Instantaneous measurement of two-dimensional temperature and density distributions of flames by a two-band-emission-CT pyrometer

Because temperature is one of the most important factors influencing combustion reactions, a variety of temperature measurement methods have been developed for burnt gas. Infrared radiation pyrometry using water vapor or carbon dioxide, which are present in high density in a burnt gas, has a long history. However, these classical methods can measure only a mean temperature or step-wise temperature distribution of several segments along an optical path. Due to the severe demand for cleaner and more efficient combustion, more detailed temperature information is required. Computed tomography (CT) applied to radiation methods (same as X-Ray CT in medical use) enables measurement of a two-dimensional temperature distribution. The authors have developed several types of infrared CT pyrometers. Because CT methods generally take a long time to obtain projection data, it is thought that they are not applicable for high speed unsteady combustion. In this report, a two-band-emission-CT pyrometer, which was developed by the authors, is further developed to enable time-resolved measurement. An algorithm and optical configuration is introduced for fan-beam scanning. The accuracy is then investigated. The experiment was performed using only one optical unit as a preliminary investigation using a jet flame with good reproducibility.