Evaporation of Renewable Fuels in a Lean Premixed Prevaporized Burner

The last decades have emphasized the requirement for alternative energy sources, particularly in the transport sector, where combustible liquid fuels are expected to dominate in the foreseeable future. In such applications, the fuel must be efficiently atomized, evaporated, and mixed with the combustion air before it reaches the flame front, in order to meet the latest pollutant emission standards.Hence, this paper investigates the utilization of nine different fossil and renewable liquid fuels. The domain of the analysis is a lean premixed prevaporized burner equipped with an air blast atomizer and a mixing tube. Analytical calculations are performed to determine the evaporation process after the atomization; then the evaporation time is compared to the residence time of the droplets in the mixing tube. The effect of preheating both the fuel and the combustion air is also examined to determine proper combustion conditions even for the low volatile crude vegetable oils

Thermal analysis of suspended single droplet evaporation measurements with a coupled lumped parameter model

The measurement data of single droplet evaporation experiments are often biased due to the extra heat input through the fiber suspension and the presence of thermal radiation in hot environments. This encumbers model validation for heat and mass transfer simulations of liquid droplets. In this paper, a thermal analysis of this measurement layout is presented with a coupled lumped parameter model, considering heat conduction through the suspension. The model was validated by experimental data from the literature and good agreements were found. The thermal analysis focused on fiber material and geometry, and thermal radiation properties. Calculations were performed on a broad range of ambient conditions for liquids with different volatility characteristics. Temporal squared droplet diameter- and temperature-profiles, furthermore, droplet stationary evaporation rate were used to characterize vaporization phenomena. The thermal balance of the droplet is dominated by the convective heat rate from the environment in the early stage of evaporation. The effect of heat conduction through the fiber becomes important at the end of the droplet lifetime when the droplet size is decreased. Temperature sensor suspension may seriously bias droplet temperature due to the larger thermal conductivity compared to quartz fiber. Large droplets in high-temperature environments show significant sensitivity to thermal radiation properties, which should be considered in measurements and model validation