Examensarbeten för kandidatexamen // Bachelor Theses

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A CFD Analysis and Aerodynamic Comparison of Two Silver Arrows
(2013) Ejresjö, Fredrik; Kange, Björn; Kjellström, David; Lindbäck, Mathias; Lundell, Stefan; Mybeck, Markus; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
During 1933 to 1939 the sport of racing was completely dominated by the German manufactures Auto Union (known today as Audi) and Mercedes-Benz. With their superior race cars (named Silver Arrows after their shining bodies and blistering acceleration) the German racing teams were victorious in most of the Grand-Prix races during this period. The cutting edge technologies in these cars remain a source of inspiration for new Mercedes-Benz and Audi cars to this day. The body shape of the Silver Arrows reveal that a great deal of time was spent optimizing the cars from an aerodynamic point of view, with the purpose of minimizing flow resistance. However, the term “downforce”, which is central to design of modern race cars, was relatively unknown. Compared to the modern use of powerful computers, the possibility of making flow calculations was also very limited at the time. In this project, two Silver Arrows (Auto Union Type C and Mercedes-Benz W25) have been analyzed from an aerodynamic point of view with the main purpose of calculating lift and drag force. No CADdata was available for the cars which is why they have been modeled from scratch. Two CMC-models of the cars, scaled 1:18 were used as a baseline. These were laser scanned at Volvo Cars. Curves for both cars have been extracted from the scanned data. With the profile curves as support, the bodies of the cars were modeled in CATIA V5 and from separate measurements the details of the cars were modeled. The final CAD-models were transferred to ANSA where initial surface meshes were generated. In STAR CCM+ high quality CFD-compatible surface meshes were generated. Volume meshes were then constructed and used in the simulations. The simulations were run with the boundary conditions rotating wheels and a moving ground at 80km/h. Pitch and yaw angels were set to 0⁰. The results of the simulation were analyzed and visualized using the post processing tools in STAR CCM+. The results of the simulations show that the Silver Arrows have good basic shapes from an aerodynamic perspective, but their design also include several drag-producing features and details. Both cars have little to no downforce, which was expected due to the lack of knowledge about the phenomenon at the time. Overall, the group is content with the result of the project and considers the objectives to be fulfilled. However, because of the emphasis on the pre processing, some planned parts needed to be excluded from the project. Originally, CFD-simulations were supposed to be performed in two different velocities. Also, wind tunnel testing of the CMC-models was to be carried out, and the obtained results were to be compared with the simulations. These parts would have contributed to a more thorough analysis of the Silver Arrows, why the project group recommends further tests and simulations.
Aerodynamiska effekter vid platooning: En simuleringsstudie på Windsormodellen i olika formationer
(2019) Björkman, Albin; Ek, Paula; Jansson, Anton; Larsson, Carl; Storckenfeldt, Carl; Wirsén, Noah; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences
Platooning är ett koncept där fordon kör i grupp med korta avstånd sinsemellan. Idag är det en säkerhetsrisk att ligga nära framförvarande fordon, därför sker utvecklingen parallellt med självkörande fordon. Potentiella fördelar med platooning är bland annat att det kan leda till reducerat luftmotstånd vilket bidrar till minskad bränsleförbrukning. Detta är också fördelaktigt för exempelvis transportsektorn ur ett kostnads- och miljöperspektiv. Tidigare studier är genomförda i vindtunnel med skalmodeller för att analysera flödesfenomen vid platooning. Testerna i vindtunnel kan vara dyra och tidskrävande vilket gör att det är av intresse att analysera platooning med Computational Fluid Dynamics (CFD) - analys. I denna studie kommer de aerodynamiska effekterna vid platooning av en kolonn med tre fordon analyseras med Star-CCM+. De huvudsakliga modellerna som används är Reynolds Averaged Navier Stokes och K- turbulens. Fordonsmodellen som används i simuleringarna är en Windsormodell med hjul. Simuleringsstudien är indelad i två testserier, den första serien med varierande avstånd och den andra med varierande sidvind för tre olika intervall. Rådata från simuleringarna bearbetas och analyseras för att upptäcka trender. I studien åskådliggörs gynnsamma trender för båda dessa testserier. I simuleringarna utan sidvind är den övergripande trenden att de två bakomvarande bilarna besitter de mest gynnsamma placeringarna. När en sidvind appliceras observeras en motsatt trend. Där har istället den ledande bilen den mest förmånliga placeringen. Då sidvind appliceras ökar luftmotståndet alltid för varje placering bakåt i kolonnen. Platooning är därmed ett känsligt koncept som har potential att ge stora förbättringar på aerodynamiken om alla omkringliggande faktorer är optimala.
Aerodynamiska krafter vid hård inbromsning - Numerisk beräkning av luftmotståndskoefficient på en personbil vid hård inbromsning med två olika accelerationsmodeller
(2018) Benjaminsson, Daniel; Jarl, Sanna; Milikic, Filip; Krikor, Nerma Sarkis; Strand, Sara; Wahid, Robin; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences
Säkerhet är en faktor som idag prioriteras högt inom fordonsindutrin. En viktig del inom området är förståelsen för inbromsningsförlopp. Det är väsentligt att förstå på vilka sätt diverse faktorer påverkar ett inbromsningsförlopp. En av dessa faktorer är aerodynamiska krafter. Syftet med studien var att studera inverkan av aerodynamiska krafter på ett fordon vid hård inbromsning. Detta utfördes med hjälp av Computational Fluid Dynamics (CFD) och en DrivAer-modell för att ge approximativa numeriska resultat. Simuleringarna visade att vid hård inbromsning påverkar vaken en personbil med en kraft i samma storleksordning som luftmotståndet på bilens framsida. Det visades även att vaken välter över fordonet efter att bilen fullständigt bromsat in. Ackumulerad cD över bilens längd visade att främre delen av bilen gav ett negativt bidrag medan bakre delen av bilen gav ett positivt bidrag till cD. Det konstaterades att en spoiler i de flesta fall ger ett högre värde på cD. Vid 60-80 km/h visade sig ett jämviktsläge där resulterande cD på bilen var noll för samtliga fall. Bromssträckan blev cirka 63 meter för fallet med spoiler, utan spoiler blev den 1 meter kortare. Sammanfattningsvis är spoilerns effekt på inbromsningen liten.
Alternative powertrain. Hybridization of Formula Student car.
(2012) Martin, Strängberg; Hermansson, Fredrik; Holder, Martin; Petersson, Carl; Stenman, David; Winqvist, Håkan; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
This report investigates the hybridization of a formula student powertrain. It starts by studying different existing solutions and technologies and continues with describing the result of this project. All decisions are driven by data and well-grounded in calculations, experiences in former Chalmers Formula Student (CFS) cars, simulations and the Formula student rules (Rules 2012). The powertrain will be a parallel hybrid with a single cylinder engine of 600 cc since its weight is much lower than the current four cylinder engine, a Yamaha Fazer. An electric machine with its sprocket on the final drive chain will be used. It will also act as a chain tensioner. The electric energy will be stored in super capacitors because of their high power per weight relation. For this application high power has higher priority than high energy content. A GT Power model of the engine has been created and delivers data for making assumptions about the predicted power of the vehicle with a single cylinder engine. Regenerative braking will be applied in order to use the braking energy for acceleration when required. All components of the powertrain will be controlled by components by National Instruments and Nira using CAN communication. The components have been packaged virtually in the CFS-10 frame, since the frame of the actual car where this powertrain is intended to be mounted is not yet built.
Analysis of Composite Chassis
(2013) Andersson Eurenius, Carl; Danielsson, Niklas; Khokar, Aneesh; Krane, Erik; Olofsson, Martin; Wass, Jacob; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
This report is the result of a bachelor thesis focusing on the chassis of a Formula Student race car. The main goal of the project is to achieve a guide of how to design the perfect chassis. This is done by identifying the areas most vital to chassis performance and exploring these by studies and analyses. An introduction to what Formula Student is, how it works and why the chassis of the cars are relevant to study is provided. A brief summary of chassis design aspects is included in order make sure the reader understands the methods and results of this report. The main focus is to identify key performance indicators of a race car chassis. This requires a comprehensive analysis concerningall aspects of the chassis. Therefore, a static model is developed to investigate the effects of chassis rigidity,material options are researched on, aerodynamic properties are explored, performance simulations are conductedandguidelines forcomposite chassis design and manufacturingare established. The most important key performance indicators were found to be weight, torsional stiffness and the torsional stiffness to weight ratio. Chassis rigidity is found to decrease exponentially with increasing torsional stiffness. This led to the conclusion that, having a torsional stiffness of more than ~3 times the roll stiffness, easily adds more weight than handling performance. The choice of a carbon composite structure for the chassis over a steel space frame leads to great weight savings without compromisingon performance. Despite the disadvantages with a carbon composite chassis, namely high cost and difficulty in manufacturing, the conclusion is that the benefits outweigh the drawbacks. There are numerous material configurations available when using carbon composites and it is important to examine these configurations closely to find one that best satisfies the performance requirements. The selection process is simplified by using finite element analysis to iterate through many different configurations, such as core thicknesses, ply layups and weave types, to customize the properties of the structure. With these properties it is possible to determine chassis performance in terms of vehicle handling and rigidity.
Aspekter kring buller och vibrationer i tunga fordons transmissioner - Teori, lagkrav och tekniska lösningar
(2013) Fatic, Armin; Karlsson, David; Bohman, Frida; Frykholm, Anna-Stina; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
Autonomt miniatyrfordon - En testplattform för utveckling och utbildning inom autonoma fordon
(2017) Lillskog, Simon; Larsson, Johan; Huke, Victor; Almquist, Gustaf; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
Detta projekt har utförts på Chalmers Tekniska Högskola och har som mål att utveckla en testplattform i form av ett fordon i skala 1:14 för utveckling och utvärdering av mjukvara för autonoma fordon. Chalmers är delaktiga i utvecklingen av mjukvaran OpenDLV, open driverless vehicle, som är en open sourcemjukvara för autonoma fordon. För att enkelt och billigt kunna testa mjukvaran krävs en testplattform som dessutom ska vara enkel för intressenter att på egen hand bygga och använda. Fokus har legat på att hålla fordonets tillverkningskostnad låg och på att göra tillverkningen simpel genom att i största möjliga mån utnyttja 3D-utskrivning. För de komponenter som inte är möjliga att tillverka genom 3D-utskrift har endast internationellt lättillgängliga komponenter använts. Filerna för 3D-utskrift samt en lista på inköpta komponenter ska publiceras tillsammans med mjukvaran OpenDLV för att erbjuda ett komplett open source-paket för autonoma fordon. Fordonet har designats för att efterlikna en personbil, det drivs på bakhjulen med hjälp av en stegmotor och styrs på framhjulen med hjälp av ett servo. Fordonet kontrolleras med hjälp av enkortsdatorn BeagleBone Black samt ett expansionskort som utvecklats under detta projekt. För datainsamling om bilens omgivning kan en rad olika sensorer användas, i detta projekt har fyra ultraljudsavståndssensorer samt en kamera vilken blickar framåt använts. Gyroskop och accelerometer har också inkorporerats i designen.
Beslutsstöd för underhåll av järnvägsfordon - En studie om utökat användande av hjulskadedetektorer i det proaktiva underhållsarbetet
(2013) Bäckstedt, Karl; Karlsson, Erik; Molander, Philip; Persson, Mikael; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
CFD-analysis of the aerodynamic properties of a Mercedes-Benz 300SLR
(2015) Stadler, Michael; Nordin, Johan; Rama, Kreshnik; Sjöstrand, Philip; Falkovén, Andreas; Rask, Andreas; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
Mercedes-Benz was one of the most prominent car manufacturers in motorsport in the 50’s. In 1955 they participated with the model 300 SLR in the Le Mans 24- hour race. What made this model standing out was the mounted air brake, which would compensate for the weaker drum brakes compared with competing models’ disc brakes. During the ongoing race the world became witness to one of the most fatal accident in motorsport history, where the Mercedes in a collision flew up and crashed into the grandstand. The aim of this work was to investigate the air brake’s effect on the car’s characteristics at the crash moment. This is done by monitoring the work of Peter Gullberg and Lennart Löfdahl performed in 2008, but with a more accurate basis. A laser scanned model of the car that was obtained from Gullbergs and Löfdahl’s work in 2008 was improved to match more with the real car and to obtain accurate results in the flow simulations performed in STAR CCM+. The results obtained confirmed the earlier work in the field which indicated that the car gets an overall higher downforce with the air brake engaged compared to the down position. Additionally, a major downforce was noted on the rear axle compared to the front when the air brake was engaged.
Comparisons of the Aerodynamic Performance of two Silver Arrows from the Thirties
(2014) Bondesson, Johan; Forsting, Henrik; Gynning Olofsson, Tim; Hjält, Gabriella; Markström, Gustav; Sjösvärd, Erik; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
In the 1930’s, the motor sport was dominated by the German manufacturers Auto Union (today Audi) and Mercedes-‐Benz. Their unique cars, known as the Silver Arrows due to their visible surface of aluminium, were then by far the most outstanding race cars at the Grand Prix. Their cutting edge technology provided great striking power and even today, engineers are astonished by their feat of engineering. A Bachelor thesis from 2013 was carried out to model and to simulate two Silver Arrows (Auto Union Type C and Mercedes-‐Benz W25) in a commercial CFD software. At the time, previous CAD data were not available for the cars, thus the models were created from scratch using two CMC models in scale 1:18. The thesis reports that the large time consumption required for the CAD modelling accompanied that the work of the simulations could not be performed as desired. The purpose of the 2014 thesis was to improve the existing flow analysis of the Silver Arrows. It was done by improving the above mentioned CAD models and to execute new, more reliable simulations of these; at different speeds and angles of the cars. This project is based on a standard procedure for any CFD process; with a three-‐module workflow. The initial stage was pre-‐processing, where the previous year’s CAD models were refined in CATIA V5. For instance, both engine blocks and parts on the cars surfaces were modified to create two more realistic models of the Silver Arrows. The complete CAD models were then processed in ANSA where a surface mesh was generated and then imported into STAR-‐CCM+. In STAR-‐CCM+ a virtual wind tunnel was created and a full volume mesh was generated. The second stage was solving in STAR-‐CCM+ by performing a number of simulations. A total of 23 simulations were completed with different angles and different velocities of the cars. In the final and third stage, the post-‐processing was performed by analysing and visualizing the results of the completed simulations. By creating a number of different scenes per simulation, the changes in pressure and velocity among others could be visualized. The simulations show that the Silver Arrows are relatively well designed in an aerodynamic perspective, which mainly applies to the Mercedes-‐Benz W25. The Auto Union Type C has a much higher drag force in comparison. The cars exhibit none or almost no negative lift force, which can be expected, considered as knowledge about its significance was minor. The conclusion is that the Mercedes-‐Benz W25 is better designed in an aerodynamic perspective regardless of angles or speed of the cars. Overall, the project has proceeded according to plan. Out of the 24 simulations that were wished to conduct, 23 received reliable results. In essence, all objectives have been answered.
Design and 3D Printing of Down-scaled Passenger Vehicle Chassis
(2017) Öhammar, Anton; Grundén, Jacob; Jaleby, Jon; Arvidsson, Kristofer; Hellsten, Oskar; Medbo, Simon; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
To close the gap between the automotive industry and newly graduated engineers the graduates need to have a better understanding for how their design affects the end result. This thesis focuses on producing 3D printed suspension scale models with correct kinematics to help students better understand how different types of suspensions behave. The suspension types chosen for the models are MacPherson and double wishbone for the front suspensions and trailing arm multi link suspension and a live axle for the rear. These models were designed in Catia V5 and then 3D printed in a scale of 1:5 and assembled together with some off-the-shelf components such as coilover dampers and ball joints. The models for the MacPherson and the trailing arm are based on Chalmers suspension setups while the live axle is based on modified values of the trailing arm. The double wishbone however is primarily based on given requirements and guidelines from the Chalmers suspension setup. The two front suspensions feature functioning steering and the MacPherson one also has a differential to illustrate the function of having a propulsion system. These suspensions are mounted on two vehicle chassis where the front suspensions can be swapped so all the combinations can be shown. The curves for camber gain and bump steer are plotted for the MacPherson and double wishbone suspensions. The 3D printed models have similar kinematics to the original models. Because of the limited accuracy of 3D printing there is some play in the suspension components reducing the similarity between the curves and the real behavior when manipulating the suspensions by hand.
Design of electrical powertrain for Chalmers Formula Student with focus on 4WD versus RWD and regenerative braking
(2013) Danielsson, Oskar; Hansson, Erik; Jonsson, Isak; Mannerhagen, Felix; Molander, Patrik; Olofsson, Niklas; Pettersson, Jens; Pluto, Adam; Sahlin, Gunnar; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
This thesis describes the design of an electric powertrain for a Formula Student race car. The main focus is the comparison of RWD versus 4WD and to investigate the possibilities to use regenerative braking and torque vectoring. 2014 will be the first time that Chalmers Formula Student team will compete with an electricly powered vehicle; this thesis gives guidelines for the design. Models of the vehicle dynamics are set up to investigate the differences between RWD and 4WD. From the longitudinal dynamics model the maximum possible acceleration is calcualted which is of great importance for a race car. This model also sets the requirements for the motors and gearings. The lateral dynamics investigates the performance of the car in cornering. The advantages in using a torque vectoring system are studied. The vertical dynamics models give data about the affect of having higher unsprung mass, which in-wheel motors will cause. From these models it is evident that major advantages can be gained by using 4WD. More traction, and thus better acceleration, is gained when the tire grip of all four wheels is used. It is also possible to implement a more powerful torque vectoring system when the driving force of all four wheels can be controlled. A torque vectoring algorithm were implemented on a RC-car to be able to evaluate the concept and control algorithms. Calculations on the regenerative braking show how much energy efficiency that can be gained. The calculations also show the large benefit of combining 4WD and regenerative braking. The most important powertrain components such as batteries, motors, gears and motor controller are investigated. Recommendations of components types and important design parameters are presented.
Development of fuel efficiency improvements for a single cylinder internal combustion engine. An investigation and implementation of five fuel efficiency improving technologies on an Eco Marathon engine.
(2015) Brandt, Adam; Engelbrektsson, Anna; Hidman, Niklas; Isaksson, Oskar; Sandberg, Marcus; Settergren, Malin; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
This thesis describes the work of developing a technology demonstrating single cylinder engine for Chalmers Vera Team. The engine was to display five different technologies that could be of use to Chalmers Vera Team in the continued development of their fuel efficient engine. The first technology investigated was the use of ceramics and low-friction materials in the combustion chamber in order to reduce heat and friction losses and hence increase the thermal efficiency. Using the ideal thermodynamic Atkinson cycle was the second technology investigated as it has a higher thermal efficiency than a conventional Otto cycle engine and can be utilized by relatively small mechanical changes of the Chalmers Vera Team existing engine. Replacing the conventional electric spark plug with a laser ignition system to achieve a more efficient combustion and lower the engine heat losses were investigated as a third fuel efficient technology. The fourth technology was the use of variable compression in the combustion chamber to achieve an optimum compression ratio over the full speed operating range of the engine, in order to get a constant high thermal efficiency. Direct injection was investigated as a fifth technology and a possibly more fuel efficient method of fuel injection, specifically the air assisted direct injection system, as the Chalmers Vera Team is limited, by competition rules, to a low pressure fuel system. The different technologies were implemented into a complete technology demonstrating engine, where only the laser ignition never was actualised with a physical component. The different technologies never got tested on the engine due to lack of time, but they all showed potential to decrease the fuel consumption.
Driver Influence on Vehicle Track-Ability on Floating Bridges
(2019) Gustafsson, Adam; Svensson, Christian; Berg, Ivan; Johnsson, Jonas; Lubell, Moa; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences
The Norwegian highway route E39 consists of many different ferry connections, which results in a travel time of 21 hours for a travel distance of 1100 km from Kristiansand to Trondheim. The Norwegian government has therefore decided to invest in new infrastructure, which would reduce the travel time to about half. One of these solutions are to implement floating bridges. Floating bridges have the capacity to cross large distances such as fjords, but would also introduce motion to the vehicles driving upon it. Having waves and wind affecting the bridge, and crosswind directly affecting the vehicle, makes it difficult to assess the problem using existing theoretical methods. Therefore, a method to investigate how a moving road surface will affect the vehicle and the driver needs to be developed in this project. The study utilized a industry-grade motion driver-in-the-loop simulator. This report describes how the method for testing these driving conditions was achieved and assesses the validity of using such method. The conclusion was that the method of evaluating the driver influence on track-ability on floating bridges is functional.
Driving Simulator Interfaces for Intelligent Vehicle Evaluations on Heavy Duty Vehicles
(2016) Danielsson, Erika; Eugensson, Julia; Johansson, Victoria; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
More and more autonomous driving solutions are implemented in vehicles today. These are used as a support in traffic to reduce environmental impact, congestion and accidents. For autonomous vehicles to become a reality, all systems and the driver's reactions to these has to be tested thoroughly before the vehicles are safe enough to drive on public roads. The main objective of the project was to develop the hardware of a desktop simulator for Heavy Duty Vehicles, more specifically long haul trucks. The sponsor is Volvo Trucks North America and the project group consists of students from Chalmers University of Technology and Pennsylvania State University. An additional objective was to offer the students an opportunity to experience working in a global environment. The customer needs considered of most importance was ease of use, exibility, and portability. From these needs, six possible concepts of different simulators was generated. These concepts were compared against each other in a Pugh-matrix, with the help of the customer needs. The concept chosen for further development was a three-screen setup with two different additions; a modified gaming steering wheel and a rack holding the screens (estimated cost $8,100, 65 700 SEK). The group at Chalmers University of Technology focused on the construction of the steering wheel and the group at Pennsylvania State University built the rack. It is possible to combine both additions to one working simulator. Before building the prototype, a material selection was done with emphasis placed on sustainability and environmentally friendly materials. Since some parts of the simulator are modified and specially manufactured for this project, instructions and drawings have been made. This, in combination with simple symmetries and manufacturing processes, make the parts easy to recreate. The simulator have many possible areas of usage depending on the additions, for example autonomous systems or HMI evaluations. There is also a possibility to add a Head Mounted Display to increase the driving experience, but this requires improvement of graphics and other things. In conclusion, the simulator hardware mainly consist of COTS-parts, with some modified additions which are easy to recreate. Since the rack is foldable and placed on wheels, it is to a high degree portable, even though it does not fulfill the requirement of a desktop simulator.
Flow structure investigation of a Volvo S60
(2016) Dekker, Tim; Efremov, Efrem; Nassiri, Sam; Storm, Simon; Wallin, Björn; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
Reducing aerodynamic drag is a major goal in vehicle design and the positive impact of reduced drag on fuel consumption is well-documented. Drag is influenced by the physical phenomena around a passenger car. It is thus imperative to better understand the flow structures on a passenger car. This study investigates the flow structures occurring on the rear of a Volvo S60, conducted in STAR-CCM+. The flow structures were observed for varying Reynolds number, varying yaw angle and with and without an antenna. The results show that the pressure coefficient and skin friction coefficient change slightly at different Reynolds numbers. How they change depends on where on the vehicle the coefficients are analyzed. The varying yaw angle impacts the pressure coefficient and the skin friction coefficient by shifting the structures away from the direction of the flow. The antenna case shows that the flow is disrupted by two opposing vortices which impact the pressure coefficient and the skin friction coefficient. The skin friction coefficient and pressure coefficient changed with the velocity but this did not have any apparent effect on the drag coefficient. For the yaw angle study it was the other way around; all three parameters changed with an increase in yaw which thus meant that the flow structure on the car had a yaw angle dependency. The antenna showed a distinct alteration of the flow structure. An increase of skin friction in line with the antenna was detected from the window to the end of the boot lid. Also an increase in pressure over the bottom of the rear window could be identified. However, the antenna did not affect the drag coefficient in any significant way.
Förebyggande åtgärder mot ACL-skador inom alpin skidåkning - Redogörelse för åtgärder vid skadesituationen slip-catch
(2017) Edvardsson, Rasmus; Elfving, Hannah-Maria; Gustafsson, Carl; Krefting, Celine; Svärling, Emma; Östlund, Siri; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
En vanligt förekommande skadesituation inom alpin skidåkning är slip-catchsituationen vilken medför risk för att främre korsbandet, ACL, i knät skadas. I rapporten utreds detta skadefall genom kartläggning av knäts anatomi och biomekanik samt en analys av slip-catch-situationen. Kartläggningen och analysen ingår i en litteraturstudie tillsammans med en utredning av pjäxor, skidor och bindningar som finns på marknaden i dagsläget. Den biomekaniska kartläggningen visar att en ruptur av ACL vid skadesituationen sker vid kombinationen flexion av knät, valgus och inre rotation av tibia. Skadan uppstår till följd av förkomsten av nämnd kombination, samt att bindningen inte löser ut. Kunskapen som erhölls från litteraturstudien ligger till grund för projektets andra del. Andra delens inriktning är framtagningen av konceptförslag till produkter som minskar risken för uppkomsten av ACL-skador vid skadesituationen slip-catch vid alpin skidåkning. Fokus har legat på konceptförslag och ej på färdiga produkter på grund av projektets tidsram. Produktutvecklingen omfattar en idégenereringsfas följt av en konceptgenerering och en koncepteliminering. Elimineringen utförs mot en kravspecifikation och en elimineringsmatris, samt genom diskussion inom gruppen och med andra inom området kunniga personer. De slutgiltiga konceptförslagen vilka presenteras i rapporten är kombinationer av sensorer och olika utlösningsmekanismer vilka lösgör pjäxan från bindningen. Förhoppningen är att sensorer tillsammans med en algoritm kan detektera en slip-catchsituation på ett sätt som ej är möjligt för en mekanisk lösning. När skadesituationen detekteras skall en signal skickas till utlösningsmekanismen vilken lösgör pjäxan. För sensorerna utvärderas följande olika placeringar: sensorer fästa längs benet, sensorer integrerade i bindningen och sensorer i en sula mellan pjäxans skal och innersko. Utlösningsmekanismerna vilka bedöms potentiellt minska skaderisken mest är bindningar där häldelen kan rotera och lösa ut pjäxan från bindningen i horisontalplanet. Denna utlösningsmekanism anses vara bäst lämpad då den möjliggör en för foten naturlig rörelse och på så sätt minskar risken för skada i en catch-slip-situation.
Förgasning av träråvara för biometanproduktion- Produktion av biobränsle till Chalmers EcoMarathon
(2017) Thureborn, Emil; Andersson, Martin; Östlund, Linnéa; Larsson, Leon Hermansson; Petersson, Ivar; Hansson, Julia Björck; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied Mechanics
Det omfattande användandet av fossila bränslen har lett till stora miljöpåverkningar. Flera av världens länder är överens om att alternativa energikällor som inte bidrar till ökad växthuseffekt behöver undersökas. Biogas produceras från kolkällor som befinner sig i kolets kretslopp. Detta innebär att det anses som koldioxidneutralt, till skillnad från fossila bränslen, som befinner sig utanför kretsloppet. I detta projekt står produktion av syntesgas från termisk förgasning av barkpellets i fokus, som är det första steget i produktionen av metan som biogas. Förgasning sker då kolvätebaserat bränsle bryts ner och reagerar med vattenånga i en syrefri miljö under höga temperaturer. De önskade produkterna är kolmonoxid och vätgas, som i era delsteg vidare i processen reagerar och bildar metan. Förgasningsförloppet har studerats, modellerats och experimenterats på för att kunna avgöra design- och driftparametrar för en förgasare i liten skala. Detta inkluderar bland annat modellering av bränslematningsfrekvens, energiförbrukning, uppehållstid samt experiment på befintlig förgasare och TGA-experiment på biobränslet som ska användas. En stor del av arbetet har dessutom bestått av materialval och konstruktion av själva förgasaren. Slutsatsen är att förgasning av biobränsle är genomförbart i liten skala, men att den termiska verkningsgraden blir betydligt lägre än för en anl
Hardware development on an autonomous formula car: A Chalmers formula student driverless project
(2019) Brokelind, Hugo; Burgman, Oskar; Calsson, David; Eklund, Edvin; Forsman, Oscar; Miltén, Petter; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences
The autonomous driving industry is currently growing rapidly due to the large demand created by our society. Formula student, the largest student engineering contest in the world, assesses the automobile production by developing and competing with formula cars. Formula student driverless is one of the branches of the large competition, Chalmers University of Technology is one of the represented universities with two attending teams. The role of this bachelor’s group is to be a part of the 2019 Chalmers formula student driverless team and maintain and develop the hardware of the car. The thesis is separated into three different sections, where each section describes a problem solving process. The sections are: the aerodynamic package, the steering actuation and the computer case. The aerodynamic package was designed for a formula car driven manually at a different speed than the current autonomous system. Therefore, an analysis of the current aerodynamic package was performed. The results were generated through simulation methodologies and it was decided that the aerodynamic package was sufficiently valuable to the car’s performance. To analyse the steering actuation, tests were made comparing sent steering requests to readings of potentiometers mounted on the linear actuator and on the steering rack. The conclusion was that the steering system had drawbacks such as play and complexity, but it was kept since it is robust and the time needed to rebuild the system could not be justified. The computer case’s function is to protect the computer from water and dust while also enabling cooling of the components. The case created in 2018 was deemed inadequate for the competition. Therefore a new case where developed to replace the old one. Different concepts were generated and condensed into a final prototype which was manufactured. The final product fulfilled the requirements to confine the computer in a water and dust proof casing. By implementing a quantitative and qualitative analysis of the three projects, a conclusion was drawn deciding that the aerodynamic package was the most valuable project to score points in the formula student driverless competition. All things considered, the entire result generated an advantageous score to the competition.
Konstruera och bygga en autoklav för härdning av kompositer i Chalmers kompositverkstad
(2018) Bredenberg, Tobias; Karlsson, Johan; Holmberg, Fredrik; Barreng, Petter; Forsström, Birk; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime Sciences
För att fortsätta försörja arbetsmarknaden med nyutexaminerade studenter från Chalmers och göra nya framsteg inom forskning krävs utveckling. Arbetet uppnår detta genom att konstruera en autoklav till maskinhusets kompositverkstad. I det första skedet används systematisk utvecklingsmetodik för att kunna ta fram koncept. Sedan genomfördes dimensionering av autoklaven med hjälp av handberäkningar på hållfastheten och uppvärmningsystemet. Följt av detta gjordes modellering med hjälp av CATIA v5, där modellerna sedan användes för simuleringar i finita elementprogrammet ANSYS 18.2. Dimensioneringen av reglersystemet genomfördes med hjälp av simuleringar i systemdesignsprogrammet Simulink. Med hjälp av dessa verktyg har gruppen tagit fram en konstruktion med tillhörande ritningar och komponenter. De huvudsakliga komponenterna är ett tryckkärl med dimensionerna ?508 × 1190 mm, ett reglersystem baserat på en Raspberry Pi 3+ och ett uppvärmningssystem med maximal effekt på 2, 3 kW. Autoklaven är dimensionerad för arbetstrycket 0, 7 MPa och högsta temperaturen 150 C. Styrsystemet visar när autoklaven är i drift och stänger av vid eventuella fel. Om styrsystemet skulle haverera finns en mekanisk övertrycksventil som försäkrar om att trycket släpps ut. Abstract To keep the supply of alumnae going from Chalmers and to make new research possible innovation is needed. This project achieves this through the design of an autoclave intended to be used in Chalmers new composite workshop. In the first phase of the project a systematic development method was used. In the next phase the product was designed with tools like basic calculations of the structural integrity and the heating system. Then models were made in CATIA v5 and simulated with the finite element method in ANSYS 18.2. A model for the control system was developed and simulated in the system design program Simulink. With the help of these tools the project group has made a complete design with blueprints and components. The major components are; a pressure vessel with the dimensions ?508 × 1190 mm, a Raspberry Pi 3+ based control system and a heating system with the maximal active power 2, 3 kW. The autoclave is designed for a working pressure of 0.7 MPa and maximal temperature of 150 C. The control system indicates when the autoclave is in use and shuts down when any errors occur. If the control system where to malfunction a mechanical pressure valve guarantees safety by releasing the air. The report is written in Swedish.

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