The combustion of spray of liquid fuels has a significant importance in the industry field. This paper describes an experimental study to understand and analyze the flame structure of a light diesel fuel. A special design of an external mixing air assist atomizer is used for the atomization. The atomizer installed through burner tube. Combustion tests in a small scale laboratory furnace are carried out to select the optimum operating conditions for good combustion and low emissions. The emissions (CO and NOx), combustion efficiency, axial and radial inflame temperature profiles and the heat transfer distribution for the water jacket are measured at various operating conditions. Visual observation of free jet flames was taken over wide ranges of atomizing air pressure. It is found that increasing the atomizing air pressure with the same air to fuel ratio, leads to decreasing the amount of heat flux to the cooling water jacket, decreasing in the combustion efficiency and increasing in CO and NOx emissions. It is noticed that increasing in air to fuel ratio (A/F) at the same fuel flow rate leads to decreasing in CO and NOx emissions.