The engine and aircraft R&D communities have been investigating the practicality of using alternative fuels in near-, mid-, and far-term aircraft. Presently, it appears that an approach of using a 'drop in' jet fuel replacement, which may consist of a kerosene and synthetic fuel blend, will be possible for use in existing and near-term aircraft. Future mid-term aircraft may use a biojet and synthetic fuel blend in ultra-efficient airplane designs. Future, long-term engines and aircraft in the 50+ year horizon may be specifically designed to use a low- or zero-carbon fuel. Synthetic jet fuels are manufactured using a Fischer-Tropsch process from coal, natural gas or other hydrocarbon feedstocks. These fuels are very similar in performance to conventional jet fuel, but contain almost zero sulfur and aromatics. This may result in lower particulate exhaust emissions. In addition, synthetic fuels exhibit excellent low-temperature properties, maintaining a low viscosity at lower ambient temperatures. Thermal stability properties are also improved, resulting in less fuel system deposits. As synthetic fuels have very good performance, and have already been in use for many years in Johannesburg airport (Sasol fuel), it will be easy to supplement current jet fuel supplies with synthetic derived fuel. If the additional CO2 that is produced during the manufacturing process can be captured and permanently sequestered, synthetic fuel could be a good near-term supplement. For a possible mid-term solution (i.e., 10 - 50 years from now) it is envisioned that alternate fuels will make up a much larger percentage of jet fuels. These fuels may also involve the blending of biofuels with the synthetic fuel. The major challenges of using pure bio fuels in a commercial aircraft are their propensity to freeze at normal operating cruising temperatures, poorer high-temperature thermal stability characteristics in the engine, and storage stability over time. Long-term solutions will need to dramatically reduce the emissions of greenhouse gases. Therefore, alternate fuels with low to zero carbon content, such as liquid hydrogen or liquid methane, might be used. To use liquid cryogenic fuels in aircraft engines, modifications are necessary to the combustor and fuel system components. Early tests with cryogenically stored fuels demonstrated that a heat exchanger will be required for vaporizing the fuel prior to combustion. Compromises must be made to the design of the airframe to address fuel tank insulation requirements and pressure issues.
Alternate fuels for use in commercial aircraft
Zukünftige Kraftstoffe für kommerzielle Luftfahrzeuge
2007
8 Seiten, 17 Bilder, 14 Quellen
Conference paper
Storage medium
English
AIAA-2007-1196 ALTERNATE FUELS FOR USE IN FUTURE COMMERCIAL AIRCRAFT
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