ID#: 179
Abstract Title: Radiant Ignition Models for Nitramine Propellants
Session Title: Poster Session I
Session Date: 7/31/01
Session Start Time: 2:50 PM
Contributing Author: Cohen, A.
Organization: U.S. Army Research Laboratory
Country: USA
Authors: A. Cohen, K. L. McNesby, R. A. Beyer, R. Wainner
Short Abstract: The ability of radiant propellant ignition models to predict initial pressurization rates in gun chambers is a prime requirement for interior ballisticians. Phenomenological models use global kinetics for condensed phase energy production rates of the propellant materials. These can be used to predict ignition delays but not pressurization rates. Recent physical radiant ignition (and combustion) models for nitramine propellants consider detailed chemical kinetic mechanisms for condensed and gas phases. These models are capable of predicting temporal variations in temperature, pressure and. chemical species. Validation of these models can be made by comparing predictions with measurements of emission delays (first light), pressurization (delays and initial rates) and transient appearances (and concentrations) of gaseous products. This paper will present recent results of an investigation of CO2 laser ignition of pressed pellet samples of neat RDX (cyclotrimethylene trinitramine) and samples cut from extruded strands of XM39, a heterogeneous gun propellant containing approximately 75% RDX in an inert binder (cellulose acetate butyrate). Experiments were conducted in a windowed chamber at atmospheric pressure in air and N2 with flux densities = 10 - 200 cal/cm2-s and pulse length < 2s Wave-length integrated emission from the plume generated near the surface of the samples were recorded with photomultipliers (wave length = 300-800 nm response). Simultaneous records of emission from excited OH and CN species were obtained using interference filters ( wave length = 310 and 388 nm, respectively). A CCD/spectrometer (Princeton Instruments) was used to record emission spectra (wave length = 250 - 850 nm) integrated over various time intervals during (laser assisted flame) and after (unassisted flame) the laser pulse. These were used to identify the various species produced during ignition. Transient pressure was measured with a piezoelectric transducer. Comparisons of measurements with predictions of phenomenological and physical radiant ignition models ( 1-D) will be presented.