Jet-A and Jet-A-1 have fueled commercial and military jets for decades. With -40°C and -47°C freeze point specifications respectively, Jet-A and Jet-A-1 have adequate low temperature operability for the current demands of jet-powered planes. However next generation military and commercial jet aircraft will need fuels with improved low temperature performance to reap the benefits of flying higher, longer and taking polar routes. The extreme cold these new routes will expose jet fuel to makes it necessary to have fuel that flows at much lower temperatures than is currently available.
Changing the jet fuel refining conditions can achieve the desired low temperature characteristics however this is very expensive. Further, the Military desires to obtain the same fuel performance worldwide regardless of the type of local jet fuel or local refining capability. keeping logistics and cost in mind, an appropriate low temperature operability additive dosed into locally available fuel is the best way to accomplish the enhanced low temperature properties.
Improving the operability performance of jet fuel has two hurdles to over come. First, there is no established operability test for jet fuel. Currently jet fuel only has freezing point and maximum viscosity at -20°C as its sole low temperature property specifications. Second, there are no established cold flow additives for use in jet fuel.
This paper shows how freezing point may not be a good indicator of jet fuel flow characteristics and how a developmental jet fuel operability test more accurately predicts the cold flow performance of jet fuel at extremely low temperatures. Also discussed is the testing of cold flow additives in jet fuel, how jet fuel differs from other middle distillate fuels, and why jet fuel additives differ from conventional middle distillate cold flow packages.