Pressure distribution measurement on a rotating disk surface by pressure-sensitive paint

A pressure-sensitive paint (PSP) measurement technique is a non-contact optical method based on the oxygen quenching of its luminescence. By using PSP, we measured the pressure distribution on the disk in a hard disk drive, which is difficult to measure by conventional contact methods such as pressure taps. In the PSP measurement, we have to take the temperature non-uniformity on the rotating disk into consideration because the temperature distribution causes measuring error. We employed pyrene sulfonic acid (PySO₃H) as a luminophore of PSP, which has small temperature dependency at appropriate wavelength of the luminescence, and successfully obtained the pressure distribution on the disk rotated at various speeds (10 000-20 000 rpm). The result showed that the pressure is higher at the disk outside than at the center, and forms a concentric circle distribution. In addition, we found that the pressure difference between the inner and outer region of the disk increases as a square of disk rotation speed and a decrease in the distance between the co-rotating adjacent disks.