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A multiwavelength pyrometer was developed for applications unique to aerospace environments. It was shown to be a useful and versatile technique for measuring temperature, even when the emissivity is unknown. It has also been used to measure the surface temperatures of ceramic zircornia thermal barrier coatings and alumina. The close agreement between pyrometer and thin film thermocouple temperatures provided an independent check. Other applications of the multiwavelength pyrometer are simultaneous surface and bulk temperature measurements of a transparent material, and combustion gas temperature measurement using a special probe interfaced to the multiwavelength pyrometer via an optical fiber. The multiwavelength pyrometer determined temperature by transforming the radiation spectrum in a broad wavelength region to produce a straight line (in a certain spectral region), whose intercept in the vertical axis gives the temperature. Implicit in a two-color pyrometer is the assumption of wavelength independent emissivity. Though the two data points of a two-color pyrometer similarly processed would result immediately in a similar straight line to give the unknown temperature, the two-color pyrometer lacks the greater data redundancy of the multiwavelength pyrometer, which enables it to do so with improved accuracy. It also confirms that emissivity is indeed wavelength independent, as evidenced by a multitude of the data lying on a simple straight line. The multiwavelength pyrometer was also used to study the optical transmission properties of a nanostructured material from which a quadratic exponential functional frequency dependence of its spectral transmission was determined. Finally, by operating the multiwavelength pyrometer in a very wide field of view mode, the surface temperature distribution of a large hot surface was obtained through measurement of just a single radiation spectrum.

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Explosion suppression barriers are devices that contain fire extinguishants that are activated to disperse at some critical point during the propagation of an explosion to suppress it. Suppression of coal dust explosions using barriers (both triggered and passive) has been investigated by the U.S. Bureau of Mines. The work reported in the present study is an update of the continuing study of passive barriers of both rigid and flexible construction. Suppressants tested were water and ABC powder (ammonium phosphate). The coal dust mixtures contained 60 to 65% total incombustible matter and were distributed in the Bureau's single entry experimental mine for a total distance of 111 m (365 ft). Dust explosions were initiated by a 7% methane-air gas zone at the face. The passive barriers were located at distances of 60 to 108 m (200 to 356 ft) from the face. At these distances, the magnitude of the explosion pressure pulse was about 0.70 to 1.14 bar (70 to 114 kPa) at the time the flame front arrived at the barrier. With the exception of the powders, the pressure pulse was sufficiently energetic to fracture the troughs and disperse the suppressants. The powder (approximately 180 kg per test) was almost totally ineffective when used with the rigid barrier because it did not disperse. One to four troughs of water effectively suppressed explosions. It was found that the mounting arrangement for the flexible troughs was most important for successful operation and release of the suppressant. Triggered barrier systems for protection against incipient gas explosions were tested in a simulated longwall panel. Results show that ABC powder was much more effective in suppressing the developing explosion than equal amounts of water released from the same pressurized reservoir. Although water was effective in stopping fully developed dust explosions, it had little effect against an explosion during its incipient stage.

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