Pressure field measurements on large-scale propeller blades using pressure-sensitive paint

Pressure-sensitive paint(PSP)is a global pressure measurement technique.Compared with pressure transducers,PSP has significant advantages such as high spatial resolution and a lack of contact when applied to fast-rotating blades.However,due to the limitations of other pressure measurement techniques,the validation of PSP measurements on fast-rotating blades is generally difficult.In this work,a comprehensive study including PSP measurement,force balance measurement,and simulation was conducted on a 1 m-diameter propeller at the China Aerodynamic Research and Development Center.First,our computational fluid dynamics(CFD)code was validated by comparing the calculated aerodynamic thrust with the results from force balance measurements.Then,the pressure distributions on the propeller blade obtained by PSP were carefully compared with the CFD results under different working conditions.The results of PSP measurements,force balance measurements,and CFD showed good agreement,and the PSP measurement errors were estimated to be less than 5% of the dynamic pressure at the blade tip.Finally,the variations in pressure distribution under different rotating speeds and free-stream velocities were discussed.

Noise reduction for temperature-sensitive paint measurement contaminated by strong background radiation in a high enthalpy hypersonic tunnel

The strong background radiation in high enthalpy hypersonic shock tunnels has posed severe challenges for measurement using luminescent coatings.We proposed a solution for reducing background radiation from time-resolved temperature-sensitive paint(TSP)measurement in a hypersonic flow with Ma=6.5 and T_(0)=3525 K.The TSP was applied on an inlet ramp model,and the images were taken by a high-speed camera at 2 kHz under a modulated excitation.The strong background radiation led to a low signal-to-noise ratio and significant errors for the first half of the 130-ms test duration.Accordingly,three noise reduction methods were developed and evaluated based on temporal reconstruction,spatial reconstruction and robust principal component analysis(RPCA),respectively.The RPCA method showed the best performance that successfully recovered high-quality TSP data for a majority of test duration(t≥40 ms).