A simple method for the design of gas burner injectors

Abstract

The performance of a fuel jet issuing through a nozzle and entraining the air for combustion in a gas burner has been systematically investigated, using well-established theory for such ‘injectors’ based on momentum conservation for one-dimensional flows. Earlier applications of this theory for injector calculations are reviewed. It is shown that neglect of property variations introducs only small errors for the cases that are likely to be considered in such combustion problems. Design charts are generated in which the ratio of entrained air flow to fuel to fuel flow is related to the area ratio of the two streams at the plane of the nozzle. The ratio is a function of generalized parameters describing the inlet and outlet resistances (ameliorated by a diffuser), the density ratio of the fluids and the Mach number of the nozzle. Predictions are compared with new experimental data for an injector with the mixing tube Reynolds number in the range 2000–12000 and shown to agree to within 10 per cent when the mixing tube is of optimum length.