviation industry had already defined a voluntary self-imposed commitment: Together with research partners from science and politics, the entire branch reached an agreement on ambitious objectives for the negative impact of air traffic on the climate. ACARE states concrete reduction goals. By the year 2020, fuel consumption and CO2 emissions are both to be reduced by 50 percent, nitric oxide emissions cut by 80 percent and noise levels during the approach and take-off should drop to half the current levels.
These targets are so high that only the overall “aviation” system will be able to achieve these savings. As the experts tell us, just reducing fuel consumption by 50 percent results in the following matrix:
Substantial improvements in the aerodynamics, the utilization of weight-saving materials such as CFRP or new aluminum alloys, innovative concepts for the on-board power supply and fundamentally different air traffic management could combine to yield savings of some 25 percent. Engine manufacturers would have to exploit new technologies to contribute the other half. In view of this situation it comes as no surprise that the three big names in the branch are working on every front. Pratt & Whitney has teamed up with MTU Aero Engines, Safran and General Electric have likewise joined forces in the CFM Consortium, while Rolls Royce is also on the lookout for strong partners. Engine manufacturers are contending with the degrees of efficiency that have to be improved and efficiency-increasing technologies here, but the real battle is against the clock. It takes five to six years to develop a new engine, and then more years pass before the engine is considered airworthy and actually takes off in a model.
And it takes 1,000 to 1,200 sold engines to offset the extremely high development costs. Pratt & Whitney and MTU Aero Engines have already started series production with their new and more fuel-efficient turbofan engines. The Pure-Power PW1000G will be the first engine in this family to fly with a new design at Bombardier. It features progressive reduction gearing that separates the engine fan from the low pressure turbine, allowing each component to run at its own optimum speed. Republic Airways has a firm order in for 40 C-series aircraft with an option for 40 more. The twin-turbo machines will be exclusively equipped with the new engine from Pratt & Whitney. The total order comprises more than 160 engines, and could produce sales of more than 200 million euros for the German engine manufacturer MTU, based on the list price. Lufthansa has also already placed an order with Bombardier for the new design. The PW1000G was also selected by Mitsubishi Aircraft Corporation as the exclusive power for the Mitsubishi Regional Jet (MRJ).
Both aircraft types are expected to go into service in 2013. “The market has once again honored the extraordinary merits of this innovative propulsion concept,” states MTU head Egon Behle. MTU and the Americans have consequently advanced the furthest with their new engine concept. “Our engines need 15 percent less kerosene, and starting in 2010 we will also be able to offer the engine for short-range jets,” says David Hess, Pratt & Whitney head. The French company Safran, General Electric’s joint-venture partner, is working at full speed to develop new solutions. “On the one hand, we are working on a new engine with a revolutionary material selection, while the construction is classic,” explains Marc Ventre, Safran board member for aircraft engines. This project, dubbed ‘Leap X’, calls for the use of innovative composite materials, for example, for the nozzle vanes. This saves weight, and consequently fuel. “Up to 16 percent,” Ventre reports. “We want to have the Leap-X engine certified for air traffic by 2016.” The first customers then will be the Chinese with their C919 aircraft program, which is to compete against the A320 from Airbus and the Boeing 737. The order has a volume of ten billion US dollars.
On the other hand, CFM is working on a revolutionary construction method using classic materials. This second project is an open-rotor engine. “We are expecting fuel burn savings of up to 30 percent, with an engine that is no louder than a conventional jet,” the Safran manager promises. The French hope to have the open propeller on the market starting in 2020, but many in the industry still view the open rotor with skepticism. The large propellers must possibly be mounted on the tail or even on the tail plane – the conventional design does not allow them to fit under the wings. This, in turn, would force the aircraft constructors to create complex new designs that they have tended to shun in the past.
But particularly for short and medium range flights, engines with an open rotor could achieve CO2 reductions of 25 percent and more thanks to their very high propulsion efficiency levels. Considerable efforts are still needed before this potential can be fulfilled, however. But like GE, Rolls-Royce is investing here for the long term, and taking on these challenges by initiating its own engine technology program. Its name is OPERO, and it is embedded in the European Union’s JTI Clean Sky program. It is intended to overcome the fundamental technical challenges and provide central technologies and conceptual design ideas for the integration and installation of open rotor propulsion. The project is broken down into the aspects of project management, installation aerodynamics and noise emissions, as well as the engine’s thermal efficiency. The German Federal Ministry of Economics and Technology (BMWi) is supporting the project. The German Aerospace Center DLR is the body responsible for the project. But just getting on to the market quickly is not enough. And so Rolls Royce has now also involved Boeing, RUAG Aerospace and Deharde Maschinenbau in a joint research agreement.
This also calls for the investigation of the possible uses for the fuel-efficient open rotor propulsion technology for future commercial aircraft. Each of the partners involved in this agreement will contribute its own technologies and methods. Tests with the model of an innovative concept aircraft and these engines are planned at the RUAG low-speed wind tunnel in Emmen, Switzerland. These tests will also draw on new metrological measures. “Open rotor propulsion technology has the potential to reduce the specific fuel consumption to far below the levels of today’s turbofan engines,” reports Michael Friend, Boeing Director of Technology in Germany. But, “Boeing has not made any decision regarding the type of propulsion system or the engine suppler for any future commercial aircraft – this investigation will help us reach a better understanding of the interaction between an open rotor engine and a cell concept for aircraft.” And this aspect in particular is lending additional dynamics now to the situation, given that airline companies are putting pressure on Airbus and Boeing to finally develop successors to the bestselling A320 and 737. Until now, both aircraft manufacturers have been referring back to the aeroengine companies, because the dimensions of the future engines have to be taken into consideration at the outset. But time is short, and Airbus already ran its own flight test on the geared turbofan technology with a PW1000G on an A340-600 testbed in 2009, chalking up 75 hours of flight experience in the process. No decision has been made to date.
“We would like to clear up this issue before the Farnborough Airshow,” Airbus COO John Leahy stated at the Singapore Airshow. Leahy suggested that the first A320 with new engines could then be delivered in the second half of 2015. This is urgently required, because Airbus needs this modernization to ensure that “our bread-and-butter program continues to sell well,” reported CEO Tom Enders at the group’s annual press conference in Seville. On the other hand, a successor to the current A320 is not expected until the year 2024. In late January, competitor Boeing also announced an engine modification for the 737.
“Should the markets make the demands, we could respond very quickly here,” said CEO Jim McNerney. But neither Boeing nor Airbus is prepared to be tied down today. “A company that makes the wrong decision on the engine issue would lose large amounts of money,” Scott E. Carson warned when he was still the undisputed head of the commercial business unit at Boeing. But this issue must be settled, and soon: the industry has only ten more years to reach the ACARE goals.
- Robert Wouters -
German Summary
Auch die in der Luftfahrt müssen die eingesetzten Systeme umweltschonender werden. Schwierig, wenn die Zahl an weltweiten Flügen jährlich steigt und doch insgesamt weniger Schadstoffe ausgestoßen werden sollen. Keine Frage: Hier sind in erster Linie die Entwickler der Triebwerkshersteller gefordert, Aber auch die Flugzeughersteller müssen konstruktiv mitspielen: „Wer in der Triebwerksfrage daneben greift, verliert viel Geld”, warnte schon Scott E. Carson, als er noch unumstrittener Chef der zivilen Sparte bei Boeing war. Der deutschsprachige Beitrag ist nachzulesen auf www.aerotec-online.com
Weitere Beiträge
→ Engine makers face reformation→ Next generation of balancing machines for jet engine applications
→ Time for engine design to lead the way
→ RUAG: Engine manufacturing concept improved
→ Metrology gives a boost to aircraft engine maintenance
