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On the modular modelling for dynamical simulation with application to fluid systems
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This licentiate thesis highlights some topics on modular modelling for dynamical simulation with application to fluid systems. The results are based on experience from the development of the fuel cell component simulation environment NFCCPP. The general application is cross-enterprise simulation of technical systems. There are four main topics: component definition including selection of interfaces, lumped modelling of fluid components, the use of dynamical equations to reduce simulation time in large systems and methods of to protect the intellectual property (IP) of a component.

An overview of different dynamical fluid simulation tools such as HOPSAN, MATLAB/Simulink and Easy5 is presented. Special focus is on interfaces, where different approaches for representing interfaces are presented using an illustrative example. Selecting interfaces is however not a separated task from how to set up and solve the underlying equations, which also is shown. Equations to model a lumped component are derived, to get a mathematical background to what problems there are to solve. These equations are derived especially to be applicable in block model software simulation tools such as MATLAB/Simulink. The equations are also compared with the bond-graph approach of representing dynamical systems. A twinscrew compressor is modelled in MATLAB/Simulink as an implementation of these equations. A method to decrease the simulation time in dynamical fluid system is also presented. The technique is to add virtual mass in the force equation to get a slower acceleration of the fluid. Using this slower response, it is possible to use larger time-steps when integrating the equations and thus the total simulation time can be reduced. The error introduced using this method is a modelling error in the time domain, and it is comparable with using unit transmission lines (UTL:s), as does HOPSAN.

The protection of the intellectual property (IP) of a component model is presented. The concept of clamping is thoroughly explained, as it often is overlooked in conventional IPprotection. Three concepts for code protection are presented: “Centralised simulation with remote user control”, “Localised simulation with simulation-time model usage control” and “Parallel distributed simulation”. The NFCCPP implementation of the concept “Localised simulation with simulation-time model usage control” is presented in more detail.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , viii, 20 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2005:30
National Category
Computer Science
Identifiers
URN: urn:nbn:se:kth:diva-566OAI: oai:DiVA.org:kth-566DiVA: diva2:14449
Presentation
2005-12-06, sal A425, KTH, Brinellvägen 83, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101221Available from: 2005-12-28 Created: 2005-12-28 Last updated: 2010-12-21Bibliographically approved
List of papers
1. Modelling of displacement compressors using MATLAB/Simulink software
Open this publication in new window or tab >>Modelling of displacement compressors using MATLAB/Simulink software
2004 (English)In: Proceedings of norddesign 2004 - product development in changing environment, TAMPERE: TAMPERE UNIV TECH PRODUCT DEVELOPMENT LABORATORY , 2004, 192-200 p.Conference paper, Published paper (Refereed)
Abstract [en]

Model based development is increasingly used to minimise costly and time consuming testing of physical prototypes during product development. Modelling and concept evaluation by using computer models for performance prediction will then be a substantial part of the PD process synthesis-analysis loop. However, easy-to-use and flexible methods have to be used for modelling, especially during product concept development, to avoid traditional coding and debugging. In this case, a twin-screw compressor has been modelled using the visual programming language MATLAB/Simulink. One of the objectives was to investigate whether it was feasible and appropriate to use MATLAB/Simulink for such a complex task. New developed methods have been used for this. The main difficulty turned out to be how to create a queue-like environment for the chambers. This problem was eventually solved, but it shows how MATLAB/Simulink can be cumbersome to use when dealing with complex problems.

Place, publisher, year, edition, pages
TAMPERE: TAMPERE UNIV TECH PRODUCT DEVELOPMENT LABORATORY, 2004
Keyword
twin-screw compressor, simulation, visual programming, MATLAB/Simulink
National Category
Reliability and Maintenance
Identifiers
urn:nbn:se:kth:diva-19441 (URN)000252984000020 ()978-952-15-1227-8 (ISBN)
Conference
5th Biannual NordDesign 2004 Conference Tampere Univ Technol, Tampere, FINLAND, AUG 18-20, 2004
Note
QC 20100810Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2011-11-02Bibliographically approved
2. Virtual Component Testing for PEM Fuel Cell Systems:An Efficient, High-Quality and Safe Approach forSuppliers and OEM´s
Open this publication in new window or tab >>Virtual Component Testing for PEM Fuel Cell Systems:An Efficient, High-Quality and Safe Approach forSuppliers and OEM´s
2005 (English)In: 3rd European PEFC Forum, Session B09, 7July, 09:15h, File No. B092, 2005, 103-120 p.Conference paper, Published paper (Refereed)
Abstract [en]

The successful introduction of fuel cell systems for future generation automotiveapplications will significantly depend on the development and realization of reliable lowcost components, which have to be highly integrated in the fuel cell system.Hence, in the course of the project NFCCPP (Numerical Fuel Cell ComponentPerformance Prediction tool) funded by the European Union, a simulation environment hasbeen worked out and a modular component tool box created, which allows the – virtual –testing of components of fuel cell systems in a highly realistic, most advanced and precise,but nevertheless confidential simulation environment. Confidentiality – in fact modelprotection - enables the combination of best state of the art simulation modules fromdifferent partners in an overall system simulation model without having access toconfidential information and data of other individual components. Even competitors cantest their components together in such an environment. Moreover, this approach enablesinvestigations based on overall system simulations (or a fixed set thereof), which have theadvantage of providing a sound reference for comparing results.

National Category
Reliability and Maintenance
Identifiers
urn:nbn:se:kth:diva-19444 (URN)
Conference
3rd European PEFC Forum
Note

QC 20100810

Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-11-16Bibliographically approved
3. The design of modular dynamical fluid simulation systems
Open this publication in new window or tab >>The design of modular dynamical fluid simulation systems
2005 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The objective of this paper is to give an overview of methods for simulation of dynamical fluid systems. Typical applications for such simulations are the design of pneumatic and hydraulic systems, internal combustion engines, cooling systems, and air management systems for fuel cells. The governing Navier-Stokes equations are presented and from them the one-dimensional lumped governing equations are derived. Different methods for solving systems of interconnected components are presented: the state-space/bond-graph method, transmission line modelling, and CFD (Computational Fluid Dynamics) methods. Finally a method to solve the problems using the fully dynamical equations is presented. The method is to use the bond-graph method to systemise the system, and then add virtual mass to the dynamical equation in order to make the simulation system faster to solve. Results from the verification of this are presented in the results section of this paper.

Keyword
air management, modular simulation, dynamic systems, simulation-based design
National Category
Computer Science
Identifiers
urn:nbn:se:kth:diva-27723 (URN)
Conference
Proceedings from the OST Conference, KTH Machine Design, Stockholm, Sweden, 2005
Note
QC 20101221Available from: 2010-12-21 Created: 2010-12-21 Last updated: 2010-12-21Bibliographically approved

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