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Controlled Start Transmissions (CST) can be described as a mechanical transmission combined with a wet clutch for controlled torque output. CST:s are commonly used to start up heavy loads for example mining conveyors. Several CST:s can work together to share the load. The transferred torque is controlled by a hydraulic wet clutch which is a proven technology for high torque transfer and low wear. This thesis is a part of a project to increase the knowledge and improve the CST design and control performance. The heat generation in the wet clutch is the focus of this thesis. Literature review shows that most research is done in order to get high accuracy for smaller clutches and most of the high torque engagements have very short transients.Models for the CST clutch heat generation together with thermal behavior have been developed and investigated. This includes a temperature model together with a kinetic model of the gearbox and a clutch torque model. Validation of separate model components and sensitivity analysis of the parameters are made. The developed model is then analyzed by comparing measurements from a commission site and simulations to get an idea of how much heat is generated.

A model to predict air temperatures inside a residential home was created, which used local and remote environmental sensor data. Space conditioning experiments were carried out in the residential home and models were created to describe the observed temperature data. Results from laboratory space conditioning experiments were used to create a new experimental prediction model. Static inputs of the experimental model were replaced with dynamic inputs and an improved model was created, capable of general prediction application in the residential home. A novel system for space conditioning control was designed, which applied the improved model for air temperature prediction. Initial prediction models showed prediction error margins of ±1°C. Residential home and laboratory space conditioning experiments were utilized to create non-linear temperature prediction models capable of application outside of the experimental scope. Improved prediction models were based on the experimental models and showed average error margins of ±0:12°C compared to observed temperature data. A novel system design was proposed, combining the improved model with a traditional heating control to create a new optimal start-stop heating application for residential homes.

Laser-assisted machining has been considered as an alternative for difficult-to-machine materials such as metallic alloys and ceramics. Machining of some materials such as high chromium alloys and high strength steels is still a delicate and challenging task. Conventional machines or computer numerical control (CNC) machines and cutting tools cannot adapt easily to such materials and induce very high costs for operations of rough machining or finishing. If laser-assisted machining can be implemented successfully for such materials, it will offer several advantages over the traditional methods including longer tool life, shorter machining time and reduced overall costs. This thesis presents the results of the research conducted on laser assisted machining of hard to wear materials used in making heavy duty mineral processing equipment for the mining industry. Experimental set up using a high power Nd:YAG laser beam attached to a lathe has been developed to machine these materials using cubic boron nitride (CBN) based cutting tools. The laser beam was positioned so that it was heating a point on the surface of the workpiece directly before it passed under the cutting tool. Cutting forces were measured during laser assisted machining and were compared to those measured during conventional machining. Results from the experiments show that with the right cutting parameters and laser beam position, laser assisted machining results in a reduction in cutting forces compared to conventional machining. A mathematical thermal model was used to predict temperatures within the workpiece at depths under the laser beam spot. The model was used to determine the effect of various cutting and laser parameters on the temperature profile within the workpiece. This study shows that laser assisted machining of hard to wear materials such as high chromium white cast iron shows potential as a possible economical alternative to conventional machining methods. Further research is needed before it can be introduced in industry as an alternative to conventional machining.

This thesis concludes a description of construction and functions of Electronically commutated motors. The main target is modelling of thermal field of Electronically commutated motors. For modelling was chosen Ansys Workbench setting with CAD geometry. There was a measurement for verifying result of simulation, and its proof is described in my thesis. This project also concludes comparison of results from simulation itself and results obtained from measuring thermal profile of EC motor.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / AFRIKAANSE OPSOMMING:Die navorsing wat hier uiteengesit word ondersoek die hipotese dat kondensasie en die gevolglike verdamping van water wat teenwoordig is in die uitlaatgas van ‘n binnebrandenjin, plaasvind in die gedeeltes van die uitlaatstelsel tussen die uitlaatklep en die katalitiese-omsetter se uitlaat. Daar word verder veronderstel dat hierdie tweefasevloeieffekte die tydafhanklike temperatuurprofiele in die uitlaatstelsel beïnvloed, wat moontlik kan lei tot ‘n vertraging in die tydsduur vir die katalitiese omsetter om temperature van 200-300 °C te bereik, wat nodig is om noemenswaardige omsetting te bewerkstellig. Om hierdie veronderstelling te evalueer is ‘n tydafhanklike, eendimensionele wiskundige model van die termo-vloei gedrag in die uitlaatstelsel gedurende ‘n koue inwerktreeding, insluitende vogtigheidseffekte, opgestel en opgelos deur van ‘n rekenaaralgoritme gebruik te maak. Warmte- en massaoordragsteorie was gebruik om die ongestadigde massa-, energie- en momentumbehoudsvergeleikings te formuleer. Die tweefasige vogeffekte was gemodelleer deur gebruik te maak van die verhouding tussen warmte- en massaoordrag, wat verdamping en heterogeniese kondensasie (die kondensasie van damp teen die pypwand) voorspel as gevolg van die dampdrukgradient tussen die grootmaat damp en die versadigde damp by die oppervlak van die vloeistoffilm. Homogene kondensasie (die kondensasie van vloeistof in die vorm van druppels in die dampstroom) was ook in aanmerking geneem indien die grootmaatgas temperatuur onder die versadigingstemperatuur van die grootmaatdamp gedaal het. ’n Eksperimentele ondersoek was gedoen deur van twee enjins gebruik te maak, ’n 1.6 L Volkswagen Bora en ’n 1.6 L Ford RoCam, in die toetsselle van Cape Advanced Engineering Pty (Ltd). Om die gastemperature so akkuraat moontlik te meet, was spesiale radiasiegeskermde sensore met vinnige reaksietyd ontwerp en installer in die pypseksies van die uitlaatstelsels van beide enjins. Die geskermde sensore het temperature van tot 50 °C hoër as konvensionele termokoppels in dieselfde areas gemeet. Dit is in koers is met resultate wat deur die foutbeperkingsteorie, geassosieer met die meet van temperature in vloeïende gas in uitlaatstelsels, voorspel word. Vergelyking van die numeriese simulasie met die eksperimenteel gemete temperature het aangedui dat in dele van die uitlaatstelsel voor die katalitieseomsetter, die vog min uitwerking het op die termiese gedrag van die stelsel. In hierdie gedeeltes is die konveksie warmte-oordrag dominant. In die katalitieseomsetter was die vogeffekte invloedryk. Die eksperimentele resultate toon ‘n duidelike vroeë toename in die gastemperature, gevolg deur ‘n tydperk van konstante temperature by nagenoeg die versadigingstemperatuur van die grootmaatdamp (verwys na as die temperatuurplato) by die katalitiese-omsetter se kern en uitlaat. Die numeries gesimuleerde gastemperature het ook hierdie gedrag getoon, maar ‘n baie hoë en skerp piek by die begin van die plato het voorgekom. Hierdie piek was nie te sien by die eksperimentele resultate nie en is toegeskryf aan nie-ewewigstoestande in die verdampingsproses, wat aandui dat die tempo van verdamping wat deur die massa-oordragmodel voorspel word te hoog is vir die model en dat dit verfyn moet word. Verdere ondersoek van die invloed van die individuele massa-oordragprosesse het getoon dat die homogene kondensasie die dominante proses is in die vorming van vloeistof in die katalitiese-omsetter. Heterogeniese kondensasie het plaasgevind, maar ‘n kleiner massa vloeistof is produseer. Die maksimum hoeveelheid vloeistof wat voorspel is om in die katalitiese-omsetter te vorm was 12 g/cm wat gelykstaande is aan ‘n film van 0.05.mm dik indien eweredig versprei oor die binneoppervlak van die monoliet. Daar was in die simulasie gevind dat beide verdamping en kondensasie benodig word om die temperatuurplato te simuleer, vanwaar die gevolgtrekking gemaak kan word dat beide prosesse wel plaasvind en dat die eerste stelling in die oorspronklike hipotese wel geldig is. Daar was egter teen die einde van die toetsperiode gevind dat beide temperature wat met en sonder vogeffekte simuleer was, die eksperimentele temperature nagevolg het, wat aandui dat die invloed van vog beperk is tot die vroeë stadiums van die katalitiese-omsetter se opwarmingstydperk. Die tweede gedeelte van die hipotese wat veronderstel dat die voggedrag ‘n vertraging in die tydsduur om omsetting te bewerkstellig veroorsaak, is dus bevind om ongeldig te wees. Die wiskundige model wat opgestel is tydens die ondersoek is weens noodsaaklikheid ‘n vereenvoudigde simulasie van komplekse termo-vloei prosesse. Dit dien as nuttige grondwerk vir verdere in-diepte ondersoeke en afronding van die teorie met betrekking tot voggedrag en die uitwerking daarvan op die tydsafhanklike temperature in ‘n uitlaatstelsel. / ENGLISH ABSTRACT: The research presented here investigates the hypothesis that condensation and subsequent evaporation of water vapour present in the exhaust gas of an internal combustion engine occur in the sections of the exhaust system between the exhaust port and the catalytic converter exit. It is further hypothesised that these two-phase moisture effects influence the transient temperature profiles in the exhaust system, and potentially cause a delay in the time it takes for the catalytic converter to reach temperatures of 200-300 °C, which are required for light-off to occur. In order to evaluate this hypothesis a transient, one-dimensional mathematical model of the thermo-fluid behaviour in the exhaust system during a cold start, including moisture effects, was created and solved by means of a computer algorithm. Heat and mass transfer theory was used to formulate the unsteady conservation equations for mass, energy and momentum. The two phase moisture effects were modelled using the analogy between heat and mass transfer, which predicts evaporation and heterogeneous condensation (the condensation of vapour against the pipe wall) due to a vapour pressure gradient between the bulk vapour and a saturated vapour at the surface of the liquid film. Homogeneous condensation (the condensation of liquid in the form of droplets in the gas stream) was also accounted for if the bulk gas temperature dropped below the bulk vapour saturation temperature. An experimental investigation was performed using two engines, a 1.6.L Volkswagen Bora and a 1.6.L Ford RoCam, in the test cells of Cape Advanced Engineering Pty (Ltd). In order to measure the gas temperatures as accurately as possible specialised radiation shielded sensors with fast time response were designed and installed in the pipe sections of the exhaust systems of both engines. The shielded sensors measured temperatures up 50 °C higher than the conventional thermocouples installed at the same positions, which is in keeping with the results predicted by the theory governing errors associated with temperature measurement in the flowing gas in the exhaust system. Comparison of the numerically simulated and experimentally measured temperatures indicated that in the sections of the exhaust system leading up to the catalytic converter the moisture has little influence on the temperature behaviour of the exhaust system. In these sections the convective heat transfer is dominant. In the catalytic converter the moisture effects were found to be influential. The experimental results clearly show an early rise in the gas temperatures, followed by a period of constant temperature at approximately the saturation temperature of the bulk vapour (referred to as the temperature plateau) at the catalytic converter mid-bed and exit. The numerically simulated gas temperatures also exhibited this plateau, but an initial very high and sharp peak in the simulated gas temperatures occurred at the start of the plateau. This was not seen in the experimental results and is attributed to non-equilibrium in the evaporation process, indicating that the rate of evaporation predicted by the mass transfer model used is too high for this application and that the model needs to be refined. Further investigation of the influence of the individual mass transfer processes indicated that the homogeneous condensation is the dominant process in the formation of liquid in the catalytic converter. Heterogeneous condensation was found to occur, but produced a smaller mass of liquid. The maximum amount of liquid predicted to form in the catalytic converter was 12 g/cm, which translates to a film 0.05 mm thick if evenly distributed over the inner surface of the monolith. In the simulation it was found that both evaporation and condensation are needed in order to simulate the temperature plateau, from which it was concluded that both these processes do occur and the first statement in the original hypothesis is valid. However, by the end of the test period temperatures simulated both with or without the moisture effects closely approached the final temperatures of the experimental investigation, indicating that the influence of the moisture is limited to the early stages of the catalytic converter warm-up. The second part of the hypothesis, postulating that the moisture behaviour caused a delay in the time taken to reach light-off temperature, is therefore concluded to be invalid. The mathematical model constructed in this research is by necessity a simplified solution to complex thermo-fluid processes. It serves as useful groundwork for further elaboration and refinement of the theory related the moisture behaviour and its influence on the transient temperatures in the exhaust system.

Dynamic modelling and optimization of three different processes namely (a) bulk polymerization of styrene, (b) solution polymerization of methyl methacrylate (MMA) and (c) emulsion copolymerization of Styrene and MMA in batch and semi-batch reactors are the focus of this work. In this work, models are presented as sets of differential-algebraic equations describing the process. Different optimization problems such as (a) maximum conversion (Xn), (b) maximum number average molecular weight (Mn) and (c) minimum time to achieve the desired polymer molecular properties (defined as pre-specified values of monomer conversion and number average molecular weight) are formulated. Reactor temperature, jacket temperature, initial initiator concentration, monomer feed rate, initiator feed rate and surfactant feed rate are used as optimization variables in the optimization formulations. The dynamic optimization problems were converted into nonlinear programming problem using the CVP techniques which were solved using efficient SQP (Successive Quadratic Programming) method available within the gPROMS (general PROcess Modelling System) software. The process model used for bulk polystyrene polymerization in batch reactors, using 2, 2 azobisisobutyronitrile catalyst (AIBN) as initiator was improved by including the gel and glass effects. The results obtained from this work when compared with the previous study by other researcher which disregarded the gel and glass effect in their study which show that the batch time operation are significantly reduced while the amount of the initial initiator concentration required increases. Also, the termination rate constant decreases as the concentration of the mixture increases, resulting rapid monomer conversion. The process model used for solution polymerization of methyl methacrylate (MMA) in batch reactors, using AIBN as the initiator and Toluene as the solvent was improved by including the free volume theory to calculate the initiator efficiency, f. The effects of different f was examined and compared with previous work which used a constant value of f 0.53. The results of these studies show that initiator efficiency, f is not constant but decreases with the increase of monomer conversion along the process. The determination of optimal control trajectories for emulsion copolymerization of Styrene and MMA with the objective of maximizing the number average molecular weight (Mn) and overall conversion (Xn) were carried out in batch and semi-batch reactors. The initiator used in this work is Persulfate K2S2O8 and the surfactant is Sodium Dodecyl Sulfate (SDS). Reduction of the pre-batch time increases the Mn but decreases the conversion (Xn). The sooner the addition of monomer into the reactor, the earlier the growth of the polymer chain leading to higher Mn. Besides that, Mn also can be increased by decreasing the initial initiator concentration (Ci0). Less oligomeric radicals will be produced with low Ci0, leading to reduced polymerization loci thus lowering the overall conversion. On the other hand, increases of reaction temperature (Tr) will decrease the Mn since transfer coefficient is increased at higher Tr leading to increase of the monomeric radicals resulting in an increase in termination reaction.