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Drag reduction in wall-bounded flows can be achieved by the passive flow control technique through the application of bio-inspired ribleted surfaces. In this paper, innovative design and manufacturing of serrate-semi-circular ribleted surfaces are presented with application to friction and drag reduction on engineering surfaces. Firstly, the design of the ribleted surfaces is described particularly focusing on the serrate-semi-circular shaped structures. Secondly, machining of ribleted surfaces by fly-cutting is investigated, covering the utilization of bespoke CVD diamond tools on a micro-milling machine and the corresponding micro fly-cutting processes. Metrology measurement results show good agreement achieved between the designed and machined surface features. Experiment conducted in wind tunnel shows the machined surface can produce 7% in drag reduction. Compared with conventional micro milling, the micro fly-cutting technique resulted from this research illustrates the unique advantage and industrial significance, particularly for manufacturing microstructured surfaces in an industrial scale.

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In the last few years, the perspective of climate change, energy, competitiveness, and fuel consumption in the transportation sector has become one of the most significant public policy issues of our time. As different methods are being adapted into light-duty vehicles like engine downsizing, on the other hand, the increase in carbon emissions of heavy-duty trucks is becoming a major concern. Although previous researches have studied the methodology for selecting optimized turbocharger performance, still further investigation is needed to create a method for achieving the highest performance for a sequential axial turbocharger. Therefore, in this study, the design of a two-stage turbocharger system that consists of a radial turbine connected in series to an axial turbine is considered. The specific two-stage turbine was designed specifically and will be tested on a MAN 6.9 L diesel truck engine. With the engine already equipped with a radial type turbine, the newly designed two-stage turbine will be adapted to the engine to give more efficiency and power to it. Firstly, the modelling and simulation of the engine were done in Gt-Power, to achieve the same power and torque curves presented in the MAN engine specification sheet. Once that was achieved, the second task was to design and optimise a radial and axial turbine, which will form part of a two-stage system, through Computational Fluid Dynamics (CFD) analysis. Necessary data were gathered from the engine's output conditions, for the ability to design the new turbo system. Lastly, the new turbine data were entered into the new two-stage turbo GT-Power model, and a comparison of the results was made. The CFD analysis, executed in ANSYS, for the radial turbine gave an 83.4% efficiency at 85,000 rpm, and for the axial turbine, the efficiency achieved was 81.74% at 78,500 rpm.Energies 2019, 12, 4433 2 of 21 rapidly [1]. A turbocharger is a turbine-driven forced induction device that works by forcing extra air to the engine's combustion chamber, which increases the efficiency and power output.The new era of turbochargers are designed to be smaller, lighter, and efficient, and one of the essential aspects of turbocharging is to reduce the rotating inertia. Throughout this investigation, an advanced turbocharging project will be undertaken. It will involve the modelling and simulation of a diesel engine but also the design and numerical simulation of a radial and axial inflow turbocharger, which will form part of an in-series two-stage turbocharger system for a diesel engine. To summarize, the axial turbine will be working along with a second conventional radial turbine turbocharger.Another aspect that is forcing manufacturers to reduce emissions is that the government in each country taxes cars regarding their emissions. Prices in the UK vary from 0 to 2000 pounds yearly [2].Therefore, in this study, the design of an axial turbine, which forms part of a two-stage turbocharger (radial-axial), will be tested to confirm if it can have positive results regarding the red...