Experimental and numerical investigation of evaporation and the dependence of flash points on the ignition spots at an open-cup method

•The factors affecting the accuracy of open-cup method are analyzed by CFD evaporation simulation.•Variation of flash point from measuring-spot to measuring-spot is confirmed.•The lower flash point is obtained at the measuring-spot with larger vapor volume fraction.•The fluctuation of vapor volume fraction and temperature is responsible for the measurement deviation of the flash points.•Suggestions for improving the accuracy of the open-cup method are presented. Flash point experiments involve heat transfer, evaporation, and combustion, but there is a large uncertainty in the results. The experiment and numerical investigation were conducted on flash points of combustible liquids. The flash points were measured at different ignition spots on open-cup test bench. The evaporation simulation of ethylene glycol was performed using the volume-of-fluid (VOF) and Lee's model. The results showed that the flash point varied from measuring-spot to measuring-spot and a lower flash point could be obtained at the measuring-spot with higher vapor volume fraction. The vapor volume fraction and temperature exhibited severe fluctuation and the measurement deviations of the flash points were closely related to the fluctuation of vapor temperature. The vapor flow characteristics and mass transfer rate were also analyzed.