A Numerical and Experimental Study of Fuel Evaporation and Mixing for Lean Premixed Combustion at High Pressure

Abstract

A prevaporizer-premix duct with complete optical access operating at pressures up to 15 bar and at temperatures up to 850 K has been built to investigate in detail the coupled processes of atomization, evaporation, and mixing of kerosene at conditions relevant to aeroengines and stationary gas turbines. Phase-Doppler anemometry (PDA) was used to measure liquid-phase properties and laser-induced fluorescence for the liquid and gaseous fuel. The evaporation and dispersion properties of the prevaporizer were simulated with a Lagrangian particle tracking computer program. For the flat prefilming atomizer used, complete evaporation was obtained within 100 mm without autoignition. Dynamic pressure, important for a sufficiently fine atomization, was about 3% of total pressure. Comparing parametric variations of the experiments with the computations, it was found that air temperature had the largest influence on evaporation, whereas pressure only had an indirect effect through atomization quality. In the same way, the initial spray temperature was shown to be an important parameter for evaporation, and it should be measured. The spray acceleration and evaporation history was reproduced sufficiently well for engineering purposes both with and without taking into account spray feedback on the gas phase. The dispersion was not sufficient for practical use in premix ducts. Turbulence generators are needed to promote spray dispersion and vapor mixing.