Summary of Simplified Two Time Step Method for Calculating Combustion Rates andNitrogen Oxide Emissions for Hydrogen/Air and Hydrogen/Oxygen

摘要

A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailedkinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space.These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions arethen used to find the conversion in the reactor. The method uses a two time step kinetic scheme. The first time averaged stepis used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function ofinitial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations(>1×10–20 moles/cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and watermole concentrations, pressure and temperature (T4). The simple correlations are then compared to the turbulent mixing timesto determine the limiting properties of the reaction.The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kineticscheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time isregressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 andNox are obtained for H2/Air fuel and for H2/O2.A similar correlation is also developed using data from NASA’s Chemical Equilibrium Applications (CEA) code todetermine the equilibrium temperature (T4) as a function of overall fuel/air ratio, pressure and initial temperature (T3). Highvalues of the regression coefficient R2 are obtained.