Using the Conditional Moment Closure Method to Assess the Effects of Turbulence Chemical Kinetics

Predicting the emission signature and radar cross-section of rocket exhaust plumes is of vital interest to the Missile Defense Agency and U.S. Army to protect the U.S. homeland and our forces abroad.  The current STTR Phase II project has shown that a single-conditioned Premixed Conditional Moment Closure (PCMC) can employ detailed chemical kinetic mechanisms while efficiently modeling combustion heat release and turbulence-chemistry interactions.  Similarly, other researchers have shown that double-conditioning can provide good predictions for ignition and extinction in non-premixed flames.  In this sequential STTR Phase II we propose to develop a more general double-conditioned CMC turbulent combustion model that will more accurately predict ignition, extinction, heat release rates and the turbulence-chemistry interaction across all premixed, non-premixed and partially premixed systems and apply it to the plume afterburning shutdown phenomena.  This effort will also include the construction and verification of a detailed combustion mechanism that is specifically suited to low pressure and high temperature plume afterburning conditions for small molecule hydrocarbon and amine fuel fragments with oxidizers like N2O4 and chlorine trifluoride.  These two developments will enable the efficient and accurate prediction of plume afterburning and afterburning shutdown along their ascent trajectories of emerging threats with new propellant chemistries.  Success in this effort is also expected to be commercially valuable in the accurate prediction of performance and pollutant formation characteristics of gas turbines, diesel engines, and Homogeneous Charge Compression Ignition (HCCI) engines.