A study has been made of the problem of steady, one-dimensional, laminar flame propagation in premixed gases, with the Lewis number differing from (and equal to) unity. Analytical solutions, using the method of matched asymptotic expansions, have been obtained for large activation energies. Numerical solutions have been obtained for a wide range of the reduced activation temperature parameter (n ≑ E/RTb), and the Lewis number δ. The studies reveal that the flame speed eigenvalue is linear in Lewis number for first order and quadratic in Lewis number for second order reactions. For a quick determination of flame speeds, with reasonable accuracy, a simple rule, expressing the flame speed eigenvalue as a function of the Lewis number and the centroid of the reaction rate function, is proposed. Comparisons have been made with some of the earlier works, for both first and second order reactions.

An analysis has been made of the effects of finite recirculation in a conical stirred reactor whose inlet and outlet are at the same end, and a theory has been developed describing the behaviour of such a reactor for a single-step reaction. Numerical solutions have been obtained for the temperature distribution along the reactor. This work evaluates the error in the values of overall reaction rates deduced from the characteristics of a stirred reactor which would result if it were assumed that the gases in the reactor were a homogeneous mixture reacting at the mean measured temperature of the reactor; this error has been expressed as a function of the flow rate, the composition of the input gases, the recirculation ratio and the activation energy of reaction. The error is least when the activation energy of the reaction is low; for activation energies of the order of those of combustion reactions, the error may be reduced below ten per cent by designing the reactor so that the injected reactant entrains more than ten times its own mass and by operating it at a flow rate which is not much below that leading to flame extinction.

The present paper deals with the theory of the burning of monopropellant droplets in an atmosphere of inert gas which may be either hotter or cooler than the adiabatic decomposition products of the monopropellant. Numerical and approximate solutions to the equations are obtained. The burning rates and burning times of a monopropellant droplet are presented in a dimensionless manner in terms of the physical and chemical properties of the monopropellant. It is shown that the approximate theory, called the ‘thin-flame approximation’ overestimates the burning rate and hence underestimates the burning time of a monopropellant droplet; however, the error is not large.

The present paper considers the effects of chemical kinetics on a one-dimensional diffusion flame. A mathematical treatment which takes the fuel fraction as the independent variable is presented and numerical solutions are obtained for a particular idealized hydrocarbon-air diffusion flame. It is shown that, at the extinction point of the particular diffusion flame considered, the fuel-consumption rate per unit area is 0·89 times the fuel-consumption rate per unit area in a premixed stoichiometric flame; at higher fuel flow rates the flame is extinguished. It is also shown that, even before extinction, some fuel escapes unburnt through the diffusion flame of the type considered.