Temperature reconstruction of an axisymmetric enclosed reactive flow using simultaneous background oriented schlieren and infrared thermography

Abstract

The temperature distribution of a premixed methane air flame running at a Reynolds number of 1300 on a circular burner, 12.7mm diameter, enclosed in a fused silica cylindrical liner has been experimentally reconstructed using a non-invasive approach combining Background Oriented Schlieren (BOS) and Infrared (IR) thermography. BOS is used to characterize both the air ambient to the system, using an existing technique called 3D ray tracing, and the reactive flow inside the enclosure, with a novel modified version of 3D ray tracing. IR thermography is used to characterize the thermal/optical characteristics of the quartz glass enclosure itself since the information is required as BOS is a line of sight imaging technique. Out of necessity, an approximated species independent relationship is used to calculate flow temperature from refractive index. A simulation is used to show this error is in the range of 5.8%-7%. Additionally, it is found that drastically simplifying the approach by removing the IR thermography system entirely and using the near outer wall air temperature from BOS/3D ray tracing to characterize the internal temperature of the quartz liner itself only causes a 1.5%-3.8% degradation in the accuracy of the reconstructed temperature field. The technique as presented is a relatively inexpensive, experimentally simple approach capable of determining the steady state temperature characteristics of optically accessible axisymmetric reactive flows.