Advanced Diagnostic Evaluation of an Ultra-Low NOx Industrial Gas Burner

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assembly. The fuel/air injector is comprised of two radial fuel/air injection zones. In the primary zone (nearest the burner tile) a fuel-lean mixture is radially introduced through two rows of ports that encircle the burner. The secondary zone consists of four discrete ports that inject a circular jet of fuel-rich gas parallel to the burner-mounted wall. An air register delivers additional air through an annular opening between the injector and the burner tile. This tertiary air register provides additional air if needed for furnace oxygen balance. The baseline operation of the burner distributes fifty percent of the fuel to the primary zone where it is premixed with most of the combustion air. The remaining fuel is supplied to the secondary zone where it is diluted with around 1.3 volumes of air. Experiments were conducted at the BERL. The BERL is a laboratory designed to provide advanced optical diagnostic access to industrial gas burners. Conventional combustion diagnostics are provided, including combustion gas analyzers, radiometers, pyrometers, and full control and monitoring instrumentation. A description of the BERL including facility capability and operation specifications were presented in a paper to the American Flame Research Committee in 1992 [7] To summarize, the combustion chamber has an octagonal cross section of 42 inch diameter and is comprised of seven vertical spool sections each 13 inches in height for a total furnace height of 91 inches. Removable and interchangeable panels on the octagonal faces can provide a variety of thermal environments while accommodating windows and ports of various geometry for intrusive and non-intrusive sampling and diagnostic analysis. Figure 2 shows a schematic representation of the furnace cross section indicating the arrangement of optical equipment and the sampling volume for laser anemometry study of the burner. Additional facility descriptions and illustrations are presented in the publication "Use~s Guide to the Burner Engineering Research Laboratory" [8]. 486 BASED COMPUTER FOURIER TRANSFORM BURST DETECTOR Ar+ LASER 4 • Figure 2. Illustration of the furnace and positioning shuttle located at the Burner Engineering Research Laboratory. The octagonal furnace geornetry accomodates eight interchangeable panels per spool section. The furnace is shown with five spool sections each thirteen iches high. The fuel and air supply systems at the BERL were configured so that mass flow rate and composition of the gas flows to the burner could be changed independently at all three injection locations. A baseline burner operating condition was established as follows: Fuel: Natural Gas Fuel distribution, primary/total: 50 % Air/fuel ratio in secondary fuel stream: 1.3 v/v Total primary/secondary air/fuel stoichiometric ratio: 0.85 Total furnace air/fuel stoichiometric ratio: 1.1 Secondary Jet Velocity 100 ftls These operating conditions were selected as being representative of the "typical" inspirated burner configuration. By varying each of these parameters a total of five "flames" were established for study in the BERL tests. Table 1 lists the experimental conditions for each of these flames. 4