Mechanical Engineering

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Design, construction and testing of a dehuller for African breadfruit (Treculia africana) seeds
(Elsevier, 1999-11-01) Omobuwajo, T. O.; Ikegwuoha, H. C.; Koya, Olufemi A.; Ige, M. T.
The African breadfruit seed is a popular food resource in several parts of West Africa. It is presently being dehulled manually in the absence of a suitable mechanical device. A machine was designed in order to remove the drudgery involved in dehulling the seeds. The machine comprised of a roller which cracks the hull, an oscillating cam follower which removes the cracked hull through repeated shearing against a stationary wall, and an aspiration unit which sifts the hull from the endosperm. A prototype was constructed and tested. Throughput was 64 kg/h; yield, 75%; completely dehulled seeds, 85%; breakage, 1% and sifting efficiency was practically 100%.
Development and Preliminary Testing of Metering Equipment for Mechanized Yam Sett Planting
(JOURNAL OF AGRICULTURAL ENGINEERING AND TECHNOLOGY (JAET) EDITORIAL BOARD, 2005) Aluko, O. B.; Koya, Olufemi A.
This paper reports the design and laboratory testing of equipment for metering yam setts, as a precursory step in the development of a mechanical yam sett planter. The metering equipment was designed to discharge a yam sett at every 1000 mm of within-row spacing using a ground-wheel drive system. Yam setts flow by gravity from a hopper into a metering drum having an internal helical screw and lift flaps, which discharge the yam setts for planting. Laboratory tests of the prototype gave a metering efficiency of 82.2% with percentages of singles, multiples and skips being 80.5%, 0.2% and 17.7%, respectively. The theoretical field capacity is 0.2 to 0.4 ha h-1 at planting speeds of 2.7 to 5.0 km h-1. The work provides a basis for the future development of a mechanical yam sett planter.
Mathematical modelling of palm nut cracking based on Hertz's theory
(Academic Press, 2005-08) Koya, Olufemi A.; Faborode, M. O.
A mathematical model based on Hertz's theory of contact stress was developed for the prediction of force required to break the palm nut. Using nuts subjected to a uniaxial compression stress, in their lateral axis between rigid parallel plates, and those propelled to impinge a rigid cylindrical seat along its lateral axis, experimental verification of the model was conducted comparing the theoretical predictions with estimates from the representations of conventional methods employed in nut cracking. Properties including size, shape and mass, required in the derived model were determined for two varieties of the palm nut. Material stiffness was obtained from the force–deformation curve. Regression analysis showed an exponential variation of the cracking force with nut deformation. Material stiffness obtained was 654 N/mm and 303 N/mm for the ‘Dura’ and ‘Tenera’ nuts, respectively. The respective ranges of geometric mean diameters were 17·07–27·68 mm and 22·32–26.51 mm. There was no significant variation of nut sphericity with size or variety. Force prediction from the Hertzian model proposed gave good prediction of cracking force that was not significantly different from that obtained from a centrifugal nutcracker driven at 1500 min−1, with a 40 cm diameter cracking chamber
Palm nut cracking under repeated impact load
(J. Appl. Sci, 2006) Koya, Olufemi A.
Cracking a whole palm nut under repeated impact load, with the object of minimizing kernel breakage, was modeled and tested. The models were based on the conservation of energy impacted on the nut by a falling weight, or the kinetic energy of a moving nut and the strain energy required in fracturing the nutshell. One of the two models predicts the falling height required to crack a nut, in terms of stiffness, maximum deformation and size of the nut and the load cycles. The second model predicts the hurling speed required to crack a nut, in terms of stiffness, maximum deformation, mass and size of the nut and the load cycles. Experimental verification, which is in good agreement with the theory showed significant reduction in kernel breakage when palm nuts were subjected to low but repeated impact.
Some engineering properties of yam setts from two species of yamsSome engineering properties of yam setts from two species of yams
(Elsevier, 2006-10-01) Aluko, O. B.; Koya, Olufemi A.
Yam production is still mainly carried out manually by peasant farmers using yam setts as planting material. Adequate knowledge of their engineering properties is an essential prerequisite for the scientific design and development of equipment for planting and handling yam setts mechanically. Some engineering properties of yam setts from two species of yams, namely white yam (D. rotundata) and yellow yam (D. cayenensis), were investigated at different moisture contents. The properties investigated include sett density, static coefficient of friction on plywood, galvanized steel and formica surfaces, force–deformation behaviour during quasistatic radial compression, stiffness moduli and sett toughness. The coefficient of friction of yam setts of both species on formica was considerably lower than the corresponding coefficients on wood and galvanized steel, respectively. The results further showed that a considerable reduction in the coefficient of friction was achieved (0.41–0.29 and 0.45–0.25 on formica, for D. rotundata and D. cayenensis, respectively) by air-drying freshly prepared setts at ambient room temperature for at least 4 days. Sett density over the drying period ranged between 1020 and 1180 kgm3 for D. rotundata and between 1030 and 1140 kgm3 for D. cayenensis. The stiffness moduli were 3.53 and 5.36 kNm1 for freshly prepared yam setts of D. rotundata and D. cayenensis, respectively. However, sett stiffness generally decreased as sett moisture content decreased. The toughness of freshly prepared yam setts initially increased, attaining a maximum value within the first 4 days of air-drying, and subsequently decreased with further sett drying. 2005 Elsevier Ltd. All rights reserved.
Upper bound analysis for extrusion at various die land lengths and shaped profiles
(International Journal of Mechanical Sciences, 2006-10-06) Ajiboye, J.S.; Adeyemi, M.B.
The effects of die land lengths, a rarely investigated die extrusion parameter on the die-shaped profiles, on the extrusion pressures are investigated and presented. The analyses of the extrusion pressures by the upper bound method have been extended for the evaluations of the extrusion pressures to complex extruded sections such as square, rectangular, I,- and T-shaped sections with power of deformation due to ironing effect at the die land taken into account. The extrusion pressure contributions due to the die land evaluated theoretically for shaped sections considered are found to increase with die land lengths for any given percentage reduction and also increase with increasing percentage die reductions at any given die land length. The effect of die land lengths on the extrusion pressure increases with increasing complexity of die openings geometry with I-shaped section giving the highest extrusion pressure followed by T-shaped section, rectangular, circular-shaped die openings with square section die opening, giving the least extrusion pressure for any given die reduction at any given die land lengths.
Separation theory for palm kernel and shell mixture on a spinning disc
(Academic Press, 2006-11-01) Koya, Olufemi A.; Faborode, M. O.
The separation of palm kernel from the shell is an important process in the recovery of the kernel for use in vegetable oil production. The inherent shortcoming of the fertiliser spinner spreader, resulting in non-uniform distribution, has led to investigations into the possibility of its use in the separation of palm kernel from shell. The differences in the physical properties of the kernel and shell provided the basis for separation. Models describing the motion of the kernel and the shell on a spinning disc with vanes, feeding a segment at a time, were developed, and comparisons between the predictions and experimental results were made. Discharge angles obtained from the predictive models and from the experiment were in close agreement. The experiment, however, indicated a mid-span, between the discharge angles for kernels and shells, containing the mixture. The models reasonably predict approximate ranges of discharge angles for palm kernels and shells on a spinning disc with specified diameter, friction coefficient and rotational speed.
Computer Aided Plumbing Design
(Academic Journals Inc., USA, 2007) Ajayi, Oluseyi; Ajayi, Oluseyi; Koya, Olufemi A.; Koya, Olufemi A.
This study has been used to eliminate the rigorous activities and time consuming mathematical analysis involved in Plumbing design. The various mathematical steps employed in the design of plumbing systems has been converted into easily interpreted hand user computer program that can be used to generate automatically all the various parameters needed for full design work, when the input data such as head available, various number of fittings, actual length of pipe run and assumed pipe diameter are provided. This has been used to provide a pathway to easy plumbing design
Effects of extrusion variables on temperature distribution in axisymmetric extrusion process
(International Journal of Mechanical Sciences, 2007-09-01) Ajiboye, J.S.; Adeyemi, M.B.
A numerical method was developed to simulate the non-steady-state temperature distributions during forward extrusion process. The velocity, strain rates, and strain fields within the deformation zones during extrusion were obtained, using upper bound method of analysis to obtain internal heat generations coupled to the necessary heat transfer conduction equations. The computer program written in C++ language essentially simulates the extrusion process and takes into account extrusion variables such as material properties, friction conditions, extrusion velocity, extrusion ratio, die preheat temperature, billet height, percentage reduction in area, and die land length. The effects of billet height and percentage reduction in area on the temperature distributions within the dead metal zone give good agreements with experimental results. It is found that the higher the billet’s heights and higher the percentages reduction in areas, the higher the temperature rises during the extrusion process. The die land zone shows increasing temperature rise with increasing friction coefficient, while increasing friction coefficient has no effect on the dead zone temperature. Also, increasing speed of deformation shows an increasing dead zone temperature rise than a more gradual die land temperature rise. It can be stated that the extrusion temperature increases proportionally to the increase of the container temperature.
The effect of selected parameters on temperature distributions in axisymmetric extrusion process
(Journal of Mechanical Science and Technology, 2007-09-30) Ajiboye, J.S.; Adeyemi, M.B.
A numerical method was developed to simulate the transient temperature distributions during forward extrusion process. The computer program simulates the extrusion process and takes into account some extrusion variables such as extrusion velocity, extrusion ratio, die preheat temperature, and percentage reduction in area. It can be seen that the higher the percentages reduction in areas, the higher the temperature rises during the extrusion process. Also, increasing speed of deformation shows an increasing dead zone temperature rise than a more gradual die land temperature rise. It is further seen that extrusion temperature increase is a function of the container temperature.
Deformation and fracture of dika nut (Irvingia gabonensis) under uni-axial compressive loadingc
(International Agrophysics, 2008-01-01) Ogunsina, B. S.; Koya, Olufemi A.; Adeosun, O. O.
Fracture behaviour of dika nut under quasi-static loading along the longitudinal axis and the transverse axis was investigated. The fracture resistance of the nut was measured in terms of average force, deformation and toughness at nutshell fracture, and nut stiffness. Physical dimensions and shape of the nut, to provide for complementary input in design of handling equipment, were also determined. The force required to crack the nut increased with nut diameter but was not significantly different in both loading orientations. The mean cracking force was in the range of 2.06 to 3.67 kN. The compression of the nut exhibited a pronounced linearity between load and deflection. Dika nuts loaded along the transverse axis required less energy for nutshell fracture than those loaded along the longitudinal axis. Minimum toughness occurred with the small size nuts loaded along the transverse axis, thus providing base-line data in future design of an appropriate nutcracker.
A Comparative Performance and Emission Analysis of Blended Groundnut Oil and Mineral Oil Based Lubricants Using a Spark Ignition Engine
(The CIGR E journal Manuscript, 2008-09) Ejilah, I. R; Asere, A. A.
This paper presents the performance and emission behaviour of a spark ignition engine run on groundnut oil blended lubricants. However, for the purpose of comparism, benchmark tests were carried out on multigrade and monograde motor oils. A 5.0 h.p engine test-bed incorporated with an A.C dynamometer and flue gas analyzer was used to conduct the tests. At maximum engine speed, the groundnut oil blended lubricants generated an exhaust temperature of 6.02% higher than multigrade oil, and 6.26% higher than monograde oil. The brake power was 12.70% and 10.94% higher than the monograde and multigrade oils. In terms of fuel economy, the monograde and groundnut oil blended lubricants are 7.50% and 2.18% higher than multigrade oil respectively. It is shown that as the proportion of viscosity modifier in the oil sample increases, exhaust temperature, brake power, brake mean effective pressure (b.m.ep) also increases, while the specific fuel consumption diminishes. At various speeds, CO2 level emitted by the use of groundnut oil blended lubricants was observed to be higher than it was the case for multigrade and monograde oils. In the light of the fast depleting fossil fuel reserve in Nigeria, this work has demonstrated the feasibility of using groundnut oil blends as lubricant substitutes in spark ignition engines.
A Comparative Performance and Emission Analysis of Blended Groundnut Oil and Mineral Oil Based Lubricants Using a Spark Ignition Engine.
(Agricultural Engineering International: The CIGR E journal Manuscript EE 07017., 2008-09) Ejilah, I. R; Asere, A. A.
This paper presents the performance and emission behaviour of a spark ignition engine run on groundnut oil blended lubricants. However, for the purpose of comparism, benchmark tests were carried out on multigrade and monograde motor oils. A 5.0 h.p engine test-bed incorporated with an A.C dynamometer and flue gas analyzer was used to conduct the tests. At maximum engine speed, the groundnut oil blended lubricants generated an exhaust temperature of 6.02% higher than multigrade oil, and 6.26% higher than monograde oil. The brake power was 12.70% and 10.94% higher than the monograde and multigrade oils. In terms of fuel economy, the monograde and groundnut oil blended lubricants are 7.50% and 2.18% higher than multigrade oil respectively. It is shown that as the proportion of viscosity modifier in the oil sample increases, exhaust temperature, brake power, brake mean effective pressure (b.m.e.p) also increases, while the specific fuel consumption diminishes. At various speeds, CO2 level emitted by the use of groundnut oil blended lubricants was observed to be higher than it was the case for multigrade and monograde oils. In the light of the fast depleting fossil fuel reserve in Nigeria, this work has demonstrated the feasibility of using groundnut oil blends as lubricant substitutes in spark ignition engines.
A table mounted device for cracking dika nut (Irvingia gabonensis)
(Agricultural Engineering International: CIGR Journal, 2008-10-13) Ogusina, B. S.; Koya, Olufemi. A.; Adeosun, O. O.
A simply designed machine for cracking dika nut was fabricated. The nut is fed by hand inbetween a toggle mechanism comprising of the slider and a fixed block. Fracture mechanism was based on the deformation characteristics of dried dika nut under uni-axial compression. When actuated, the slider compresses the nutshell to failure along its line of symmetry. The experimental machine gave 100% cracking efficiency but with 24% kernel breakage in cracking sun-dried dika nut at 6.6% moisture content (w.b). The machine provides a viable and effective technique for safe dika kernel extraction.
Development of an intermittent solar dryer for cocoa beans
(Agricultural Engineering International: CIGR Journal, 2009-07-15) Fagunwa, Ayokunle O.; Koya, Olufemi A.; Faborode, Micheal O.
A solar dryer with thermal energy storage was developed for intermittent drying of cocoa beans. The prototype was built using readily available local materials. Drying mechanism was based on a combination of convective heating and direct radiation, with a provision for controlling the rate of airflow through the beans. The experimental model dehydrated cocoa beans from 53.4 to 3.6% moisture content (wb) in a 72 hours inter-mittent drying process against ambient temperature and relative humidity in the range 25-30 o C and 58-98%, respectively. Quality assessment of the dried beans showed that beans of good quality attributes: pH of 6.35, acid value of 3.40 mg/g, with mildly bitter taste were obtained under free convective drying; whilst, increase in moisture re-absorption and acidic flavour were indicated with forced convective drying. The work, thus, provides a viable system for producing cocoa beans of good quality attributes, comparable with using the traditional sun-drying, but without the associated drudgery.
Biodiesel production by transmethylation of Nigerian palm kernel oil
(Ife Journal of Technology, 2009-11) Shote, AS; Betiku, Eriola; Asere, AA
The need for this study arose from the recent energy crisis coupled with the huge potential that Nigeria has for the production of Palm Kernel Oil (PKO). Locally produced PKO was chemically modified (methanolysis) to produce PKO-based biodiesel. The reaction temperature and the catalyst loading were maintained at 60 o C and 1.0% weight of oil, respectively. The methanol to oil molar ratio was kept at 6: 1. The production of PKO-based biodiesel (at 60 o C for 1.5 hours) by transmethylation process in the presence of NaOH as catalyst yielded crude products, Glycerol and biodiesel. Subsequently, PKO (parent oil), automotive gas oil (AGO) and PKO methyl esters transesterified were characterized to determine their properties and suitability as fuels in Compression Ignition Engine (CIE). Results of the transmethylated PKO showed that properties such as viscosity (3.359 cSt), specific gravity (0.8728), water content (nil) and flash point (100 o C) conformed to standards (ASTM, BIS). Properties of the PKO biodiesel were comparable with properties of AGO. Emissions assessment showed that CO concentration was reduced by 30% when PKO biodiesel was used in CIE compared with AGO. Hence, PKO-based biodiesel has a promising prospect for partial or total replacement for petro-diesel in CIE.
The Effect of Surface Conditions on Friction by Tip Test
(Journal of Tribology, 2009-11-09) Jung, K.H; Lee, H.C.; Ajiboye, J.S.; Kang, S. H.; Im, Y
In the present investigation, a tip test based on upsetting and backward extrusion was utilized to characterize the effect of surface roughness of the billet and forming tools, and the type of lubricants on friction. For the test, cylindrical specimens made of aluminum alloys of 6061-O and 2024-O, and single punch and two die sets with different surface topologies, were used with four lubricants such as VG32, VG100, corn oil, and grease. The load levels and tip distances were measured for both materials, and compared with each other to determine shear friction factors at the punch and counter punch interfaces separately, depending on the variation in surface topologies and lubrications using finite element simulations. As a result, a linear relationship among the dimensionless load, tip distance, and shear friction factors at the punch and counter punch interfaces was derived for the experimental conditions investigated. The slope change of this linear relationship from negative to positive clearly depends on the variation in surface conditions at the billet/punch and billet/counter punch interfaces. Also, it was demonstrated that the dimensionless tip distance for the frictionless case can be extrapolated from the experimental data. This value can be used for characterizing the relative effect on friction due to surface conditions at the punch and counter punch, and lubrication quality of the lubricant for the given processing conditions.
EMISSION CHARACTERISTICS OF LIQUEFIED PETROLEUM GAS COMBUSTION IN A PREMIXED SWIRL BURNER
(Ife Journal of Technology, 2010) Akinlalu, B.Z.; Asere, A.A.
Liquefied petroleum gas (LPG) is widely used as a fuel in domestic and industrial heating appliances throughout the world because its combustion products are relatively clean. However, due to its direct association with people, its combustion pollutants are of great concern. To this end, a study was carried out to investigate the effects of swirl intensity and equivalence ratio on emission produced during combustion of liquefied petroleum gas under fuel-lean conditions in a premixed swirl burner. Experiments were carried out using liquefied petroleum gas whose composition is 75% butane, 25% propane and air as charge. Tests were done for vane angles between 35 and 60o in steps of 5o. Employing EGA4 gas Analyzer in measuring NOx and COx emission level, it is shown that emission levels were strongly influenced by swirl intensity and equivalence ratio that strongly decrease pollutant emissions. Between equivalence ratio of 0.65 and 0.90, NOx emission of less than 5ppm and CO emission of less than 60ppm were achieved. Result also showed that at temperature ranges between 927oC and 1012oC, NOx and CO emission generated from combustion of LPG were low.
Characterization of Frictional Behavior in Cold Forging
(Tribology Letter, 2010-10-15) Jung, K.H.; Lee, H.C.; Ajiboye, J.S.; Im, Y.T.
In the present investigation, tip test was utilized to characterize the effects of surface roughness of the specimen and forming tools, rate of deformation, and type of lubricants on friction in solid and solid contact under high contact pressure at room temperature. For the test, a cylindrical specimen made of aluminum alloy of 6061-O was used and grease, corn oil, VG100, and VG32 were applied as lubricants. Single punch and two counter punch sets with different surface roughness of Ra = 0.08 and 0.63 lm were manufactured in order to investigate a frictional behavior during the test. In addition, two different deformation speeds of 0.1 and 5.0 mm/s were used for the test to check their effect on friction as well. Load levels and tip distances obtained from the test were compared to find out any correlation between the two. The change of surface topology of the specimen was monitored by optical measurement technique to better understand a frictional behavior at the punch and counter punch interfaces. Present investigation clearly shows that tip test is easy to apply to experimentally characterize the frictional behavior in cold forging under various processing conditions considered.
PARABOLIC SOLAR COOKER DISH: DESIGN AND SIMULATION
(Solar Energy Society of Nigeria (SESN), 2011) Dasin, D. Y.; Asere, A. A.; Habou, D.
ABSTRACT A complete design and simulation of a parabolic dish solar cooker was carried out. The cooker can be used for boiling water as well as cooking in an isolation. A simulation model for transient state was introduced to predict the absorber (cooking pot), pot cover, cooking fluid and air gap temperatures. Linear regression was used to analyzed the data, an average standard error limit of 12.458345% and R2of 85.725% for the model was obtained which indicate a satisfactory agreement by comparison of experimental and theoretical result. An average instantaneous efficiency of 84% was determined at beam radiation of 650W/m2.

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