Optimum Product Freeze Temperatures For Analytic Cylinder Velocity Calculations

Cylinder  velocities calculated with the  Baker analytic cylinder model utilizing JWL  parameters generated from the Jaguar  thermochemical equilibrium program with a nominal 2200 K product reaction freeze temperature   have been found to be generally  in agreement with experimental streak data to within 2%  at high expansions.  However,  analyses of recent  cylinder test data  obtained by PDV procedures indicate larger deviations at high  expansions  for  values calculated  with these procedures,  with an average positive  deviation of  about 3% at 7 area expansions.   A previous study has suggested that higher freeze temperatures  are required for highly nonideal  explosives such as TNT.   In order to investigate the effects of the freeze temperature and corresponding oxygen balance for optimum   agreement with    cylinder velocity PDV values, results for a number of standard formulations have been analyzed in detail.  The formulations  include  HMX or RDX -based systems  and literature data for a Cl-20 based explosive LX-19.  Ratios of calculated  to experimental cylinder  velocities for the  HMX and RDX formulations  decrease   with increasing freeze temperature in the range 2200 K to 3000 K.   There is no apparent trend with oxygen balance for these explosives, but the ratio for the more ideal LX-19 explosive  is close to 1.0 for the entire  temperature range.   For the explosives considered the average error  between calculated and experimental velocities is reduced to under  1% at 7 area expansions with  a 3000 K freeze temperature.