Advanced Engineering Forum Vol. 35

Abstract: The tensile deformation behaviour of magnesium alloy AE44 (Mg-4Al-4RE) under strain rates ranging from 10^-6 to 10^-1 s^-1 has been investigated. Present study shows that the deformation mode begins with the activation of elastic (Stage 1), followed by <a> basal slip and twinning (Stage 2), <a> prismatic slip (Stage 3) and finally to <c+a> pyramidal slip (Stage 4). The commencement of these deformation mechanisms results in four distinct stages of strain hardening in the stress-strain curve. In this work, the four stages of deformation behaviour are modelled, and an empirical equation is proposed to predict the entire stress-strain curve. Overall, the model predictions are in good agreement with the experimental data. This study on the decomposition of stress-strain curve into four stages provides insights into the contribution of individual deformation mechanism to the overall deformation behaviour and opens a new way to assess mechanical properties of die-cast magnesium alloys.

Abstract: In this study, deep eutectic solvent (DES) used as co solvent for enzymatic biodiesel production from degumming palm oil (DPO). DES is formed from the salt compound choline-chloride (ChCI) with glycerol at 1:2 molar ratio. Furthermore, the effectiveness of the DES was tested by enzymatic reactions using novozym 435^® for the production of palm biodiesel with raw materials DPO. The use of enzymes with the DES system can maintain the activity and stability of the novozyme enzyme measured by the yield produced until the 10th usage produces biodiesel yield > 99% with a concentration of DES 0.5% with a molar ratio of 0.5% water. Spectra of DES ChCI:glycerol and ChCI:glycerol:water characterized by FTIR, morphological structure novozym by characterized SEM and then biodiesel product analyzed by GC-MS. This shows that the ChCI:glycerol:water system in enzymatic biodiesel production has good potential to maintain enzyme activity and stability.

Abstract: Non-equilibrium molecular dynamics simulations have been employed to study the explosive boiling phenomena of water over a hot copper plate. The molecular system was comprised of three sections: solid copper wall, liquid water, and water vapor. A few layers of the liquid water were placed on the solid Cu surface. The rest of the simulation box was filled with water vapor. Initially, the water molecules were equilibrated by using Berendsen thermostat at 298 K. Then heat was given to the copper plate at different temperatures so that explosive boiling occurs. After achieving the equilibrium by performing the previous two steps, the liquid water at 298 K is suddenly dropped on the hot plate. NVE ensemble was used in the simulation and the temperature of the copper plate was controlled to different temperatures with phantom atom thermostat. Four temperatures (400K, 500K, 650 K and 1000K) were taken to study the explosive boiling. The simulation results show that, the explosive boiling temperature of water on Cu plate is 500 K temperature. At this point, the energy flux was found 1.79x10⁸ J/m³ which is very promising with the experimental results. Moreover, if the temperature of the surface was increased the explosive boiling occurred at a faster rate. The simulation results also show that explosive boiling occurs earlier for the hydrophilic surface than hydrophobic surface as for the hydrophilic surface the water attracted the Cu plate more than the hydrophobic surface and so the amount of energy transfer is more for the hydrophilic surface.

Abstract: ‘Smallsats,’ originated in the 1990s and popularized again since 2005, is a newly emerging miniaturized form of conventional satellites. Characterized by low mass (usually under 500 kg) and compact dimensions, Smallsats are one of the most sought-after forms of satellites, thanks to the ease offered by the lightweight. However, this privilege brings with itself the significant impediments such as excessive heat generation arising from the compact stature during peak hours of operation, external heat load as a result of radiation. These heat loads manifest themselves as the direct solar flux, earth’s albedo, and earth’s infrared radiation. Sudden temperature drop within the eclipse region results in the permanent-equipmental damage of the electronic circuitry involved, the direct consequence of which is the out-of-tolerance performance of the satellite. Thermal Control Systems (TCS) is the most plausible solution in this regard whose chief objective in any spacecraft or a satellite is to maintain all the subsystems along with the payload components within the stipulated temperature limits for each mission phase. This paper presents the passive thermal control systems (PTCS) in cube-sats. Starting with the discussion of the thermal environment, typical concepts like albedo, earth IR are shed light on. Subsequent discussions follow the study of thermal surface finishes and multi-layer insulations (MLI). Finally, the applications of phase-change materials (PCM) in thermal control systems of cube-sats are introduced. The constant trade-offs between the optimal thermal finish and the overall performance, arising due to incurrence of contamination during synthesis, SLI-MLI thickness and cost associated with increasing thickness and the phase-change materials (PCM’s) and their compatibility, have always been at the pin-point of the research. The widespread importance of thermal control systems is attributed to its ability to ensure the meetings of the gradient requirements, a parameter playing a crucial role in spacecraft dynamics.

Abstract: With each passing day companies are looking more and more in the initial phase of the project, to understand the phenomena arising, so that in the execution of the project there are no failures, much less when the project is in operation. For this, the numerical simulation has been shown an increasingly efficient tool to assist the engineers and designers of machines and equipment. The Kaplan turbine design requires a high level of engineering expertise combined with a high level of knowledge in fluid mechanics, as poor design of a diffuser fin can lead to disordered turbulent flow which, when mixed with a high pressure drop, can cavitate into turbine blades. The aim of this study is to evaluate different types of diffuser fin profiles in the inlet at Kaplan turbines. For this, numerical computer simulation was used with the aid of the Ansys Fluent software, in which simulations of water flow in a steady state occurred. The software works with the finite volume method for the discretization of the Navier-Stokes equations. The simulations have proved to be efficient in capturing current lines and pointing out the best flow profile in a project, avoiding more complex turbine blade problems.

Abstract: The push-over nonlinear evaluation of four eccentrically braced frame performance was conducted to assess the plastic deformation and location of plastic hinges in buildings with six, nine, twelve and fifteen stories. The excessive plastification of out-of-beam members is revealed in the majority of these buildings while the AISC design provision allows the moderate plastification in these members. Therefore, the beams out of link might be in danger of fracture of web and flange. Likewise, this was controversial evidence in Chrischurch earthquakes. In order to modify this problem either using fixed connection of braced members or using the very short shear links which have less end moment force than out-of-link beams moment strength are recommended. By this modification, the response modification coefficients are calculated for these buildings which are almost equal to the provision value. The maximum plastic rotation of shear links recommended by provisions (0.08 radian) is the upper ultimate limit to prevent emerging of out-of-link member`s instability.

Abstract: IMO ANNEX VI has enacted TIER III since 2016; one of the regulated emissions is NO_X. The effective NO_X reducing method is by using Exhaust Gas Recirculation (EGR). EGR valve with air-cooled angle globe valve type has been developed in Marine Diesel Laboratory, Department of Marine Engineering, Sepuluh Nopember Institute of Technology (ITS). EGR is in use on the Yanmar TF 85-MHDI diesel engine to study performance of engine, combustion processes, and NO_X emitted experimentally. EGR varies from 0, 10, 20, and 30% respectively. To learn the performance of engine speed varied from 1800-2200 rpm. While the combustion process and NO_X follow of IMO ANNEX VI. EGR without air cooling (HOT-EGR) is also studied for use as a reference of COLD-EGR achievement. The result of emission examine according to statistical data that modified diesel engine with HOT-EGR and COLD-EGR system are able to be within the threshold of emission test in TIER 2, at EGR valve opening 20% and 30% for load of 25%, 50%, and 75%. While for 100% load at EGR valve opening of 20% and 30%, the emission of diesel engine is capable of entering the TIER 3. In terms of performance the SFOC value can be improved on 10% of COLD-EGR condition with decrease of 14.62%, result for combustion process Peak pressure on the diesel engine becomes low and the heat release decreases.

Abstract: Wind energy conversion systems (WECS) have developed rapidly in recent years in terms of capacity and wind turbines design. This development led to improve power quality, to reduce the costs and increase the energy yield. WECS are expected to be reliable, effective and more cost-competitive. A comprehensive analysis and review on electrical machines in WECS (viz., wind turbine generators) has been presented in this paper. Design, (dis) advantages, and market penetration of different wind turbine generators are analyzed and discussed. Some comparisons have been made on the permanent-magnet (PM) synchronous machines, promising generator for future wind turbines, especially offshore wind turbines.

Abstract: Installation of distributed generations (DGs) could be an effective solution to the problem of shortage of the electric energy especially in populated areas. Installation of DG in non-suitable places can result in more energy losses and voltage instability which leads to higher operating cost. DGs should be placed optimally in the network to get maximum efficiency of the system. This paper presents a new method to solve the optimal sizing and placement of DGs with the aim of minimizing real power loss and improving voltage profile in a distribution system. A power flow technique based on Backward/Forward (BW/FW) sweep is used to calculate the system losses through different branches. Particle Swarm Optimization algorithm is used to find out the optimal size and to identify the DG units placement in a radial distribution system simultaneously. Different scenarios of DG capacity are considered. The constraints of voltage and current through branches are investigated. The method is tested on 33-bus and 69-bus radial distribution systems to demonstrate the performance and the effectiveness of the proposed method. The results obtained are discussed and analyzed where they proved the usefulness of the applied algorithm.

Abstract: Drilling engineers and operators are stuck with challenges associated with loss circulation of drilling fluids in wellbores during drilling operation. At such times, a clear and careful decision is required in order to minimize cost or save resources that would have been lost in the bid to remedy the situation. This then informs the need to deploy reliable tools that will inform useful decisions as drawn from a thorough risk-analysis coined from the information gathered from the formation characteristics and operating pressure. In this study, a real-time statistic based approach was adopted in carrying out risk-evaluation of loss circulation events in a wellbore. Based on the expected opportunity loss analysis, it is often non-negotiable to consider other options when the analytical solution suggests that the well should be “abandoned”. For the decision tree, at the decision node, D₁, the expected loss of the seal off zone option is $161.25, the expected loss of the drill ahead option is $19.2 and the expected loss of the abandon option is $13.2. Since the expected loss of the abandon option is less than the expected value of both the seal off and the drill ahead option, it is recommended to abandon the well. Furthermore, the risk analysis proved to be a veritable tool considering the cost implications of other options; and can also serve as basis for automated decision-making.