Design and application of a high-pressure combustion chamber for studying propellant flames with laser diagnostics

This manuscript presents the design and initial application of a high-pressure combustion chamber (HPCC). The HPCC exhibits several unique design attributes to enable high-fidelity studies of propellant-combustion physics at high pressures. The HPCC employs a flangeless and weldless design to provide a compact, easy to access, and relatively light weight (for its size and pressure capability) test chamber. It has a cylindrical test volume of 13.1 L and is capable of operating at pressures from approximately 0.4 mbar to 200 bar. The vessel is equipped with a ZnSe window to enable the laser ignition of propellants and energetic materials and 4 sapphire windows (2″ diameter and 4″ × 2″ slots) to enable the use of multiple optical diagnostics spanning the ultraviolet to mid-infrared. The sapphire windows are mounted in plugs with adjustable length to bring the windows inside of the test volume and facilitate line-of-sight optical measurements. The vessel can be accessed from the top and bottom via removable 5″ diameter plugs, and the bottom plug can be modified to enable studies of gaseous jets and flames. Some of the HPCC's testing capabilities are demonstrated via high-speed IR imaging and laser-absorption-spectroscopy measurements of temperature and CO in laser-ignited HMX (i.e., 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane) flames at pressures from 2 to 25 bar.