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RISS 인기검색어
- 검색키워드
- 저자 : Bennie Du Toit (검색결과 4 건)
- 무료
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Flow Network Modeling of the Priming of Spacecraft Propulsion System
Vincent Britz,Bennie Du Toit,전형택 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12
The evacuated pipeline of the propulsion system of a spacecraft has to be filled during the start-up at high altitude. This process is known as priming and can generate severe pressure peaks due to propellant slamming against a closed thruster valve. Previous studies [1] investigated these large pressure surges (peaks as high as 200 bar) as they can potentially damage flow components in the fuel system if not correctly accounted for. In this study a commercial flow network tool, Flownex®, was used to model an experimental setup of this priming procedure. The integrated mass, momentum and energy balance is solved using the continuity, momentum and energy equations applied to nodes and elements. These nodes and elements are the modular building blocks, typically semi-empirical and allow users to either select appropriate built-in correlations, or to define using specific equations through scripting. An appropriate model to capture the pressure pulse was created using the components in Flownex®. Results produced from the network were compared with test data obtained from the DLR Lampoldshausen test-bench. Overall good agreement resulted, showcasing the success of the approach followed.
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Flow Network Modelling of a Nuclear Reactor Rocket
Vincent Britz,Bennie Du Toit,전형택 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12
Nuclear thermal propulsion (NTP) has been identified as the preferred propulsion technology for manned missions to Mars in NASA"s Design Reference Architecture (DRA) [1]. The ability to predict the system performance of a nuclear reactor rocket under a variety of operating conditions is a critical part in the development of NTP. The development of system models has the potential to reduce the design, testing, time and cost required to reach flight-ready status. In this study a commercial flow network tool, Flownex®, was used in the development of a system model to model a nuclear reactor rocket. The integrated mass, momentum and energy balance is solved using the continuity, momentum and energy equations applied to nodes and elements. These nodes and elements are the modular building blocks, typically semi-empirical and allow users to either select appropriate built-in correlations, or to define using specific equations through scripting. By using Flownex®, a nuclear reactor rocket could be modeled and various operating conditions could be investigated during steady-state and transient simulations.
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Rapid Preliminary Combustor Design Using a Flow Network Approach
Vincent Britz,Bennie Du Toit,전형택 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12
Preliminary combustor design usually requires that an extensive number of geometrical and operational conditions be evaluated and compared. During this phase important parameters the designer sought after are typically the mass flow rate distribution through air admission holes, associated pressure losses as well as liner wall temperatures. The process is therefore iterative in nature and can become expensive in terms of engineering analysis cost considering the time required to build and execute 3D CFD models. Network codes have the potential to fill the gap during this stage of the design since they can be setup and solved in timeframes that are orders of magnitude less than comprehensive CFD models, essentially leading to cost savings since overall less time is spent on 3D simulations and rig tests. An additional advantage using this approach is that results from the network solution can be applied as boundary conditions to subsequent more detailed 3D models. In this study a commercial flow network tool, Flownex®, was used to model a complete combustor including flow distribution, combustion and heat transfer. The integrated mass, momentum and energy balance is solved using the continuity, momentum and energy equations applied to nodes and elements. These nodes and elements are the modular building blocks, typically semi-empirical and allow users to either select appropriate built-in correlations, or to define using specific equations through scripting. Flow equations are fully compressible and applied to the gas mixture. The chemical composition of the reactants forming during combustion as well as the adiabatic flame temperature is determined from the NASA CEA package incorporated into the solution. Heat transfer mechanisms included in the model are gas-surface radiation, film convection, forced convection in ducts, surface-surface radiation, and 2D axially-symmetric conduction through solid walls. Results produced from the network were compared with test data obtained from the NASA E3 development combustor. Overall good agreement resulted, showcasing the success of the approach followed.
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Rapid Design of Secondary Flow Geometry Using a Flow Network Modelling Approach
Vincent Britz,Bennie Du Toit,전형택 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12
Accurate prediction of turbo machinery flow is essential during the design process of gas turbines. Substantial progress has been made in this area with three-dimensional calculation techniques of increasing complexity helped by computer hardware developments. Encouraging results are obtained from this work, however three-dimensional analysis is still very time consuming, both to describe the machine geometry and to obtain the results. These methods consequently are appropriate for use in the design context only when a finalized design is approached. In preliminary design a need exists for a less sophisticated but none the less reliable prediction technique suitable for use in iterative type calculations. In this study a commercial flow network tool, Flownex®, was used to model a portion of the secondary flow path in a gas turbine. The integrated mass, momentum and energy balance is solved using the continuity, momentum and energy equations applied to nodes and elements. These nodes and elements are the modular building blocks, typically semi-empirical and allow users to either select appropriate built-in correlations, or to define using specific equations through scripting. The method is tested using an optimization exercise. The results prove that this method of flow network modeling is an efficient way to optimize secondary flow geometry in the preliminary design stages of turbo machinery.
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