International Journal of Engineering Research in Africa Vol. 54

Abstract: This work is based on a numerical study of the fluid-structure thermal coupling in a concrete slab intended for habitable heating. A rectangular cross-section pipe in which a hot fluid flow is installed in this concrete slab. The Navier-Stokes equations that govern this flow have been solved numerically. To this end, these equations have been discretized by an implicit finite difference method. The systems of algebraic equations thus obtained have been solved by the Gauss and Thomas algorithms. The conduction equation in the concrete slab was solved using the same methodology as that of flow. In fact, we have based on an algorithm that makes an unsteady solid medium interact with a fluid medium consisting of permanent states series while ensuring the equality of fluxes and temperatures on the common interface between both media at every moment. The numerical simulation of heat transfer and the thermal behavior of the heating slab were analyzed for different parameters influencing thermal diffusion. The results obtained by the numerical model adopted for the control of the fluid-structure coupling are in good agreement with those of the literature results.

Abstract: Turbine blade failures are among the leading causes of steam turbine failure. Failure types typically include cracking, rubbing, blade fouling, and foreign object damage. There is currently a range of non-destructive testing methods used to detect damage at the blade-disk attachment zone, all of which involve disassembling of the blade from the disk for periodic inspection. Evidence indicate that a method to detect damage at the blade-disk attachment zone using a non-contact, non-destructive in-situ off-line modal-based structural health monitoring technique could be useful under some circumstances. Such a technique would have the advantage of eliminating the necessity to disassemble blades during inspection. This would result in significant cost savings. Also, defects associated with the disassembly and reassembly of blades would be avoided. Thus, the aim of this study was to develop a modal-based turbomachinery blade disk attachment inspection technique. Modal parameters were acquired from a robust experimental modal analysis of freely supported low-pressure steam turbine blade-disk segment assemblies. Artificial single-location cracks were intentionally introduced into the turbine blades by cutting a 1 mm thickness notch at three probable damage locations, namely, at the upper pinhole on the leading-edge pressure side, above the root at the base of the aerofoil on the leading-edge and on the trailing-edge. In this work, a finite element analysis of the bladed disk segment assemblies was carried out with and without damage. To validate the reliability of the numerical models, the numerical results were correlated with the measured values, the results of which showed a strong correlation. Finally, a parametric study was conducted in which various healthy and damaged blade-disk cases were systematically investigated. This was done to examine the sensitivity of the blade natural frequency to damage. The artificial damage above the root was found to cause the largest changes in natural frequency. These changes were even more pronounced for assemblies with two blades. Receiver operating characteristic curves were used to assess the discriminatory ability of the results. Each damage case was found to be unique and therefore identifiable from its corresponding healthy case.

Abstract: The expanding and highly greedy Algerian transport sector is totally depending on petro-products, due to the rising numbers of automobile fleets and the excessive dependence on road transportation. Irrecoverable Greenhouse gases GHGs emitted by this sector are constantly increasing. As a result, consumption of diesel and gasoline reached record levels. Consequently, there is a strong need of cleaner, eco-friendly and economically viable alternative fuels. Biofuels, electric, compressed natural gas CNG, liquefied petroleum gas LGP vehicles, are expected to play a crucial role in meeting energy and environmental policies targets. In this paper, the Algerian transport sector perspectives and Greenhouse gases mitigations, in different shaped scenarios based on semi-empirical models, are analyzed and discussed. For adequate policy shaped in a scenario, in 2050, annual Algerian consumption could decrease up to 35%, 43% of CO2 emissions and 73% of NOx emissions could be mitigated compared to no-intervention scenario. These promising findings indicate the huge potential of resource diversification on the transportation sector. Therefore, implementing such policies is fundamental for a durable Algerian’s transportation sector transition policy.

Abstract: Performance of activated sludge wastewater treatment plants are mainly dependent on bacterial growth, which is limited by many factors. These factors include availability of suitable substrate, limiting nutrients, environmental conditions, and energy. In activated sludge model no. 3 (ASM3), constituents in wastewater are divided into two main categories: carbonaceous compounds and nitrogenous compounds, which are further subdivided depending on their solubility and biodegradability. These compounds are not mutually independent; hence, the fate of one compound in the biological processes is affected by one or more of the other compounds. In this study, a steady-state analysis was conducted to investigate the effect of initial readily biodegradable substrate, oxygen, ammonia nitrogen, nitrite plus nitrate, and heterotrophic organisms’ concentrations on the effluent concentrations of readily biodegradable COD and nitrogen compounds. The studied ranges of the selected wastewater state variables were identified based on literature surveys including previous studies concerning domestic, industrial, and synthetic wastewaters. The results proved that the effluent readily biodegradable substrate and ammonia nitrogen concentrations are reduced as the initial dissolved oxygen and nitrite plus nitrate concentrations are increased. Moreover, better nitrification-denitrification process is achieved at lower initial readily biodegradable concentration leading to lower nitrite plus nitrate concentrations.

Abstract: The paper focuses on Information and communication technologies (ICT) deployed by Logistics service providers (LSP), particularly for the monitoring and companies. Indeed, nowadays ICT are essential for any implementation of efficient traceability, notably for the outsourcing of logistics activities. This paper is structured around two parts: the first part presenting the state of the art in terms of outsourcing logistics activities and traceability. The second part concerns a comparative study combining a set of LSP operating in Morocco and those operating abroad through several criteria. These criteria include the services offered and the technology deployed for rigorous traceability. The comparative study will determine the profile of the LSP operating in Morocco and adopting an effective and efficient traceability strategy based on innovative technology.