脉冲热激励对液滴蒸发特性影响的实验研究

In order to investigate effects of pulsed thermal excitation on evaporation characteristics of liquid fuel，a pulse power is used as an external thermal excitation to heat a microscale burner，where a suspended droplet is formed by continuously supplying liquid n-heptane，and unsteady evaporation characteristics of the droplet under pulsed thermal excitation are studied. Firstly，output signal of the pulse power is obtained by oscilloscope，and the air temperature and flame temperature are measured to obtain response of the temperature to the pulse power. Secondly，oscillation of the droplet diameter with time is obtained by the image processing method. Finally，the droplet evaporation rate is calculated to explain the droplet oscillation. The results show that，the droplet evaporation rate always oscillates around the fuel supply rate，and the difference between them leads to the droplet oscillation. The pulsed thermal excitation first induces the air temperature oscillation，and causes the flame temperature，droplet diameter and evaporation rate to oscillate at the same frequency，but all of them lag behind the air temperature. Increasing the heating frequency or reducing the heating power can accelerate response of the flame temperature to the air temperature oscillation，but delay response of the droplet diameter and evaporation rate to the air temperature oscillation. The heating power significantly affects the average droplet diameter. When the power is lower than 16.0W，the droplet diameter exceeds the critical diameter of 2.6mm，and the droplet falls to form a liquid film.