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  • Post
    Handling increased need of maintenance to meet future freight demands: Deterioration and effective maintenance strategies for track system and rail vehicles
    (2022) Mattsson, Klara; Lee, Jaseung; Ligmajer, Oskar; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Kabo, Elena; Ekberg, Anders
    This report addresses future increased demands of freight on the Swedish railways. To achieve an increase in total freight, different forms of operations can be utilized like increasing the axle load, speed, or frequency which are all scenarios that will be evaluated in the report. The impact caused by those measures will affect both deterioration and the need for efficient maintenance regarding rail vehicles and track systems. Different methods of maintenance, both currently used and newly developed methods are discussed in this report to be able to evaluate how it is possible to become more efficient. The deterioration that occurs during the operation of freight trains is described in the report since an understanding is needed to address the problems and possible solutions. What also plays a vital role in the maintenance plan is to detect faults efficiently. To get an idea about how all of these issues are handled in the industry, interviews have been held with professional staff at four large companies in Sweden. Together with literature studies, this forms the foundation of this report.
  • Post
    Increasing freight transport capacity
    (2022) Carlsson, Johan; Edberg, Marcus; Gullberg, Viktor; Nieswand, Niklas; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Kabo, Elena; Ekberg, Anders
    The main objective of this report is to investigate how freight train capacity can be increased to enable transportation related to carbon capture and storage (CCS) on the Swedish railway system in order to achieve the carbon dioxide climate target. The increased need for sustainable transport will create a large demand on the existing railway network. To meet these demands, several measures need to be taken. To investigate this further, literature study, interviews, a case study and analysis of the current network were conducted. As the railway network is a complex system, a range of measures is suggested to counter a high capacity utilization within both shorter and longer time frames. In the report several line segments limiting the system capacity were identified. Several measures were suggested with regards to both railway infrastructure and train set-up. It is concluded that additional investments have to be made to handle ccs transportation.
  • Post
    Flow uniformity characterization in catalytic converters under turbulent inlet conditions
    (2022) Tylén, Oskar; Larsson, Jacob; Murali, Aravind; Rangaswamy, Sunil; Peyvandi, Ehsan; Larsson, Axel; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Johansson, Håkan; Ström, Henrik; Sjöblom, Jonas; Nagarajan, Pratheeba Chanda
    In the sectors utilizing the combustion of fossil fuels, catalytic converters are commonly employed to reduce dangerous gases generated by combustion engines. For greater efficiency, it is critical to understand the exhaust flow homogeneity inside the converter. This work attempts to evaluate the added value of using Detached Eddy Simulation (DES) simulation over Reynolds-Averaged Navier-Stokes (RANS) simulation for analysis of turbulent flow inside catalytic converters. The meshing and simulation of the domain was carried out using ANSYS FLUENT and ANSYS Workbench. Initially a RANS simulation with k-ω SST turbulence model was carried out for a specific case to understand the behavior of the time averaged flow field with modeled turbulence and its effect on uniformity index. The results from the RANS simulation were, together with definitions of turbulent length scales, used to develop a mesh for DES simulation. In this process it was found that in order to resolve a sufficient amount of turbulence upstream of the monolith inlet, the DES simulation required a considerably finer grid than the RANS simulation. The DES simulation with k-ω SST model was used to simulate multiple retention times, attempting to achieve a quasi steady flow with resolved velocity fluctuations. However due to constraints on computational power, simulating until statistical convergence was not possible. The time averaged quantities were extracted from the DES simulation in order to make a fair comparison with RANS results. The uniformity indices of RANS and DES were then compared throughout the monolith of the catalytic converter. A difference of ∼1-1.5% in uniformity index was found from this comparison. Further more it was found that the resolved turbulence in the DES generates fluctuations of ∼3-6% in the uniformity index based on instantaneous quantities. The work concludes that for the exact case simulated, the possibility of increased accuracy when predicting uniformity index with DES instead of RANS does not outweigh the increased computational cost. However for different flow conditions, with larger mean velocity magnitude and less uniform flow, the measured difference between RANS and DES could make a larger difference for prediction of catalytic conversion efficiency. Hence in these cases it is possible that DES simulations are worth their computational cost. Whether this is the case or not would have to be examined through further research before coming to any definitive conclusions.
  • Post
    Model Exchange for Virtual SIL/MIL Verification of Passenger Cars with Electric Axles
    (2022) Tsobanoglou, Christian; Jayanna Kundur, Ganesh; Siam Siraj, Mohammad; Anil Kumar Nikkam, Nitesh; Tsobanoglou, Simon; Ramakrishnan Bharadwaj, Varun; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Sjöblom, Jonas; Jacobson, Bengt J H
    In the present day, stiff competition in the automotive industry and shorter timelines for introduction of new passenger vehicles has forced vehicle manufacturers and component suppliers to cut down on development time. Virtual simulations help in bringing down this time drastically and are a critical phase in the design and development of new vehicles. Multiple subsystems make up a vehicle and these subsystems need to be tested before being used in production. In the case of system development in electric vehicles, virtual verification of subsystems early in the project phase is important given the platform modularity of the driveline in such a scenario. It also helps if the simulation models are modular, since model exchange between vehicle manufacturer and subsystem suppliers have to take place to build virtual prototypes. This report explores the modelling and simulation of such type of modular drivetrain for electric passenger vehicles. The modelling of drive axle as a subsystem is a key aspect in this project. Three types of drive axles, i.e., Torque Vectoring Dual Clutch (TVDC), Electric Torque Vectoring (e-TV) and an Open Differential axles are considered. Modelling the powertrain, specifically the motor, is done to determine the energy consumption of this driveline. Modellica language uses an equation-based modelling approach which has a higher flexibility when compared to the library-based modelling. For this reason, the open-differential model was modelled in Modellica and was exported as a Functional Mockup Unit (FMU). The TVDC model and the e-TV model is given as inputs by the concerned stakeholders from the project. Further, these models were integrated with a control model and a vehicle model in a VVE, namely, IPG CarMaker. To establish a comparison between these different models, vehicle performance and energy consumption of these drivelines were studied. Validation and verification of the developed models were carried out as a precursor to simulation in the project. Sanity check of the model was done to make sure that the given vehicle does not run off the desired path. This ticks off the basic physics involved in the models. This was an iterative process based on the validation results of the models. Further, to draw a comparison between the different powertrains, the models were simulated with an open diff at the rear wheel (RWD) as a reference. Plots for dynamic variables and energy were used to analyze the results and compute measures like vehicle performance and energy consumption. AWD, as expected, performed the best in terms of vehicle stability. However, the interesting comparison was between e-TV and the TVDC models. To establish a comparison for the RWD configurations, the open differential at the rear axle is taken as a reference. Apart from the deduced results, the most relevant aspect of the project, i.e., the modularity of the subsystems (specifically, the drive axles) was achieved. i
  • Post
    Pilot Naturalistic Riding Study (NRS) with VOI e-scooters to improve traffic safety
    (2022) Schmidt, Daniel; Lindelöw, Fredrik; Gunashekara, Gowtham; Pai, Rahul Rajendra; Chalmers tekniska högskola // Institutionen för mekanik och maritima vetenskaper; Sjöblom, Jonas; Bianchi Piccinini, Giulio; Dozza, Marco; Dankert, André
    Increase in traffic and emissions resulting from the rise in vehicle population and the first/last mile issue associated with the use of public transport has led to a rise in the micro-mobility market. The e-scooters take a major share of this market and can be attributed to the e-scooter rental service. Introduction of e-scooters into the traffic environment has resulted in new traffic conflicts hence, possible hazards that can lead to new types of near-crashes or crashes. To better understand how e-scooters interact with other road users and identify underlying risk factors that may lead to a crash, naturalistic data collection is a suitable tool for proactive traffic safety work. In fact, the naturalistic data offer the unique opportunity to understand the cause of crashes and the genuine road user behaviour in critical situations. In the past, naturalistic data has been collected mainly from motorized vehicles. In this pilot project an e-scooter has been equipped with a data logger that is connected to cameras and numerous on-board sensors. The sensors provide kinematic information of the e-scooter while the cameras provide a visual representation of the ride environment. Each of the hardware components is placed in a casing developed with additive manufacturing technologies. The data collected is stored locally and then can be transferred to a computer for data analysis. The data collection has been carried out in two stages with the initial one being to identify any vulnerability of the system. The second set of data collection include participant-based riding data. Graphical User Interface (GUI) has been developed to enable easier analysis and visualisation of the data. Several other tools required for data processing along with the GUI have been developed using MATLAB. These tools will enable frame by frame analysis of the ride and aid in the understanding of the cause of every critical event recorded. This thereby enables detection of the causation mechanism behind the safety-critical scenarios. The project has proven that it is fully possible to equip an e-scooter with instrumentation for naturalistic data collection. A GUI has been proven to be a necessary asset when it comes to evaluating the logged data. The results from this pilot study may be the basis for a large naturalistic data collection, that may cast light on safety of e-scooters.