Simulation and visualization of combustion processes

The My Pulverized Coal Combustion is a realtime interactive application for modelling and analysis of combustion in industry boilers. It is based on a simple fluid simulator, which allows realtime simulation of air flow inside the boiler area. The computation of combustion process is maintained using special particle system, which is by its nature suitable for both visualisation and simulation of the combustion processes inside the boilers. The application is suited especially for interactive design of boilers and for education purposes.

Detailed abstract

Design of coal combustion processes is very time consuming activity accompanied by immense costs. The traditional approach is based on theoretical boiler design and verification of the design on the real model of the boiler designed. The tests performed on the boiler are used for modification of the design. This cycle (design - verification - modification) is repeated several times until the design reached some satisfactory level.

In last decades this process has been considerably accelerated by means of computers where complex simulation programs are used. They allow the designer to experiment extensively with the model of the boiler designed without necessity to build a physical model of the boiler. These simulation methods are widely used and several program packages (e.g. Fluent) are available on the market. The use of these systems led to increased quality of the design and their use has been widely adopted by designers around the world.

General disadvantage of this approach is the complexity of simulation which results in very time consuming calculations. This situation does not allow to investigate on-line various conditions in the boiler and especially the results of parameter changes during the combustion process. Generally speaking - it is not possible to follow the dynamics of the combustion process and in such a way one important dimension of the simulation of the combustion processes - time, is not reflected enough.

Our approach is based on a new model of the simplified fluid flow and combustion process computation. We use structured grid of the 2D combustion space. In each cell its state is calculated according to conditions in this particular cell. The conditions are described by means of information about the amount of coal, amount of oxygen, burnout of the coal, velocity and pressure in the cell, temperature in the cell etc. We use fast methods for determination of the air fluid flow inside the corresponding voxels. We Namely simple computational scheme for solution of model described by Euler equations, based on Newton's second law and continuity equation. Thus, for the specified time step, we compute changes of the mass flow pressure, velocity and other characteristics inside the selected cell. The changes of the cell characteristic are also based on the characteristics of the nearest neighbors beside the cell. The results of the air flow simulation are immediately used for the other parts of the computation.

The concept of the virtual particles, based on the interaction of the air mass inside the cell with the coal particles, allows both to speed up the combustion simulation and also possibility of easy tracking the flow of the combustibles as well. We have also implemented visualization of the results from our fluid simulator. We use effective and fast particle systems visualization of the virtual coal particles flow and OpenGL graphics library for fast and portable visualization of our results. Our implementation allows real-time interaction with the boiler model - e.g. changing up the jets characteristic, such as mass flow of the air and coal, speed of the flow, positions without need to restart the simulation. All of the computations and visualization are running on the current low-cost hardware.

The high speed of the fluid simulator and combustion powered by the virtual coal particle system and simplified combustion engine allows real-time visualization of the resulting characteristics and dynamics using hardware accelerated contour visualization, Image Based Flow Visualization (IBFV) and particle system. The system has been implemented in 2D grid cell space, with variable depth – z-axis. The system is suitable for educational purposes, where clarity, real-time interactivity and universality of computation if important.

The most powerful and new feature of our system is the simulation and visualization interactivity, which is available during real-time computation of the combustion process, without needing to stop or restart the system. Tens of input parameters, including coal inlets setup can be modified on the fly.

Our results make it possible to get a good preview of the dynamics of combustion processes in a boiler. Based on this concept, the students and eventually designers of boilers, making use of the fast, preview based design and approach, could now test many configurations and modifications of the pulverized coal boilers interactively. The system by itself can in an interactive, efficient and attractive form, give an overview of how powerplant boilers work, with an overview of fundamental boiler parameters. The system optionally supports above described hierarchical tree storage and playback based on the pre-calculated Fluid Simulator States Trees and Unsteady Data Sets trees. The interactive modelling can bring the student basic knowledge and fundamentals of constructing performance and efficient boiler solutions and more. With this technique, we can get a good preview of the dynamics of combustion processes in a boiler.

Keywords

Combustion, computer animation, computational fluid dynamics, visualization, particle systems, simulation, FLUENT

Screenshots taken from our system

The pictures has been taken on an todays's average computer systems based on an AMD Athlon 1.2Ghz processor and nVidia GeForce2MX graphics card and a Pentium M with 1.6Ghz with ATI Mobile FireGL. The pictures are taken from the current implementation of our 2D combustion simulation/visualization system with combined simulation/visualization speed about 20 FPS. This allows us dynamic visualization (animation) of the velocities, pressures, burnout rates, species concentration and other characteristics inside the boiler with possiblity for designers and developers of realtime interaction inside the boiler - e.g. adding/moving/modifying characteristics of coal and air jets etc.

Contours Isolines	Contours2	Flame1
Flame6 Inverted	Fsstree App	Ibfv1
Ibfv2	Ibfv3	Mentos
Mypcc2	Particle Tracking	Particle Tracks Large
Particle Tracks2	Particle Vis Detail	Particle Vis Detail2
Particle Vis	Particle Vis2	Particles Viz2 Color
Particles Viz2	Spline After1	Spline Isolines2
Stats	Stats2 Inv	Stats2

Awards

The real-time pulverized coal combustion system and its portions formed by techniques presented at previous chapters of this thesis received the following awards:

• 2003, CTU FEE at Prague, Czech Republic

  Award of Dean of the Faculty of Electrical Engineering of the Czech Technical University in Prague for work Simulation and Visualization of Combustion Powered by Fluid Simulator, presented at conference CTU Poster 2003

• 2003, Brno University of Technology, Faculty of Electrical Engineering and Communication (BUT FEEC), Czech Republic

  Award of Dean for the best work in the International Competition of student creative projects Student EEICT 2003

• 2003, CTU in Prague, Czech Republic

  Price of the rector for placing between the best projects of PhD students, that were solved within scope of CTU internal grants and that were presented on conference CTU Workshop 2003