A SPECTROPHOTOMETRIC DETERMINATION OF EXHAUST GAS TEMPERATURES IN THE PULSE-JET ENGINE
This paper describes a spectrophotometric method whereby instantaneous values of a variable flame temperature, in the particular case of nonluminous flames, may be determined and continuously recorded.This new technique, which depends upon the establishment of monochromatic black-body radiation conditions in the flame for a small region in the visible spectrum, involves the continuous measurement of radiation intensity in the above region, the intensity being, thereafter, correlated with the temperature of the flame.The problem of temperature measurement in the general case of nonluminous flames (flames which do not contain an appreciable amount of free carbon in the form of soot) is considered and a brief review of previous techniques employed for this purpose over the past 50 years is given. The basic theory and preliminary experimental justification of the present method are discussed.A description of the apparatus and the experimental arrangement used by the author in a specific application of the present method in the determination of the time variation of temperature in the exhaust flame of a pulse-jet engine is given. This includes details of a special type of spectrophotometer which employs a multiplier photocell as the radiation detecting and measuring element and, also, a "black-body" cavity constructed as a standard radiation source for the calibration of the former instrument. An original technique used to investigate the emissivity of flames colored by alkali metal vapors is described and its application to the present problem shown.Finally, the measurable temperature range of the present apparatus is considered together with the inherent limitations of the new method.