|Institution:||The Ohio State University|
|Keywords:||Mechanical Engineering; PSP; single-shot; lifetime; measurements; rotating surfaces; rotorcraft|
|Full text PDF:||http://rave.ohiolink.edu/etdc/view?acc_num=osu1285044595|
In this work, the viability of using pressure-sensitive paints as a pressure sensor on rotating surfaces with unsteady pressure fluctuations has been investigated. A lifetime-based single-shot technique is demonstrated on a small prototype rotor with blade-tip speeds on the order of 50 m/s. In the single-shot approach, all of the required intensity information is acquired from excitation by a single pulse of light to avoid any errors caused by non-uniformities of the illumination and paint application on the surface. This technique eliminates the need of image averaging, and provides instantaneous surface pressure even for low-speed applications. PSP with pressure sensitivity of 0.8% change in ratio of image-intensity per kPa, a 532nm PIV laser system, optics, and a fire-wire CCD camera are used for this application. The lifetime sensitivity to oxygen concentration of some widely used pressure-sensitive paints has been investigated using a photomultiplier tube as well as a CCD camera, with respect to possible abilities and limitations of the paints for the discussed application. The results of the phase-locked lifetime measurements in environments having overall surface pressure gradients as small as 3.0 kPa show that this technique is capable of accurately resolving small pressure changes. An unrecognized patterned noise is observed when the emission intensity of the PSP is low for the single-shot mode and an analytical filtering is proposed to remove the impact of “patterned noise” in the reduced ratioed image. This filtering approach is based on applying a low-pass filter on the convolution of histogram obtained for the ratioed image along horizontal axis of image which is determined by the direction of “patterned noise”.