Abstract
This study addresses combustion air/flue gas system dynamic problems in fossil fuel power plants. These problems are characterized in terms of significant pressure and flow dynamic variations. These dynamic pressure variations have led to equipment and ductwork vibrations in a number of plants which have eventually resulted in ductwork and/or equipment failure. Methods have been developed for instrumenting plants and analyzing data to identify sources of air/gas system dynamic problems. These techniques were applied to two oil-fired, balanced-draft plants to obtain data for cold and hot operation. The data analysis identified low-frequency periodic oscillations in both plants that resulted from air preheater rotation. Also pressure spectra were measured for forced-draft, induced-draft, and recirculation fans and the associated ductworks. The data analysis indicated that forced-draft fans in both plants had relatively low variations in pressure amplitude, and induced-draft fans had significant levels of pressure variation. The recirculation fans in both plants had high levels of pressure variation, which excited recirculation duct-acoustic modes. The analysis of data for one plant indicated the existence of conditions in the recirculation loop at low-load levels in which a component of fan rotating stall noise matched in frequency and was amplified by a duct-acoustic natural modemore » of vibration. This pressure vibration excited fan and duct structures to noticeable levels of vibration.« less
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