Examensarbeten för masterexamen

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https://odr.chalmers.se/handle/20.500.12380/47

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Active aerodynamics of an autonomous car
(2023) Malali Obaiah, Samarth; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Benderius, Ola; Benderius, Ola
Autonomous cars are one of the nascent technologies being focused on by many of the major automobile manufacturing companies. These new smarter cars allow for new possibilities in terms of integrated systems such as powertrain and safety. In the same way, manufacturers are trying to integrate vehicle aerodynamics into this smart ecosystem, making the car even more efficient and with improved performance. The first step towards smart aerodynamics can already be seen in present vehicles with features like active grille shutters, an extending tail section, and, in higher-end vehicles, the change in the angle of attack for the rear spoiler. The advantage of introducing smart aerodynamics into an autonomous Formula student car is very beneficial as the system already knows the path that the car is going to take. The basic function of the system is to feed the upcoming driving trajectory into the smart aerodynamics system, which in turn adjust aerodynamic character of the vehicle for example with help of wing profiles. As a result, the car will be ready to traverse the track in a more efficient manner. The objective of this thesis is to develop a control system for the aerodynamics of the car to alter its track characteristics to best suit the needs of track topology and for other performance enhancements. Furthermore, the methods that are implemented to the car will is backed up with numerical simulation using fluid simulation software and validated through the results obtained. Various techniques have been employed to enhance the aerodynamic characteristics with combinations of rear wing and front wing angle of attack manipulation. As a result, the improvements in terms of drag and lift are achieved.
Finite Element Simulation of Energy Loss in Friction Brakes
(2023) Nikkam, Nitesh; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Lundén, Roger; Sabiniarz, Patrick
The focus of the automotive industry is shifting towards the development of electric vehicles due to the advances in battery technology and increasing environmental concerns. One of the main challenges with electric vehicles is "range anxiety" or the worry over the distance a vehicle can travel before needing to be recharged. Energy efficiency is therefore an important factor in improving the range of electric vehicles, and understanding the mechanisms that contribute to energy loss in a vehicle is crucial. Brake drag is one such mechanism, and it is estimated to account for around 3% of energy loss in a vehicle. Improving the energy efficiency of friction brakes can help address range anxiety and improve the overall performance of electric vehicles. Virtual validation of brake drag torque was carried out using the finite element tool Abaqus to validate the brake drag mechanism of a friction brake assembly on both a qualitative and quantitative level. The approach involved creating an augmented model of the friction brake assembly and defining boundary conditions and contacts to simulate the behavior of the system under static conditions. A parametric study was conducted to investigate the influence of the longitudinal stiffness of the caliper housing and friction pad lining on brake drag torque. The study also included an investigation of the impact of modifying the stiffness of the omega spring. The results of the simulations were used to mimic the relationship between brake pressure and brake drag (including the "drag knee-point") and to validate the model. The virtual environment model developed in this work can be used to quickly and accurately model and simulate different design prototypes, leading to reduced development time and optimized brake performance. The caliper housing stiffness and friction pad stiffness were found to be major factors that influence the brake drag, and the deflection behavior of the omega spring was also an important factor. It was observed that the virtual environment model can help achieve drag torque reduction with optimal brake performance. The results of the simulations were compared with existing research data and were found to be accurate. Overall, this work demonstrates the usefulness of virtual modeling and simulation in the design and optimization of friction brake assemblies.
Assessing the feasibility of replacing a specific diesel truck with a Battery Electric Vehicle using the Operating Cycle format
(2023) Emvin, Carl; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Jacobson, Bengt; Bruzelius, Fredrik; Andersson, Rickard; Romano, Luigi
While facing continuously stricter legislation due to the threat of global warming, vehicle manufacturers strive to find alternative means of transportation such as the Battery Electric Vehicle (BEV). While doing so, uncertainties regarding performance are halting the shift to more sustainable alternatives. This thesis will therefore build a framework for retailers to predict and estimate to which degree a BEV can replace a fossil-driven vehicle in specific missions. The framework will try to describe the details of transport missions while remaining relatively computationally light. This framework developed within the COVER project is called Operating Cycle (OC). It is a description of a road transport mission with an adequate level of detail that captures the physical and practical phenomenon of a transport mission. It can be divided into two sub-descriptions, the deterministic Operating Cycle (dOC) and stochastic Operating Cycle (sOC), which are the representations adopted in this thesis. Using vehicle log data from a specific Internal Combustion Engine Vehicle (ICEV), the OC format is extended to include models for Payload, Mission stop and EV-Recharging. Using the models of the OC format, a feasibility analysis of replacing a specific vehicle with a BEV is conducted. The resulting analysis shows that the current BEV fleet is not able to complete all the missions that the ICEV completed without alteration of specific transport missions.
CFD applied to decanter centrifuges
(2023) Bhat, Anirudh; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Sasic, Srdjan; Ghirelli, Federico
Decanter centrifuges have become a crucial part of numerous industrial solid-liquid separation pro cesses. Its use in dewatering of municipal sewage slurries has made it an immensely valuable tool in combating water pollution. The flow and separation of various phases through a decanter centrifuge can be influenced by a host of parameters such as the slurry rheology, the solid phase size distribution, and operational parameters of the the operation such as the mass flow rate of the slurry through the machine, geometrical design features of the centrifuge and many more. The development of a feasible and reliable computational model would facilitate the qualitative testing of the influence of many of these parameters on the performance of the decanter without relying on expensive experimental tests. In this project, computational fluid dynaimcs (CFD) has been used to model the flow of municipal sewage slurry within a decanter centrifuge. A sliding mesh approach was used to model the rotation of the decanter centrifuge and a moving wall boundary condition is applied to the surface of the centrifuge drum to simulate the speed differential. The multiphase flow equations were solved by using the Eulerian mixture multiphase model by modelling the slurry as a two phase mixture of water and the heavier phase to be separated wherein the heavier phase is modelled as a relatively thick and viscous liquid. Direct validation of the developed model against experimental data was not feasible, but a qualitative judgement about the model was made based on the literature survey and the insights provided by the decanter centrifuge manufacturer. Four test cases were run on the developed model to test how it reacts to a change in certain parameters. Three of the cases test the effect of varying the heavier phase’s viscosity and the fourth case tests the model at a higher inlet mass flow rate.
Engine lubrication system model calibration and fidelity
(2023) Tsobanoglou, Christian; Tsobanoglou, Simon; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences; Koopmans, Lucien; Carlsson, Lars-Olof; Sedarsky, David
In the present day, tough competition in the automotive industry and shorter timelines for the introduction of new passenger vehicles have forced vehicle manufacturers to cut down on de velopment time. Virtual simulations help in shortening the time vastly and increase efficiency in the development phase avoiding unnecessary waste. The engine is one of the most impor tant subsystems of a car making up the heart of any combustion-driven vehicle, the blood of this engine being the oil, making the lubrication system one of the most critical parts of any engine. With the help of today’s advanced technology, computer software programs like GT-Suite can be used to simulate and predict the oil’s behavior inside an engine in a rather accurate way. This report explores the calibration and validation process of a turbocharged four cylinders engine’s oil system and analyses its accuracy at steady- state conditions. A model of the engine’s oil system is given and the calibration process begins where nine dif ferent calibration parameters, i.e, oil flow rate multiplier, orifice hole diameters, thicknesses, and pressure drop multiplier are used. These are eventually reduced to just two parameters. The calibration process is carried through at a high main gallery pressure mode at tempera tures of 60 and 130 ◦C. Moreover, the system sensitivity is tested where different parameters like the bearing clearances and engine load among others are changed to see their effect on the simulations’ accuracy and time. The model is then validated at all pressure levels and differ ent temperatures. Successful calibration and tuning of the model have yielded highly accurate results in a rea sonably short computational time, thus achieving the most relevant part of this project.

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