Patent ID: 8926317
Filing Date: 2015-01-06
Classification: F23L,F23N

Abstract:
1. A method of controlling the operation of a combustion device to reduce NOx emission from the combustion device, wherein the combustion device having a flame, comprising: providing a flow of fuel from a fuel source and diluent from a diluent source at a determined volume ratio to a flame in the combustion device; providing at least one flame stability sensor to generate a measurement of a characteristic of the flame; determining a predetermined critical flame instability threshold using a controller, wherein the controller determines the predetermined critical flame instability threshold from calculation of a flame stability factor F, wherein wherein F is determined by the ratio of the sum of frequency content for two specified frequency ranges from a frequency spectrum, f wherein R is a time varying measurement signal, wherein FT denotes a short-time Fourier transform performed on R from a rolling initial point in time of the measurement, t wherein C is a scalar value used to manipulate the amplitude of F, wherein controlling the determined volume ratio of fuel:diluent using the controller based upon at least one of (i) at least one threshold value from at least one measurement from the at least one flame stability sensor, and (ii) at least one flow measurement from each of the fuel source and diluent source, wherein controlling the determined volume ratio of fuel:diluent includes decreasing the volume ratio of fuel:diluent until the predetermined critical flame instability threshold is reached to reduce NOx emission from the combustion device and increasing the volume ratio of fuel:diluent when predetermined critical flame instability threshold is exceeded, wherein the controlling the determined volume ratio of fuel:diluent includes adjusting at least one of the flow of the fuel from the fuel source and the flow of the diluent from the diluent source.