Emissions spectral radiometer/fuel flow instrument

An emissions spectral radiometer including a source instrument disposed on one side of an exhaust gas duct and a detector instrument disposed on an opposite side of said duct from said first side, said instruments comprising,

• in said source instrument:
• a radiation source heated to between 1000 and 1700 degrees Kelvin and producing pure black body infrared radiation having an emissivity of at least 0.90,
• a reflector which produces parallel radiation from said source and directs it across the combustion exhaust gas duct,
• a rotating cage assembly which encloses said radiation source and said reflector, said cage assembly having at least one opening therein aligned with said reflector to allow the parallel radiation to escape from the cage assembly as it rotates to provide an alternating flow of radiation across the exhaust gas duct,
• an optical switch including a light emitting diode located inside the cage assembly and an optical sensor located outside of the cage assembly which is actuated by rotation of the cage assembly allowing the light emitting diode to activate and deactivate the optical sensor resulting in an on-off flow of current through the switch thereby controlling the cage assembly speed of rotation.
• a reflector shroud for directing the infrared radiation from the cage assembly to a sapphire window disposed in the exhaust gas duct, and
• cooling means for the source instrument utilizing a circulating flow of gas which is refrigerated by thermoelectric coolers, and
• in said detector instrument;
• an array of optical reflectors which causes the parallel radiation to form a line image of finite length at a first focus point and then to form a focusing image at a second focus point, said optical array including:
• a spherical concave mirror which is positioned to reflect in both horizontal and vertical views to a cylindrical plano-convex reflector, the infrared radiation in the vertical view being reflected parallel from the cylindrical plano-convex reflector to focus at the first focus point, and
• a pair of cylindrical plano-concave reflectors optically opposed to each other which focus the infrared radiation on the detector by folding and converging the radiation,
• a rotating circular variable filter disposed at said first focus point for allowing only specific radiation to pass therethrough and which operates between 1300 and 5500 nanometers and is rotated at a speed to have a natural response frequency,
• an optical slit located immediately in front of said circular variable filter to intercept stray radiation reflected by said cylindrical plano-convex reflector, and
• an infrared radiation detector disposed at the second focus point for receiving radiation which has passed through said circular variable filter and producing an electronic signal output for input to a computer, said detector being sensitive to radiation between 1000 and 6000 nanometers.