Temperature-corrected pressure sensitive paint measurements for aerodynamic applications

Pressure-sensitive paint (PSP) technology is an important new technique, which allows pressure mapping of surfaces under aerodynamic conditions. The principle used is that oxygen in the airflow around the surface quenches luminescence from an oxygen-sensitive dye in the paint and by imaging the illuminated surface with a gated CCD camera, the oxygen profile, and hence the pressure profile of the surface is mapped. The temperature dependence of these paints is a problem. Temperature correction of the surface pressure measurement is often carried out by incorporating a second temperature-sensitive luminophore to provide a surface temperature profile. This usually complicates the measurement process by requiring a second camera or sophisticated filtering to distinguish between the two luminescent processes. In this work, a new oxygen permeable sol-gel coating containing both a temperature (manganese doped magnesium fluorogermanate(MFG) and pressure (Ru(dpp)₃²⁺) sensitive luminophore is described. The luminescent lifetimes of each luminophore are separated by several orders of magnitude, allowing pressure and temperature-dependent lifetime measurements to be separated in the time domain. The luminophores were selected such that their absorption bands overlap and their emission spectra occur in adjacent spectral regions thus enabling the use of a single excitation source and single camera. Both lifetimes were measured with a single camera with gated image intensifier. The system thus provides a temperature-corrected surface pressure profile.