Faculty of Engineering

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    Open Access
    Vertical Vibration of Rigid Bodies with Rectangular Bases on Elastic Media
    (University of Lagos, 1973-05) Tabiowo, Haboghene Peter
    The vibration of rigid bodies with finite rectangular bases of semi-infinite elastic media presents difficult analytical problems which have hitherto not been resolves. The mixed boundary-value problem is completely formulated for the first time, in terms of a pair of ''Dual Double Integrated Equations'', both for the static case which has a formidable theoretical solution and for the dynamic case where more complication is added to an already complex problem.
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    Open Access
    Seismic Vibration Due to Detonation in Oil Exploration
    (University of Lagos, 1973-12) Olusesan, Ayodeji Sobayo
    The present work is concerned with a fundamental social problem which arises on account of the continual detonation of explosive charges during oil exploration.
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    Open Access
    The Upgradeing of Privy Methods of Sewage Disposal by the Biodisc Process
    (University of Lagos, 1976-10) Aluko, Tomothy Mofolorunso
    This thesis describes studies carried out on the septic tank and the nightsoil conservancy system , the two most widely used methods of sewage disposal in Lagos and other parts of Nigeria.
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    Open Access
    A Study of Box Girder Behaviour based on Extension and Bending Plate Theories.
    (University of Lagos, 1976-11) Somolu, O. A.
    The thesis deals with the study of box girder behaviour under load and examines the deplexion and membrane stresses which arise as a consequence of loading. An extensive survey of the existing methods of analyses is carried out and two of them are outlined. A composite concrete-steel box was used for the laboratory investigation.
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    Open Access
    An Investigation into Nigerian Guidance Counsellors' Professional Value Commitments in Guidance and Counselling with Particular Reference to Two States of Nigeria: Lagos State and Cross-River State.
    (1980) Arene, Violet Nwakaego
    Guidance and Counselling is usually designed to achieve certain ends for a particular society. It is therefore practiced with a frame work of values and goals. Guidance and counselling cannot therefore successfully be practised in the Nigerian setting without a synthesis of the values and ultimate goals of its services. The major problem tackled by the present study is what Guidance and Counsellors' value commitments are in the Nigerian setting where Guidance and Counselling has been witnessing stalling development. An investigation such as this, of Guidance Counsellors' value commitments will help to ensure that the demands and needs of the Nigerian setting and the expectations of Guidance and Counselling consumers are being satisfied. It will also help to direct the development of the Guidance and Counselling services successfully.
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    Open Access
    Design of Digital Filters Using Incremental Changes in Processing
    (University of Lagos, 1980) Falaki, Samuel. Oluwole.
    Procedures are developed for designing high-speed, modular digital filters. The techniques presented here are based on the use of differences in the data signal in processing. The use of one-bit word, and the use of mapping of differentials in processing to produce a multiplication free, fast, and modular structured digital filters is considered in details in this thesis.
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    Open Access
    Heat Transfer by Steady Laminar Free Convection in Triangular Enclosures.
    (University of Lagos, 1980-01) Coleman, T. A.
    Two Dimensional Laminar Free Convection in a fluid contained in a long horizontal right triangular enclosure has been investigated using numerical techniques and experimental study. The geometry of the enclosure is that the base is assumed horizontal while the vertical height is adiabatic. Motion in the region is set up by heating the hypotenuse while cooling the horizontal wall. This model simulated heat transfer problems associated with pitched-roofs with suspended ceilings, roof-type solar Stills etc.
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    Open Access
    Combined Free and Forced Laminar Convection in Inclined Wide Rectangular Channels Heated from Below and Cooler from Above.
    (University of Lagos, 1980-12) Ochende-Bello, F. L.
    The steady-state two-dimensional problem of combined free and forced laminar convection with upward flow in inclined rectangular channels heated from below and cooled from above, has been investigated by numerical, parameter perturbation and experimental methods.
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    Open Access
    Correlation of Load-Point Reliability Indices with Power System Fault Levels
    (University of Lagos, 1982) Awosope, C.O
    Extensive literature abounds on the evaluating techniques of load-point reliability indices of electrical power systems. On the whole, all the efforts of the published works have been the establishment of conventional methods to evaluate load-point reliability indices from raw component reliability data. Any system change that warrants new set of load-point reliability indices would require the whole process of reliability evaluation to be repeated. That is an inherent characteristic of these conventional evaluation techniques. For consistent and proper system operation and monitoring, the effects which any changes (such as addition of new lines, transformers or shunt reactors or their removals in order to cater for changes in the load demands) in the system have on the various load-point reliability indices, must be adequately assessed. In effect, this means that a new set of load-point reliability indices will have to be evaluated for the modified system in order to get the true picture of the system performance at the load point. Thus, repeated reliability indices evaluation can not be avoided in a successful system operation. Experience with the conventional method of reliability indices computations indicates that this repeated evaluation could be very expensive and time consuming in terms of repeated component data collection, computer storage requirements and the associated computer time. In order to repeatedly estimate these changing load-point reliability indices without the need to seek new set of component reliability data and indirect estimating technique is proposed in this thesis. This new technique involves the normal fault level analysis. The principle of the method is based on model building techniques. By the application of regression and correlation analysis to the separate calculation of both the load-point reliability indices and the associated load bus fault levels, models are carefully built and analysed. The conforming models permit the prediction of the reliability indices for the relevant outage conditions given that the system corresponding load busbar fault levels are known. Foe each of the above models, a test of satisfaction significant is performed. This gives the probability of error in the model’s prediction of reliability index of failure rate from the knowledge of faults levels. This significance test follows t-distribution with (n-2) degrees of freedom where n is the number of data points. In this way the criterion for choosing the optimal prediction model is formulated. The resulting model so constrained is found to have a high degree of statistical confidence and is unique to the system so long as the number of load busbars of the original system remains unaltered. The validity test is carried out on the models built for the three samples selected for study in the Thesis, for each system, the validity test shows that such an optimal prediction model will always correctly represent system structure in the face of any branch outage. This is so, because in each case, the results obtained are in agreement with those obtained using the binary formulation algorithm of the minimal cut-set theory. The Nigerian (NEPA i.e National Electric Power Authority) 330-KV system 1980 stage is one of the three simple electrical power systems selected for study in the Thesis. As far as the author is aware, the research work carried out in this Thesis on the reliability assessment of electrical power system is the first of its kind in Nigeria (i.e. reliability studies on NEPA system). This is a break – through in the past and present efforts to solve the varied and numerous Engineering, Technological and scientific problems.
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    Open Access
    The Invariants of Water Waves Breaking On Beaches with Variable Slope
    (University of Lagos, 1982) Oyegoke, S.E.
    The breaking of water waves is examined experimentally on four different laboratory beach slopes of 1:40, 1:20, 1:10 and 1:5. Several measurements of shoalling variables are made in the wave tank both before and after wave breaking. The variables measured in the breaker zone include breaker height and depth, plunge point (when applicable), breaker travel distance, end of aeration, run-up and run-down points. Graphical techniques and the statistical method of least squares are used to investigate the various relationships that exist between breaker and deep sea parameters. In order to make the conclusion of the analysis undertaken to be of wider applications, the data published on the subject by several accredited investigators such as Iversen (1952). Galvin (1968), Iwagaki et al (1974) and Van Dorn (1978) are re-analysed and their results are compared with those arrived at through the analysis of the data obtained in this experimental investigation. In several cases, the agreement is remarkably close. On the whole, the joint analysis of the data from the study with those of the other investigators present a more complete picture of the shape and kinematics of breaking waves. In the shoalling Zone where turbulence limits the application of detailed analysis, the laws of motion are derived as time and depth averaged equations. A numerical model is also developed that uses one form of the two dimensional Boussinessq equations formulated in terms of mass and momemtum conservation laws. Differential equations are approximated by finite difference scheme that employs a three level preissmann scheme so as to provide the high order of accuracy needed to simulate the various non-linear terms of the governing equations. The numerical model developed is used to simulate the propagation of solitary waves in a channel of constant depth averaged equations.
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    Open Access
    Kinetic Analysis of C8 Dehydrocyclization Reactions on Mono and Bifunctional Platinum -Alumina Catalyst
    (University of Lagos Postgraduate School, 1984) Ako, C. T
    The dehydrocyclization of n-octane and iso-octane to ethyl benzene, o-, m-, and p- xylenes was investigated on a mono - and bifunctional Pt/A12O3 catalyst, using pulse technique with hydrogen as carrier gas at a pressure of 1.8 atm and between 563 and 7630K. Similarly, the isomerization of the C8 - aromatics was also studied in the temperature range 513 -6730K and 1.8atm pressure. The total conversions of n-octane and iso-octane on bifunctional catalyst were found to decrease with increasing temperatures for all pulse sizes investigated. On monofunctional Pt/A12O3, however, the total conversion of n-octane increased with temperature, passing through a maximum at 6130K. The total conversion of each of the xylene isomers and of ethyl benzene also went through a maximum as the temperature increased. There was a large initial production of iso-octane when n-octane reacted on bifunctional Pt/A12O3, catalyst, the iso-octane production went through minimum as the temperature increased: For iso-octane reaction on hifunctional Pt/A12O3 and n-octane reaction on monofunctional Pt/A12O3, however, there was a large initial production of ethylbenzene which also went through a minimum as the temperature increased. Each of the yields of ethyl benzene and o-xylene went through a maximum as temperature increased for n-octane dehydrocylization on acidic Pt/A12O3. As regards iso-octane dehydrocylization on Pt/A12O3, O, p- xylenes yield went through their respective maxima. The same behaviour was observed when n-octane reacted on monofunctional Pt/A12O3. The selectivity of ethylbenzene to O-xylene increased with temperature for all pulse sizes investigated, while that of ethylbenzene to iso -octane went through a maximum when noctane reacted on bifunctional catalyst. On mono-functional catalyst, however, the selectivity of ethyl benzene to o-xylene decreased with temperature and passed through a minimum. With respect to the reactions of the C8-aromatics on bifunctional and mono functional Pt/A12O3, the onset of reaction occurs at a lower temperature and the initial rates were higher on the bifunctional Pt/A12O3. Furthermore the bifunctional catalyst was found to be very selective in the production of p-xylene and p- and o-xylene at temperature less than 563 and 5930K, respectively. The Wei-Prater method was used for the calculation of absolute rate constants for ethylbenzene isomerization on both catalysts. Generally, the rate constants were higher on bifunctional Pt/A12O3. Estimated activation energies appears to account for the high yield of ortho from meta xylene during ethylbenzene isomerization on bifunctional Pt/A12O3.
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    Open Access
    Oblique Incidence Ionospheric Absorption Near the Magnetic Equator
    (University of Lagos, 1984-07) Shamsi, S.
    Measurement of equatorial ionospheric absorption made by the A3 Method for quiet conditions near a period of maximum solar activity (1979 to 1981) are used for a detailed examination of Absorption of Radio Waves in equatorial ionosphere. Assuming an index law of the form L = L0COSmX for the absorption (X being zenith angle of the sun), the diurnal and seasonal characteristics of the variation are obtained for two frequencies (4.9 MHz and 7.1 MHz) and compared with existing theories. Problems posed for an index law for seasonal variation of absorption by the experimental evidence as indicated. Effect of solar activity on absorption of radio Waves is studied and an improved form of the variation of absorption with solar activity is presented. The new form of variation of absorption with solar activity also explains the seasonal variation of absorption. Examples of solar flare effects on the ionospheric absorption are presented for the two frequencies. A study has been made for the correlation between the occurrence of solar flares as reported in Solar Geophysical Data (Noaa Boulder Colorado) and the observed ionospheric effect. Special features observed include a pronounced absorption near layer sunrise, and an apparent enhancement of signal strength around sunset. Arguments are advanced for possible physical mechanism governing these phenomena.
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    Open Access
    Pulse Mycrocatalytic Investigation of Model Hydrogenation Reaction on Platinium-Rhnium\Aluminium Oxide Catalyst
    (University of Lagos, 1985) Daniel, B.A
    The hydrogenation and dehydrogenation of benzene, cyclohexene and cyclohexane were investigated on a 0.3% Pt- 0.3% Re on Al203 catalyst (Catalyst (A)) using the pulse micro-catalytic technique. Reactions were carried out in hydrogen and in nitrogen containing 0.66% oxygen (labelled N2/O2) under the following conditions: 4 atmospheres total pressure, 500C to 4000C and 120cm3 min-1. Kinetic data were obtained on clean coked and CS2-poisoned catalyst. The theory of Sica et al (1) was applied to extract kinetic parameters. The activation energies were found to be identical for reactions carried out on coked, CS2-poisoned (at 3730C) and clean catalyst, thus suggesting that deactivation of catalysts by CS2 and coke occur predominantly by geometrical blockage of active sites. A slight enhancement of the selectivity for hydrogenation of cyclohexene to cyclohexane over dehydrogenation to benzene by CS2 poisoning suggested that the poison also exerted some electronic effect on the reactions. The u-6 bond shift mechanism of Ruiz - vizcaya et al (2) for the dehydrogenation of cyclohexan on Pt/Pd catalysts was found to account for most of the observed kinetic phenomena. The kinetic parameters determined by the pulse experiments were largely confirmed by continuous (plug) flow microreactor experiments. The order of reaction was found to be zero and the activation energy was found to be about 8 kcal/mole for benzene and cyclohexene hydrogenation to cyclohexane. For cyclohexane dehydrogenation, the order of reaction ranged between 0.7 to 0.9 while the activation energy varied more significantly. For the pulse experiments, it was 33 kcal/gmol (30000 - 3350C) and 16.5 kcal/gmol. (3350 - 3900C) while a single value of 24 kcal/gmol (3150 - 3750C) was calculated for the flow experiments. The deactivation of catalyst (A) by cyclohexene and cyclohexane in very dry and high purity helium in the temperature range 3000C to 4000C and 4 atmosphere total pressure was studied. A model developed in this thesis was used for data analysis. The deactivation of catalyst (A) by cyclohexane and cyclohexene was found to be described by the relation. da = kda dt With zero activation energy. Deactivation was rapid when catalyst surface was contacted with oxygen before reaction. Catalyst (A) was charaterised by means of the conventional H2/O2 titration in helium and by the titration of H2 and O2 in N2/O2 carrier (a method proposed here). Charaterization was also done by monitoring the Temperature Programmed Desorption (TPD) profile of oxygen adsorbed on the catalyst. The H2/O2titration and the TPD results suggest the existence of bimetallic clusters of Pt and Re which segregates to Re-rich and Pt-rich clusters in the presence of oxygen. The observed increase in the hydrogenolysis of cylohexane on oxidised catalyst is also consistent with this concept.
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    Open Access
    Pulse Microcatalytic Investment of Model Hydrogenation and Dehydrogenation on Platinum. Rhenium/ Aluminium Oxide Catalyst.
    (University of Lagos, 1985) Ayo, Daniel. Babatunde.
    The hydrogenation and dehydrogenation of benzene, cyclohexene and cyclohexane were investigated on a 0.3% Pt- 0.3% Re on A1203 catalyst (catalyst (A)) using the pulse microcatalytic technique. Reactions were carried out in hydrogen and in nitrogen containing 0.66% oxygen (labelled N2/02) under the following conditions: 4 atmospheres total pressure, 500c to 4000c and 120 cm3 min -1. Kinetic data were obtained on clean, coked and CS2-poisoned catalysts. The theory of Sica et al (1) was applied to extract kinetic parameters. The activation energies were found to be identical for reactions carried out on coked, CS2-poisoned (at 3730c) and clean catalysts, thus suggesting that deactivation of catalysts by cs2 and coke occur predominantly by geometrical blockage of active sites. A slight enhancement of the selectively for hydrogenation of cyclohexene to cyclohexane over dehydrogenation to benzene by CS2 poisoning suggested that the poison also exerted some electronic effect on the reactions. The II-σ bond shift mechanism of Ruiz – Vizcaya et al (2) for the dehydrogenation of cyclohexane on Pt/Pd catalyst was found to account for most of the observed kinetic phenomena. The kinetic parameters determined by the pulse experiments were largely confirmed by continuous (plug) flow microreactor experiments. The order of reaction was found to be zero and the activation energy was found to be about 8 kcal / mole for benzene and cyclohexene hydrogenation to cyclohexane. For cyclohexane dehydrogenation, the order of reaction ranged between 0.7 to 0.9 while the activation energy varied more significantly.
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    Open Access
    Design and Fabrication of a Prototype Press Tool for the Manufacture of an Item of Cutlery
    (University of Lagos, 1985-08) Okoli, J.U.
    Metal forming is a production technique which enhances economic use of engineering materials by minimizing metal wastage that occurs in machining processes such as lathe turning and milling. This technique employs a press tool for mass production of parts that are dimensionally compatible.The press tool comprises the section that provides the force- the press, and the tooling section- the die. Investigation of stretch-forming conditions to produce a simple dome in order to determine the optimum condition of punch nose radius, die corner radius is established. This relationship provides a basis for determining forces, clearance, travel and profile of the die, thereby eliminating the trial and error method of tool design and of finding punch force. A tool of simple design and easy to maintain is developed for use in a press machine. A 60 KN, non-geared, open-fronted eccentric press with straight box frames, and with flywheel mounted on the shaft and operating at 90 strokes per minute is developed. The fundamental requirements of a press include a frame of adequate rigidity and strength to reduce deflection and absorb shock of stamping, appropriate flywheel energy and torque capacity to form parts in the tooling.The principle adopted for developing a transmission system which harnesses the power of the electric motor through the flywheel, clutch unit, shaft and connecting rod to the tooling is presented.
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    Open Access
    Comparative Kinetic Investigation of the Prolysis of Pure Hydrocarbons and their Mixtures
    (University of Lagos, 1985-11) Aribike, D. S.
    The kinetic and product distributions of the thermal decompositions of the n-butane, n-heptane, cyclohexane and methyl-cyclohexane as well as liquified petroleum gas (LPG), cyclohexane methylcyclohexane (CYH-MCH) and cyclohexane - heptane - benzene (CYH-HEP-BEN) synthetic mixtures were investigated in a stainless steel annular reactor at one atmosphere pressure and with excessive nitrogen dilution. Experimental data were obtained over a wide range of conversions at temperatures from 6400 to 8600C and residence times of 0.26 - 1.87 seconds. Ethylene, propylene, methane and hydrogen were formed as major products of n-butane pyrolysis. Besides, mole percent of propylene and methane did not change with temperature below 7600C, while ethylene increased. Mole percent of propylene was considerably higher than that of methane in contrast to the results of Blakemore et al (74) who observed equal molar amounts of these two products. The ratio ([C3H6] + [CH4]}/{[C2H4] + [C2H6]) decreased with increasing temperature (conversion). Methane, propylene and ethylene were the main products of LPG pyrolysis. Also methane selectivity generally increased with residence time, while those of ethylene and propylene passed through maxima. There is evidence of the accelerating effect of the H2S additive on the cracking reactions of LPG. Relatively substantial amount of methane and less ethylene and propylene were produced in the pyrolysis of LPG than pure n-butane. In n-heptane pyrolysis selectivities of ethylene and methane increased steadily with conversion, while propylene selectivity went through a broad maximum and those of the higher &-olefins (1-butene, 1-pentene and 1-hexene) decreased. R-k theory is inadequate in predicting the secondary reactions of &-olefins, though it predicts their formation. N-heptane pyrolysis was well represented by first order kinetic law; the estimated Arrhenius parameters are E = 206.1' kJ mo1-1 and A = 5.88 x 1010 sec-1. Selectivities of ethylene, propylene and methane increased with conversion in cyclohexane, pyrolysis while 1, 3-butadiene decreased. In addition, ethylene and propylene yields increased with residence time at 7000C - 8600C, while yield of 1, 3-butadiene increased at 7000C - 8600C, passed through a maximum at 6200C and decreased at 8400C. Similar observations were made by Levush et al (30) in cyclohexane pyrolysis at 9000 - 13000C. Relatively lower selectivities of ethylene and propylene and higher 1,3-butadiene selectivity were observed in cyclohexane pyrolysis than n-heptane. Ethylene, propylene, methane and 1,3-butadiene were the major products of CYH-MCH pyrolysis. Appreciable yields of benzene and isoprene were also formed. Selectivities of ethylene, methane and 1,3-butadiene showed little or no change with increasing conversion, while propylene decreased tremendously. Less methane, ethylene, 1,3-butadiene and hydrogen and more of propylene were formed in MCH pyrolysis than cyclohexane. The Arrhenius plot of MCH pyrolysis showed appreciable curvature in the region of temperature below 8000C; an evidence of strong surface effect and hence of heterogeneous mechanism on the kinetics of MCH pyrolysis. Ethylene, propylene and 1,3-butadiene were the major products of CYH-MCH pyrolysis. The order of the quantities of ethylene formed from the pyrolyses of CYH-MCH, pure cyclohexane and MCH was: Cyclohexane > CYM-MCH > MCH Conversely more propylene was formed in MCH pyrolysis than the other two reactants. The comparison of the variations of the major product yields and selectivities with temperature and residence time for the three hydrocarbon reactants showed that the decomposition reactions of the components play central role in overall mixture cracking. Comparison of the Arrthenius parameters of pure components with those estimated for mixture cracking showed that cyclohexane strongly inhibited in former slightly. Ethylene, propylene, 1,3-butadiene, methane and hydrogen were the main products of CYH-HEP-BEN pyrolysis. The order of the amounts of ethylene formed in the pyrolyses of CYH-HEP-BEN, pure cyclohexane and heptane was N-Heptane > CYH-HEP-BEN > Cyclohexane. Conversely, the order in the case of 1,3-butadiene was Cyclohexane > CYH-HEP-BEN > N-Heptane. Selectivity to products of pure component decomposition was maintained in the mixture cracking, confirming the results of Murata et al (36). There was strong effect of component interaction on the overall decomposition reactions of CYH-HEP-BEN. Futhermore, higher yields of C2+C3 olefins and lower yields of liquid products (C6+) were produced in CYH-HEP-BEn pyrolysis than CYH-MCH. Mechanistic models that fit the pyrolyses of n-butane and n-heptane fairly well were developed. Simulated radical concentrations showed appreciable changes with reaction time thus the assumption of pseudo steady stage for radical concentrations is not valid in reality. Molecular model developed for cyclohexane pyrolysis predicted the product distributions fairly well.
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    Open Access
    Design of Adaptive Control Schemes for an Industrial Robot Arm.
    (University of Lagos, 1986-03) Katende, J.
    This study has investigated the techniques for motion control of industrial robots with an application in which the robot’s end-effector is required to track prescribed paths under conditions of changing payload masses, friction and elasticity in the gear boxes. In particular, the minimal configuration (the first three degree-of-freedom) necessary for positioning the end-effector of a revolute industrial robot arm, MIMO, has been studied in terms of kinematics, dynamics and control. The lagrangian formulation of the equations of motion was applied to the robot arm. This showed that the robot’s equations of motion are highly nonlinear, complex second-order differential equations. A review carried out in this thesis, of robot controllers reported in the technical literature, has also identified where technical problems still remain to be resolved. Simulation studies which have been carried out show that a conventional robot controller can not cope with parameter variations due to large displacements and fast motions. Thus in this thesis, the theories of perfect model following control, hyperstability, quadratic optional regulators and model control are deployed in conjunction with adaptive control techniques, resulting in robust controllers suitable for robot trajectory tracking control purposes. Simulation results highlighting the performance of the adaptive schemes are presented.
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    Lamina Free Convective Heat Transfer in Parabolic Enclosures
    (University of Lagos, 1987-10) Nwabuko, U.
    The lamina free convection heat transfer characteristics of parabolic enclosures have been investigated using numerical computation and experimental modeling methods. The geometry is a long cavity made up of a parabolic wall bowed over a horizontal wall. Due to symmetry, the analytical model is one half of a two-dimensional cross-section consisting of a hot parabolic upper-wall, a cold horizontal base-wall of width B, and an adiabatic vertical wall of height, H. Two cases of heat-inputs from the parabolic wall have been considered viz; case I; isothermal conditions on hot wall and, case II; constant-heat-flux conditions through hot wall. The base and vertical walls remained isothermal and adiabatic respectively. This model has practical applications in air conditioning considerations of curved-roof housings and in the designs of more efficient solar energy collectors. A finite difference technique called the ‘Staggered Differencing’, SD, for both regular and irregular boundaries, have been deployed, tested and applied successfully in the iterative solutions of the mass, momentum and energy transport equations.
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    Reactivity of Some Complex Hydrocarbons on Constant and Variable Activity Reforming Catalysts
    (University of Lagos, 1988-04) Onukwuli, D.O
    The product distributions, kinetics and catalyst mortality of the reforming reactions of n-octane, iso-octane and methylcyclophentane (MCP) were investigated on constant and variable activity Pt/A12O3 and Pt-Re/A12O3 catalysts. The Berty CSTR was used for data collection at total pressure of 1atm, various reactant and H2 diluent partial pressures, W/F and temperature, depending on the reactant. The dehydrocyclization of n-octane on 0.3% Pt/A12O3 catalyst was investigated at temperature between 4000C and 4600C in H2. The products of the reaction were: hydrocracked products, iso-octane, ethylbenzene, m-xylene, p-xylene, O-xylene and toluene. Experimental data showed that the yields of cracked products and aromatics generally increase with increase in W/F and temperature, but the aromatic yield decreased with increased in n-octane partial pressure. Results obtained with varying hydrogen partial pressures show that, at constant temperature, the total conversion and the yield of aromatics each passed through a maximum. Another n-octane isomer (1, 1,3-trimethyl-pentane was the sole product of the reaction) of 2,2,4-trimethyl pentane (iso-octane) on Pt/A12O3 catalyst at temperatures between 3900C and 4300C. The conversion of iso-octane on 0.6% Pt/A12O3 catalyst was found to be approximately the same as that obtained with 0.3% Pt/A12O3 catalyst at the same conditions. The reactions of MCP on 0.3% Pt/A12O3 and 0.3 Pt-0.3% Re/A12O3 catalyst were studied at temperature between 3700C and 4100C and MCP partial pressures between 0.058atm and 0.1816atm. At these conditions, the products of reaction were hydrogenolysis products, cylohexane and benzene. The beneficial effect of rhenium in Pt-Re/A12O3 catalyst was clear from the total conversion and benzene yield obtained with Pt/A12O3 (DRIED) catalyst. Experimental results showed that the total conversion and benzene yield obtained with the Pt/A12O3 (DRIED) catalyst was about 1.5 times greater than that obtained when the bimetallic catalyst was not dried before reduction. In addition to the high conversion and high benzene yield, the dried bimetallic catalyst was found to be more stable than both the Pt-Re/A12O3 catalyst and Pt-Re/A12O3 (UNDRIED) catalyst.Mechanistic kinetic equations of these reactions were developed on both steady and unsteady state catalyst surfaces. The development of mechanistic rate equations for the surfaces state kinetics of n-octane conversion was based on the mechanisms obtained from the modified reaction network proposed by Ako and Susu1. Nineteen rate equations were derived and discrimination among rival models were based on positiveness of rate and equilibrium constants, on the goodness of fit and also on the increase of the value of the rate constants with increase in temperature. The rate models that best fitted the data were based on: 1. Dissociative adsorption of hydrogen and conversion of adsorbed n-octane to adsorbed iso-octane as rate limiting step (Eqn. 3.1.5).2. Dissociative adsorption of hydrogen and desorption of adsorbed iso-octane (Eqn. 3.1.6).3. Dissociative adsorption of hydrogen and conversion of adsorbed iso-octane to adsorbed ethylbenzene as rate limiting step (Eqn. 3.1.7).4. Dissociative adsorption of hydrogen and conversion of adsorbed iso-octane to adsorbed o-xylene as rate limiting step (Eqn. 3.1.8). 5. Molecular desorption of hydrogen and conversion of adsorbed n-octane to adsorbed iso-octane as rate limiting step (Eqn. 3.1.13) Good fit and positive values of rate and equilibrium constants were obtained when models eqns. (3.1.7) and (3.1.8) were used to predict the conversion obtained with varying hydrogen partial pressures at constant temperature.The kinetic rate equations for the isomerization of iso-octane in the absence of coking (steady-state kinetics) were derived on the basis of the generally accepted mechanism for skeletal isomerization. The rate models that best fitted the data were based on: 1. Reaction of adsorbed unsaturated iso-octane on the acidic site to adsorbed iso-octane as the rate determining step (Eqn. 3.1.25). 2. Desorption of iso-octane from the acidic site as the rate determining step (Eqn. 3.1.27). Kinetic rate equations for the aromatization of MCP in the absence of coking (steady state kinetics) were derived on the basis of the reaction network proposed by this author (see chapter 6, section 6.1.3). Eleven rate equations were derived and tested. Five out of the eleven models satisfied the set criteria when Pt-Re/A12O3 catalyst was used for the conversion of MCP. The five rate equations that best fitted the data were based on: 1. The rate model is based on the dehydrogenation of adsorbed methylcyclopentene as the rate determining step (Eqn. 3.1.44) 2. The rate model is based on the conversion of adsorbed methylcyclopentene to adsorbed olefinic hydrogenolysis products as the rate determining step. (Eqn. 3.1.46) 3. The rate model is based on the hydrogenation of adsorbed olefinic hydrogenolysis products to adsorbed hydrogenolysis products as the rate determining step (Eqn. 3.1.48) 4. The rate model is based on the hydrogenation of absorbed cyclohexane to adsorbed cyclohexane as the rate determining step (Eqn. 3.1.49) 5. The rate model is based on the desorption of hydrogenolysis products as the rate determining step (Eqn. 3.1.50) Using the Pt-Re/A12O3 (DRIED) catalyst, however, only two rate equations (Eqns 3.1.48 and 3.1.49) satisfied the set criteria.For deactivation kinetic studies of Pt-Re/A12O3 catalyst iso-octane and MCP were used as reactants while for the deactivation kinetic studies of Pt-Re/A12O3 catalyst only MCP reactant was used. The reactant and hydrogen partial pressures were varied. To describe the distribution of products with time, and activity an a deactivation function of the non-separable type used. Model equations 3.2.11 and 3.2.19 were used to evaluate the constants of deactivation at various values of n (0, 1, and 2).Catalyst mortality experiments were also carried out with all the reactants investigated. Seven deactivation - regeneration cycles were carried out using iso-octane on fresh Pt-/A12O3 while forty deactivation - regeneration cycles were carried out with MCP on the Pt-/A12O3 catalyst used previously for the mortality study with iso-octane. Twelve deactivation regeneration cycles were carried out on dried and undried Pt-Re/A12O3 catalyst using MCP. Two stability states, characterized by the difference in the coke levels, were established in the life of Pt-/A12O3 during the mortality investigation with MCP. The transition from the first state to the second state occurred in the 6th cycle. The coke level in the first state was about 0.045gC while the coke level in the second state was about 0.09gC. The coking levels of the reactants investigated were in the order MCP > N-Octane Iso-Octane.
  • Item
    Open Access
    Experimental and Analytical Investigation of Soil Cutting
    (University of Lagos, 1989) Osho, A.P
    The objective of this work is first to determine experimentally the horizontal and vertical force components of the operative forces during soil cutting. Since previous work in soil cutting had been empirical and involved curve fitting techniques therefore the second objective is to predict these horizontal and vertical force components. In order to achieve these objectives a special apparatus was designed and fabricated for experimentation. It comprises the soil bin, the horizontal and vertical carriages, the proving rings, carriage seat frame, soil hopper, manually operated jack, and the blades. In order to reduce cost and weight of the apparatus, and also because of the limited space available, the carriages and the cutting blades were made of aluminium. In order that this investigation can be applied to a variety of soils, Ogun river sand and beach sand were chosen because they are granular materials, but with different angles of intboth cohesion C and angle of to have a good control to obtain repetitive results. In order to predict accurately, the horizonal and vertical operative forces in soil cutting, it is essential that some specific properties of the soil be known. The soil properties chosen for this work are cohesion, C, perties were determined using triaxial apparatus. Also the shear box apparatus, imposing directional horizontal failure plane was used to The cutting blades inclination B0 to the vertical was varied from O0 to 750 in increments of 150. The soil bin was filled with soil by the soil hopper, whilst the blade was inserted and pushed horizontally by manually operated 10 tonne (98.07 KN) jack, at a horizontal speed of about 0.11 cm/sec. The soil bin perspex glass enabled the tests to be observed visually. The horizontal and vertical force components operating during soil cutting was measured by standard Wykeham-Ferrance proving rings, with maximum load of 200 kgf (1962 N) and with E.L.E. dial gauge of 0.001N/division (0.0254 mm./division). configurations in soil cutting show that whereas 100% of the angle of internal friction, is mobilised for cohesive soil, typified by black cotton soil at failure, only about 80% of the es of the soils were therefore used to evaluate the horizontal and vertical components of operative forces in soil cutting. Other soil parameters like void ratio, and a new soil particle size distribution parameter index (SPI) 0.025 SPI = (Dmax - Dmin) 100 EDX/distribution dervied from grading tests, are found to be true in evaluating these horizontal and vertical components of operative forces. From these findings, empirical formulae were derived, which will be of great benefit and advantage to design engineers, who can quickly estimate the horizontal and vertical components of the operative forces during soil cutting. It was found that as blade inclination Bo and width-to-depth of cut ratio w/d, increased, the horizontal component of force in soil cutting, decreased. The horizontal force decreased by 93%, when width-to-depth of cut ratio w/d = 1, and blade inclination B0 increased from O0 to 750. The passive rankine force is less than the horizontal components of the forces in soil cutting. These forces like the Rankine force are proportional to the square of depth of cut, for vertical blades, that is, blades with inclination B = O0, the horizontal components of the forces can be evaluated by multiplying the Rankine force by constant K which is 7.025 for cohessions soils and 1.06 for cohesive soils. The present work also shows that the optimum performance of the blades occurred at an angle of inclination B = 570 for cohensionless soils. Whilst the optimum performance of the blade for cohessive soils occured at a blade inclination B = 450. A theoretical solution of the boundary energy theory which considers the kinematics of the soil-blade system, predict most accurately the horizontal and vertical components of operative forces in soil cutting, than any other theory hitherto in use. The maximum and minimum errors in horizontal components of forces for Ogun river sand, at blade inclination B0 from zero up to the optimum performance of the blade, were 10.6% and -5% respectively. Similarly the maximum and minimum errors in horizontal components of forces at same blade inclination, for beach sand and black cotton soil, taken in pairs were (9.2% -23.2%) and (2.8%, -0.47%) respectively. At a blade inclination of B = 300, and & = 1/horizontal components of forces, taken in pairs for Ogun river sand were (130N, 126N) and error of 3%. Whilst for beach sand and black cotton soil, at the same blade inclination, the values were (100N, 101N) an error of -1% and (135N, 135N) an error of 0% respectively. Similarly experimental and theoretical vertical components of forces, taken in pairs, at blade inclination B = 300 river sand and black cotton soil, at same blade inclination, the values were (40N, 27N) and 58N, 55N) respectively.