| 1. |
- Ghaviha, Nima
(författare)
-
Increasing Energy Efficiency in Electric Trains Operation : Driver Advisory Systems and Energy Storage
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Electric traction is the most efficient traction system in the railway transportation. However, due to the expensive infrastructure and high power demand from the grid, the share of electric trains in the railway transportation is still lower than other trains. Two of the possible solutions to increase the share of electric trains are: optimal train operation to minimize energy consumption, the use of batteries as the energy source for driving electric trains on non-electrified lines. This thesis aims to extend the knowledge in the field of energy optimal operation of electric trains and battery-driven electric trains.Energy optimal operation of electric trains is supervised using a driver advisory system (DAS), which instructs the driver to operate the train in an energy-efficient manner. This thesis contributes to DAS technology under two topics: the increase of energy efficiency and the design of DAS.This thesis presents a complete procedure of designing a DAS from the mathematical formulation to application on the train. The designed DAS is in the form of an Android application and is based on a dynamic programming approach. The computational performance of the approach is enhanced using heuristic state reducing rules based on the physical constraints of the system. The application of the DAS shows a potential reduction of 28% in energy consumption.This thesis considers the detailed energy losses in the whole propulsion system using a regression model that is generated from validated physical models. The application of the regression model instead of a previous constant efficiency factor model results in 2.3% reduction in energy consumption of the optimum speed profiles.Based on the solution for the normal electric trains, a solution is also offered for the optimal operation of battery-driven electric trains, in which the characteristics of the battery as one of the main components are considered using an electrical model. The solution presented in this thesis, is to combine the popular single mass point train model with an electrical circuit battery model.Furthermore, this thesis evaluates the performance of the optimization approaches and validates the models against the measurements from actual drives of a real-life battery train. The results show a potential of around 30% reduction in the charge consumption of the battery.The results of this thesis (algorithms and the Android application) are provided as open source for further research in the field of energy efficient train control.
|
|
| 2. |
- Karlsson, Christer
(författare)
-
On the On-line Tools for Treatment of Deterioration in Industrial Processes
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For industrial processes high availability and efficiency are important goals in plant operation. This thesis presents studies and development of tools for on-line treatment of process deterioration and model and sensor errors in order to achieve these goals. Deterioration of measurement devices, process components and process models has caused economical losses, plant failure and human losses. The development of on-line methods to prevent such losses is of special interest and has been conducted at The Department of Energy Technology, Mälardalen University. Important technological obstacles to implementing automatic on-line methods have been identified, such as data selection for adaptation and adaptation of data-driven models to new states.A new method has been developed for decision support by combining artificial intelligence methods and heat and mass balance models, and concepts are proposed for decision support in order to detect developing faults and to conduct appropriate maintenance actions. The methods have been implemented in simulation environment and evaluated on real process data when available. The results can be sumarised as successful development of a decision support method on a steam turbine by combining artificial neural networks and Bayesian networks, and identification of important obstacles for automation of methods for adaptation of heat and mass balance process models and data-driven models when they are subject to deterioration.
|
|
| 3. |
|
|
| 4. |
- Pourian, Bijan, 1962-
(författare)
-
ANALYZING THE HYDRO DYNAMICS AND THE CHEMICAL REACTIONS IN PULP DIGESTER SYSTEMS USING CFD MODELLING
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to use differential analysis and finite volume method (FVM) to model and analyze a continuous pulp digester in order to create a detailed picture of the flow behaviour and chemical reactions in the digester. This information will be used to optimize wood chip flow and reactions and to diagnose and avoid faults such as hang-ups and channelling. As digesters increase in size, the importance of control of the liquor flow in the wood chip bed also increases. Pulping reactors are often faced with production disturbances that cause reduced fibre quality, non-uniform chemical reactions and damaging channelling phenomena. The models that are proposed in this thesis aim to consider the fluid dynamics, thermodynamics and chemical reactions together in order to create a model with more detail than has been previously reported. The digester is of the continuous type and has a circular cross-section, with a height of 60 m and a diameter that increases stepwise from 6 m at the top to 7 m at the bottom. The geometry of the digester, including an internal pipe with three different diameters, three inlet flows at three levels of the digester, inlets and outlets at the top and bottom, and a number of peripheral circulation pipes connected to the screens at three levels, is represented in simulations by a 2D axisymmetric model constructed in Gambit. The interactions between the two phases - the wood chips and the alkaline liquor - are studied using the finite volume method (FVM). Eulerian and Mixture numerical methods are evaluated for solving a mass transfer multiphase model with a porous matrix, species transport and reaction system in FLUENT. Variable porosity is used to model channelling in the digester. Comparisons of the results of simulations with real digester data indicate that the multiphase model, with the species transport and mass transfer modules accurately predict the pulping chemical reactions inside the digester and are able to evaluate pulp quality. The species transport model with reaction scheme is able to predict the mass balance equation and stoichiometry of the pulping reaction. The porous media scheme complements this approach to give a more complete view of pulp production, including the effect of faults in the process. The approaches to the FVM described in this thesis enable an accurate view of the pulping process which can contribute to improved control and optimization of the process.
|
|
| 5. |
- Farrokh, Mohammad, 1964-
(författare)
-
Thermodynamic process modeling and simulation of a diaspore bauxite digestion process
- 2013
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bauxite ores which originated from separate mines have different characteristics, i.e. each bauxite ore has its own individual specifications. Jajarm bauxite is of the diaspore-chamosite type and its alumina to silica mass ratio is lower than other diaspore ores. Diaspore bauxite digestion in comparison with other bauxite types has more complicated operational conditions and requires higher temperature, pressure and caustic concentration. The present study was thus performed on the above mentioned digestion process and include two parts. First, the behavior of some key parameters of the process was experimentally investigated. Second, a simulation model was developed to predict the performance of the process, particularly thermal energy consumption. The model was validated with several sets of the industrial data and close agreement was found. The effects of various trends in pressure drops of the flash tanks on the slurry preheating were analyzed. The results showed that the proposed pressure profile can lead to an increase in the furnace inlet slurry temperature. Alternatively, it can lead to an appreciable decrease in the furnace fuel consumption, which is required for having the existing operating temperature. The generated vapor in different stages of the process was determined. A considerable amount of the generated water vapor and thermal energy were lost. The model was further developed to study the effect of using a part of these vapors on heat recovery. The simulation results showed that in the new design, the pre-heater sections can gain 5.71GJ/h additional heat and the fresh slurry temperature increases by 11°C. Therefore, the furnace required energy is reduced by 11.9%. The new design was implemented in the refinery and according to the energy department report, it has reduced the furnace fuel consumption by 8%, which is around 200kg of natural gas /h less than the earlier condition for every digestion line.
|
|
