Year 3 of the National Jet Fuels Combustion Program: Practical and Scientific Impacts

摘要

The transportation sector is increasingly looking towards lower carbon intensive technologies as governments and industry are more mindful of the impending consequences of conventional carbon energy sources. A potential solution to limiting the impact of anthropogenic carbon from the aviation transportation sector is the use of non-fossil based jet fuels. These non-conventional or alternative jet fuels (AJFs) additionally offer the potential of tailored performance characteristics for mission specific demands and an opportunity to develop domestic sustainable and diverse energy capacity. While the most significant hurdle to market penetration of these fuels is economics, the certification process of these alternative fuels can be significantly demanding enough to preclude some AJF options. The National Jet Fuels Combustion Program (NJFCP) is established to streamline the certification process of AJFs via the development of experimental, computational and theoretical tools. This year we report brief summaries on each Working Group of the NJFCP as they relate to informing the fuel approval process and additional scientific findings relevant to the gas turbine combustion and jet fuels research communities. 1. The Lean Blowout (LBO) Working Group, composed of 9 experimental rigs, is reporting that 8 of the 9 rigs show first order dependency on the Derived Cetane Number (DCN), a previously overlooked chemical property that is calculated from the ignition delay time under ASTM D6890. Additional chemiluminescence experiments suggest that LBO is limited by the autoignition propensity of a fuel, directly related to the DCN. AJFs below a DCN of 30 are expected to have lower stability limits than conventional fuels. 2. The Ignition Working Group has developed expanded experimental capabilities, i.e. the ability to conduct experiments with chilled fuel and air at sub-atmospheric pressures. Initial results suggest that the relative ignitability of fuels is related to the physical properties of the liquid fuel, viscosity in particular, and a fuel's distillation curve. Detailed results are under analysis. 3. The Spray Working Group has shown modest spray effects for the so-called Referee Rig nozzle and swirler at LBO conditions. Spray differences for the various fuels at ignition conditions are under analysis. 4. The Kinetics Working Group has developed advanced diagnostics capabilities to measure more than 85% of the carbon as a fuel is shocked. These diagnostic capabilities are enabling higher confidence kinetic models, and illuminating the relative chemical pathways. Additionally, the Kinetics Working Group has shown that fuels with varying DCNs have distinguishable ignition delay times in the hot ignition region (>1100 K at 4 atm), with fuels having lower DCN have longer ignition delay times (IDT). 5. The Computational Fluid Dynamics (CFD) Working Group has continued to align boundary conditions across several research groups to reconcile differences in results for near LBO simulations. 6. The Common Format Routine (CFR) Working Group has developed a plug-in which can utilize the latest Flamelet theory. This CFR is intended to enable the evaluation of an AJF in proprietary Original Equipment Manufacturer (OEM) hardware. Year 4 anticipates additional ignition data and analysis, predictions of LBO via CFD, and spray data at relevant chilled conditions. Beyond these expectations, prioritization will be critical to deliver optimal tools and other capabilities which can enable a cheap, reliable, and a faster certification process for AJFs.