Numerical Modelling of Grate Combustion

Předkládaná práce je zaměřena na numerické modelování spalování tuhých paliv na roštu metodami výpočtové dynamiky tekutin (CFD). Jelikož výsledky CFD simulací roštového spalování závisí na kvalitě vstupních dat, která zahrnují i údaje o teplotě, hmotnostním toku a chemickém složení spalin vystupujících z lože, pozornost je věnována především procesům, probíhajícím v loži během spalování na roštu. Velká část práce je věnována vývoji spolehlivého modelu spalování v sypaných ložích, jelikož může napomoci zkvalitnit výsledky simulací i rozšířit znalosti principů spalování tuhých paliv v sypaných ložích. V rámci práce byl vyvinut jednorozměrný nestacionární model spalování v experimentálním reaktoru a implementován do počítačového programu GRATECAL 1.3 včetně grafického uživatelského rozhraní. Zvláštní důraz byl kladen na konzervativnost modelu. Proto byla vyvinuta metoda pro kontrolu hmotnostní a energetické bilance systému a následně aplikována v řadě studií, v rámci nichž byly odhaleny některé chyby týkající se definic zdrojových členů, které byly převzaty z literatury a opraveny. Pomocí modelu byla provedena analýza šíření čela sušení a reakce hoření koksu po výšce lože pšeničné slámy. Na základě výsledků těchto analýz bylo doporučeno zahrnout i modelování změny porozity částic paliva, aby šířka reakční zóny byla predikována korektně v případě, že je uvažována změna porozity celého lože. Rovněž vyvinutá bilanční metoda byla použita k analýze vlivu kritérií konvergence na hmotnostní a energetickou nerovnováhu simulovaného systému. Bylo zjištěno, že škálovaná rezidua rovnic všech veličin by měla poklesnout aspoň na hodnotu $10^{-6}$, aby bylo dosaženo nízké hmotnostní a energetické nerovnováhy a tudíž uspokojivě přesných výsledků ze simulací v loži. Druhá část práce je věnována vývoji a implementaci knihovny uživatelem definovaných funkcí pro komerční CFD nástroj ANSYS FLUENT, které slouží k propojení modelu lože s modelem komory reálné spalovací jednotky, aby byla umožněna dynamická změna okrajových podmínek na vstupu do komory v závislosti na výstupech ze simulací v loži. Vytvořené rozhraní pro propojení těchto dvou modelů je dostatečně obecné pro aplikaci na širokou škálu modelů roštových kotlů. Popsané výsledky přispívají k lepšímu porozumění numerickému modelování spalování na roštu, a to zejména ve fázi sestavování numerického modelu a nastavení parametrů řešiče pro kontrolu konvergence.The present work is focused on numerical modelling of grate combustion of solid fuels by means of computational fluid dynamics (CFD) methods. Since CFD results from simulations of grate combustion depend on the quality of input data including information on temperature, mass flux and chemical composition of flue gas leaving a fuel bed, the attention is turned to modelling of processes, that take place within the fuel bed on a grate. A great part of the work is devoted to development of a reliable numerical model of packed-bed combustion as it may help improve both results from simulations and knowledge of principles of solid fuel combustion in fixed or moving beds. A one-dimensional transient numerical model of combustion in an experimental reactor is developed and implemented into a computer program called GRATECAL 1.3 with a grapical user interface. A special emphasis is put on the conservativeness property of the model. Therefore, a method for control of mass and energy balance over the system is developed and applied to a series of case studies, which have revealed certain errors in definitions of mass source terms, so that data adopted from literature have been reconciled. The model is used for analysis of propagation of drying and char combustion reaction fronts in a bed of wheat straw particles. It is suggested to include modelling of particle internal porosity change in order to obtain correct reaction zone thickness, if porosity of the bed is allowed to change during combustion. The balance-based method is also used to analyse effects of convergence criteria on mass and energy imbalance of the modelled system. It is found that all the scaled residuals must drop to as low as $10^{-6}$ or lower in order to obtain sufficiently accurate results from in-bed simulations in terms of mass and energy conservation within the packed bed. The second part of the work is devoted to development of a library of user-defined functions for the commercial CFD software ANSYS FLUENT for coupling the bed model with a freeboard model of a real combustion unit in order to specify the boundary conditions indirectly using results from in-bed simulations. The created interface is general enough to be used for a wide range of models of grate furnaces. The presented results contribute to better understanding of numerical modelling of grate combustion, especially in the setup of a numerical model and parameters of solver for the control of the convergence.

The hydraulic impact and alleviation phenomena numeric modeling in the industrial pumped pipelines

The issues of the hydropercussion phenomena mathematical modeling in the industrial pumped piping systems, with the pumps and dampeners included, to determine the impact absorbers effectiveness on the amplitude-frequency charac- teristics of these hydro-mechanical systems are considered. It’s still actual and many authors are still looking for the systems CFD issues research and resolution, see [6, 7]. Method of calculating the transient and frequency characteristics of the pipeline that contains a pump and a dampener, is based on nonlinear mathematical model. Simulation of overlapping stream with using industrial valves is provided by introducing the exponential law of diminishing cross-sectional area of the pipeline. The basis of calculation is the method of characteristics applied to the simplified Navier- Stokes equations

Design, Analysis, and Simulation of Rocket Propulsion System

This document details the functionality of a software program used to streamline a rocket propulsion system design, analysis and simulation effort. The program aids in unifying the nozzle, chamber and injector portions of a rocket propulsion system design effort quickly and efficiently using a streamlined graphical user interface (GUI). The program also allows for the selection of common nozzle profiles including 80% rao, conical, a user selected percentage bell, and a minimum length nozzle (MLN) using method of characteristics (MOC). Chamber dimensions, propellant selections, and injector selection between doublet or triplet allow for further refinement of the desired rocket system design. The program takes the available selections and specifications made by the user and outputs key design parameters calculated from the input variables. A 2-D graphical representation of the nozzle and/or chamber is plotted and coordinates of the plotted line are displayed. Additional design calculations are determined and displayed within the program such as specific impulse, exhaust velocity, propellant weight flow, fundamental instability frequencies, etc. The rocket propulsion system design coordinates are saved to a *dat file which can be used in a CAD program to plot a 3-D model of the rocket propulsion system. The *dat file is compatible for creating splines in Unigraphics NX, Catia, and SolidWorks. Coordinates of the injectors are saved to a *dat file to be modeled in a CAD program as well. The program currently provides a symbolic link in the form of a button on the output page which will open Unigraphics NX CAD program. The post-processing simulation of the rocket propulsion system is done in a computational fluid dynamics (CFD) program such as ANSYS ICEM CFD mesh generation software and ANSYS FLUENT CFD. The program provides a button on the output page which will open the ANSYS ICEM CFD mesh program and the ANSYS FLUENT CFD program. The user inputs the parasolid or IGES/STEP file of the CAD 3-D modeling of the rocket propulsion system into the ANSYS ICEM CFD meshing software. The geometry tolerant mesher program produces a volume or surface mesh to be read into the ANSYS FLUENT CFD software. Using ANSYS FLUENT CFD software, the user can choose to model the flow, turbulence, heat transfer, air flow over the rocket, combustion in the chamber, or various other options of the rocket propulsion system. The rocket propulsion system is a graphical user interface (GUI) which is run through Matlab and is compatible for 2009-2011 Matlab versions

Graphical User Interface (GUI) In MatLab for Solving the Pulsatile Flow in Blood Vessel

Blood flow analysis is a study of measuring the blood pressure and finding its equivalent flow rate, velocity profile and wall shear stress. In this article, the relationship between blood pressure gradient, velocity profile, centreline velocity, volumetric flow rate and wall shear stress is determined analytically through a Graphical User Interface (GUI) developed using MatLab. If one of these time-dependent blood flow properties is known, i.e. pressure gradient, velocity profile, volumetric flow rate or wall shear stress, then the remaining properties can be calculated. A code is developed to solve these blood flow properties. Any time-dependent blood properties can be used as input data. These data are then digitized and saved in this code. Subsequently, these data are curve-fitted using the Fourier series. The corresponding coefficients of Fourier series are then used to calculate the blood property. Once this is obtained, the remaining three other flow properties can be subsequently calculated. This GUI serves as a learning tool for students who wish to pursue his/her knowledge in understanding the relationship of various blood flow properties of pulsatile blood flow as well as the mathematics governing pulsatile flows. (Authors' abstract

Main specifications of CFD codes for WUIVIEW activities

CFD simulations will be the core activity of the WUVIEW performance based fire safety analysis. The purpose of this document is to provide WUIVIEW partners with a general overview of the CFD codes to be used in the Action. The general simulation framework is described, particularly highlighting data inputs and scenario description requirements, to be developed in subsequent WUIVIEW WPs. This TN provides the technical foundations and main specifications of the databases to be designed within the WUIVIEW working program (ongoing action by UPC).Postprint (updated version

An Automated Optimal Design of a Fan Blade Using an Integrated CFD/MDO Computer Environment

The objective of the investigation is the development of more efficient design methodologies based on the applications of established design tools including Computational Fluid Dynamics (CFD) and non-linear Multidisciplinary Design Optimization (MDO) algorithms. Well known evolutionary type optimization algorithms include the Particle Swarm Optimization (PSO), Response Surface Optimization (RSO) and Genetic (GA) Algorithms. The benchmark case study is the optimal design of a low speed fan for an industrial air-conditioning application using the Response Surface Optimization (RSO) algorithm. The optimization algorithm controls the variations of parameters that describe the three-dimensional geometry of the blade while applying performance and geometrical constraints on blade shapes that are investigated. The optimal design is defined as the blade geometry which produces the maximum total efficiency subject to specified constraints on the volume flow rate (CFM) and rotational rate (RPM) of the fan

Solar Splash Senior Design Project

Indiana University Purdue University IndianapolisThe Solar Splash senior project is the first attempt at creating an entirely solar propelled watercraft. The initial project intent was to design and create a supplement meets the specifications and compete in the competition. With this in mind, a budget approach was taken in order to be able to fund the task at hand. As the project progressed toward the end of the low-level design phase it was evident that the competition would not occur. At the midpoint of the project, the goals and objectives had changed entirely. The new focus was targeted at proving the operation of the systems involved in the watercraft. Having been faced with a new series of objectives and an entirely new scope, the project began to appear doable. The primary focus of the project at this point entirely relied on simulation data and data analysis. The idea was not reinventing the wheel but rather verifying that the wheel rolled. Using the designed propulsion, solar and sensors systems, with the help of a combination of software programs, the idea of a budget solution can be seen. The software used tell the story of the boat that would have been created had the project continued down the original proposed path. As systems were tested and analyzed, they were also adjusted and improved upon. The analysis process consumed a lot of time but acted as a highlighter for all the flaws that the system suffered from. This document introduces the design concepts and schematics of the Solar Splash senior design project. Within are detailed drawings and diagrams for the electrical systems devised for the construction operation of the watercraft. This report is a means of displaying the layout of the final product and how all systems tie together. The report will contain detailed information on not only hardware aspects but also software and how those will bridge together. The report is meant to be in layman’s terms and should be easily interpreted at all levels. The bulk of the information found in the report will be found in the testing sections where analysis of a theoretical boat is done. The motor design, solar design, and fluid dynamic analysis of the boat hull and propeller can be found in their respective section. The innerworkings, testing processes and thoughts behind each decision can also be found in these sections. The document begins with a table of contents identifying each main and subcategory of information. The next page is the document identification, revision history, and lesser known definitions. Following that is the introduction and scope. Specification requirements for the ‘general requirements’, ‘electrical requirements’ and ‘mechanical requirements’ are found on the following page. A system flowchart can be found in the high-level Design along with the design decision matrices for each system. The design portion then begins starting with the System-wide design changes and decisions. The hardware and software designs and schematics follow and cover the proposed schematics and drawings for the system. Cost breakdowns for each individual system are also found in the low-level section. Testing methodologies, results and an explanation of the testing software can be found after the low-level design. A summation of all these testing results is found near the tail of the document. Conclusions, recommendations, and appendixes can be found as the last three sections, respectively.Electrical Engineering Technolog

Free-Piston Stirling Convertor Model Development, Validation, and Analysis for Space Power Systems

The Advanced Stirling Convertor (ASC) is a free-piston Stirling engine coupled with a linear alternator currently being under extended testing at the NASA Glenn Research Center (GRC). Using the Sage 1-D Stirling modeling software, a linear alternator model was developed using two separate methods and integrated with an existing ASC Stirling engine model. One used a simplified transducer method, while the other was developed from first principles. The combined models were tuned and validated against test data and then compared against each other. Both validated models are able to match test data within 7% or better. In addition, a MATLAB graphical user interface (GUI) was developed to interface and operate Sage models. The GUI enables the Sage models to be run with varied input parameters, displays simulation results, and creates phasor diagrams of ASC forces and voltages. This tool also enables users with limited modeling experience to run Sage model simulations and could be useful in space mission planning

Computational Thermodynamics and Kinetics in Materials Modelling and Simulations

Over the past two decades, Computational Thermodynamics and Kinetics have been tremendously contributed to materials modeling and simulations and the demands on quantitative conceptual design and processing of various advanced materials arisen from various industries and academic institutions involved in materials manufacturing, engineering and applications are still rapidly increasing

Zipping Towards STEM: Simulation Wind Tunnel

The simulation wind tunnel program created for this project is implemented within a larger, National Science Foundation funded project titled Zipping Towards STEM: Integrating Engineering Design into the Middle School Physical Science Curriculum. Over the course of the next two years, all Akron Public School 8th grade students will go through the Zipping Towards STEM project curriculum. The students will be exposed to the typical steps of engineering design (computer modeling, simulation, building, and testing) and learn about the fundamentals of aerodynamics through the design of their own Soap Box Derby mini-cars. The virtual wind tunnel will be used during the simulation portion of the curriculum to show the 8th grade students how performance prediction software is used during the engineering design process