Insights from a new method providing single-shot, planar measurement of gas-phase temperature in particle-laden flows under high-flux radiation

Abstract

Insights from a new method providing single-shot, planar measurement of gas-phase temperature in particle-laden flows under high-flux radiation

The effect of particle size and volumetric loading on the gas temperature distributions in a particle-laden flow heated with high-flux radiation

“…As such, in-situ, spatially resolved measurements are required to further improve the understanding of heat transfer in these systems. Planar measurements of the temperature in particle-laden flows with strong thermal gradients generated by high-flux radiation are currently available for both the particle-phase (Kueh et al 2017) and gas-phase (Lewis et al 2021). The current work extends these measurements by experimentally investigating the effect of particle diameter and volumetric loading on the spatial distribution of the gas-phase temperature in a radiatively heated particle-laden flow.…”

“…This is done by calculating the ratio of the fluorescence intensity measured in two separate wavelength ranges (Luong et al 2006). This technique has already been demonstrated to be suitable for gas temperature measurements in particle-laden flows with volumetric loadings of up to ϕ ≈ 10 −3 (Lewis et al 2020), and for planar measurements in flows heated using high-flux radiation (Lewis et al 2021). Importantly, the advantage of using the two-colour ratio is that it corrects for the spatial non-uniformity of the signal intensity that can arise in particle-laden flows due to attenuation of the excitation beam and the mixing of tracers with unseeded, ambient fluid.…”

“…The SSSTS combines the output from a bundle of infra-red (910 nm) diode lasers using fibre-optics (Alwahabi et al 2016) to provide a collimated beam at output powers up to Q0 = 2840 W with an approximate diameter of 15 mm at the focal plane, which was aligned with the jet axis 17.6 mm from the exit plane. The intensity profile of the SSSTS beam on the jet axis is described by Lewis et al 2021, with an approximate peak heating flux on the beam axis of 42.8 MW/m 2 when operating at Q0 = 2840 W. The beam powers used for the current experiments are listed in Table 1. A water-cooled power meter (Gentec model HP100A-4KW-HE) operating at 10 Hz, positioned down-beam from the wind tunnel, measured the power of the SSSTS that was transmitted through the flow, Qt r. The total power absorbed by the particles was then estimated using the equation Qabs = α( Q0 − Qtr ), where α ≈ 0.89 is the absorptivity of the particles (Siegel et al 2014).…”

“…Additional filters were used to limit the transmitted signal to narrow spectral bands. The details of filters used and the resultant transmission for each channel are presented by Lewis et al 2021. Each channel was imaged using a separate camera and lens.…”

“…Examples of the instantaneous images from each camera, together with the calculated gas-phase temperature, are presented in Figure 3. Each step of the process is described in detail by Lewis et al 2021, so that only a summary is presented here. Firstly, the average background signal, collected with the lasers on and camera uncapped but without a flow, was subtracted from the raw images.…”