Treatment of systematic errors in intrusive concentration and temperature measurements

Typical systematic errors that are made during intrusive concentration and temperature measurements in combustion chambers are illustrated. To decrease the errors, it is necessary to ensure rapid quenching of combustion gases and freezing of the composition of combustion products. Analysis is performed using a simple analytic model for heat transfer in a sampling probe. Results are given in the form of temperature-time dependences, temperature profiles, and quench rates inside the probe. The measurement results are validated on the basis of formulation of a material balance (conservation of number of atoms). The main errors of high-temperature thermocouple measurements are discussed in detail, with emphasis on the radiation correction.