Combustion Science and Technology

NICHOLLS, J. A.; KAUFFMAN, C. W.; PELACCIO, D. G.; GLASS, D. R.; DRISCOLL, J. F.

doi: 10.1080/00102208008952411pmid: N/A

Abstract In this program, a research gas turbine combustor is used to study the influence of individual variables (in particular, fuel spray characteristics) on the local level of emissions species concentrations within the primary zone flame. The unique combustor is designed to provide realistic conditions and to allow for independent control of drop size, fuel-air ratio, residence time, air inlet temperature, pressure and reference velocity. This is one of the few combustors in which the residence time has been measured and controlled. The simple flow pattern, with no large scale recirculation, allows for unambiguous interpretation of results Measurements were made of the local concentrations of NOx, CO and unburned hydrocarbons, the local gas temperatures and, using laser velocimetry, local gas velocity and turbulence levels. To explain the unexpectedly high levels of hydrocarbons and low flame temperatures that were observed, it is believed that the spray burns in a manner similar to a gaseous turbulent diffusion flame. It is concluded from the data that the effect of increasing drop size (keeping residence time and other parameters fixed) is to cause an increase in unburned hydrocarbons and a decrease in the flame temperature gradients. Increasing residence time results in sharp decreases in hydrocarbons and CO and an increase in NOx. Increasing equivalence ratio causes an increase in temperature and NOx and a corresponding decrease in hydrocarbons. Some unexpected trends in NOx levels are discussed.

HIRANO, TOSHISUKE; SUZUKI, TAKUJI

doi: 10.1080/00102208008952412pmid: N/A

Abstract Detailed gas movements ahead of propagating flames through layered flammable mixtures have been theoretically simulated on the basis of convenient models. In the analysis, two-dimensional inviscid flow fields and constant flame velocities during propagation are assumed. Thermal expansion of gas due to combustion at the flame front is replaced by an imaginary source behind the flame front. Two cases are analyzed. In one case, a flat, flammable mixture layer, through which a flame propagates, is assumed to be established in an open space, and in the other case, it is assumed to be established in contact with a liquid or solid surface parallel to the layer. Equations representing the flow fields, fuel concentration distributions, gas particle paths, and flame front shapes are derived. The theoretical results obtained in the present study are shown to agree fairly well with the experimental results presented in previous reports.

SALIMIAN, S.; HANSON, R. K.

doi: 10.1080/00102208008952413pmid: N/A

Abstract Detailed kinetic calculations have been carried out to evaluate candidate schemes for the removal of NO from combustion gases by injection of compounds leading to homogeneous NHi-NO reactions (i = 2, 1, 0). NO removal is calculated as a function of temperature and reaction time for prescribed initial levels of NO in otherwise equilibrated fuel lean combustion gases. Four different compositions are considered, chosen to include mixtures representative of the Thermal DeNOx Process (injection of NH3 or NH3/H2), as well as alternative mixtures (NH3/H2O2 and NH2/CO, the latter chosen to simulate urea) which may have advantages for particular applications, for example in shifting the temperature for optimum NO conversion or in reducing the required reaction time.

ZATURSKA, MARIA B.

doi: 10.1080/00102208008952414pmid: N/A

Abstract The simple theory for the prediction of criticality in thermal ignition problems, which was based on a step-function reaction rate approximation and presented in a previous paper, is here applied to problems in which temperature is a function of more than one space variable. Boundary conditions corresponding to both fixed temperature and to surface cooling are considered. Results for dimensionless parameters of Frank-Kamenetskii type again agree well with those based on more realistic reaction-rate assumptions where these are available.

GIRDHAR, H. L.; ARORA, A. J.; MALIK, G. N.

doi: 10.1080/00102208008952415pmid: N/A

Abstract Ignition times for composite propellants containing nitrophenolic resins as fuel binders and NH4ClO4 or KClO4 as oxidizers are measured by the hot plate technique. Activation energies of ignition process are calculated using thermal explosion theory. The results show the possibility of two different mechanisms of ignition process depending upon the heating temperature.

MANSOURI, S. H.; HEYWOOD, J. B.

doi: 10.1080/00102208008952416pmid: N/A

Abstract Correlations are presented for the viscosity and Prandtl number of hydrocarbon-air combustion products for the temperature range 500 K to 4000 K, pressure range 1 to 100 atm, and fuel-air equivalence ratio range of 0 to 4. The required thermodynamic properties for calculating the thermal conductivity from the Prandtl number, cp and γ, are also given. The principal advantage of these correlations is computational speed; they have been developed primarily for internal combustion engine performance calculations.

PATCH, R. W.; SAVAGE, K. I.

doi: 10.1080/00102208008952417pmid: N/A

BUSH, WILLIAM B.

doi: 10.1080/00102208008952418pmid: N/A

Abstract The zeroth- and first-order approximations for the eigenvalue Damköhler number are determined for the steady, one-dimensional isobaric adiabatic combustion of a fuel-lean gaseous premixture under a direct one-step Arrhenius-type exothermic chemical reaction in the physically interesting limit of (1) activation temperature large relative to the hot-boundary temperature; (2) (constant) Lewis-Semenov number of order unity; and (3) fuel and oxidant stoichiometric coefficients of order unity. It is shown that, to zeroth-order of approximation, the bimolecular system behaves as a monopropellant decomposition. The dependence on the parameters of the departure of this system from such behavior, to first-order of approximation, is established.