Combustion considerations for future jet fuels

Abstract

This paper presents recent results which contribute to the combustion technology base necessary for the future development of aircraft jet fuels from non-petroleum resources. Specifically, the effects of fuel hydrogen and nitrogen content have been studied using a T56 combustor rig. Although most of this work has involved fuel blending to simulate alternate fuel properties, data acquired using an actual oil shale jet fuel have been included. Increases of combustor liner temperature with decreased fuel hydrogen content were found to be substantial. A new, non-dimensional temperature parameter is presented which provides an excellent means of correlating results for combustors having rich primary zones designs. Limited data for new, low-smoke lean designs indicate much less sensitivity of combustor liner temperature to fuel hydrogen content. Although smoke emission also increased with decreased hydrogen content, gaseous exhaust emissions were unchanged. Fuel bound nitrogen conversion to NO x under practical aircraft combustion conditions (up to 838°K inlet temperature) was found to be dependent on both fuel nitrogen concentration and combustor inlet temperature. Finally, future directions for alternate jet fuel combustion efforts are summarized. Recommendations range from an expanded scope of combustor and engine testing to required fundamental combustion research.