Single-shot pressure-sensitive paint lifetime measurements on fast rotating blades using an optimized double-shutter technique

Abstract

A pressure-sensitive paint (PSP) system is presented to measure global surface pressures on fast rotating blades. It is dedicated to solve the problem of blurred image data employing the single-shot lifetime method. The efficient blur reduction capability of an optimized double shutter imaging technique is demonstrated omitting error-prone post-processing or laborious de-rotation setups. The system is applied on Mach-scaled DSA-9A helicopter blades in climb at various collective pitch settings and blade tip Mach-and chord Reynolds numbers (M tip = 0.29−0.57; Re tip = 4.63− 9.26 • 10 5). Temperature effects in the PSP are corrected by a theoretical approximation validated against measured temperatures using temperature-sensitive paint (TSP) on a separate blade. Ensemble averaged PSP-results are comparable to pressure-tap data on the same blade to within 250 Pa. Resulting pressure maps on the blade suction side reveal spatially high resolved flow features such as the leading edge suction peak, footprints of blade-tip vortices and evidence of laminar-turbulent boundary-layer (BL) transition. The findings are validated by a separately conducted BL transition measurement by means of TSP and numerical simulations using a 2D coupled Euler/boundary-layer code. Moreover, the principal ability of the single-shot technique to capture unsteady flow phenomena is stressed revealing three-dimensional pressure fluctuations at stall.

An Europium (III) Luminophore with Pressure‐Sensing Units: Effective Back Energy Transfer in Coordination Polymers with Hexadentate Porous Stable Networks

“…Recently, time‐resolved analysis using the emission decay profile of phosphorescent materials has been a focus for fluid dynamics, aeronautical and environmental engineering . The emission lifetime‐based PSP systems have shown significant potential for unsteady flow diagnostics of aircrafts, high‐speed vehicles and turbomachinery .…”

Experimental Investigation of Rotor Tip Film Cooling at an Axial Turbine with Swirling Inflow Using Pressure Sensitive Paint

“…iii. Single-Shot Methods based on PSP Lifetime: A laser is used as a high-energy excitation source leading to a high SNR [19][20][21][22]. A double shutter particle image velocimetry (PIV) camera records a set of images with very short exposure times, minimizing the effects of cycle-to-cycle instabilities and blade movement.…”

Investigation of Factors Causing Nonuniformity in Luminescence Lifetime of Fast-Responding Pressure-Sensitive Paints

“…By eliminating the “wind-off” images, we can reduce the measurement errors caused by the deformation or movement of the model and changes in the distribution of excitation light and temperature on the model between the “wind-on” and “wind-off” conditions. Much effort has been made to develop the lifetime imaging method [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. However, it is known that the luminescence lifetime of PSP is not spatially uniform, even under uniform pressure and temperature conditions [ 12 , 13 , 15 , 16 , 17 ].…”

“…Much effort has been made to develop the lifetime imaging method [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. However, it is known that the luminescence lifetime of PSP is not spatially uniform, even under uniform pressure and temperature conditions [ 12 , 13 , 15 , 16 , 17 ]. Sugioka et al reported that a polymer-based PSP applied to a real wing showed considerable spatial variation in the luminescence lifetime [ 13 ].…”