CEM India - Abstract

Abstract Information :

Higher pollutant emissions from combustion systems cause harmful effects like acid rains, smog and haze resulting in global warming. Therefore, it is necessary to discover the new combustion techniques with lower pollutant emissions and higher efficiency. MILD or flameless combustion has the promising features of low pollutant emissions and uniform temperature distribution. In MILD/flameless combustion, hot combustion products are recirculated back into the fresh fuel-air mixture. This dilution reduced the oxidizer concentration in the mixture and slows down the reaction rate. It results in the uniform/distributed reaction zone inside the combustor.
In the present work, effect of fuel injection pressure and air-preheating on different combustion characteristics has been investigated experimentally for the bio-diesel fuel. Solid cone type pressure swirl nozzle of 0.187 mm diameter, N1 was considered with different fuel injection pressures (14, 30, and 48 bar) to achieve different fuel flow rates of 2.5 kg/hr (30 kW), 3.12 kg/hr (37.27 kW), and 4.46 kg/hr (53.23 kW). Measured cone angles for the given operating conditions were 56°, 59°, and 64° respectively. A 60° diverging angle single stage combustor was considered and fuel was supplied from the bottom. Air was preheated at a temperature of 800K and supplied through four tangential ports. Higher fuel injection pressure results in the finer spray formation which helps achieving better mixing and recirculation of the hot combustion products. Better recirculation leads to uniform temperature distribution inside the combustor and very low pollutant (CO, NOx) emissions. The measured CO and NOx emissions were in the range of 194-286 ppm and 11-319 ppm for all heat inputs and equivalence ratio (Φ= 0.6 to 0.92), respectively. Temperature was measured using OMEGA made R-type thermocouple of 0.25 mm wire diameter and corrected for convective and radiative heat losses. Maximum temperature of 1652 K was measured at the center of the combustor for the thermal input of 53.23 kW. Measured temperature showed more uniformity at higher thermal inputs as the difference between centerline and wall temperatures was measured as 237 K, 220 K, and 211 K for the thermal inputs of 30 kW, 37.27 kW, and 53.23 kW respectively.