Turbulent Flame Velocities in Premixed Sprays Part I. Experimental Study

Abstract

This investigation was conducted to examine the influence of the flow velocity, turbulence intensity, droplet size distribution and fuel-air ratio on the turbulent flame velocities in premixed sprays. Premixed sprays of kerosene or light diesel oil were burnt either in a combustion chamber 450 mm long and of 75 mm × 75 mm cross section, or on an inverted-cone-flame burner of 21.6 mm diameter. The flame velocities were measured, and the physical structure of flames was observed by schlieren and high-speed photographies. As a result, the following empirical relation was obtained where S_T denotes the turbulent flame velocity [m/sec], K is a constant whose value is 6,800 for kerosene sprays, d the Sauter mean diameter [microns], φ the fuel-air ratio [g/g] and u' the turbulence intensity of the approach flow. For light diesel oil sprays, the value of A“ was estimated to be 4,300 for u' around 0.1 m/sec from experiments on inverted-cone-flames. It is noticed from the above relation that, besides the mixture strength, the average diameter of droplets, intensity of turbulence and volatility of the liquid fuel exert significant influences on the turbulent flame velocity.