Edmond Green

Luminescent barometry in wind tunnels

A flexible and relatively inexpensive method and apparatus are described for continuous pressure mapping of aerodynamic surfaces using photoluminescence and imaging techniques. Platinum octaethylporphyrin (PtOEP) has a phosphorescence known to be quenched by oxygen. When dissolved in a silicone matrix, PtOEP may be distributed over a surface as a thin, uniform film. When the film is irradiated with ultraviolet light, the luminescence intensity provides a readily detectable, qualitative surface flow visualization. Moreover, since the luminescence intensity is found to be inversely proportional to the partial pressure of oxygen, a quantitative measure of pressure change may be obtained using a silicon target vidicon or a charge‐coupled device video sensor to measure intensity. Luminescent images are captured by a commercial frame buffer board. Images taken in wind tunnels during airflow are ratioed to images taken under ambient ‘‘wind‐off’’ conditions. The resulting intensity ratio information is converted ...

Ideality of pressure-sensitive paint. I. Platinum tetra(pentafluorophenyl)porphine in fluoroacrylic polymer

The pressure sensitive paint (PSP) properties of a fluoroacrylic polymer, FIB, with the luminophor platinum tetra(pentafluorophenyl)porphine (PtTFPP) are presented. This paint forms a hard coating that displays Stern–Volmer plots with a high dynamic range (∼ 0.9) [defined as (Ivac − Iatm)/Ivac], good photostability, a response time of less than 1 s and a relatively low temperature dependence (∼ 0.6% per degree). The temperature dependence is low because FIB has a unusually low activation energy for the diffusion of oxygen. Pressure and temperature affect intensity independently making this PSP “ideal.” The basecoat affects the functionality of the PSP it underlies, and the optimal basecoat used to date also includes the FIB polymer. The synthesis of the FIB polymer is a copolymerization that occurs in one step with a peroxide initiator. Annealing the painted model above Tg = 70°C procures adhesion and ideality.

Surface pressure field mapping using luminescent coatings

In recent experiments we demonstrated the feasibility of using the oxygen dependence of luminescent molecules for surface pressure measurement in aerodynamic testing. This technique is based on the observation that for many luminescent molecules the light emitted increases as the oxygen partial pressure, and thus the air pressure, the molecules see decreases. In practice the surface to be observed is coated with an oxygen permeable polymer containing a luminescent molecule and illuminated with ultraviolet radiation. The airflow induced surface pressure field is seen as a luminescence intensity distribution which can be measured using quantitative video techniques. Computer processing converts the video data into a map of the surface pressure field. The experiments consisted of evaluating a trial luminescent coating in measuring the static surface pressure field over a two-dimensional NACA-0012 section model airfoil for Mach numbers ranging from 0.3 and 0.66. Comparison of the luminescent coating derived pressures were made to those obtained from conventional pressure taps. The method along with the experiment and its results will be described.

High Performance Liquid Chromatography Separation and Analysis of Metallotetra(Pentafluorophenyl)Porpholactone

Abstract The analytical separation and analysis of silver, nickel, zinc and palladium complexes of tetra(pentafluorophenyl)porpholactone (TFPL) from free bases is described. An isocratic mobile phase of n-hexane and diethyl ether was developed to separate these complexes using a normal phase μPorasil HPLC column (150 × 3.9 mm I. D.) at a flow rate of 1 mL/min. In addition, two porphodilactone isomers were also isolated from the reaction products, a result which we were unable to achieve with flash chromatography nor with a reversed phase C18 Ultrasphere HPLC column (250 × 4.6 mm I. D.). The optical absorption spectra of the metal derivatives show two bands in the visible region, compared to the four bands shown by the free base. The retention of these metal complexes on a normal phase column was found to be increasing in the order Pd(TFPL) < Ag(TFPL) < Zn(TFPL) < Ni(TFPL).