Identification based thermal reflection compensation for radiation based temperature measurements in combustion chambers

When monitoring wall temperatures in reactors and combustion chambers using infrared cameras, significant measurement errors occur due to the reflection of hot objects such as flames. The radiation received in the camera from the measured wall segment results from the sum of inherent wall radiation and reflected radiation. The reflection depends on the geometrical arrangement of wall, flame and camera as well as on material properties of the wall. To compensate the reflected radiation, existing methods require either detailed information about the geometrical arrangement and material properties of the reactor or a high level of technical equipment like multi-spectral cameras and polarization filters. In this paper we present a method, which does not require this information and equipment. It uses a simplified radiation model and experimental identification to determine the influence of hot objects (flames) on each wall segment of the reactor. The identified model can then be used to compensate flame reflections during normal operation of the reactor. We will demonstrate the new method using near infrared image sequences from a combustion chamber of a pilot-scale power plant.