Effect of radiant energy on vaporization and combustion of liquid fuels

Berlad, A. L., Hibbard, R. R.
naca-rm-e52i09
1952


The radiative processes involved in combustion were investigated to determine the present role of radiant energy transfer in combustors. It was shown that at present the amount of radiant energy transfer from flame to fuel is quite small in a turbojet combustor. In order to find techniques for making this radiant energy transfer from flame to fuel significant, methods of increasing the equivalent gray-body emissivities of the fuel drops and the flame, as well as the efficiency of the energy transfer itself, were examined. The equivalent gray-body emissivity of a hydrocarbon fuel may be increased by the use of liquid or solid, soluble or nonsoluble, additives. It was found that the nonsoluble solid additive was the most desirable one. In addition to the fact that a slurry-type drop may have a greater emissivity, the suspended solid additive may also greatly contribute to the emissivity of the flame. An approximate equation was derived from which the equivalent gray-body emissivities of such slurry-type drops may be calculated. Data necessary for these calculations were obtained by spectrophotometric analysis of thin slurry films. In addition to the fuel additive, the use of radiation-reflecting walls in a combustor was considered as a means of maintaining the efficiency of the radiative transfer of energy from flame to fuel drop. It was then shown that more than half the heat of evaporation of the hydrocarbon constituent of this slurry-type drop might be supplied by radiant energy transfer in such a modified turbojet combustor.

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