Mario Baburić

Application of the Conservative Discrete Transfer Radiation Method to a Furnace with Complex Geometry

ABSTRACT A conservative form of the discrete transfer radiation method (DTRM) has been applied in a computational fluid dynamics (CFD) simulation of the radiative heat transfer in an experimental furnace with complex geometry. The furnace was operated under nonpremixed conditions, burning preheated heavy fuel oil. For combustion simulation a semiempiric oil combustion model has been applied, while for the flow field resolution an unstructured CFD code has been used. The simulation results are compared with available experimental data, showing acceptable level of prediction accuracy. The conservative DTRM formulation is shown to be superior to the original formulation in this particular case.

Implementation of discrete transfer radiation method into SWIFT computational fluid dynamics code

The Computational Fluid Dynamics (CFD) has developed into a powerful tool widely used in science, technology and industrial design applications, whenever fluid flow, heat transfer, combustion, or other complicated physical processes, are involved. During decades of development of CFD codes, scientists were writing their own codes, that had to include not only the model of processes that were of interest, but also a whole spectrum of necessary CFD procedures, numerical techniques, pre-processing and post-processing. That has arrested much of the scientist effort in work that has been copied many times over, and was not actually producing the added value. The arrival of commercial CFD codes brought relief to many engineers that could now use the user-function approach for modelling purposes, entrusting the application to do the rest of the work. This paper shows the implementation of Discrete Transfer Radiation Method (DTRM) into AVLs commercial CFD code SWIFT with the help of user defined functions. Few standard verification test cases were performed first, and in order to check the implementation of the radiation method itself, where the comparisons with available analytic solution could be performed. Afterwards, the validation was done by simulating the combustion in the experimental furnace at IJmuiden (Netherlands), for which the experimental measurements were available. The importance of radiation prediction in such real-size furnaces is proved again to be substantial, where radiation itself takes the major fraction of overall heat transfer. The oil-combustion model used in simulations was the semi-empirical one that has been developed at the Power Engineering Department, and which is suitable for a wide range of typical oil flames.

Optimization model for EL-TO Zagreb cogeneration plant

A mathematical model for the cost optimization of the EL-TO Zagreb thermal power plant has been developed. The plant supplies hot water for district heating, process steam for industry and electric power. The rather detailed mathematical model of the plant includes models of all main components like gas turbine facilities with heat recovery boilers, high pressure steam generators, back-pressure turbines, peak load boilers and other equipment like heat exchangers, deaerators and pressure reduction valves. All boilers can use alternatively natural gas or heavy oil as fuel while gas turbines are supplied with natural gas only. The generalized reduced gradient method was used for solving the strongly nonlinear optimization problem. The goal of the mathematical model was to minimize the production cost by satisfying the district heat and industrial steam consumption. Results of the sensitivity analyses of the influence of extraction steam pressure levels on cost function are presented as well as a comparison of optimization results with operational data.

A new approach to CFD research: combining AVL's FIRE code with user combustion model

A new oil-combustion model was implemented into the AVLs CFD code FIRE and validation performed. The validation consisted of the simulation and the comparison with the existing Magnussen model. For the simulation purpose the domain was determined first, while user-defined functions simulating conditions at the inlet were done subsequently. The comparisons with the Magnussen results as with some approximate experimental results were done at the end. The paper shows flexibility of AVLs code in usage of user-defined functions, which enables combining the advantages of a commercial code and user modelling.

Numerical Simulation of Jet Diffusion Flames With Radiative Heat Transfer Modeling

Beside appropriate turbulence and combustion modeling, the problem of an accurate prediction of turbulent diffusion flames usually requires accurate radiative heat transfer predictions as well. In this paper it is shown that the inclusion of radiation modeling into the overall numerical simulation is important if accurate temperature profiles are needed. Two different jet diffusion flame configurations are simulated in this work — a diluted hydrogen jet flame (80% H2 and 20% He by volume) [1–4], and a piloted methane jet diffusion flame (flame D) [5, 6]. The predictions are compared to experimental data. Radiation is modeled by a conservative discrete transfer radiation method (DTRM) [7, 8]. Turbulence is modeled by a classical k-e and by a hybrid procedure, as proposed in [9]. Combustion modeling is based on the stationary laminar flamelet model (SLFM) [10], where the combustion/turbulence interaction is accomplished via the presumed β probability density function (β-PDF).Copyright