Spectral flame emission was measured with two MMS-spectrometers (Zeiss) in the range of 0.45 to 0.90 and 0.90 to 2.25 µm and a filter wheel spectrometer produced at Fraunhofer ICT in the range of 2.4 to 14 µm with a sampling rate of 100 spectra per second [16], [21]. Both systems were calibrated on intensity per wavelength with a technical black body radiator.
To measure radiation temperatures of the flame a fast scanning 2-colour-pyrometer also developed at Fraunhofer ICT with a sampling rate up to 1 MHz was used [18], [16]. The system presumes grey body radiation with constant emissivity. The detector consists in a Si/Ge-sandwich detector with nominal sensitivities at 0.85 and 1.55 µm. The quotient of the diode voltage that is proportional to the emission intensity is calibrated to temperature using a black body radiator.
For the recent application a sampling rate of 10 kHz proved as adequate.
All spectrometers and the pyrometer were focused to various locations in different flame zones using a lens system. The resolution of the detected area was estimated to about 100 mm2
The temperature of the comparatively cold and nonlighting pyrolysis zone in the centre of lower flame was measured with Pt-RhPt thermo-couples.