Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 70-71).

Made available in DSpace on 2014-06-11T19:30:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-08Bitstream added on 2014-06-13T20:00:02Z : No. of bitstreams: 1 sugahara_d_me_guara.pdf: 1088347 bytes, checksum: a45380105015e0a3025c75e707484f21 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Esse trabalho destina-se ao estudo da relação entre as condições de operação e o nível de emissão de CO2 em um forno de soleira rotativa, a óleo, utilizado para o reaquecimento de blocos de aço carbono para forjamento de rodas ferroviárias. O foco principal foi a redução na emissão de CO2 e a possibilidade de geração de créditos de carbono. Inicialmente foram apresentadas as características do sistema de aquecimento e suas influências no desempenho geral do forjamento. Em complemento foram expostas algumas condições de emissões relacionadas ao combustível e ao funcionamento do sistema de combustão. Foram selecionados parâmetros para a correção das condições de operação e ajustados para o tipo de combustível utilizado. A verificação foi feita através de análises de atmosfera. A metodologia foi eficiente e mostrou uma redução de 0,5% na concentração de CO2 nos gases de combustão que equivale a uma redução de 3,6% na emissão total de CO2. / This work studied the relation between the operation condition and the level of CO2 emission in an oil rotary furnace used to reheat steel carbon blocks to forge rail wheels. The main focus was a CO2 reduction emission and carbon credits revenue. Initially, the heating system characteristics and its influence in the forging performance were presented. Additionally, some emission conditions related to the fuel and combustion system working were exposed. Parameters were selected to correct the operation condition and adjusted to the type of the fuel used. The results were verified by atmosphere analysis. The methodology was efficient and shows 0,5% reduction in the concentration of CO2 in the combustion gases or 3,6% reduction in CO2 total emission.

Submitted master’s thesis deals with rotary draw bending of tubes as a subprocess of automobile’s stabilizer bar production. The main goal of the thesis is to clarify the influence of the process parameters of the bend on the resulting shape and properties of the product. Submitted thesis includes theoretical description of the chosen tube bending technology, description of defects and possibilities of their removal. The description of the bending machine used for stabilizer bars production is done afterwards. Practical part of the thesis includes experiments clarifying influence of parameters on the resulting shape of the stabilizer bar.

Stiffness identification of an impacted constraint is the main issue discussed in this thesis. Primarily, a change of stability (bifurcation) is used to determine the dynamical stiffness of an impacted beam for a piecewise-linear impact oscillator. Detailed one- and two-parameter bifurcation analyses of this impacting system are carried out by means of experiments and numerical methods. Particularly, the two-parameter numerical continuation of the obtained codimension-one bifurcation (period-doubling bifurcation, or fold bifurcation) indicates a strong monotonic correlation between the stiffness of the impacted beam and the frequency at which this bifurcation appears. In addition to the bifurcation techniques, another method for stiffness identification is analysis of impact duration. To accurately detect impact durations from numerical or experimental signals, nonlinear time series methods are utilised. Two impacting systems, including the piecewise-linear impact oscillator and a drillbit-rock vibro-impact system, are studied to demonstrate this proposed method. For either system, the impact duration is relatively constant when the response of oscillator is a period-one one-impact motion, and it is approximated as a half of the natural period of the oscillator-constraint system. When the mass of oscillator is constant, for an impacted constraint with a certain stiffness, the higher the stiffness, the lower the impact duration. This monotonic correlation provides another mechanism to estimate the stiffness of the impacted constraint. Based on the developed two dynamical methods for stiffness identification, a control algorithm for parameter adjustment of the axial vibration for rotary-percussive drilling applications is designed. This control algorithm aims to maintain the optimal drilling state under the varying formations. By this way, the efficiency of rotary-percussive drilling is expected to be promoted.

This master thesis deals with design of compression part of Braysson engine which is instrumental to energy producing. The first part addresses generally the problem of Braysson cycle and briefly sums the knowledge about compressors. The next part focuses on the projection of design itself. It contains proposals of various possibilities of solutions, choice of optimal variants. Individual parts of the machine are described and design and control computations are provided. The final part contains evaluation.

This work focuses on an innovative Rotary Displacer SE (RDSE) configuration for Stirling engines (SEs). RDSE features rotary displacers instead of reciprocating displacers (found in conventional SE configurations), as well as combined compression and expansion spaces. Guided by the research question "can RDSE as a novel configuration achieve a higher efficiency compared to conventional SE configurations at comparable operating conditions?", the goal of this study is to characterize, analyze, and optimize RDSE which is pursued in three technical stages. It is observed the RDSE prototype has an optimum phase angle of > 90° and thermal efficiency of 15.5% corresponding to 75.2% of the ideal (Carnot) efficiency at the source and sink temperatures of 98.6° C and 22.1° C, respectively. Initial results indicate that 125° phase angle provides more power than that of the theoretically optimum 90° phase angle. The results also show comparable B_n and significantly higher W_n values (0.047 and 0.465, respectively) compared to earlier studies, and suggest the RDSE could potentially be a competitive alternative to other SE configurations. Furthermore, due to lack of a regenerator, the non-ideal effects calculated in the analytical approach have insignificant impact (less than 0.03 kPa in 100 kPa). The clearance volume in the shuttled volume has a dramatic negative effect and reduces the performance up to 40%. Ultimately, utilizing CFD, it is proved that the existing geometry is relatively optimized where the optimum phase angle is 121° and geometric ratio D\/L for the displacer is 0.49.

The preparation of a glide path prior to the use of rotary nickel titanium instrumentation reduces torsional stress and the risk of rotary nickel titanium instrument separation. The objective of this in vitro study was to evaluate 3 different glide path preparation techniques in respect of:  Percentage change of curvature from original canal anatomy; and  The occurrence of aberrations in canal anatomy (ledging, zipping and elbows). One hundred and twenty S-shaped Endo-Training-Blocks were selected. The canals were injected with India ink dye. The blocks were indexed with 3 bur marks and placed into a template before pre-instrumentation images were acquired digitally. The blocks were randomly divided into four groups of thirty each. Glide paths were prepared by a single operator with stainless steel hand K-files only, up to ISO size 20 (group 1, control), stainless steel hand K-files in the M4 reciprocating hand-piece up to ISO size 20 (group 2), hand K-files to ISO size 10 then NiTi rotary PathFiles (group 3) and hand K-files to ISO size 10 then NiTi rotary X-Plorer files (group 4). After glide path preparation the blocks were replaced into the template and post-instrumentation images were digitally acquired. Percentage change of curvature from original canal anatomy: Pre-instrumentation and post-instrumentation images were imported into Rhinoceros software to determine the end points of the canal curves and calculate the percentage change of canal curvature for the radii of apical and coronal curves. The data was collected and tabulated. Differences in canal curvature modification were statistically analysed with respect to logarithmic transformed change from baseline using ANCOVA (p<0.001) with logarithmic transformed pre-instrumentation values as covariate. After establishing preparation differences, both for change from baseline (pre-instrumentation) for apical and coronal curves, specific differences were tested using Fisher’s LSD for pairwise comparisons. Prepared groups differed significantly (p<0.001) and in particular, group 1 (Hand K-files) (control) and group 2 xiii (Hand K-files in M4 Safety reciprocating hand piece) differed significantly from all the other groups while group 3 (Hand K-files and PathFiles) and group 4 (Hand K-files and X-Plorer files) did not differ significantly. Group 3 (Hand K-files and PathFiles) and group4 (Hand K-files and X-Plorer files) were also superior to group1 (Hand K-files) (control) and group2 (Hand K-files in M4 Safety reciprocating hand piece). The occurrence of aberrations in canal anatomy (ledging, zipping and elbows): Pre-instrumentation and post-instrumentation images were superimposed using Adobe Photoshop software. The images were imported into a PowerPoint presentation and examined by three different blinded clinicians independently, for the presence of aberrations. There were no differences between the examiners in their assessment of the images. The data was collected and tabulated. The incidence of canal aberrations was analysed using Fisher’s exact test (p<0.05). The groups differed significantly regarding the number of aberrations (p=0.005). In particular, group 1 (control) (Hand K-files) and group 2 (Hand K-files in the M4 reciprocating hand piece) did not differ statistically (p=0.254; 20% and 6.67%). However group 2 (hand K-files in the M4 reciprocating hand piece) also did not differ significantly from group 3 (Hand K-files and PathFiles) and Group 4 (Hand K-files and X-Plorer files) (p=0.326). There were no aberrations detected in the rotary NiTi groups (group 3 and group 4). / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Odontology / unrestricted

Bluff bodies immersed in a fluid stream are susceptible to flow-induced vibrations. Depending on the body dynamic characteristics and flow conditions, different types of flow-induced vibrations may occur. The failure of a blade in a large mixing vessel in a chemical plant raised the question of the response of a parabolic cross-section bluff body to the flow excitation. Experiments were conducted in a wind tunnel using two- dimensional “sectional” models. Models with parabolic, semi-elliptic and semi-circular cross-section were investigated. In the dynamic experiments, flow velocity was increased from 0 to 22 m\s, and the oscillating amplitude and wake response were monitored. Vortex-induced vibrations were observed with Strouhal numbers for parabolic and semi-circular cross-sections of 0.13 and 0.12, respectively. Steady lift force and fluid moment for different angles of attack were monitored in the static experiments. From these results, lift and moment coefficients were calculated. For the closed semi-circular cross-section, Reynolds number had a strong influence on the lift coefficient. With an increase in Reynolds number, the lift coefficient decreased. The largest difference was noted at an angle of attack a = 45°. In contrast, the open semi-circular model lift coefficient was independent of Reynolds number. In the experiments where the elastic axis of the model coincided with the model centre of gravity, galloping was not observed in the plunge mode. When the model elastic axis was moved to a position 90 mm behind the test model centre of gravity, galloping was observed for the semi-elliptic and parabolic models. The onset of galloping coincided with the vortex-induced resonance. Changing the model elastic axis position introduced a combination of plunge and torsional motion, and latter is believed to be responsible for the existence of galloping. The parabolic model was modified in an attempt to eliminate galloping instability. Fins were added at the separation points to widen the wake and prevent the reattachment of the flow to the afterbody. With these changes, galloping was not observed, although the oscillation amplitudes remained unacceptably high. The present investigation revealed previously unknown characteristics of semi-elliptical and parabolic cross-section bluff body behaviour in fluid flow. At the same time, it laid a foundation for the solution to the practical problem encountered when a parabolic cross-section bluff body was used as a mixing blade. / Thesis / Master of Engineering (ME)

The deflections of screw rotors under machining forces cause mismatch between the male and female rotors and, consequently, accelerated wear and suboptimal efficiency in their performance. Optimizing the machining process to minimize the generated forces and accounting for the resulting mismatch in the design of the rotor profile requires accurately computing the machining forces in computer simulations. Virtual machining systems combine graphics-based computation of the Cutter-Workpiece Engagement (CWE) with the physics-based models of machining mechanics to simulate the forces during complex machining processes. However, because of the high computational load of graphical simulations, virtual machining is not suitable for the repetitive force simulations that are required for optimizing the design and manufacturing of rotors. In this work, we present a new method that simulates screw milling forces based on the process kinematics instead of graphical simulations. Utilizing mathematical equations that describe the process kinematics, the theoretical rotor profile is determined for feasible combinations of cutting tool profile, setup angle, and centre distance. Subsequently, to find the milling forces, the cutting edge is discretized into multiple small edge segments and a mechanistic cutting force model is used to determine the local cutting forces at each segment. After geometric and kinematic transformations of these local forces, the screw milling forces are obtained for each roughing and finishing pass. Instead of graphics-based methods, the engagement conditions between the cutter and workpiece are determined by the ensemble of 2D rotor and tool profiles; as a result, the computational efficiency is increased substantially. The semi-analytical nature of the presented method allows for computing the forces with arbitrary resolution within a reasonable time. The accuracy and efficiency of the presented method is verified by comparing the simulated forces against a dexel-based virtual machining system. / Graduate

No / This paper presents a new-designed compact power pack for a series hybrid vehicle. A new type of rotary induction machine with an outer rotor construction is designed to be coupled with the novel rotary internal combustion engine (ICE) with cylindrical crankcase in order to form the compact power unit. The starting and generation performance of the designed machine as well as the overall vehicle performance is analysed. Results show that the proposed power pack has the best performance in terms of fuel economy, emissions and battery charging compared to the existing power units in ADVISOR. Over a city cycle, fuel economy is increased by up to 47% with emissions reduced by up to 36% and over the highway cycle, fuel economy is increased by up to 69% with emissions reduced by up to 42%.