S. L. Chang

Integral Combustion Simulation of a Turbulent Reacting Flow in a Channel with Cross-Stream Injection

A new integral one-step reaction submodel has been developed for an Argonne combustion computer code to simulate reacting flows of an advanced combustor for magnetohydrody-narmic power generation. The integral combustion code makes numerical calculations of a reacting flow more efficient and mart stable while still preserving the major physical effects of the complex combustion processes. Results of the simulation indicate that (1) fluid mixing is mainly responsible for combustion performance and (2) counterflow injection with an injection angle in the range of 120° to 140° yields the best mixing and combustion performance.

COMPUTATION OF TWO-DIMENSIONAL, NONREACTING JET/MAIN FLOW MIXING IN A MAGNETOHYDRODYNAMIC SECOND-STAGE COMBUSTOR

A numerical solution describing a two-dimensional turbulent flow field with multiple gas species was used to study the interaction and mixing of opposed slot jets with the main flow in a rectangular channel. This study is part of a program to use computer modeling to aid in the design of a magnetohydrodynamic second-stage combustor. The effects of varying the jet angle and main inlet flow symmetry on the mixing patterns and rate of mixing were evaluated using computed velocity and species concentration fields. Mixing depends strongly on jet angle, and jet angles greater than 90° produce better mixing.

Impacts of radiation heat transfer on NO/sub x/ calculation in industrial furnaces

A computational glass furnace model was developed for the glass industry to evaluate the glass furnace performance. GFM simulates the major flow and heat transfer characteristics in both the combustion space and glass melter of the furnace, including fluid mixing, combustion, soot/NO/sub x/ formation and transport, radiation heat transfer, batch melting, and glass flow. A computational fluid dynamics code is used to simulate the combustion space flow including NO/sub x/ formation and transport, and spectral radiation heat transfer from soot, gaseous species, and walls. Major features of the model include the time-integral lumped oxy-fuel combustion model and direct integral solution of spectral radiation transport equation. The furnace model has been validated with experimental data from commercial glass furnaces. Radiation heat transfer in a furnace includes three major components: emission from soot and gaseous species, absorption of these species, and emission/reflection of the surrounding walls. The results of a parametric sensitivity study show that the radiation heat transfer components have significant impacts on the calculation of the gas temperature and NO/sub x/.

A numerical investigation of combustion parameters in various industrial furnaces

A computational fluid dynamics (CFD) code, developed at Argonne national laboratory to simulate turbulent mixing, combustion reaction, radiation heat transfer, and pollutant kinetics of combustion flow, has been used to study various melting furnaces. The code employs an integral approach to incorporate a lumped combustion reaction model in the flow calculation and a separate hybrid technique to perform pollutant kinetics calculations. The CFD code has been validated with experimental data collected from industrial furnaces and then used for a parametric study of various furnace geometries and operation conditions. The furnace configuration greatly effected the flow property distribution as well as the combustion efficiency. The air injection velocity effected the flow penetration and the species mixing. The injection angle also significantly effected the species mixing. And finally, the equivalence ratio effected the temperature and pollutant concentrations. The study demonstrates that CFD can be a useful tool for analyzing the flow field of the combustion space in industrial furnaces.

A Simulation Approach for Bubble Flow in a Glass Melter

Combustion heat is used in glass furnaces to melt sand and cullet (scrap glass) into liquid glass to make products. The glass flow in a melter consists of solid particles of sand/cullet, liquid glass, and bubbles. Bubbles formed in the melting processes due to the glass reactions have strong impacts on glass quality and furnace efficiency. Smaller bubbles entrained in the liquid flow degrade the glass quality. Larger bubbles rise to the top of the melter and form a foam layer that impedes the radiation heat transfer from the combustion space and lowers the furnace efficiency. An Eulerian approach was developed to simulate the bubble flow in a glass melter. The approach divides bubbles into various groups and treats each group of bubbles as a continuum. The mass, momentum, and energy conservation equations of the bubble flow are derived to solve for local bubble properties. The approach was incorporated into a multiphase reacting flow computational fluid dynamics code that simulates overall furnace flows to evaluate the impacts of bubbles on glass quality and furnace efficiency.Copyright

Modeling of Regenerative Furnace Ports

In order to increase overall efficiency, many industrial glass furnaces are regenerative; that is, the heat from the exhaust gases is used to preheat in the in-coming combustion air. The ports on these furnaces inject stream(s) of fuel into the preheated air stream and then combustion occurs inside the combustion chamber. Modeling of the exact detail of these furnace ports in addition to modeling the combustion space proper becomes computationally burdensome since many of these furnaces are extremely large. This paper presents an engineering approach using computational fluid dynamics to model both the major effects of the furnace ports in addition to calculating the detailed flow field in the combustion space. This approximation has been incorporated into a complete (combustion space/glass melt) furnace simulation. This engineering approach significantly reduces run time while still maintaining results that represent the conditions seen in the furnace. This paper will present this approach as well as some preliminary comparisons with actual furnace data/observations.Copyright

The effect of gases emitted from batch/glass reactions on the combustion space flow field.

The concept of ‘coupling’ a combustion space CFD code to a code that models the molten glass flow is not a new idea. However, this concept has been limited to an energy coupling; the heat flux calculated in the combustion space model is used to drive the glass melt while the calculated surface temperature is used in the radiative heat transport calculation in the combustion space computation. In reality, there is significant mass (mostly gas) transport from the batch/molten glass into the combustion space. This is an important phenomenon to be modeled since these gases, particulates and volatiles will be removed from the combustion chamber and hence raise environmental considerations. In addition, these released gases have a distinct influence on the flow field in the combustion space. The ANL Glass Furnace Model has been augmented to calculate the chemical reactions that release gases in the batch and in the melt. This work presents preliminary results indicating the effect of these gases on the combustion space.Copyright

Modeling and Preliminary Validation of a Regenerative Furnace Using the ANL Glass Furnace Model

The ANL Glass Furnace Model (GFM) was developed for steady state simulation of industrial glass furnaces. Unfortunately, a large fraction of the operating glass furnaces do not operate in a steady state mode and computational costs make it prohibitive to run the simulations in a transient mode. A solution methodology was developed to model these transient furnaces in steady state mode. This solution methodology was used to model a small, industrial furnace on which a relatively comprehensive set of data was taken. This paper presents the solution methodology in detail along with some of the qualitative validation results indicating the validity of the modeling approximation.Copyright

Numerical simulations of industrial melting furnaces.

A computational fluid dynamics code developed at Argonne National Laboratory was used to simulate turbulent mixing, combustion reaction, radiation heat transfer, and pollutant kinetics of the combustion flow in industrial melting furnaces. The code employs an integral approach to incorporate a lumped combustion reaction model in the flow calculation and a separate hybrid technique to perform pollutant kinetics calculations for NOx and soot. The code validated with experimental data collected from industrial furnaces, was used to evaluate the impacts of burner operation conditions on the energy efficiency of furnaces. The results indicate that the furnace configuration has a significant effect on the combustion efficiency; the burner injection velocity affects the flow penetration and the species mixing; and the burner injection angle has a significant impact on the flow patterns and heat transfer. The study demonstrates that CFD can be a useful tool for analyzing the combustion flow of an industrial furnace.© 2003 ASME

A numerical study of multicomponent vaporization effects in FCC riser reactors

The petroleum refining industry uses fluidized catalytic cracking (FCC) to convert heavy feed oil into lighter molecular weight, more valuable components such as olefins, gasoline, and diesel fuel. Hot catalyst particles are used for the conversion, which occurs in a riser reactor. The interphase mixing, vaporization, and chemical reactions are the controlling processes inside the FCC riser. The interactions between the feed oil spray and the gas/solid flow determine the final products of the cracking process, and ultimately the profitability of the FCC unit. The complex nature of the multiphase interactions and chemical reactions that occur in the riser reactor presents a huge challenge for analysis. Numerical simulation provides the means to facilitate and reduce the design time of new units, and also optimize existing units. A new vaporization model is incorporated into an existing three-phase reacting flow computational fluid dynamics (CFD) code developed at Argonne National Laboratory. In this study, ICRKFLO is used to simulate a low profile FCC riser. A low profile riser has a shorter residence time than standard FCC risers, and the modeling of the droplet vaporization process is of great importance. Because feed oil droplets are composed of many hydrocarbon components, each of which vaporizes at a different temperature, a new vaporization model is developed to include multicomponent vaporization of a droplet. The model allows the boiling point temperature of the droplets to vary as the vaporizing droplet loses mass to the gaseous phase. Comparison between vaporization models indicates a significant change in predicted product yields.