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Show packages were installed in the fuel line, the axial air line, and the swirl air line. Each sensor and valve is referred to collectively as a mass flow controller (MFC). Figure 2 is a block diagram representing the general control scheme employed in this study. The burner is the plant, or object under control. The sensor is composed of a bank of gas analyzers, similar to continuous emissions monitoring systems installed in many industrial/commercial burner operations today. A continuous sample is extracted and pulled through five analyzers which measure [CO], [C02], [HC], [02] and [N0x]. NATURAL GAS EXHAUST BURNER AIR AIR FLOW GENERATOR EA Sf CONTROLLER [NOx] SENSOR 1'\: Figure 2. General control scheme. The controller consists of a 486-based computer which reads emissions signals from the analyzers and calculates NOx concentration (corrected to 3% O2), and combustion efficiency. Using a specialized optimization algorithm, the controller determines new values of S' and EA, and sets the air flow accordingly. Performance Definition. For a given burner, optimum performance can be qualitatively defined as the value of swirl intensity, S', and excess air, EA, where [NOx] is relatively low and combustion efficiency remains relatively high. In order to make an objective evaluation, performance is quantified by a weighted sum called a performance index, which is denoted as J. This performance index is a function of [NOx] and T}c. The performance index is defined such that an increase in combustion efficiency and a decrease in NOx concentration both lead to an increase in J. That is, performance of the burner is considered optimized when J is maximized. 3 |