Abstract
Simultaneous gas-phase temperature and velocity imaging using micrometer-size thermographic phosphor particles seeded into the flow is demonstrated at a 3 kHz repetition rate. The velocity field is measured using a standard particle image velocimetry approach, while the temperature is determined from the temperature sensitive phosphorescence emission of the particles following excitation at 355 nm. Since the particles are very small, they rapidly assume the temperature and velocity of the surrounding gas. A single shot temperature precision of better than 5 % was achieved at 500 K. Time-resolved measurements in the wake of a heated cylinder are presented, demonstrating the utility of these imaging diagnostics to observe transient, coupled heat and mass transfer phenomena.
Highlights
Optical measurement techniques have greatly improved the understanding of fluid flows and their coupling with heat transfer and chemical reactions
The recent development of both diodepumped solid-state (DPSS) lasers and high framing rate CMOS cameras has extended the application of some diagnostic techniques to multi-kHz rate measurements [3, 4]
We present an alternative high-speed measurement technique based on thermographic phosphor particles
Summary
Optical measurement techniques have greatly improved the understanding of fluid flows and their coupling with heat transfer and chemical reactions. The investigation of such flows and these interactions requires diagnostics that allow two-dimensional combined vector-scalar measurements. CMOS cameras are available with large onboard memory, so sustained measurements that record many thousands of frames can cover a wide range of temporal scales This allows rapid accumulation of measurements to capture rare events such as engine misfire [5], and the post-triggering of a recording sequence to capture the flow behavior preceding transient combustion events such as flame extinction [6]
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