Behaviors and trajectory of horizontal spray flame induced by transformer insulating oil

In this study, a set of experiments were conducted to determine the characteristics of horizontal spray flame made by transformer insulating oil with different mass flow rates. The overall results indicate that increasing the mass flow rate of horizontal spray could enhance the atomization effect and also accelerate both fuel evaporation and diffusion mixed with oxygen. The lift-off distance is inversely proportional to the 0.75 power of mass flow rate, which contrasts with the positive correlation of gas jet flame. The atomized evaporation of liquid spray allows it to have a larger cross-section area of flow compared to gas jet, and the flame enters the buoyancy-dominated region earlier. The horizontal projection length of spray flame is proportional to the 0.61 power of mass flow rate and the flame height can be predicted using the Richardson number and ratio of height to length. The difference in evaporation times of droplets with different sizes leads to bimodal flames. The dual flame trajectories can be normalized based on the relative positions to the main flame body. A modified cross-section radius of flow, b*=βs+M0.875, is proposed to simulate the expansion of flow cross-section caused by droplet evaporation. Meanwhile, the predicted flame trajectories which considering the evaporative diffusion present a good agreement with the experimental measurements.