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.