<p> An experimental effort has been completed in which water injection was investigated as a means of enabling increases in engine output and high load efficiency. Water was injected into the intake port of a direct fuel injected, 4-cylinder, boosted engine with dual independent variable valve timing. The water was shown to increase volumetric efficiency and decrease the onset of knock which in turn enable more optimal combustion phasing. Both of these affects resulted increases in load of up to 5.5% at the same manifold pressure as the baseline case. The advancement of combustion phasing, combined with elimination of fuel enrichment resulted in an increase in full load thermal efficiency of up to 35%. Analysis is provided around these affects, as well as the phase transformation of water throughout the engine cycle.</p><p>

No description available.

The thesis is presented in two parts. In part one, the excess thermodynamic properties have been determined for several binary liquid mixtures, with the aim of testing theories of liquid mixtures. The excess molar enthalpies, Hem, have been determined using an LKB flow microcalorimeter, and the excess molar volumes, Vem, have been determined using an Anton Paar densitometer. The HemS and VemS have been measured at 298.15 K for binary systems involving an alkanol (methanol, ethanol, I-propanol, 2-propanol) mixed with a hydrocarbon (l-hexene, I-heptene, l-octene, I-hexyne, I-heptyne, l-octyne, toluene, mesitylene, 0-, m-, or p-xylene, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane). The results show trends relating to the degree of unsaturation, or size, of component molecules as well as the position of the hydroxyl group on the alkanol. Measurements were also made on mixtures involving an (n-alkane + a pseudo-n-alkane) and ( a cYcloalkane + a pseudo-cycloalkane). Two theories of liquid mixtures were tested in this work. The first theory tested was the theory of Congruency. This theory was tested, by means of a null test, on a novel set of mixtures involving an n-alkane (hexane, heptane, octane, decane, dodecane) + a pseudo-nalkane,and mixtures of a cycloalkane (cyclopentane, cyclohexane, cycloheptane, cyclooctane)+ a pseudo-cycloalkane. Deviations from the theory was less than the experimental error for the (n-alkane + pseudo-n-alkane) mixtures. However, significant deviations were observed for the mixtures of (a cycloalkane + a pseudo-cycloalkane). The second theory tested was the Flory theory, which has been used to predict the excess molar enthalpies and excess molar volumes for the mixtures involving (a 1-alkene, or 1-alkyne, or methyl-substituted benzene) + an alkanol. The results show that the theory does not hold for hydrocarbon mixtures involving an alkanol. In the second part of this thesis, the partial molar volumes, at infinite dilution, of binary solution involving a solid solute (18-crown-6 ether, dibenzo-18-crown-6 ether, dicyclohexanov 18-crown-6 ether, 15-crown-5 ether, or cryptand-222) are determined in various solvents. The results were repeated with a view to determine the volume changes at infinite dilution upon complexation, ΔV∞ of the crown ether or cryptand with a metal halide salt, MX (NaCl, NaI, KCl, KI, CsCl, CsI). The ΔV∞ results were compared with results in the literature for cryptand-222 (c-222) and dibenzo-18-crown-6 ether (B₂CE6) complexed with MX, and the study was extended to include further MX complexes with c-222 and B₂CE6, as well as MX complexes with 15-crown-5 ether and dicyclohexano-18-crown-6 ether. ΔV∞ results were correlated with the Hepler prediction of the electrostriction solvent effect.

<p> In the interest of studying the propagation of shock waves, this work sets out to design, construct, and characterize a pneumatic accelerator that performs high-velocity flyer plate impact tests. A single stage gas gun with a dual diaphragm breach allows for a non-volatile, reliable experimental testing platform for shock phenomena. This remotely operated gas gun utilizes compressed nitrogen to launch projectiles down a 14 foot long, 2 inch diameter bore barrel, which subsequently impacts a target material of interest. A dual diaphragm firing mechanism allows the 4.5 liter breech to reach a total pressure differential of 10ksi before accelerating projectiles to velocities as high as 1,000 m/s (1570-2240 mph). The projectile&rsquo;s velocity is measured using a series of break pin circuits. The target response can be measured with Photon Doppler Velocimetry (PDV) and/or stress gauge system. A vacuum system eliminates the need for pressure relief in front of the projectile, while additionally allowing the system to remain closed over the entire firing cycle. Characterization of the system will allow for projectile speed to be estimated prior to launching based on initial breach pressure.</p><p>

Personal experiences of almost 17 years as an academic in engineering education in South Africa indicate that with the current teaching methods which are in use, course outcomes as required by the South African Qualification Authority (SAQA) are not achieved in learning Thermodynamics 2 (MTHE 2). The purpose of this research was to investigate alternative methods of teaching and learning MTHE 2 which would assist to improve the students’ academic performance. The population for this research was students registered for National Diploma Mechanical Engineering and the accessible population was 40 students registered for MTHE 2 from Walter Sisulu University, Chiselhurst campus. Out of these 40 students, 20 voluntarily agreed to be the sample. The theoretical framework for this study was social constructivism. Social constructivism states that learning is an active process and the process of knowledge construction occurs in a socio-cultural context where the student and environment actively interact. The student involves himself/herself and does neither remain nor be allowed to remain just as a passive observer. This was an action research where students were exposed to Guided Enquiry Based Learning (GEBL) in groups. From a social constructivists approach to learning, GEBL was used to engage students in social groups during the teaching-learning process with specific focus on selected academic discipline. All ethical considerations applicable to a study of the present nature were adhered to and in addition, signed informed consent forms were obtained from participants prior to the study. Students were given an introduction to the concepts and principles as per the pre-set syllabus for MTHE 2 and this was followed by problem solving sessions in which they were divided into four groups of five students each. The students were given a guided enquiry- and work-based example with an additional list of questions on each module of the syllabus. They had to select the most relevant questions from the list to analyse and develop a solution for each problem. The lecturers’ role was that of a facilitator who assisted each group with problems which the group encountered. This approach engaged students more actively in the learning process and placed more responsibility on them for their own progress in learning. This process also created an atmosphere for interaction with peers and assisted them to develop interpersonal and group communication skills. Key performance indicators were developed to measure the extent to which these outcomes were achieved. The researcher made use of an instrument structured in terms of Likert-type scale in order to objectively assess the extent of achievement. Data collected from the pilot study done in 2009 indicated that GEBL improved the students’ understanding of course content and problem analysis. Quantitative data were collected by means of standard assessment i.e. semester tests, an oral test, final examination and a KPI instrument. The KPIs were formulated to measure the extent to which the outcomes for MTHE 2 had been achieved. Qualitative data were collected through 30-minute interviews, using an open-ended interview schedule, with each member of the sample. The interviews were done by a person who qualified both as an ‘insider and outsider’ in order to minimize the risk of bias and to maintain rigour in the research. In order to qualify as an ‘insider and outsider’, one ought to be as an insider: (a) from the same ethnic group, (b) qualified in Mechanical Engineering with Thermodynamics as a major course, (c) had no power disposition e.g. a former student or a laboratory assistant (excluding staff members within the mechanical engineering department) and as an outsider, one who was not part of the GEBL process. The quantitative scores from the assessments were analysed with Predictive Analysis Software (PASW) to determine the extent to which interventions had assisted student performance. The qualitative data from the interviews were analysed with N-Vivo to reveal the impact of GEBL on student learning and understanding of MTHE 2. The results indicated that with GEBL, the students’ overall scores improved from the first assessment score of 46% written on half of the first module to the final assessment score of 55% written on all seven modules. Students could handle larger volumes of work and still obtain a higher percentage. GEBL assisted students’ in recalling factual MTHE 2 concepts, understanding of MTHE 2 concepts, principles and applications. GEBL also enhanced students’ ability to communicate procedures and processes related to MTHE 2. KPIs formulated to measure the extent to which the outcomes were met in terms of student achievement indicated a 57% achievement thereof. The KPIs developed gave a percentage achievement of the specified outcomes for MTHE 2 with GEBL. Theses KPIs can be used in future to measure the effectiveness of different teaching and learning methods in terms of achieving the outcomes. It is therefore recommended that GEBL be introduced into other engineering courses also to assist students in understanding course content and in achieving the course outcomes.

No description available.

The object of this investigation was to examine the transient heat flow through a composite wall. This wall was chosen to represent the type used in house construction. It consisted of a fir frame, covered on one side with hardboard and on the other with cedar, and the space between the hardboard and cedar was filled with fibreglass insulation. A vapour barrier was not included as it would offer little resistance to heat flow. This structure, therefore, offered resistances to heat flow in series and parallel. The theoretical analysis was numerical owing to the anisotropic properties of the materials and to the composite structure of the wall. Two analyses were made of the transient heat flow, an exact analysis and an approximate analysis which neglected the effect of the frame. The heat flow was three dimensional in the first analysis owing to the difference in the magnitude of the parallel resistances and was one dimensional in the approximate analysis. The two theoretical solutions both showed exponential cooling rates and agreed within five percent of each other, which shows that the effect of the frame is negligible when its surface area is small as compared to the total surface area of the wall. The ratio of total wall surface area to frame area for the wall studied was 9.6 to 1.0. The wall was mounted in a guarded hot-box apparatus and experiments were performed in order to verify the results of the theoretical analysis. The experiments consisted of establishing a steady state temperature gradient across the wall and then eliminating the heat source. The ensuing transient temperatures were measured by thermocouples and were compared with those predicted by theory. The experimental results varied from the exact solution by 14 percent and from the approximate solution by 18 percent. The experimental results indicated that the tests were consistent. The difference between the theoretical and experimental results was attributed to: (1) contact resistances, (2) nonhomogeneous wall materials, (3) nonuniform surface coefficients of heat transfer, and (k) the effect of neglecting certain heat capacities which actually were not negligible. The results indicated that the transient temperatures varied according to the equation T = Ti e [formula omitted] where T represents temperature, t represents time, and [formula omitted] is the time constant. The results also showed that the method of analysis was acceptable and that the approximate analysis is suitable for walls with small frame areas. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

In the first part of this work the thermal reaction [Formula omitted] was studied thermodynamically and kinetically in the gas phase and at the temperature range 150 to 210°C. The equilibrium composition was found to be very unfavourable to 3-butenal which constitutes 0.35% of the mixture at 150°C and 1.04% at 210°C. The enthalpy of the reaction was estimated to be 7.20 ± 0.09 kcal/ mole. In the kinetic study both the forward and reverse reactions were found to be heterogeneous and of the first order with respect to surface area and pressure of reactant. The rate constants obeyed the relations [Equation omitted] k₁ was determined in a vessel with surface to volume ratio equal to 1.2 and k₋₁ in a vessel with ratio equal to 4.1. The significance of the experimental Arrhenius parameters was discussed in terms of the theory of absolute rates as applied to surface reactions and of a mechanism based on a fast adsorption-desorption of the Langmuir type. In the second part of the work the photochemical isomerization of crotonaldehyde to 3-butenal was studied in the gas phase and at the temperature range 25 to 140°C. Exciting radiation of the wavelengths 3130, 3340 and 3660 Å was used. It was found that the quantum yield of the isomerization obeys the Stern-Volmer equation 1/ϕ = a + bP ein/mole at the temperature and wavelength range studied. The pressure, P, of crotonaldehyde was varied from 0.4 to 34 mm Hg. The value of parameter a varies from 11 to 37 ein/mole with the low values observed at 3130 Å and the high values at 3660 Å. The parameter b varies from 0.19 to 7.5 ein.mole⁻¹ (mm Hg)⁻¹ with the low values also observed at the shorter wavelength. At constant wavelength b decreases with increasing temperature. A mechanism was discussed according to which the excited singlet '(n,π* ) is the reacting species and it was shown that a "strong collision" deactivation and a classical energy distribution function predict qualitatively the dependence of b on temperature and wavelength. An attempt to predict this dependence in a quantitative manner failed. A refinement to the "strong collision" mechanism using the same energy distribution function could not be tested numerically because of computational difficulties. An alternative mechanism was discussed involving a cis-trans equilibrium of crotonaldehyde in the ground state and it was shown that the parameters a and b may be interpreted in more than one way. In the third part of the work the photolysis and photochemical oxidation of 3-butenal were studied in the gas phase and the temperature range 25 to 140°C. In the photolysis exciting radiation of 3130 and 3340 Å was used. The products were carbon monoxide, propylene and biallyl. They were found to obey the relation CO ≤ propylene + 2.biallyl The overall quantum yields taken as equal to ϕ (propylene) + 2 ϕ (biallyl) obeys the Stern-Volmer equation (1). The Value of the parameter a varies from 0.994 to 1.226 ein/mole and that of b from 1.15 x 10⁻² to 3.75 x 10⁻² ein. mole⁻¹ (mm Hg)⁻¹ . The lowest values for both parameters are observed at 3130 Å and 140°C and the highest at 3340 Å and 25°C. The significance of parameter a was discussed and it was shown that its dependence on temperature and wavelength can be predicted within the limits of the experimental error by using the classical energy distribution function. In the photochemical oxidation radiation of 3130 Å was used. The major products with the quantum yields at 25°C shown in paranetheses were: carbon monoxide (3.0-3.4), allyl alcohol (1.1-2.4), acrolein (1.2-1.9), carbon dioxide (0.4-1.0), propylene (0.4-0.5), peroxide (0.20-0.27) and ethylene (0.22-0.27). Variation of the experimental conditions at constant temperature had little effect on the quantum yields. Increase of temperature to 140°C resulted in decrease of the yield of allyl alcohol and acrolein and increase of the yield of all the other products. A mechanism was discussed which explains the results in a qualitative way. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

abstract: My dissertation research broadly focuses on the geochemical and physical exchange of materials between the Earth’s crust and mantle at convergent margins, and how this drives the compositional diversity observed on the Earth’s surface. I combine traditional petrologic and geochemical studies of natural and experimental high-pressure mafic rocks, with thermodynamic modeling of high-pressure aqueous fluids and mafic-ultramafic lithologies allowing for more complete understanding of fluid-melt-rock interactions. The results of the research that follows has important implications for: the role of lower crustal foundering in the geochemical origin and evolution of the modern continental crust (Chapter 2; Guild et al., under review), metasomatic processes involving aqueous metal-carbon complexes in high pressure-temperature subduction zone fluids (Chapter 3; Guild & Shock, 2020), natural hydrous mineral stability at the slab-mantle interface (Chapter 4; Guild, et al., in preparation) and water-undersaturated melting in the sub-arc (Chapter 5; Guild & Till, in preparation). / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2020