Vol.17, No.4, 2021-Table of Contents
  • Optimizing the Exhaust System of Marine Diesel Engines to Improve Low-speed Performances and Cylinder Working Conditions
  • Abstract Proper design of exhaust systems in marine high-power turbocharged diesel engines can contribute to improve the low-speed performance of these engines and make the working conditions of the cylinders more uniform. Here a high-power marine 16-cylinder V-type turbocharged diesel engine is simulated using the GT-Power software. The results reveal the differences induced by different exhaust system structures, such as an 8-cylinder-in-pipe exhaust system with single/double superchargers and a 4-cylinder-in-pipe exhaust system with a single supercharger. After a comparative analysis, the 8-cylinder type with double superchargers is determined to be the optimal solution, and the structure of the exhaust system is… More
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  • Analysis of the Flow Field Characteristics Associated with the Dynamic Rock Breaking Process Induced by a Multi-Hole Combined External Rotary Bit
  • Abstract The characteristics of the flow field associated with a multi-hole combined external rotary bit have been studied by means of numerical simulation in the framework of an RNG k-ε turbulence model, and compared with the results of dedicated rock breaking drilling experiments. The numerical results show that the nozzle velocity and dynamic pressure of the nozzle decrease with an increase in the jet distance, and the axial velocity of the nozzle decays regularly with an increase in the dimensionless jet distance. Moreover, the axial velocity related to the nozzle with inclination angle 20° and 30° can produce a higher hole… More
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  • Macromolecule’s Orientation in a Nanofiber by Bubble Electrospinning
  • Abstract In the search for sustainable alternatives to harmful synthetic fibers, an increasing amount of research focuses on biomimicry and natural fibers. Sea silk is an exceptional textile material. It is a kind of natural silk produced using the long silky filaments secreted by a specific bivalve mollusk (Pinna nobilis); now at edge of extinction. This paper suggests a simple but effective way to prepare artificial sea silk from Mytilus edulis. A sea silk solution is prepared using a Mytilus edulis protein, and a polyvinyl alcohol (PVA) solution is mixed with the sea silk solution in order to produce artificial sea… More
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  • CFD Analysis and Optimization of an Engine with a Restrictor Valve in the Intake System
  • Abstract In some competitions the rules clearly state that all participating cars must install a restrictor valve structure in the intake system of the engine. The intake air volume of the engine is considerably affected due to the existence of such a valve. Indeed, a small interface diameter through which gas flows can lead to considerable flow resistance and loss. In this study, a four-cylinder engine for FSC racing is analyzed using a combined method based on numerical simulation and experiments. The analysis reveals that the main factors affecting the intake air volume are the intake manifold and the volume of… More
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  • Thermal Analysis of a Novel Oil Cooled Piston Using a Fluid-Solid Interaction Method
  • Abstract Thermal load has a vital influence on the normal operation and service life of diesel engines. In this study, the thermal load and oil-cooling effect on diesel engine pistons were investigated by means of computational fluid dynamics. In particular, the flow and heat transfer characteristics of the cooling gallery were determined during the oscillation of the piston. Moreover, the temperature field distribution of the piston with and without the cooling gallery were compared. The results revealed that the cooling gallery has a prominent effect on reducing the thermal load on the piston crown and piston lands. To fully understand the… More
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  • Mixed Convection in a Two-Sided Lid-Driven Square Cavity Filled with Different Types of Nanoparticles: A Comparative Study Assuming Nanoparticles with Different Shapes
  • Abstract Steady, laminar mixed convection inside a lid-driven square cavity filled with nanofluid is investigated numerically. We consider the case where the right and left walls are moving downwards and upwards respectively and maintained at different temperatures while the other two horizontal ones are kept adiabatic and impermeable. The set of nonlinear coupled governing mass, momentum, and energy equations are solved using an extensively validated and a highly accurate finite difference method of fourth-order. Comparisons with previously conducted investigations on special configurations are performed and show an excellent agreement. Meanwhile, attention is focused on the heat transfer enhancement when different nano-particles:… More
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  • Thermo-Mechanical Analysis of the Sealing Performance of a Diesel-Engine Cylinder Gasket
  • Abstract Taking the combustor composite structure of a high-strength diesel engine as the main research object, dedicated tests have been conducted to verify the accuracy of three distinct cylinder gasket pressure simulation models. Using the measured cylinder gasket compression rebound curve, a gasket unit has been designed and manufactured. For this unit, the influence of the bolt pretension, cylinder body and cylinder head material on gasket sealing pressure has been investigated systematically in conditions of thermo-mechanical coupling. The results show that the bolt pretension force is one of the most important factors affecting the cylinder gasket sealing pressure. The change of… More
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  • A Research on the Flow Characteristics of a Splitter-Based Water Cooling System for Computer Boards
  • Abstract The splitter is an important component of water-based cooling systems used to extract heat from computer boards. In the present study, the flow characteristics of a 16-splitter structure were numerically simulated and compared with experimental results to verify the reliability of the numerical simulation method. Accordingly, the concept of splitter structural coefficients was proposed. Based on the results of this study, we recommend a selection range of 5 ≤ k ≤ 6 for the structure factor k of the splitter; after optimization, the maximum deviation of the splitter outlet flow was reduced from the original value of 100% to 8.3%. More
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  • Coupled Effects of Heat and Moisture of Early-Age Concrete
  • Abstract In order to analyze the coupled influence of temperature and humidity on early-age concrete (including cement and copper tailings), a mathematical model is introduced on the basis of the Krstulovic-Dabic hydration reaction kinetic equations. In such a framework, the influence of hydration-released heat and water consumption are also taken into account. The results provided by such a model are verified by means of experiments and related sensor measurements. The research results show that this model can adequately predict the internal temperature and the humidity temporal evolution laws. More
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