Calculation of Free-Atom Fractions in Hydrocarbon-Fueled Rocket Engine Plumes for Engine Health Monitoring

摘要

Free-atom fractions (P) of nine elements are calculated for the exhaust plume of CH4-oxygen and RP-1-oxygen fueled rocket engines using free energy minimization method. The Chemical Equilibrium and Applications (CEA) computer program developed by NASA's Glenn Research Center was used for this purpose. Values of p in both fuels as a function of temperature (1600 K -3100 K) and oxygen to fuel ratios (2.0 to 2.5 by weight for CH4 and 1.75 to 2.25 by weight for RP-1) is presented in both tabular and graphical forms. A recommendation is made for the p value for a tenth element, Palladium. The CEA computer code was also run to compare with experimentally determined p values reported in literature for some of these elements. A reasonable agreement between the calculated and reported values is observed. Values reported in this work will be used as a first approximation for pilot rocket engine testing studies at the Stennis Space Center for six elements Al, Ca, Cr, Cu, Fe and Ni - until experimental values are generated. The current estimates will be improved when more complete thermodynamic data on the remaining four elements Ag, Co, Mn and Pd are added to the database. A critique of the CEA code is also included.