Development of next generation lifetime PSP imaging systems

Abstract

This paper describes a lifetime PSP system that has recently been developed using pulsed light-emitting diode (LED) lamps and a new interline transfer CCD camera technology. This system alleviates noise sources associated with lifetime PSP systems that use either flash-lamp or laser excitation sources and intensified CCD cameras for detection. Calibration curves have been acquired for a variety of PSP formulations using this system, and a validation test was recently completed in the Subsonic Aerodynamic Research Laboratory (SARL) at Wright-Patterson Air Force Base (WPAFB). In this test, global surface pressure distributions were recovered using both a standard intensity-based method and the new lifetime system. Results from the lifetime system agree both qualitatively and quantitatively with those measured using the intensity-based method. Finally, an advanced lifetime imaging technique capable of measuring temperature and pressure simultaneously is introduced and initial results are presented.

Development of a Pressure Sensitive Paint System for Measuring Global Surface Pressures on Rotorcraft Blades

“…The outer 15% of each blade was coated with a sol-gel-based PSP formulation using ruthenium bathophenanthroline (Rubath) as the luminophore [15]. This probe was chosen specifically due to its relatively short excited-state lifetime (approximately 5 μs at vacuum), allowing for an effective freezing of the blade motion mitigating excessive blur as images are acquired.…”

“…A second method of PSP data acquisition is known as "lifetime-based" PSP [11][12][13][14][15]. In the lifetime-based technique, excitation of the PSP is accomplished using a modulated light source (e.g.…”

“…The second image (Gate 2) is taken at a later time after the excitation pulse and usually has a longer gate width, ensuring maximum pressure (and temperature) sensitivity. More information on the lifetime technique used in this work can be found in [15]. This paper will present results from a proof of concept test for using PSP to measure surface pressure distributions on rotorcraft blades in hover.…”

Pressure Sensitive Paint Measurements on 15% Scale Rotor Blades in Hover

“…In Configuration C, which had the maximum separation between the camera and imaging area, the camera was binned to increase its light gathering capability at the expense of spatial resolution. More information on the lifetime techniques used in this work can be found in Watkins et al 22 …”

Blade Tip Pressure Measurements Using Pressure-Sensitive Paint

“…Dynamic PSP may enable high resolution pressure measurements on helicopter rotors, thus allowing more accurate analytical prediction methods. Work in this area has been very limited to date [3][4][5][6][7] . Over the last several years, the US Army Aeroflightdynamics Directorate, Joint Research Program Office and the NASA Subsonic Rotary Wing Project have partnered to develop PSP measurement techniques for use on rotor blades.…”