In our previous article, “Future Technologies – Retrofits and Upgrades to support the Aircraft Technology Road Map, ” we discussed a series of retrofits and upgrades which would be available to aircraft before 2030.
This web story covers the next series of TRM opportunities that are highly oriented to engine concepts and architecture.
The principal source of fuel efficiencies in the years 2020 – 2025 is proposed to come from new engine architecture, which is resolved by improving the Ultra-High Bypass (HBP) Ratio. New engine technologies are the most significant contribution to fuel burn reduction in recent and imminent new aircraft models. Some of these engines have already entered service, and others are expected to be installed on new aircraft soon. These engines will all have higher bypass ratios (BPRs) than previous engine models. In the case of regional jets and single-aisle aircraft such as the MRJ[1], the Embraer E2[2] family, A220[3] (formerly C series), A320neo[4] and 737MAX[5], new engines operating on these aircraft have a BPR of 9 to 12, which allow fuel burn reduction of about 15% compared to earlier engines with a BPR of typically 5 to 6. New engines for wide-body aircraft, including A330neo and 777-9, will reduce fuel burn by 10% compared to previous jet engines.
Rolls Royce – Advance and Ultrafan new engine technologies
The Advance Turbofan from Rolls Royce uses a unique HPB ratio and approach. At the time the IATA TRM was written, the RR people believed that entry into service (EIS) would be about 2020.
Later, in February 2014, Rolls-Royce detailed its Trent future developments. The Advance is the first of these designs and would be ready from the end of the 2020s and would aim to offer at least a 20% better fuel burn than the first generation of Trent engines. The Advance bypass ratio should exceed 11:1, and its overall pressure ratio would be 60:1. The technology approach here is that the higher the pressure ratio, the more power is derived from the fuel that is ultimately directed to flight.
In previous Trent engines, the HP (high pressure) spool was of a similar design, and the engine grew by expanding the intermediate pressure (IP) spool work. The Advance reverses this trend, and now the load is shifted towards the high-pressure spool, resulting in a greater overall pressure ratio. There are now up to 10 stages in the compressor compared to 6 previously on the Trent XWB and other two-stage turbines. The Intermediate Pressure compressor consequently also shrinks from the 8 stages of today’s XWB to 4, and the IP turbine will only be a single instead of two stages.
Enhanced with further technologies and innovative high-temperature materials, the UltraFan pushes the Advance3 core overall pressure ratio to more than 70:1 for a typical large engine application. UltraFan also features a new geared architecture. Here a power gearbox is introduced between the fan and intermediate pressure compressor, ensuring that the fan, compressors and turbines all continue to run at their optimum speed. As odd as it seems, this gearbox offers the same assistance as a transmission provides to a car, allowing the car engine to operate in an optimal range of RPM (Revolutions Per Minute) while the transmission converts the engine’s force into a proper speed.
The Advance Engine is expected to have at least a 20% reduction in fuel burn and CO2 emissions relative to the Trent 800.
The Ultrafan Engine is a further development of the Advance Engine, with an expected minimum 25% improvement in fuel burn and CO2 reduction.
Figure 1: A graphic showing the transition from the current Trent XWB to the Advance and Ultrafan jet engines
The following Figure 2 shows the mapping of the CO2 from the RR engine family against time, indicating the progress made by the Advance and UltraFan jet engines.
Figure 2: CO2 reduction over the RR family of jet engines
GE9X and LEAP plans
GE has similar plans of their own to gain jet engine efficiencies. Their GE9X is a high-bypass turbofan that has been developed exclusively for the Boeing 777X. This jet engine was derived from the General Electric GE90 , now with a more significant fan and that uses advanced materials such as ceramic matrix composites (CMCs). Additionally, with the higher bypass and compression ratios, fuel efficiency improves by 10% over its predecessor. The GE9X is rated at 110,000 lbf (490 kN) of thrust. Figures 3 and 4 are provided below to show a cross-section and the identification of vital jet engine parts.
Figure 3: GE9X engine cross-section
Figure 4: The GE9x with identified sections.
The CFM International LEAP (“Leading Edge Aviation Propulsion”) is a high-bypass turbofan produced by CFM International, which is a 50-50 joint venture between American GE Aviation and French Safran Aircraft Engines. The LEAP engine is used to power narrow-body aircraft which is the most popular selling type.
The LEAP’s basic architecture uses flexible fan blades that are manufactured by a resin transfer molding process. These blades are designed to untwist as the fan’s rotational speed increases. While the LEAP is designed to operate at a higher pressure than the CFM56 (which is partly why it is more efficient), GE plans to set the operating pressure lower than the maximum to maximize the engine’s service life and reliability. Currently proposed for the LEAP is greater use of composite materials and other changes ever-improving the engine’s efficiency. The LEAP Ultra-High Bypass Ratio engine is expected to enter into service by 2025 and will increment current LEAP efficiencies by a further 5 – 10%.
In conclusion, these four examples from some of the key jet engine manufacturers point to engine efficiency improvements of up to 25% which will be entered into service by 2025.
[1] MRJ – Mitsubishi Regional Jet is a family of 70~90-seat next-generation aircraft featuring the Pratt & Whitney’s revolutionary PurePower® engine and state-of-the-art aerodynamics to drastically reduce fuel consumption, noise, and emissions, while offering top-class operational benefits, an outstanding cabin designed for heightened passenger flying comfort, with large overhead bins.
[2] The Embraer E-Jet E2 family are medium-range jet airliners developed by Embraer, succeeding the original E-Jet. The program was launched at the Paris Air Show in 2013. The first variant, the E190-E2, took its first flight on 23 May 2016 and was certified on 28 February 2018 before entering service with Widerøe on 24 April.
The three twin jet variants share the same four-abreast narrow-body fuselage with different lengths and three different new wings, Pratt & Whitney PW1000G turbofans in two sizes, fly-by-wire controls with new avionics, and an updated cabin.
[3] The Airbus A220 is a family of five-abreast narrow-body airliners and is powered by Pratt & Whitney PW1500G.
[4] The Airbus A320neo family (neo stands for for New Engine Option) is a development of the A320 family of narrow-body airliners produced by Airbus. The A320neo family is based on the previous A319, A320 and A321 (enhanced variant), which was renamed the A320ceo, for “current engine option”.
The A320neo was re-engined with CFM LEAP-1A or Pratt & Whitney PW1000G engines and fitted with sharklets as standard, it is 15% to 20% more fuel efficient than the A320ceo (Enhanced) family. It was launched on December 1, 2010, and made its first flight on September 25, 2014. Lufthansa took one of the first A320 deliveries on January 25, 2016.
[5] The Boeing 737 MAX is the fourth generation of the Boeing 737, a narrow-body airliner manufactured by Boeing Commercial Airplanes (BCA), a division of American company Boeing. It succeeds the Boeing 737 Next Generation (NG) and competes with the Airbus A320neo family. The 737 MAX is based on earlier 737 designs, with more efficient CFM International LEAP-1B engines, aerodynamic changes, including its distinctive split-tip winglets, and airframe modifications. The new series was announced on August 30, 2011. It took its maiden flight on January 29, 2016 and was certified by the United States Federal Aviation Administration (FAA) in March 2017. The first delivery was a MAX 8 in May 2017 to Malindo Air, with whom it commenced service on May 22, 2017.