Combustion Control Using Infrared and Visible Light Devices

Economics and overall experience have acted against the installation of infrared carbon monoxide or carbon dioxide analyzers on smaller systems for air fuel ratio control. This paper discusses an interesting control signal which can be derived from flame radiation. Electronic sensing of certain bands of infrared radiation provides a signal with a pronounced peak as a function of air/fuel ratio, which can easily be found by a peak-seeking control system. This peak-sensing control system does not need calibration, is insensitive to dirty windows, can identify individual burners in multiple burner applications, and is insensitive to noise. Additional components of separate infrared source and optics not required, making the cost of the system attractive for smaller boilers. Thermal efficiency is monitored directly by the system through the measurement of heat input and output so that the control system can 'remember' and periodically update the most efficient air and fuel control settings as a function of load. Tests of the sensing system and results are discussed