Clean combustion of different liquid fuels using a novel injector

This study demonstrates low-emission combustion of diesel, biodiesel and straight vegetable oil (VO) in a fuel-flexible combustor employing a flow blurring (FB) injector for fuel atomization. Measurements of gas temperature and CO and NOx concentrations at various axial and radial locations of the combustor are acquired using custom-designed thermocouple and gas sampling probes. Heat loss rate through the combustor is estimated from wall temperatures measured by an infra-red camera. A simple droplet model is used to predict fuel vaporization behavior in the dark-region near the injector exit. Results show that the FB injector produced clean blue flames indicating mainly premixed combustion for all three fuels. Matching profiles of heat loss rate and product gas temperature show that the combustion efficiency is fuel independent. NOx emissions for the three fuels agree with each other within the measurement uncertainties. CO emissions of straight VO are slightly higher than those for diesel and biodiesel. This difference in CO emissions is explained by the slower evaporation rate of straight VO droplets compared to diesel or biodiesel droplets. This study shows that with FB injector, straight VO without preheating or chemical pre-processing can be cleanly combusted in furnaces, boilers, or stationary power generation systems, thereby offering significant economical and environmental benefits.