AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Filter Leak Detection by Various Gases Using the Schlieren Imaging Technique
SHIGERU KIMOTO, Lin Li, David Y. H. Pui, University of Minnesota
Abstract Number: 481 Working Group: Instrumentation and Methods
Abstract There are several detection methods for filter leaks (e.g., scanning, fluorescence, particle image velocimetry, thermal imaging, etc). For aerosol related methods, particles passing through the filter leak can be detected by a scanning probe connected to a particle counter to locate the leakage, or by Particle Image Velocimetry (PIV), obtaining the flow speed and direction using the scattered light from particles. In the fluorescence detection, a UV light source is used to examine the filter bags for leaks. Wherever there is a leak, the tracer powder will glow brightly under the detector lamp. However, the aerosol methods are usually time consuming and particles are loaded on the filter, which is avoided in some applications and test environment. The imaging methods, (e.g. thermal imaging using infrared radiation to form an image, and Schlieren imaging technique), have the advantage of visibility, quick response, simplicity and prevention of particle loading.
In this study, we use a Schlieren imaging technique for filter leak detection. Schlieren technique uses light from a single collimated source shining on or from behind a target object (the space downstream of the filter). Variations in refractive index caused by density gradients in the fluid distort the collimated light beam, creating a spatial variation of light intensity, which can be visualized directly. Gas composition affects the Schlieren image because density gradient is changed. The effect of purge gas composition is evaluated and the detail results will be presented.