20 kHz dual-plane stereo-PIV measurements on a swirling flame using a two-legged burst-mode laser.

Abstract

Dual-plane stereoscopic particle image velocimetry (PIV) is capable of quantifying the flow field in terms of three-component (3C) flow vectors and 3C vorticity vectors simultaneously. Here, we present a test rig to carry out the 20 kHz dual-plane stereo PIV measurements on a premixed swirling flame by using a two-legged burst-mode laser. Other than the traditional methods employing the laser polarization direction and the two-color separation methods, two same-color laser sheets with a 100 ns delay were adopted to separate the imaging processes for the two pairs of cameras using the image straddling method. Each laser sheet with the same wavelength of 532 nm has a pulse cyclic frequency of 20 kHz within each burst generated by the high-repetition-rate burst-mode laser. 3C velocity vectors of a swirling flame were obtained based on the sequential particle images for each laser sheet. In spite of non-perfect simultaneous flow measurements on the two spatially separated laser sheets, the velocity error caused by the 100 ns delay on top of a 50 μs duration, which was used for the velocity vector calculation, is negligible. This short-delay separation method significantly simplifies the experimental setup for dual-plane stereo PIV measurements, especially for low-speed flows.