Absorption, emission, and schlieren imaging of liquid and gas flows using an LED and a webcam

Abstract

Abstract The analysis and investigation of flow processes is a key task in many science and engineering disciplines. In this context, optical diagnostic methods represent versatile tools that allow the determination of concentration, temperature, and flow velocity fields. However, most of the established tools are based on complicated and expensive equipment including advanced laser sources and specialized cameras. In the present work, an alternative approach employing low-cost components in terms of a commercial light-emitting diode (LED) and a webcam is demonstrated. A single experimental setup for emission, absorption, and schlieren imaging has been assembled. Proof-of-concept measurements were carried out in flames and a liquid mixing process. Two-color pyrometry of the thermal radiation from soot particles was used for planar thermometry in a candle flame. Schlieren imaging was employed to visualize the refractive index and hence the temperature gradient in a premixed welding torch butane/air flame. LED-absorption imaging was used to study the mixing of ink and water. In conclusion, this work demonstrates that advanced flow diagnostics can be performed at low cost, which is of particular interest in teaching and training, where expensive equipment may not be available.