Devices for maintaining optical access in high-temperature coal combustion environments. II. Sonic and supersonic flow regions.

Application of optical diagnostic techniques and instruments in the high-temperature coal combustion environments of large-scale facilities requires a clear optical path into and out of the particle-laden gas stream for long periods of time. In this paper, we describe devices for making long-term optical measurements in the sonic and supersonic regions of a coal combustion flow where, in general, the gas stream is a high-speed flow at high temperature and pressure. The design and operation of the devices are discussed and schematics are presented. Successful operation of the devices for over 900 h demonstrates their long-term reliability. [ABSTRACT FROM AUTHOR]