| Abstract | To reduce the carbon footprint and in turn the impact on global climate change, aviation sectors around the world are trying to increase engine efficiency and support the use of alternative fuels. Not only are current fossil fuel reserves getting low, the marginal extraction costs are significantly increasing. That creates a new global requirement for fuels from renewable sources. The challenge is to find a source that can be transformed into fuel having the same performance characteristics as current jet fuels in order to be used in current engine configurations and to be supplied via the current fuel handling infrastructure and supply chain.
One of the processes for producing alternative fuels having physico-chemical properties similar to current aviation fuel is the Fischer-Tropsch (F-T) Synthesis. The F-T process is a catalyzed chemical reaction where synthesis gas, a mixture of carbon monoxide and hydrogen, derived from coal, natural gas or biomass, is converted into liquid hydrocarbon fuel.
F-T processed fuels have low aromatic content and almost zero sulfur contents and as such have the potential to reduce emissions of Particulate Matter (PM) and Sulfur Oxides (SOₓ) in comparison to the conventional fuels [1]. In addition, the availability of a F-T processed jet fuel also reduces dependency on foreign crude oil supplies, because it may be produced wherever there is a supply of coal, natural gas or biomass. However, the current F-T production process does produce significant greenhouse gases which must be addressed.
Since the original F-T processed SASOL Iso-Paraffinic Kerosene (IPK), the new synthetic kerosene fuels have been known to contain a significant fraction of normal paraffins as well. In addition they may also contain small, but non-negligible, fractions of cyclo-paraffins. Hence, according to the current accepted terminology, the F-T processed fuels are called Synthetic Paraffinic Kerosene (SPK). Similarly, SPK blended in 50-50 ratio with conventional fuels like Jet Al or JP-8 (NATO F-34) is now termed as Semi-Synthetic Jet Fuels (SSJF).
Semi-Synthetic Jet Fuel obtained using the F-T process has been identified as an alternative fuel for use in military aircraft engines [2]. Since mid-2006 the USAF has conducted a number of fleet-wide engine and flight tests using SSJF comprising various SPK fuels. Their certification process has found no significant differences in operation, performance and handling of engines with SSJF compared to conventional fuel. However, General Electric (GE) F404-400 engines, installed on the F-18, were not certified because they are not used by the USAF. To ensure continued interoperability among TTCP nations that use the F404 engine, Department of National Defense (DND) Canada, US Navy and RAAF cooperated on a project to test an augmented F404 engine in the configuration currently in use with the Canadian Forces (CF). The work was performed at the National Research Council (NRC) Canada.
This report presents the major results of this project, which was conducted to identify any shortcomings of operating the F404 on a semi-synthetic jet fuel comprising a 50-50 blend of SPK and NATO F-34 fuels. |
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