Simultaneous velocity and pressure measurements using luminescent microspheres

Abstract

Using the technique of modified rapid lifetime determination, pressure-sensitive microspheres, known as PrSBeads, were used to make quantitative oxygen measurements over two-dimensional areas within gaseous flows. Aerosolized PrSBeads in carrier gases of varying oxygen concentrations demonstrated point measurement precisions on the order of 0.1%-1%. A charge-coupled device featuring a double image frame (DIF) feature was used to make spatially resolved pressure measurements within gas phase flows. Errors on the order of 0.5 atm for one standard deviation were demonstrated when 2 x 2 pixel binning (162 x 128 pixel overall resolution) was used, but improved to 0.003-0.005 atm with the use of 32 x 32 pixel binning (10 x 8 pixel overall resolution). Experiments demonstrate the ability to resolve the oxygen concentration differences between a N(2) jet and the surrounding ambient air environment and the ability to measure instantaneous air pressure changes within a square syringe as the plunger is moved in and out. In addition, instantaneous velocity measurements of the airborne PrSBeads in a square syringe were achieved using digital particle image velocimetry at frame rates of 6.4 Hz, thus validating PrSBeads as a tool to simultaneously measure the velocity and pressure within an aerodynamic flow.

Particle-based temperature measurement coupled with velocity measurement

“…Im et al [116], Kimura et al [115,118], and Kim et al [114] fabricated pressure sensitive microbeads using PtOEP. Im et al [116] fabricated polystyrene beads with the incorporation of pressure sensitive and insensitive luminophores.…”

“…The size of the particles could be controlled at between 0.5 and 2.6 µm by adjusting the concentration of the polymerization initiator used. The particles produced were used to demonstrate the measurement of the partial pressure of oxygen in a narrow gas jet (Kimura et al [115,118]). Images of these pressure sensitive beads with a narrow particle size distribution can be seen in figure 15.…”

Characterization of multi-dye pressure-sensitive microbeads

“…The response time of PSPs has been described as being dependent on three important parameters: Luminescent lifetime of the luminophor, the oxygen diffusivity, and thickness of matrix layer. Kimura et al 18 found the lifetime in a previous study where it was shown that the scope of the luminophors' lifetime expands from 1 μs to 50 μs. The estimation of the 99% rise time of a thin PSP layer can be expressed as…”