Accession Number : ADA473517


Title :   Evaluation of Catalytic and Thermal Cracking in a JP-8 Fueled Pulsed Detonation Engine (Postprint)


Descriptive Note : Conference paper


Corporate Author : AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIRECTORATE


Personal Author(s) : Helfrich, Timothy M ; Schauer, Frederick R ; Bradley, Royce P ; Hoke, John L


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a473517.pdf


Report Date : Sep 2007


Pagination or Media Count : 15


Abstract : Pulsed detonation engines (PDEs) depend on rapid ignition and transition from deflagration to detonation. The prospect of converting the PDE from experimental to operational use necessitates a considerable reduction in the time required to ignite and detonate a liquid hydrocarbon fuel in air, such as JP-8. This research effort is focused on PDE operation enhancements using dual detonation tube, concentric-counter-flow heat exchangers to elevate the fuel temperature levels sufficiently to induce thermal cracking. Additionally, a zeolite catalytic coating is applied to the heat-exchanger surfaces to stimulate further cracking of the fuel and reduce coke deposition. To quantify the PDE performance, three parameters are examined: ignition time, deflagration-to-detonation transition (DDT) time, and DDT distance. Once cracked, the JP-8/air mixture results in a shorter ignition time, DDT time, and DDT distance for the majority of equivalence ratios, with a reduction in ignition time of up to 60% at 908 K, as compared to flash vaporized JP-8/air mixtures. Furthermore, both the ignition and detonability limits are expanded by cracking the fuel, with lean limits at an equivalence ratio of 0.75. Coke deposition found in the fuel filter consists of carbon as well as substantial concentrations of silicon and aluminum, due to breakdown of the silica-alumina zeolite structure. Additionally, poisoning of the catalyst is shown to occur after five hours of operation, although no degradation in performance was observed.


Descriptors :   *PULSES , *JET ENGINE FUELS , *CATALYTIC CRACKING , *DETONATIONS , HEAT EXCHANGERS , COOLING , SILICON , ENDOTHERMIC REACTIONS , DEFLAGRATION , SUPERCRITICAL FLOW , THERMAL STRESSES , IGNITION , HYDROCARBONS , ALUMINUM , DEPOSITION


Subject Categories : Fuels
      Jet and Gas Turbine Engines


Distribution Statement : APPROVED FOR PUBLIC RELEASE