Modeling of a Thermoacoustic Flue Gas Analyzer

Reliable monitoring of industrial flue gases is essential for maintaining optimal combustion efficiencies, and thus lesser environmental impacts, in the processing of typical combustion systems. Typical modern-day sensors rely in their operations on either electrochemical or nondispersive infrared technologies. Although such technologies are well established, they also have their drawbacks, which include the relatively high cost, drift effects, the need for frequent calibration, and limited lifetime. This study investigates the performance of a proposed self-powered thermoacoustic flue gas analyzer, where the exhaust gas is introduced into a compact resonator containing a porous medium, commonly known as the stack. Quasi-steady temperature distributions are allowed to develop along the stack under controlled heating/cooling. At a certain axial temperature gradient, self-sustaining thermoacoustic instabilities are induced inside the resonator that help determine the molar concentrations of quaternary gas mixture components. Here, the existing theoretical framework is first revised by addressing some of its underlying linear approximations. The improved algorithm is then applied to a large number of gas mixtures for the development of more realistic operational ternary diagrams. The present theoretical model achieves a [Formula: see text] increase in the onset temperature difference span and hence better detection capability for the flue gas analyzer compared to the original theoretical model. Next, a two-dimensional computational model is constructed and tested where the present predictions show good agreement with the reported experimental results at low mean pressures, which demonstrates the validity of the adopted theoretical model.