NOx Emission of Lean Premixed-Prevaporized Combustion for Liquid Fuels

An experimental study was conducted to examine NOx emission of a premixing-prevaporizing flame stabilized with a bluff body. The liquid fuels, such as kerosene and light oil, were sprayed into the premixing-prevaporizing chamber with an air-atomizing nozzle. The size distribution of fuel spray, vaporizing time and heterogeneity of the mixtures were varied by varying the degrees of atomization and the length of the premixing-prevaporizing chamber. Velocity, concentration and Sauter mean diameter of the fuel spray in the vaporizing process were measured by means of a particle dynamics analyzer (PDA). The NOx emissions from premixed -prevaporized flames decreased with decreasing size of sprayed fuel droplets and increasing vaporizing rate. It was possible to reduce the NOx emissions from kerosene flames to the same level as methane-air premixed flames. While light oil has the lowest vaporizing rate, the temperature profile of its flame became similar to that of the methane flame and its NOx emission level also approached that of the methane flame with the promotion of vaporization.