abstract: An airborne, tethered, multi-rotor wind turbine, effectively a rotorcraft kite, provides one platform for accessing the energy in high altitude winds. The craft is maintained at altitude by its rotors operating in autorotation, and its equilibrium attitude and dynamic performance are affected by the aerodynamic rotor forces, which in turn are affected by the orientation and motion of the craft. The aerodynamic performance of such rotors can vary significantly depending on orientation, influencing the efficiency of the system. This thesis analyzes the aerodynamic performance of an autorotating rotor through a range of angles of attack covering those experienced by a typical autogyro through that of a horizontal-axis wind turbine. To study the behavior of such rotors, an analytical model using the blade element theory coupled with momentum theory was developed. The model uses a rigid-rotor assumption and is nominally limited to cases of small induced inflow angle and constant induced velocity. The model allows for linear twist. In order to validate the model, several rotors -- off-the-shelf model-aircraft propellers -- were tested in a low speed wind tunnel. Custom built mounts allowed rotor angles of attack from 0 to 90 degrees in the test section, providing data for lift, drag, thrust, horizontal force, and angular velocity. Experimental results showed increasing thrust and angular velocity with rising pitch angles, whereas the in-plane horizontal force peaked and dropped after a certain value. The analytical results revealed a disagreement with the experimental trends, especially at high pitch angles. The discrepancy was attributed to the rotor operating in turbulent wake and vortex ring states at high pitch angles, where momentum theory has proven to be invalid. Also, aerodynamic design constants, which are not precisely known for the test propellers, have an underlying effect on the analytical model. The developments of the thesis suggest that a different analytical model may be needed for high rotor angles of attack. However, adding a term for resisting torque to the model gives analytical results that are similar to the experimental values. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2019

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Dairy farming as one part of agriculture has thousands of year’s history. The increasingdemands of dairy products and the rapid development of technology bring dairyfarming tremendous changes. Started by first hand milking, dairy farming goes throughvacuum bucket milking, pipeline milking, and now parlors milking. The automatic andtechnical milking system provided farmer with high-efficiency milking, effective herdmanagement and above all booming income.DeLaval Automatic Milking Rotary (AMRTM) is the world’s leading automatic milkingrotary system. It presents an ultimate combination of technology and machinerywhich brings dairy farming with significant benefits. AMRTM technical milking capacityis 90 cows per hour. However, constrained by farm management, cow’s condition andsystem configuration, the actual capacity is lower than technical value. In this thesis, anoptimization system is designed to analyze and improve AMRTM performance. The researchis focusing on cow behavior and AMRTM robot timeout. Through applying knowledgediscover from database (KDD), building machine learning cow behavior predictionsystem and developing modeling methods for system simulation, the optimizing solutionsare proposed and validated. / Mjölkproduktion är en del av vårt jordbruks tusenåriga historia. Med ökande krav påmejeriprodukter tillsammans med den snabba utvecklingen utav tekniken för det enormaförändringar i mjölkproduktionen. Mjölkproduktion började inledningsvis med handmjölkningsedan har mjölkproduktionsmetoder utvecklats genom olika tekniker och gettoss t.ex. vakuum mjölkning, rörledning mjölkning, fram till dagens mjölkningskarusell.Nu har det automatiska och tekniska mjölkningssystem försedd bönder med högeffektivmjölkning, effektiv djurhållningen och framför allt blomstrande inkomster.DeLaval Automatic Milking Rotary (AMRTM) är världens ledande automatiska roterandemjölkningssystemet. Den presenterar en ultimat kombination av teknik och maskinersom ger mjölkproduktionen betydande fördelar. DeLaval Automatic Milking Rotarytekniska mjölknings kapacitet är 90 kor per timme. Den begränsas utav jordbruksdrift,tillståndet hos kor och hantering av systemet. Det gör att den faktiska kapaciteten blirlägre än den tekniska. I denna avhandling undersöks hur ett optimeringssystem kan analyseraoch förbättra DeLaval Automatic Milking Rotary prestanda genom fokusering påkors beteenden och robot timeout. Genom att tillämpa kunskap från databas (KDD), skapamaskininlärande system som förutsäger kors beteenden samt utveckla modelleringsmetoderför systemsimulering, ges lösningsförslag av optimering samt validering.

This thesis project investigates the granular flow of wood pellets inside a pilot-scale rotary kiln and its impact on the pyrolysis process. The study focuses on two key factors that must be determined to evaluate their effects on pyrolysis: the mass flow rate delivered by the feeding system at different motor frequencies and the mean residence time (MRT) of the wood pellets. The research is divided into two parts: the first characterizes granular flow without heat application, while the second examines the system behavior under high-temperature pyrolysis conditions. For the first part, the mass flow rate was assessed by measuring the emptying time of the feeding silo at different screw velocities. In contrast, the MRT was determinedwith two scenarios: (1) batches of different masses of wood pellets and (2) continuousfeed until a stable solid bed was formed that allowed tracer particle tracking. In the second part of the study, the drum’s rotational speed and fed mass flow rate were varied. Results indicated a direct proportionality between the mass flow rate delivered by the feeding systems and the screw motor frequency. Additionally, the MRT was found to follow an inverse relation with the drum’s rotational speed if the process was done in batches. In contrast, the MRT was 20 minutes at a feeding rate of 51 kg h-1 and a drum’s rotational speed of 0.36 rad s -1 with a continuous feeding process. Finally, the study concludes that the wood pellet feed rate and drum rotational speed significantly influence the pyrolysis process in the rotary kiln. The system remained stable for wood pellets inside the rotary drum, starting with a feeding rate of 8 kg h-1 and scaling up until a maximum of 21 kg h-1. This behavior is evidenced by the direct proportionality between the evolution of flue gas and pyrolysis gas temperatures over time and the necessity to adjust air supply to maintain system stability.

Doctor of Philosophy / Department of Industrial & Manufacturing Systems Engineering / Zhijian Pei / Titanium alloy is one of the most important materials used in major segments of industries such as aerospace, automobile, sporting goods, medical and chemical. Market survey has stated that the titanium shipment in the USA has increased significantly in last two decades, indicating its increased usage. Industries are always under tremendous pressure to meet the ever-increasing demand to lower cost and improve quality of the products manufactured from titanium alloy. Similar to titanium alloys, silicon carbide and dental ceramics are two important materials used in many applications. Rotary ultrasonic machining (RUM) is a non-traditional machining process that combines the material removal mechanisms of diamond grinding and ultrasonic machining. It comprises of a tool mounted on a rotary spindle attached to a piezo-electric transducer to produce the rotary and ultrasonic motion. No study has been reported on RUM of titanium alloy, silicon carbide and dental ceramics. The goal of this research was to provide new knowledge of machining these hard-to-machine materials with RUM for further improvements in the machining cost and surface quality. A thorough research has been conducted based on the feasibility study, effects of tool variables, effects of machining variables and wheel wear mechanisms while RUM of titanium alloy. The effects of machining variables (such as spindle speed, feed rate, ultrasonic vibration power) and tool variables (grit size, diamond grain concentration, bond type) have been studied on the output variables (such as cutting force, material removal rate, surface roughness, chipping size) and the wheel wear mechanisms for titanium alloy. Feasibility of machining silicon carbide and dental ceramics is also conducted along with a designed experimental study.

The aim of this thesis is to design a kilowatt three-phase step-down rotary transformer for a permanent magnet DC motor. The permanent magnet DC motor has an on-rotor drive system, and therefore requiring a power supply that can transfer power to its drive unit without mechanical contact. The rotary transformer has a detached magnetic coupling structure that qualifies it as a potential method for the wireless power transfer. This thesis studies the rotary transformer as a static device, focusing on its core loss. By using a transient finite element analysis of COMSOL Multiphysics and an iron loss prediction model, the rotary transformer was optimized in terms of efficiency and power density for the on-rotor drive system through proper material selection and geometry exploration. After this, a mechanical design, which based on a literature review of the influences of manufacturing processes on electrical steels, was proposed for realizing the core fabrication and the rotary transformer assembly. The results show that the rotary transformer can step down 400 V/50 Hz three-phase voltage to 13.15V in a Delta-wye connection and output 1.17kW power over an air-gap of 0.3mm with 95.94% overall efficiency. The proposed mechanical design enables the transformer to minimize the core loss and the manufacturing cost. Without using resonant inductive coupling, this transformer design simplifies the power supply for the motor, thereby decreasing the motor manufacturing and maintenance cost.