Blar i USN Open Archive på forfatter "Lie, Bernt"
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On-Off and PI control of methane gas production of a pilot anaerobic digestion reactor
Haugen, Finn; Bakke, Rune; Lie, Bernt (Journal article; Peer reviewed, 2013)A proposed feedback control system for methane flow control of a real pilot anaerobic digestion reactor fed with dairy waste is designed and analyzed using the modified Hill model, which has previously been adapted to the ... -
One-dimensional model of turbulent flow of non-Newtonian drilling mud in non-prismatic channels
Welahettige, Prasanna Kumara Welahetti; Lundberg, Joachim; Bjerketvedt, Dag; Lie, Bernt; Vågsæther, Knut (Peer reviewed; Journal article, 2019)One-dimensional model of non-Newtonian turbulent flow in a non-prismatic channel is challenging due to the difficulty of accurately accounting for flow properties in the 1-D model. In this study, we model the 1-D Saint–Venant ... -
OpenHPL for Modelling the Trollheim Hydropower Plant
Vytvytskyi, Liubomyr; Lie, Bernt (Peer reviewed; Journal article, 2019)An increase of tightly integrated, renewable energy sources with highly varying production leads to a greater need for flexible hydropower plants to “balance” the intermittent production from these sources. From a systems ... -
Optimal design and operation of a UASB reactor for dairy cattle manure
Haugen, Finn; Bakke, Rune; Lie, Bernt; Hovland, Jon; Vasdal, Knut (Journal article; Peer reviewed, 2015-02-01)Optimal design and operation of a planned full-scale UASB reactor at a dairy farm are determined using optimization algorithms based on steady state simulations of a dynamic AD process model combined with models of the ... -
Optimal Operation of the Peat Drying Process in Steam Tube Dryers
Kulakovsky, Leonid; Rosen, Victor; Sharma, Roshan; Pfeiffer, Carlos Fernando; Lie, Bernt (Journal article; Peer reviewed, 2015-11-25)Ukraine is an energy-dependent country and aims to reduce the import of natural gas, heat, and power in general. This implies extracting fuel from her own natural resources; one relevant and readily available energy carrier ... -
Oxygen Effects in Anaerobic Digestion II
Botheju, Deshai; Lie, Bernt; Bakke, Rune (Journal article, 2010)Standard models describing bio-gasification using anaerobic digestion do not include necessary processes to describe digester dynamics under the conditions of oxygen presence. Limited oxygenation in anaerobic digestion can ... -
Parameter estimation for externally simulated thermal network models
Brastein, Ole Magnus; Lie, Bernt; Sharma, Roshan; Skeie, Nils-Olav (Peer reviewed; Journal article, 2019)Obtaining accurate dynamic models of building thermal behaviour requires a statistically solid foundation for estimating unknown parameters. This is especially important for thermal network grey-box models, since all their ... -
Population balance modelling for fertilizer granulation process
Vesjolaja, Ludmila; Glemmestad, Bjørn; Lie, Bernt (Journal article; Peer reviewed, 2018)Few granulation plants are operated optimally. It is common to operate granulation plants below their maximum design capacity, and in many cases, periodic instabilities may also occur. From a process control and optimization ... -
Power System Stability Using Modelica
Øyvang, Thomas; Winkler, Dietmar; Lie, Bernt; Hegglid, Gunne John (Journal article; Peer reviewed, 2014-12-09)This paper is concerned with power system modeling using the Modelica language in comparison to a traditional simulation tool. Though most common power system simulation tools are computationally efficient and reasonably ... -
Pressure wave propagation in Managed Pressure Drilling- model comparison with real life data
Berg, Christian; Stakvik, Jon Åge; Lie, Bernt; Vågsæther, Knut; Kaasa, Glenn-Ole (Peer reviewed; Journal article, 2019)Drilling for oil and gas is a complex process, involving pumping of fluid through kilometers of pipes. Even though the drilling fluid has a high speed of sound (˜1000 m/s), the large lengths involved make pressure wave ... -
A Real-Time Flow-Measuring Algorithm for Open Venturi Channel Non-Newtonian Flow
Welahettige, Prasanna Kumara Welahetti; Lie, Bernt; Vågsæther, Knut (Peer reviewed; Journal article, 2019)A real-time flow measuring algorithm is developed for the open Venturi channel non-Newtonian flow measurement. Using a single level sensor reading at downstream of the open Venturi channel, a drilling-well return flow rate ... -
Relaxed Ziegler-Nichols closed loop tuning of PI controllers
Haugen, Finn; Lie, Bernt (Journal article; Peer reviewed, 2013)A modification of the PI setting of the Ziegler-Nichols closed loop tuningmethod is proposed. The modification is based on a combination of the Skogestad SIMCtuning formulas for ´´integrator plus time-delay´´ processes ... -
Second Order KP Scheme for the Solution of flow in a Venturi Channel
Dissanayake, Susantha; Sharma, Roshan; Lie, Bernt (Journal article; Peer reviewed, 2018)In many different applications, a Venturi channel is used as a tool to compute fluid flow rates. The Saint-Venant equation is a hyperbolic type Partial Differential Equation (PDE) which can be used to model fluid flows ... -
Simulation of Transcritical Flow in Hydraulic Structures
Agu, Cornelius Emeka; Lie, Bernt; Elseth, Geir (Journal article; Peer reviewed, 2015-11-25)In hydraulic engineering, transcritical flows are often required in some applications. One example is in a Venturi channel where the occurrence of critical depth is used to estimate flow rate in the channel. In this paper, ... -
State estimation and model-based control of a pilot anaerobic digestion reactor
Haugen, Finn; Bakke, Rune; Lie, Bernt (Journal article; Peer reviewed, 2014)A state estimator and various model-based control systems have been designed for a real anaerobic digestion (AD) pilot reactor fed with dairy manure. The model used is a modified Hill model which is a relatively simple ... -
State Estimation of a Thermal Model of Air-cooled Synchronous Generator
Pandey, Madhusudhan; Øyvang, Thomas; Lie, Bernt (Peer reviewed; Journal article, 2019)In this paper, we extend a previous study on a totally enclosed thermal model of a synchronous generator, with temperature state estimation using experimental data. The extension includes a new formulation of the system ... -
Structural analysis in Julia for dynamic systems in OpenModelica
Vytvytskyi, Liubomyr; Lie, Bernt (Peer reviewed; Journal article, 2019)In control theory for dynamic systems, the information about observability and controllability of states plays a key role to evaluate the possibility to observe states from outputs, and use inputs to move states to a desired ... -
Structural observability analysis of large scale systems using Modelica and Python
Perera, M. Anushka S.; Lie, Bernt; Pfeiffer, Carlos Fernando (Journal article; Peer reviewed, 2015)State observability of dynamic systems is a notion which determines how well the states can be inferred from input-output data. For small-scale systems, observability analysis can be done manually, while for large-scale ... -
Study of Fluidization Regimes using OpenFOAM Computational Fluid Dynamics
Welahettige, Prasanna Kumara Welahetti; Lie, Bernt; Vågsæther, Knut; Moldestad, Britt Margrethe Emilie (Journal article; Peer reviewed, 2017)The objective of this study was using computational fluid dynamics simulation with OpenFOAM to study the fluidization properties for four types of particles classified as Geldart A, B, C and D. Fluidization regimes were ... -
Surrogate and Hybrid Models for Control
Lie, Bernt (Peer reviewed; Journal article, 2019)With access to fast computers and efficient machine learning tools, it is of interest to use machine learning to develop surrogate models from complex physics-based models. Next, a hybrid model is a combination model where ...