Utilizing X-Ray Computed Tomography in Spray Nozzle Analysis

Abstract

Characterizing the near-nozzle region of liquid sprays is a challenge for spray system designers due to the lack of optical accessibility in this dense region of the spray using traditional imaging techniques. A novel diagnostic technique, utilizing standard medical X-ray computed tomography equipment, is developed to investigate the time-averaged mass distribution of the liquid phase of the spray within 50 diameters downstream of the nozzle exit. Reconstructed images provide the three-dimensional concentration of the liquid phase of the spray. Analysis of several iodine-based liquids was conducted based on physical properties and non-dimensional parameters. To compare a general procedural approach for obtaining the three-dimensional concentration field from an X-ray CT system, a traditional optical analysis was conducted using Mie Scattering and Shadowgraphy. Results for a full-cone pressure swirl atomizer with an orifice of 0.79 mm are presented for both water and Povidone Iodide. Qualitative and quantitative results gave insight into the spray cone angle, atomization of the spray, and the droplet size and velocity distribution 50 diameters downstream. The water (Re ≈ 20,000) atomizes further upstream than the Povidone Iodide (Re ≈ 6,100) with a larger spray cone angle. The images obtained from the traditional optical techniques were qualitatively compared to the new diagnostic technique. The three dimensional mass distribution of Hypaque from a 0.79 mm nozzle has a number of similarities with the water spray, measured with an isotropic spatial resolution of 200 μm and noise per voxel less than 0.02 g/cm3.

A Comparison of Shadowgraphy and X-Ray Computed Tomography in Liquid Spray Analysis

“…Noise, however, is a random phenomena in radiology, and there are several processes that can cause it. These include the number of photons that leave the source, the number of photons that pass unaffected through the object, and the number of photons captured by the detector [23]. Steps were taken during set-up, experimentation and processing to help decrease the noise.…”

Quantitative imaging of single-shot liquid distributions in sprays using broadband flash x-ray radiography

“…Void fraction measurements made at kHz-rates were shown by (Char et al, 1990;Woodward et al, 1995). Time-averaged three-dimensional data by (Meyer et al, 2008;Meyer et al, 2010: Balewski et al, 2010Eichner, 2013;Coletti et al, 2014;Marchitto et al, 2015) were collected. Multiple sources were employed to make time-resolved tomographic measurements by (Lim et al, 2013).…”