The race to come up with a new mid-thrust engine has begun and all the major international engine companies are involved
Manufacturers are always hard at work developing new engine technologies to improve fuel efficiency and make significant reductions in noise and emissions. Today, this activity is being driven by continuing high oil prices, more stringent Chapter 4 noise regulations coming into effect from January 2006 for new aircraft designs and CAEP/6 emission standards due in 2008, and crucially the promise of new Airbus and Boeing narrowbody aircraft launches towards the end of the decade.
Although existing engines already meet present and anticipated future standards on noise and emissions, work on improvements is a continuous process, while a prospective 1% cut in specific fuel consumption being offered in the short term will be welcomed.
It is the mid-thrust engines in the 18,000-32,000lb (80-142kN) range powering the 100- to 220-seat single-aisle aircraft that dominate the market in terms of numbers and will continue to account for 60% of new aircraft deliveries over the next 20 years. So it is not surprising that while there are only two competing engines, all the major international engine companies are involved.
Major players
The undisputed leader in this sector is CFM International, the joint venture between GE Aircraft Engines and Snecma. The company's CFM56 series powers most of the earlier Boeing 737s and all Next Generation 737 aircraft, and around half of the Airbus A320 family. The International Aero Engines (IAE) V2500 accounts for the other half of the installed engines on the A320 family. IAE is a partnership between Japan Aero Engines (comprising Ishikawa-Harima, Kawasaki and Mitsubishi), MTU Aero Engines, Pratt & Whitney and Rolls-Royce. P&W, in partnership with MTU, is also targeting the lower end of the range with its PW6000, being offered on the Airbus A318 and a potential candidate on the proposed Bombardier CSeries jets, although a new engine from IAE or CFMI is the most likely option. However, neither has committed itself to this project. The PW6000 has had a troubled gestation, but its low acquisition cost and low noise levels should help it gain marketshare.
CFMI logged orders for 683 commercial and military engines in 2004, valued at around $4.1 billion. In addition, the company received orders for a total of 118 3-D upgrade kits for the CFM56-3 and CFM56-5C/P engines. Since its formation in 1974, CFMI has delivered more than 14,450 engines (10,600 for the A320/737), and ended last year showing an order backlog of 2,600 engines. Total flight hours exceed 265 million. Last September, it launched the Tech56 Insertion Programme for the CFM56-5B and -7B variants, designed to create what Pierre Fabre, chief executive of CFMI, calls "customer value through lower cost of ownership", adding that what the customer will get is "a better engine for the same price".
Improved efficiency
Central to Tech56 is a new technology core and low-pressure turbine nozzle. Improved efficiency and more thrust from the same diameter fan are achieved through a new swept fan blade, while a recontoured high-pressure turbine blade lowers interaction losses between the turbines. Better cooling in the current single-annular combustor significantly reduces nitrogen oxide (NOx) emissions. These enhancements are said to add up to increased time on the wing, higher durability of components in hot section for reduced wear and lower repair costs and a 1% cut in specific fuel consumption – 40% of which will be achieved on delivery and the other 60% over time.
A number of tests have been completed, with further performance validations to be undertaken before a full analysis of results can be initiated. Flight tests in the GE Boeing 747 testbed are set for this year, and 10,000-cycle endurance and Airbus and Boeing flight tests will lead to certification in the last quarter of 2006. This will become the new production configuration, but an upgrade package, either as a complete kit or sub-kits, will also be offered.
According to IAE, a policy of continuously improving the V2500 means "we are seeing a constant reduction in ownership/maintenance costs through our Total Maintenance Cost Reduction programme". The VISTA enhancement programme, which draws on technology developments from all partners, has already delivered increased thrust at hot/high conditions, better durability, a new high-pressure turbine blade, and the Talon III (Technology for Advanced Low NOx) combustor. The Talon technology was developed by P&W in conjunction with NASA's Glenn Research Center and MTU Aero Engines, and has produced a 15% reduction in emissions. Testing will be carried out this year on a further improvement with the goal of reducing NOx by an additional 5%.
Airbus and Boeing agree that demand for single-aisle aircraft within the thrust range of the present engines will increase dramatically over the next 20 years, although there is a difference between the two manufacturers on the numbers. According to the most recent Airbus forecast, traffic will treble over the next 20 years, generating a need for some 10,900 new single-aisle aircraft or 65% of total deliveries. Boeing believes airlines will require just over 14,700 aircraft over the period, 35% more than the Airbus prediction. Demand will come largely from Europe and North America, particularly from low-cost carriers, although the Asia-Pacific region will still account for 20% of all deliveries.
The Airbus figures offer a great deal of encouragement to engine manufacturers. While deliveries of existing aircraft will rise gradually over the next few years, single-aisle retirements are due to increase sharply from 2012, accelerating the demand for new aircraft. The ongoing technology programmes will meet known and expected standards for noise and NOx emissions, but engine companies are in a quandary about the next generation of new centreline engines.
All accept that new aircraft will enter the market in the next decade, but Airbus and Boeing have yet to reveal what type of airframe may replace their A320 and 737NG families, although Boeing is reported to be working on the Y-1 design covering the 120- to 190-seat market. As CFMI and IAE rely on these two programmes, their successors will provide the necessary follow-on business and engines will need to be ready. Bombardier's CSeries would also fit within the thrust range of the CFM56 and V2500.
CFMI and IAE are working towards further improvements and a new engine in the longer term. CFMI says that to meet an anticipated requirement after 2012, it will have to launch a new engine in 2008 and has to start work now. According to Fabre, there will be more composites, probably a counter-rotative fan and "more electric will definitely be part of the game". The manufacturer has set itself some tough goals, measured against the current CFM56-5B and -7B engines, including a minimum 12% reduction in engine-related operating costs, 3-4% lower fuel burn, 25% reduction in maintenance costs, 10dB margin against Chapter 4 regulations, 50% lower NOx and first on-wing life of 25,000h.
The aims of the IAE VISTA mission are broadly similar. Targets envisage 5% lower specific fuel consumption, NOx 40% below CAEP/2, 15,000h minimum time on wing, no in-flight shutdowns and a 30% reduction in maintenance costs. P&W has teamed with MTU for the Joint Technology Demonstrator Programme (JTDP), a PW6000-sized demonstrator with a single-stage high-pressure turbine and an intermediate-sized high-pressure compressor designed to develop components for future engines.
The JTDP is also being used to validate low-pressure turbine technologies, low-emission combustors, a new fuel-management unit, health management and more. A new MTU six-stage high-pressure compressor demonstrated significant performance improvements and has been incorporated into the PW6000.
Noise and emissions cut
Cambridge, UK-based Camcon Technology has revealed its Binary Actuating Technology (BAT), which controls how fuel is injected into the combustion chamber and is said to markedly cut noise and emissions. At the Berlin Technical University, Camcon's BAT valves have confirmed a reduction of more than 20dB in front-end high-pitched noise emitted by jet engine blades.
Engine makers are participating with research institutes to develop future technologies. In the USA, under the stewardship of NASA, GE, Honeywell, P&W, R-R, Williams International and airframe manufacturers are engaged in the Ultra Efficient Engine Technology programme, due to report in 2007, which aims to cut emissions by up to 70%, and improve fuel efficiency for the smaller subsonic jets by 20%. Similar work is being undertaken under the umbrella of the Advisory Council for Aeronautics Research in Europe. The Vision 2002 programme focuses on halving perceived noise, reducing NOx by 80% and carbon dioxide by 50% per passenger kilometre.
As research involves emerging, as well as unproven technologies, these ambitious targets may not be achieved in the near term. With ongoing economic and environmental pressures, a revolutionary rather than an evolutionary approach may be needed.
GÜNTER ENDRES LONDON
Source: Airline Business
