Transition Detection on Rotating Propeller Blades by Means of Temperature Sensitive Paint

Boundary-layer transition on a rotor blade measured by temperature-sensitive paint, thermal imaging and image derotation

“…One rotor blade was coated with Ru-phen-based temperature-sensitive paint. This TSP has a short fluorescent lifetime of 0.6 μs at 303 K and high temperature sensitivity of −2.5 %/°C at 303 K (Yorita et al 2012). The Ru-phen luminophore has excitation and peak emission wavelengths of 450 and 580 nm, respectively.…”

“…Synchronization of the mirror and the rotor blade has been maintained by means of an encoder signal (200/rev) fed into the controller of the rotating mirror stepper motor (requiring 400/rev). By this technique, we are able to achieve a camera exposure time of 300 µs, which is significantly larger than that used in the earlier investigations (e.g., Yorita et al 2012).…”

“…Dark images (I dark ) and reference images (I ref , temperature constant) were taken under these stable conditions. Dark images are needed to correct the TSP-reference images and TSP-run images for the influence of remaining ambient light and dark current from the CCD camera (Yorita et al 2012). Next, the heating spotlight was turned on, and after 60 s, when the temperature of the blade surfaces became locally constant, the spotlight was turned off, and the "warm" run images (I run , acquired during a temperature change) were taken.…”

“…Transition measurements were successfully made on both static (Fey et al 2006a) and rotating aerodynamic surfaces (Yorita et al 2012). TSP contains active molecules (luminophores), which are excited by a certain wavelength of light.…”

“…Recently, efforts have been focused more toward optical techniques for their high spatial resolution and relative ease of use. Investigations include the detection of boundary-layer transition and flow separation in propellers, helicopter rotors and turbine blades by temperaturesensitive paint (TSP) and pressure-sensitive paint (PSP) (Yorita et al 2012;Klein et al 2013), thermography (Mori et al 2007;Richter and Schülein 2014;Schülein 2014), oil film interferometry (Wadcock et al 1999;Schülein et al 2012) and micro-tuft imaging (Yamauchi et al 1997).…”