The use of porous-media burners in air-heating systems, gas turbine combustors, and steam generators is a potential method to reduce pollutant emission levels. Biofuels, such as canola methyl ester (CME), are an attractive alternate energy resource; however, pure biofuels have lower energy content than petroleum-based fuels. Therefore, the combustion characteristics of blends of Jet A and CME were studied in a porous-media burner. Two silicon carbide coated carbon-carbon matrix porous media of square section were used. The upstream porous medium with a pore size of 8 pores per centimeter (20 pores per inch) served as the evaporation porous medium; the downstream porous medium with a pore size of 31 ppcm (80 ppi) was used as the combustion porous medium. The CME-Jet A fuel blends were injected from an air-blast atomizer into a coflow of hot air, which entered the evaporation porous medium. The combustion characteristics of three blends (volume percentages of CME equal to 25%, 50% and 75%) were studied at four different initial equivalence ratios. The global pollutant emissions, axial temperature profiles and the radiative heat fraction of the flame downstream of the combustion porous medium were measured. The results indicated that for lean air-fuel mixtures, the addition of CME to Jet A resulted in a reduction of the CO emission index. However, the NOx emission index was increased with the CME content in the blend for a given equivalence ratio. Also, the maximum flame temperature increased with equivalence ratio. In general, it was found that the porous-media burner was useful in reducing emissions and controlling flame temperatures.
Combustion characteristics of porous media burners under various back pressures: An experimental study
