Next-Gen Engines

From the time the Wright Brothers had their first flight, efforts are continuously on to bring in advanced materials in airplane development. One of the first experimenters, the Wright Brothers substituted an aluminium engine for one made of steel due to weight. Engine development is complex and weight is just one factor, while factors such as temperature resistance, corrosion resistance, durability and performance are critical elements. Next-gen engine technologies factor in all these parameters and more to ensure that the airline industry is not only responsible ‘environmentally’ but also gets highly efficient and sustainable engines.

Engineers are improving engines include manufacturing fan blades out of strong, lightweight carbon fibre, so they won’t be so heavy and engines will burn less fuel; and designing special gear systems that allow the turbines to spin at more efficient speeds to save fuel.

New materials

Pratt & Whitney sometime back had a panel discussion on next-gen engine technologies and the materials that were required to deliver that technology. Future aero engines will be determined by substantive improvements in both propulsive and thermal efficiencies. Propulsive efficiencies require optimising fan performance, and the decision to choose between metallic and composite blades. Inside the engine core, a variety of materials are available to withstand higher temperatures and pressures to improve thermal efficiencies. The portfolio of materials include powdered metal alloys that provide better bore and creep resistance, single crystal and fine casting of passages to reduce cooling air, and high temperature ceramic matrix composites. The next-generation of materials include advanced alloys including cobalt, molybdenum, monolithic ceramics, etc, with higher temperature fibres.

And in this development process, all engine manufacturers are heavily investing in automation in manufacturing, besides using new materials. Automated coating, finishing, inspection, and other functions are being incorporated into new assembly lines, and process modelling techniques are being used to determine how to optimise manufacturing of parts. Additive manufacturing has been used at Pratt & Whitney since they were a pioneer in the use of stereo lithography in the 1980s. Pratt & Whitney will be delivering the first ‘3D printed’ parts on the GTF engine.

PurePower first on Bombardier

The process has undergone a radical change as Pratt & Whitney prepares to deliver the first PurePower PW1500G engines to Bombardier. With nearly twice the horsepower of conventional turboprops, the 5,071shp PW150A is the most advanced commercial turboprop engine available today. Featuring full authority digital electronic control (FADEC), centralised diagnostics and low fuel consumption and emissions, the engine allows the aircraft to offer significantly lower operating and maintenance costs. The aircraft features six-bladed, all composite Dowty propellers that deliver more thrust and less noise than propellers turning at higher revolutions per minute (RPM). This latest engine will feature what are called ‘entry-into-service jet engine parts,’ and they’re produced using additive manufacturing techniques and space-age metals.

In the past, Pratt & Whitney has built more than 1,00,000 prototype parts using additive manufacturing – and hundreds more to support the PurePower GTF engine development process – but this marks the first time additive manufacturing technology has been used to produce compressor stators and synch ring brackets for a production engine. The project means dozens of parts produced using 3D manufacturing processes made from titanium and nickel have been flight-tested for use in Airbus and Bombardier aircraft.

Tom Prete, Pratt & Whitney’s Engineering Vice President, said: “We are a vertically integrated additive manufacturing producer with our own metal powder source and the printers necessary to create parts using this innovative technology. As a technology leader, we are intrigued by the potential of additive manufacturing to support our suite of technologies and benefits to customers and the global aerospace industry.”

Pratt & Whitney has been actively testing all key components of the PurePower PW 1000G engine family, with 15 technology rigs running around the world. Hundreds of hours of ground testing of the first PW1500G engines for the Bombardier CSeries and PW1200G engines for the Mitsubishi Regional Jet further validate the engine family’s many benefits. It has also been selected by Russia’s Irkut Corporation to power the Irkut MC-21 aircraft and also it is an ultra fuel-efficient new engine option (neo) for the A320neo family of aircraft. Most recently, Embraer has selected the Pure-Power engine as the exclusive power for its new second-generation of the E-Jet aircraft family.

CFM LEAP, next-gen single-aisle engines

CFM combines the resources, engineering expertise and product support of two major aircraft engine manufacturers: Snecma (Safran) of France and GE of the US. CFM is developing the futuristic LEAP engines. If all goes as planned, by 2016 these engines will be attached to the wings of new single-aisle, narrow-body airliners that will generally seat about 150 to 200 passengers, depending on the configuration.

The CFM LEAP family represents the engines of choice for the next-generation single-aisle aircraft. The LEAP-1A is an option on the Airbus A320neo; the LEAP-1B is the exclusive powerplant for the Boeing 737 MAX; and the LEAP-1C is the sole Western powerplant for the COMAC C919. These engines had garnered more than 8,000 operates from more than 50 customers across the globe.

Two engine families have contributed significantly to the design of the LEAP engine, the CFM56 and the GE90/GEnx series of engines. The GE90/GEnx contributed the high efficiency core architecture to minimise fuel consumption, while the CFM56 legacy drove reliability and maintenance cost design practices. At entry into service in 2017, it is estimated that the GE90/GEnx architecture will have generated 80 million flight hours of revenue service, while the CFM56 family will have over 700 million flight hours of experience. The LEAP engine family offers proven, material advantages over any other engine, with 5,50,000 hours of proven experience with 99.98 per cent reliability, and 22,000 engines delivered on time and on spec. The CFM LEAP pedigree ensures with confidence the ability to deliver a 15 per cent improvement in fuel efficiency, as compared to the CFM56-7BE, while maintaining the same level of dispatch reliability and life-cycle maintenance costs as the CFM56-7BE. With its simple architecture and $2 billion annual investment in technology, the LEAP engine family offers the lowest cost and highest revenuegenerating ability, saving an estimated nearly $3 million per plane.

GE9X high on composites

GE is utilising a next-generation carbon fiber composite for the fan blades that will debut in the GE9X engine on the Boeing 777X. The composite material is letting engineers build the GE9X with thinner and fewer blades, which will contribute to 5 per cent less fuel being burned compared with all other similar engines when the engine is ready in 2020. “The GE9X team is combining the lessons learned from those fielded blades with the next-generation of material and aero technologies to push the envelope and maintain our competitive edge,” states Tod Davis, the GE9X composite fan blade design leader.

More than 700 GE9X engines have been ordered so far because of the fuel savings inherent in the composite fan blades and other advanced materials, like the tough ceramic matrix composite material that will withstand extreme temperatures in the engine’s combustor and turbine. The weight savings from all of these advances mean the GE9X fan will be lighter than its predecessor, the GE90, while also being the largest fan produced by the company. The composite fan case at the front of the engine will measure 134 inches in diameter, about the length of a compact car.

Rolls-Royce UltraFan is futuristic

Rolls-Royce is working with ITP to support a 43 million euros research programme to test intermediate pressure (IP) turbine technologies that will go into its future engine design, UltraFan which is likely to be available for service from 2025. It is expected to offer at least 25 per cent improvement in fuel burn and emissions compared with first-generation Rolls-Royce Trent engines.

The future will continue to see different and diverging requirements for the military and commercial sectors. Time on wing and efficiency will continue to be the engine drivers for commercial aircraft. The future for civil engines will require improvements to both propulsive and thermal efficiencies and all the engine manufacturers are investing heavily in technologies which will not only be sustainable but also cost-effective.