Multi-component droplet evaporation model incorporating the effects of non-ideality and thermal radiation

Abstract

Currently, sophisticated fuel formulation and high temperature combustion in gas turbine and internal combustion engines make it important to investigate the effects of mixture non-ideality and radiation absorption on fuel droplet evaporation. In this study, an improved evaporation model by considering activity coefficients (AC) and external thermal radiation was established to simulate the evaporation process of multi-component non-ideal fuel droplets, and droplet suspension experiment was performed to validate the proposed model. It was found that the accuracy of simulated results was enhanced by considering activity coefficients and radiation absorption, and both effects were dependent on ambient temperature. The effect of activity coefficient was significant at low temperature (503 K), under which the droplet evaporation rate in the initial period was obviously faster than that at later stage. Consequently, the droplet lifetime decreased by about 8% at low temperature when activity coefficient was taken into consideration. At high temperature (703 K), however, the effect of activity coefficient or non-ideality on the droplet evaporation rate turned out to be insignificant. The radiation had a strong influence on evaporation at high temperature with the droplet lifetime decreasing 48% when ambient temperature increased from 503 K to 703 K. There seemed to be a critical diameter, under which the effect of radiation became negligible. It is also demonstrated that the component concentration gradients existed inside the non-ideal droplets in the initial period because of relatively low mass diffusion rate. As time elapsed, the gradients gradually disappeared due to the fact the components with large activity coefficient nearly completely evaporated.