Effects of particle size and concentration on the pulsation characteristics of transformer oil

The presence of particulate matter in oil has a great impact on the pulsation characteristics of the oil, it is important to understand the effects of particle size and concentration on the pulsation characteristics of oil for safe operation of oil equipment. Oil flow with different particles was tested in a square tube using PIV measurement technology. The instantaneous velocity vector data of the flow field were acquired in oil with different particle sizes and concentrations of the particles, and the distributions of the transient speed and average speed and the pulsation intensity of oil along the streamwise and wall-normal directions were analyzed. The results showed that the distribution of the streamwise pulsation intensity of oil changes more gently along the wall-normal direction in the center region and changes more steeply in the near-wall area. With increasing particle concentration, the streamwise pulsation intensity of oil decreases gradually. The distribution of the wall-normal pulsation intensity of oil along the wall-normal direction is roughly "w"-shaped under different particle grain diameters. The amplitude value of the wall-normal pulsation intensity of oil is larger in the center region and near-wall area, and the effect of the particle concentration in oil on the distribution of the wall-normal pulsation intensity of oil is not unidirectional. With increasing particle concentration, the main frequency trend of the oil speed along the streamwise and wall-normal directions decreases, and the streamwise average speed of the oil increases. The change in the wall-normal average speed of oil decreases when the particle concentration is under 3.00 ppm, and the normal velocity of oil increases when the particle concentration is over 3.00 ppm.