An experimental setup is constructed to generate a steady flow of air at high pressures and temperatures. The experimental setup comprises of an air system, a test section, and an imaging system (Fig. 1). The Air System: Heated Air from a 3" line is first passed through a flow straightening plate. This plate is made of SS316 with 44 holes in various radii. Each hole has a diameter of 1/4" and the plate thickness is 1/2". The overall diameter of the plate is 5" and is placed between two flanges. The air is then passed through a ceramic honeycomb (with aspect ratio ~20, and rectangular orifices ~0.75mm) and finally through screens. The honeycomb and the screens are positioned against the 25mm × 35mm rectangular entry section of the cooling pipes. The Test Section: The test chamber is designed to withstand high temperatures and pressures. It is a rectangular section with optical windows made of synthetic fused silica glass, corning 7980 (quartz), with a maximum operating temperature of 1400°C. A 25mm thick glass is used in order to meet the pressure requirements. The glass windows can withstand pressures up to 14 bars with standard safety factor of 11 for the glass. A step is machined all around one face of the glass to allow the glass to sit flush with walls of the chamber. The chamber is designed to be fitted with 1/16" thick Thermiculite 815 with tanged core gasket. The channel has a cross-section of 25mm × 35mm. The chamber is made of only two sections in order to make its machining and assembly easier. The top section is T-shaped and slides over the bottom section which is U-shaped. The nozzles are designed to sit flush with the walls of the channel. They are positioned so that there is 50 mm of optical access downstream and 100 mm upstream of the injection point. The nozzles have a simple design which allows for easy exchange without disassembling of the chamber. The nozzles are first drilled from the liquid entry side with a 1/8" drill. The drill has a 90° tip. The tip is used to minimize the effect of flow separation inside the orifice. The nozzle orifices are first drilled using an EDM drill (Electric Discharge Machining) from the jet exit face of the nozzle. Afterwards a high-speed miniature drill-press is used to reach the final size for the orifice.
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