Millions of dollars are being invested to find the step changes in fuel consumption, noise and emission reduction, and improved reliability which airlines want from their next generation of powerplants.
There was a time when designing an engine meant two things: to make it go as fast as possible and use as little fuel as possible in doing so. Today engine designers have a vastly expanded range of challenges. They have to find the balance between the ever-present requirements of speed and efficiency on the one hand, while constantly making their powerplants quieter and less noxious on the other. An extra burden is the need to bring them to market faster.
Airlines are also becoming more demanding of the engine manufacturers. They want all these things and more. They want more inexpensively priced engines and products that are cheaper to operate over their entire lifetime.
Over the next decade, engine makers believe they can deliver. To seek the step changes in performance across this broad vista of parameters they are pumping in millions of dollars in research and development. They are also changing the way they develop new powerplants. "What we are doing is technology stalking," says Mike Benzakein, general manager for advanced engineering at GE Aircraft Engines. "It is something we need to do continuously, looking five to 15 years ahead."
Gone, it seems, are the days where a raft of technologies were developed specifically for an engine on an individual aircraft type. Today there is an entirely new powerplant design philosophy of "technology acquisition", as Benzakein puts it. This sees the manufacturers developing generic advanced engine technologies that can effectively be put "on the shelf" for the designers of all types of engine to acquire. These technologies are often geared towards a certain thrust size, but are by no means bound by it.
"The main motivation is, if you look through the history of the engine business we were always developing engines for a given aircraft. We tried to do it in the shadow of the aircraft development but never did," he says. It was often found that the engine, the design of which was generally fixed early on during a five-year aircraft project, could not keep up with changes in performance requirements from the airframer as the programme evolved.
In the mid-1990s, GE assembled a team to bring the engine development cycle down. "As part of this philosophy, we have shortened our development cycle where we say to Airbus, Boeing or Bombardier: 'We can give you an engine in 24 months.' In the past it would take four to five years," says Benzakein. For example, GE's first GE90 variant took it five years to deliver. For the latest version, the GE90-115B, it will deliver in 24 months, he says. GE will not stop here, however. It is taking on the "very challenging" task of reducing development time to just 18 months.
A major proving ground for this approach will be the engines that will power Boeing's proposed Sonic Cruiser. More than ever, it is the performance of the engines that will dictate whether this Mach 0.98 airliner will succeed. Although Boeing is a couple of months from releasing the specifications for the Sonic Cruiser engine, it has told GE, Pratt & Whitney (P&W) and Rolls-Royce that it is updating the baseline engine requirements from 777 derivatives to a totally new powerplant.
Boeing says its motivation to build a new engine was arrived at by looking at the difference between how much improvement in environmental performance it could get with a new engine compared to a derivative. It says: "Technological improvements at the engine companies are ongoing and we felt the best way to get the value of the improvements that are already available, plus whatever may come in the next few years, would be with a new engine."
P&W has defined the basic architecture and technology for its Sonic Cruiser engine offering, says Jean Colpin, vice-president of Commercial Engine Programs. "We have pulled in the best of our knowledge from different sectors of our business," he says, including building on its environmental leadership and technology from its military projects. "Economics will be a key item and we have been able to help our customer make the product more affordable."
Benzakein agrees on the economic emphasis, but also stresses the environmental side of equation. The 250-seater aircraft presents a unique challenge because it is planned to climb faster to higher cruise altitudes - dubbed 'cruiser space' by Boeing - compared to conventional airliners. Sonic Cruiser engines will have to operate at higher fan pressure ratios compared to the GE90 to obtain the required climb and cruise performance. Achieving this and keeping an eye on the environmental side of the equation will be tough.
The technology that addresses this balance is increasingly being developed in state-supported programmes, supplementing work conducted by the manufacturers. For instance, GE's study engine for the Sonic Cruiser - dubbed GEN X - is based on a smaller version of the GE90-115B high-pressure compressor. This design comes from one developed with NASA.
Industry partners
NASA is playing a central role in developing technology for future generation engines through its Ultra Efficient Engine Technology (UEET) programme. With a host of industry partners, including the three engine giants, the top level goals for UEET are to develop technologies to "enable increases in efficiencies and therefore fuel burn reductions of up to 15% [and equivalent reductions in CO2]" and to "develop combustor technologies which will enable reductions in landing/take-off NOx of 70% relative to 1996 ICAO [International Civil Aviation Organisation] standards".
P&W's Colpin acknowledges that finding a step change in both noise and emissions improvement is hard. But it is essential. "We know that emissions could become an economic factor in the future through a carbon tax," he says. One of the weapons P&W has in its armoury against emissions is the Technologically Affordable Low NOx (TALON) combustor design, which P&W originally developed for the PW4000. "The TALON combustor can be considered as a step change compared to conventional combustors," says Colpin. The TALON II combustor, a further advance in the technology, has been used on the PW6000 that will first enter service on the Airbus A318.
Colpin also expects more airports to follow the lead of London Heathrow, Geneva and Washington Dulles in taking an even tougher approach to noise than current ICAO standards require. "There is an increasing trend for airports to become stricter and accordingly we need to invest in noise reduction technologies, and are doing so. Under-standing noise reduction at source is a key technology to be able to compete and make a difference," he says.
"On noise, this means looking at integration technology to provide a significant difference and not just focusing on the engine. You have to think of the complete system and try to understand more appropriate airframe integration [for the engine], such as noise attenuation."
The design of the GE/P&W Engine Alliance GP7200 engine for the Airbus A380-800 shows how critical noise has become. "It was the first time we modified the design of an engine for noise," says Benzakein. Originally the GP7200 was to have a 2.8m (110in) diameter fan, but airlines asked for an engine that would meet the toughest airport noise requirements. The partners responded with a quieter 2.95m diameter fan. "This was a big change driven directly from the environmental side," he says.
Research action
With the Efficient and Environmentally Friendly Aero-Engine project, Europe is pioneering its own pan-industry European Union (EU) research programme to rival similar activities in the USA. This will see two technology platforms being developed over the coming decade. The Affordable Near Term Low Emissions vehicle (ANTLE) is being led by Rolls-Royce, while the Component vaLidator for Environmentally-friendly Aero-eNgines (CLEAN) is headed by Snecmaand MTU, says ANTLE chief engineer Steve Morgan.
Both will see engine demonstrators being run to validate new technologies, with ANTLE aimed at powerplants of 45,000lb-thrust (200kN) and above, and CLEAN directed towards engines of 35,000lbs thrust for 150-seat narrowbodies. The ANTLE target is for a 30% reduction in the time it takes to get an engine to market, a 12% reduction in fuel consumption, and a 60% fall in emissions, compared to a 1990s generation powerplant, says Morgan. The engine should run in 2004 and certified ANTLE technologies could find their way into new engines by 2008, he adds, leaving room for Sonic Cruiser engine applications.
The CLEAN project has a longer timescale - with technologies ready for market by 2015 - and will use a concept based on a thermodynamic cycle where exhaust gas energy is recovered, giving a potential 20% improvement in fuel burn compared to current engines.
In addition to their government-sponsored work, GE and Snecma are investing $200 million of their own in the CFM International TECH56 project - a platform from which to develop a suite of new technologies in the lower thrust range. It will take care of advancing the CFM56 series and for the CF34 regional-jet engine, says Benzakein.
The timescale for a new lower thrust engine to replace the popular CFM56 and International Aero Engines (IAE) V2500 depends on when Airbus and Boeing need a new product to power the next generation narrowbody airliner. CFM is positioning itself ahead of the requirement with TECH56. IAE is doing the same with its Vista programme, a project not confined to making sure the consortium (owned jointly by P&W, R-R, MTU and Japan Aero Engines) develops the right engine, but also addressing the design of the optimum engine manufacturer for the year 2010.
For this class of engine, the "next step will be environmentally driven", says Peter Johnson, IAE's manager product marketing and development. IAE is the ultimate engine technology shopper, using the technology groups at each manufacturer as its warehouse to bring together the elements that will make the next generation V2500.
Although there are no timetables yet, the company is in discussions with the airframers and airlines about their engine needs for a future 150-seater to enter service around 2010. So far these have produced a demanding checklist. There is a 5% improvement in fuel consumption, substantially lower noise compared to today's engines and NOx emissions that are 20% better than those of the V2500, says Johnson. In addition, airlines want reliability, with an in-flight shutdown target of zero, and for engines to remain on wing twice as long as they do today. "We are shooting for maintenance costs that are 30% better than for today's engines," he adds. "It will be a very balanced engine design and has to be a lot of things to all people."
Nagging problems
On the large engine side, GE and R-R are set to continue engine developments around their GE90 and Trent programmes, respectively. P&W continues to invest in improving its PW4000 family, which first entered service in 1987, and particularly on finding a solution to "nagging problems" such as the surge issue that has affected this engine. Without going into specifics, Colpin says P&W is looking at "the new generation of some of our older engine models, with a horizon of the end of this decade".
For GE, the GE90 core provides it with the technology platform for long-range aircraft such as the Sonic Cruiser and for the GP7200 engine for the Airbus A380-800. After this, GE will probably base its next platform around the UEET in the 60,000lb-thrust (265kN) range, says Benzakein. "We have some pretty ambitious goals for where fuel burn will be for that engine. We are looking at a 15% reduction compared to the GE90. To do this we will need a whole series of technologies, starting from the fan all the way to the back end of the engine." Such an engine could possibly enter service in 2015.
Beyond the task of bringing the right technologies together for an engine, P&W is studying how it can play a greater role in bringing all related sub-systems together in an optimised way, says Colpin, such as the auxiliary power unit and environmental control systems. He says one problem under study is how to integrate different sub-technologies to come up with much smarter systems. P&W is working in this fashion with Airbus on the A380 in a much deeper way than before, and would like to go even further, perhaps into the automotive model where tier-one suppliers are responsible for entire system modules.
As the manufacturers attempt to fill their shelves with the appropriate technology, there appears one shelf that insists on remaining empty - the supersonic engine. Although the Sonic Cruiser work is going some way towards filling this space, US government studies on supersonics stopped around three years ago.
The manufacturers do have one supersonic outlet however - work on engines for a possible supersonic business jet - demonstrating that the technology acquisition process might slow, but it never stops altogether.
Source: Airline Business