International Journal of Engineering Research in Africa Vol. 25

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Authors: Yuri M. Baron
Abstract: Blanks made from sheet steel or other materials have burrs on their edges. The burrs are formed on the blanks at cutting down or processing of them by cutting tools. Removing of the burrs requires a lot of manual work. Frequently the blanks have small rigidity, and it especially complicates removal of the burrs. This article describes intensification of the magnetic abrasive finishing method (MAF) with a goal to eliminate the manual deburring and to raise productivity of deburring on the flexible blanks. The study goal was achieved by optimization of MAF conditions and a of the work area geometrical form.
Authors: S.T. Selvamani, S. Divagar, M. Vigneshwar
Abstract: Aluminum alloys are widely used in engineering structures and components where light weight or corrosion resistance were required. Friction welding is classified as a solid-state welding process where metallic bonding is produced at temperatures lower than the melting point of the base metals. Friction time, friction pressure, forging time, forging pressure and rotation speed are the most important parameters in the friction welding process. The Response Surface Methodology (RSM) is used to optimize the process parameter and also useful in developing a proper approximation for the right functional relationship between independent variables and the response variable that may differentiate the nature of the joints. The empirical relationships are developed with the help of ANOVA design matrix to obtain the maximum tensile strength in the joints. The integrity of the joints are evaluated by Optical Microscopy (OM) and Energy Dispersive X-ray Analysis (EDAX) in this research work.
Authors: Yun Qing Gu, Qiang Wang, Qiang Liu, Yao Lin Sun, Tian Xing Fan, Deng Hao Wu
Abstract: Vortex pump is a kind of non-clogging pump, which will cause a large amount of vortex during transportation. Four kinds of mathematical model of vortex pump are introduced with continuous improvement. Moreover, the internal flow state, calculation and design method are also presented. In addition, the influent of slurry and structure parameters is introduced. After analyzed above, the design method of vortex pump can be further investigated specific to different concentration, viscosity and particle sizes under different specific speed. The focus of future research is testing internal flow by the advanced technology, building up a new flow model and proposing complete and practical calculation method.
Authors: M. Ganesan, S. Sendilvelan
Abstract: Control of harmful emissions during cold start of the engine has become a challenging task over the years due to the ever increasing stringent emission norms. Positioning of the catalytic converter closer to the exhaust manifold is an efficient way of achieving rapid light-off temperature. On the other hand, the resulting higher thermal loading under high-load engine operation may substantially cause thermal degradation and accelerate catalyst ageing. The objective of the present work is to reduce the light-off time of the catalyst and at the same time to reduce the thermal degradation and ageing of the catalyst to the minimum possible extent. In the present work two innovative approaches namely Parallel Catalytic Converter System (PCCS) and Telescopic Catalytic Converter System (TCCS) have been adopted to reduce the light-off time of the catalyst. The tests were conducted on a 4 cylinder Spark Ignition Engine under cold start condition. It was established that considerable reduction in the light-off time was achieved by using TCCS. Further reduction in the light-off time was achieved by using pre catalysts (40%vol. & 20%vol.) and hot air injection. It has been found that 13% reduction in CO light-off time was achieved with pre-catalyst (40%vol.), 50% reduction with pre-catalyst (20%vol.) and 66% reduction with hot air injector system, when compared to TCCS. Also 14% reduction in HC light-off time was achieved with pre-catalyst (40%vol.), 43% reduction with pre-catalyst (20%vol.) and 63% reduction with hot air injection system, when compared to TCCS. It was also established that light-off time of TCCS can be brought down to 10 seconds using hot air injection.
Authors: Salman Abdu, Song Zhou, Malachy Orji
Abstract: Highly increased fuel prices and the need for greenhouse emissions reduction from diesel engines used in marine engines in compliance with International Maritime Organization (IMO) on the strict regulations and guidelines for the Energy Efficiency Design Index (EEDI) make diesel engine exhaust gas heat recovery technologies attractive. The recovery and utilization of waste heat not only conserves fuel, but also reduces the amount of waste heat and greenhouse gases dumped to the environment .The present paper deals with the use of exergy as an efficient tool to measure the quantity and quality of energy extracted from waste heat exhaust gases in a marine diesel engine. This analysis is utilized to identify the sources of losses in useful energy within the components of the system for three different configurations of waste heat recovery system considered. The second law efficiency and the exergy destroyed of the components are investigated to show the performance of the system in order to select the most efficient waste heat recovery system. The effects of ambient temperature are also investigated in order to see how the system performance changes with the change of ambient temperature. The results of the analysis show that in all of the three different cases the boiler is the main source of exergy destruction and the site of dominant irreversibility in the whole system it accounts alone for (31-52%) of losses in the system followed by steam turbine and gas turbine each accounting for 13.5-27.5% and 5.5-15% respectively. Case 1 waste heat recovery system has the highest exergetic efficiency and case 3 has the least exergetic efficiency.
Authors: L.V. Trykoz, I.V. Bagiyanc, V.Yu. Savchuk, O.M. Pustovoitova, S.M. Kamchatnaya, O.S. Saiapin
Abstract: The article deals with the measuring results of the specific conductance of multicomponent systems which consist of more than three materials of various characteristics. As it was shown the electrical conductivity of systems composed of soil, slag and water depends in a lesser degree on the amount of slag and in a greater degree on slag’s chemical composition. The value of specific conductance decreases when the amount of slag increases for basic slag, and increases for acid slag. For a system, which includes gravel particles coated with organic substances, the value of specific conductance correlates with the electric properties of the materials used, namely the function of chemical composition of the musticomponent system. Thus, there is a possibility to design a mathematical model for forecasting electric properties of multicomponent systems, which is based on an objective characteristic, namely, chemical structure of the materials used.
Authors: Macharla Jayachandra Babu, Naramgari Sandeep
Abstract: Three-dimensional magnetohydromagnetic slip flow of chemically reacting fluid over a variable thickness stretching sheet with space and temperature dependent heat source/sink was analysed numerically. Runge-Kutta and Newton’s methods are employed for solving the reduced ordinary differential equations with the help of similarity variables. Plots are demonstrated and examined for several parameters of concern. Also the effect of the same parameters on skin friction coefficient, heat and mass transfer rates are presented in tabular form. We found a good agreement of the present results by comparing with the published results. It is observed that space and temperature dependent heat source/sink parameters acts like controlling parameters of heat transfer. Slip effects reduce the development of concentration and thermal boundary layers.
Authors: Tariq Rahim, Jia Dong Xu
Abstract: The high frequency field expressions are analyzed for perfect electromagnetic conducting (PEMC) elliptical reflector embedded in isotropic, homogeneous and reciprocal chiral medium. Geometric optics (GO) method is used to find the caustic region field for the PEMC elliptical reflector. However, GO fields are not valid around the caustic region due to the occurrence of un-realistic singularity around the caustic region. Therefore, Maslov’s method is used to derive the high frequency fields which are also valid in the vicinity of the caustic region. The effect of admittanceM of the PEMC boundary and the chirality parameter on the high frequency fields are illustrated by plotting the numerical results using MATLAB software. A special case of PEMC circular reflector is also discussed.
Authors: Cherif Khelifi, Fateh Ferroudji, Mohammed Ouali
Abstract: Wind and solar resources are diluted and intermittent on the earth; their combination allowed increasing their availability and stability. At great scale, the use of Solar Chimney Power Plant (SCPP) technique constitutes a promising alternative to fossil fuel for generating electrical power particularly in rich regions of natural resources such as solar, wind, terrain, built material, water…etc.). Recently, various research works investigate the design and optimization of these systems under operating conditions. The analysis of different studies carried out on (SCPP), allowed to develop a parametric modelization approach in steady state, founded on 1D heat and mass transfer inside the (SCPP) in order to describe, optimize and to assess its performances under the influence of geometric, operating and ambiance conditions using Matlab-Simulink code. From the present simulation results, the (SCPP) appeared feasible since the temperature gradient of the airflow between the inlet and outlet of the chimney attains 13°C and remains constant during operating cycle. The (SCPP) output is strongly influenced by solar radiation intensity, air heater surface, and chimney height. The solar air heater, the tower (chimney) and the (SCPP) efficiencies obtained are 22.6%, 19.2% and 2.6% respectively.
Authors: Chuang Liu, Zhao Wei Sun, Ke Ke Shi, Feng Wang
Abstract: In this paper, we address the mixed H2/H control approach for linear time-invariant system based on linear matrix inequality (LMI). First, the problem to be solved is stated, and the satellite attitude dynamics is established and converted into a corresponding state space form. Then, the mixed H2/H controller based on LMIs is designed in order to attain the state feedback gain matrix. To validate the efficiency and practicability of the proposed controller, simulation results based on satellite attitude system are presented, from which we can observe that under the condition of external disturbances, the system will be stable within 150s, and the maximum of control torque will be no more than 0.025Nm. Expanding the controller gain will affect the stabilizing process, but not the stabilization time, and it will increase the control input which will bring pressure to the actuator.

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