1 4 A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A R C H 2 0 2 3 2) ensuring that P&W engines are fully compatible with approved sustainable aviation fuels, 3) developing advanced technologies for hybrid-electric propulsion, and 4) developing advanced technologies for hydrogen propulsion (Fig. 2). Geared Turbofans. Gas turbine propulsion systems are reliable, efficient, and fuel-flexible generators of thrust power. Currently, aircraft that operate Pratt & Whitney’s GTF (Geared Turbofan) engines yield up to 16% lower thrust specific fuel consumption and CO2 emissions relative to legacy turbofan engines such as the V2500. Furthermore, GTF engine operations generate 50% fewer nitrous oxide (NOx) emissions and 75% lower noise footprint around airport communities than legacy engines. As a result, GTF engines provide reliable thrust power while reducing the impact to the climate, local air quality, and airport communities. The Pratt & Whitney GTF Advantage engine, which is scheduled for certification in 2023, will deliver increased thrust, matured reliability, 1% lower specific fuel consumption relative to the GTF base engine, and 100% SAF compatible combustion technology (see Fig. 3). Pratt & Whitney will continue to invest in advanced gas turbine technologies, such as high temperature materials, advanced cooling and sealing technologies, advanced turbomachinery, and advanced combustion systems that increase fuel efficiency and lower greenhouse gas emissions on future aircraft. Sustainable Aviation Fuels. A sustainable aviation fuel (SAF) is a liquid hydrocarbon that is made from renewable energy sources and meets the technical and certification requirements for use in commercial aircraft[2,3]. Essentially, the carbon emitted during the flight is offset by carbon sequestered during the SAF feedstock biological and manufacturing processes. However, these processes take energy and are not completely carbon-neutral today. Burning SAF could yield up to an 80% reduction in life cycle carbon emissions relative to fossil-derived jet fuels[5]. The feedstocks for sustainable aviation fuels include animal matter (cooking oil, fats, greases), municipal solidwaste, and plant matter (algae, jatropha, camelina, forestry waste). In the future, electricity generated from renewable energy sources combined with CO2 that is captured from industrial processes or from the ambient air could be used to make SAF as well. Today, there are seven ASTM-approved bio-derived sustainable aviation fuel blends that have been certified for commercial engine use. Five of these SAF blends have been approved up to a 50% blending limit with conventional jet fuel[6]. Additional technology pathways for sustainable aviation fuel blends are under evaluation by ASTM International. The currently approved blended SAFs contain properties that meet the conventional jet fuel specifications. As a result, these approved SAF blends are interchangeable with conventional jet fuel, do not harm engine performance or operability, would require no change to aircraft technology or design, nor any change to airport infrastructure. Moreover, aircraft that operate on SAF blends up to 50% may yield up to 40% lower net CO2 emissions relative to aircraft that operate on fossil-derived jet fuels. In the future, sustainable aviation fuel blends up to 100% may be approved for use by ASTM International. P&W has been testing engines on 100% SAF for over 16 years to ensure maximum readiness. P&W successfully conducted operability testing on the PW1100G-JM with 100% hydro- processed esters and fatty acids synthetic paraffinic kerosene (HEFA-SPK) inMarch 2022. This testing was followed with successful on-wing ground and flight demonstrations of the PW1900G operating on 100% HEFA-SPK in June 2022. These tests showed that there was no difference in GTF engine operation with 100% HEFA-SPK and with 100% conventional jet fuel. Moreover, Pratt &Whitney Canada, a business unit of Pratt & Whitney, successfully completed a two-hour flight test of the two PW127 turboprop engines with 100% HEFA-SPK on a Braathen Regional Airlines ATR 72-600 aircraft in July 2022. Hybrid-Electric Propulsion. Electrification will play a key role in enabling smarter and cleaner aircraft engines. P&W and Collins Aerospace are strongly positioned to lead the development of integrated hybrid-electric propulsion technologies. The Scalable Turboelectric Powertrain Technology (STEP-Tech) Demonstrator, a P&W and Collins Aerospace technology demonstrator program, was established to mature scalable and adaptable technologies for advanced air mobility, regional aircraft, and single-aisle air- craft applications. These activities are initially aimed at 100 – 500 KW-class propulsion systems to address the emerging field of advanced air mobility. The scalable and modular technology solutions in the STEP-Tech program will also support the accelerated development of hybrid-electric propulsion systems for regional and single-aisle aircraft applications. Moreover, P&W Canada is collaborating with De Havilland Canada, Collins Aerospace, H55 S.A., Ricardo PLC, National Research Council of Fig. 3 — GTF Advantage engine. Fig. 4 — 100% SAF readiness with engine testing: (a) Supporting up to 50% SAF operational use today; (b) ground and flight testing up to 100% SAF; and (c) ensure future engines ready for 100% SAF standard. (a) (b) (c)
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