VALIDATION OF 3-DIMENTIONAL MODELS OF NATURAL GAS COMBUSTION AND TEMPERATURE MEASUREMENTS

Abstract

Technological combustion processes present serious environmental problems due to the emission of harmful substances, predominantly in gaseous state. According to the generally accepted view, the nitrogen oxides mostly originate in combustion plants in the high temperature zones. Therefore, determination of such zones within the combustion applications at a stage of design calculations or by means of directs measurements are of a major importance. The problems associated with the thermocouple errors at temperature measurements in the flames and combustion product flows are being dealt with. A model has been derived aimed at the evaluation of correction factors that are to be applied, when processing data of the direct thermocouple readings. The model takes into account convective heat transfer, irradiation from the combustion products on a part of the thermocouple bead. It also takes into consideration that a part of the thermocouple bead irradiates in the direction of the cooled surrounding. As a result, a transcendent fourth order equation has been obtained and solved numerically by MathCad. A set of correction coefficient was obtained which, when added to the direct readings of thermocouples, have shown a close conformity to the results obtained from the 3-D modeling of natural gas combustion in the cylindrical downflow reactor. Thus developed correction methodology may be recommended for use in practice, when temperature measurements are performed by bare thermocouples, when bead sheathing or suction pyrometer can not be used.