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Show A NUMERICAL SIMULATION METHODOLOGY AND ITS APPLICATION IN NATURAL GAS BURNER DESIGN G. W. Butler, Jaesoo Lee, Kenji Ushimaru, Samual Bernstein Energy International, Inc. Bellevue, Washington, USA ABSTRACT A numerica 1 me thodo logy has been de ve loped for the design and analysis of gas-fired combustion systems. The fundamental element of this approach is TEACH-3E/II, a three dimensional numerical simulation code for turbulent f lows developed at Imperial College. The simulation technique can treat a wide variety of boundary condi tions, is numerically stable at all Reynolds numbers, and can be applied to a broad class of burner geometries and flows. Examples are presented which demonstrate its use as an effective engineering tool for the analysis of fluid dynamics, heat transfer, and the suppression of pollutants in thermal processing systems. A SIGNIFICANT FRACTION of on-line industrial combustors use natural gas as a preferred fuel. Boilers alone, for example, account for more than 40 percent of the total gas consumed by the U.S. industrial sector. It follows then that a key element in the commercial success of industries using gas-fired thermal processing systems is a properly designed combustor. Moreover, stringent demands are placed on modern burner designs since industrial users also require other significant advantages, such as higher produc ti v i ty, improved energy efficiency, and reduced pollutant emissions. Unfortunately, the basic physical processes of mixing and chemical reaction are highly coupled for most fuels. Moreover, the physical interaction of injectors, walls, heat exchangers, reactant inlet conditions, and fuel chemical properties strongly affect burner performance. Without reliable engineering too 1 s, combus t ion and hea t transfer equipment have, for the most part, been designed by cost ly trial-and-error l ethods. Al though the industry has long 109 A. David Gosman Imperial College of Science & Technology London , UK recognized the need to develop numerical descriptions of combustion processes, it is only in recent times that advances in computer hardware and computational methods have permitted the problem to be addressed in earnest. The objective of this paper is to describe the development of a numerical simulation code which is suitable for the analysis of many kinds of thermal processing systems. The code, which can accurately model steady turbulent flow fields with recirculation, is an advanced fluid dynamics and heat transfer tool which can be utilized to analyze the design of direct and indirect gas-fired burners, radiant tube burners, and selective catalytic reduction processes. A synopsis of the numerical model and examples of its application to industrial thermal processes follow directly. SIMULATION MODEL The technique is based on the TEACH- 3E/II three-dimensional (3-D) code which was originally developed at Imperial College. The fluid dynamics of systems with irregular boundaries may be described since the technique employs a general 3-D orthogonal coordinate system with a boundary fitted orthogonal mesh. In addition to sol ving the conservation equations of mass, momentum, and energy, the code uses a two-equation turbulence model to describe the transport of turbulent kinetic energy. Many different boundary conditions can be accomodated, and the solution technique is numerically stable for all Reynolds numbers. The theoretical basis and the details of the TEACH family of codes are well documented in the literature (Ref. 1-7). The governing equations and constants used in the simulation are summarized in Table 1, and the basic numerical approach is discussed below. FINITE VOLUME APPROACH- The numerical |
