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Alternate Fuels for use in Commercial Aircraft
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Short Description: Future mid-term aircraft may use a bio-jet and synthetic ... of commercial jet aircraft in the 1960s. Next-generation. aircraft will see another 15-20 ...
Content Inside: Alternate Fuels for use in Commercial Aircraft David L. Daggett1 Boeing Commercial Airplane, Seattle, WA, 98124 Robert C. Hendricks NASA Glenn Research Center, Cleveland, OH, 44135 Rainer Walther MTU Aero Engines GmbH, Munich, Germany Edwin Corporan Air Force Research Laboratory, Dayton, OH Abstract fuels in a commercial aircraft are its propensity to freeze at normal operating cruising temperatures, its The engine and commercial aircraft research and poorer high temperature thermal stability characteristics development communities have been investigating the in the engine, and its storage stability over time. For practicality of using alternative fuels in near, mid, and these reasons, bio-jet fuels need to be developed that far-term aircraft. Presently, it appears that an approach address these issues and so will be especially tailored of using a "drop in" jet fuel replacement, which may for jet aircraft. Another drawback is that, because of consist of a kerosene and synthetic fuel blend, will be limited excess farmland, present bio-fuels are not possible for use in existing and near term aircraft. capable of supplying a large percentage of fuel without Future mid-term aircraft may use a bio-jet and synthetic displacing food production. However, higher yielding fuel blend in ultra-efficient airplane designs. Future, future feedstocks, such as algae, may dramatically long-term engines and aircraft in the 50-plus year improve supply capability. The advantages of using horizon, may be specifically designed to use a low or bio-fuels would be its environmentally balanced CO zero-carbon fuel. 2 impact, its capability to become a sustainable fuel, and it may result in lower engine emissions. If the Synthetic jet fuels are manufactured, using a performance and resulting cost liabilities can be Fischer-Tropsch process, from coal, natural gas or other overcome, bio-fuels are envisioned to be blended with hydrocarbon feedstocks. These fuels are very similar in synthetic jet or Jet-A fuels. performance to conventional jet fuel, but have almost zero sulfur and aromatics. This may result in lower Long-term solutions will need to dramatically particulate exhaust emissions. In addition, synthetic reduce the emissions of greenhouse gases. Therefore, fuels exhibit excellent low-temperature properties, alternate fuels with low to zero carbon content, such as maintaining a low viscosity at lower ambient liquid hydrogen or liquid methane, might be used. To temperatures. Thermal stability properties are also use liquid, cryogenic fuels in aircraft engines, improved, resulting in less fuel system deposits. As modifications are necessary to the combustor and fuel synthetic fuels have very good performance, and have system components. Early tests with cryogenically already been in use for many years in Johannesburg stored fuels demonstrated that a heat exchanger will be airport (Sasol fuel) it will be easy to supplement current required for vaporizing the fuel prior to combustion. jet fuel supplies with synthetic derived fuel. If the Compromises are necessary to the airframe to address additional CO2 that is produced during the fuel tank insulation requirements and pressure issues. manufacturing process can be captured and permanently The need for heavy insulated fuel tanks would result in sequestered, synthetic fuel could be a good near-term a decrease in the aircraft's energy efficiency on short supplement. range flights. On the other hand, vast quantities of methane currently trapped in the forms of methane For a possible mid-term solution (i.e., 10-50 years hydrates could become readily available in the future. from now) it is envisioned that alternate fuels will make Either of these new aircraft fuels will require an up a much larger percentage of jet fuels. These fuels enormous change in infrastructure and engine-airplane may also involve the blending of bio-fuels with the synthetic fuel. The major challenges of using pure bio- 1 Copyright © 2007 by The Boeing Company. All rights reserved
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