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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers B
Journal Basic Information
Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 39, Issue 12 - Dec 2015
Volume 39, Issue 11 - Nov 2015
Volume 39, Issue 10 - Oct 2015
Volume 39, Issue 9 - Sep 2015
Volume 39, Issue 8 - Aug 2015
Volume 39, Issue 7 - Jul 2015
Volume 39, Issue 6 - Jun 2015
Volume 39, Issue 5 - May 2015
Volume 39, Issue 4 - Apr 2015
Volume 39, Issue 3 - Mar 2015
Volume 39, Issue 2 - Feb 2015
Volume 39, Issue 1 - Jan 2015
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Conical Diffuser Design and Hydraulic Performance Characteristics in Bioreactor Using Empirical and Numerical Methods
Lee, Seung-Jin ; Ko, Kyeong-Han ; Ko, Myeong-Han ; Yang, Jae-Kyeong ; Kim, Yong-Guk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 39, issue 8, 2015, Pages 633~643
DOI : 10.3795/KSME-B.2015.39.8.633
In this study, we develop a highly efficient conical-air diffuser that generates fine bubble. By inserting a sufficient number of aerotropic microorganisms with dissolved oxygen from an air diffuser and minimizing the air-channel blockages within the air diffuser, we expect to improve the efficiency and durability of the decomposition process for organic waste. To upgrade the conventional air diffuser, we perform experiments and numerical analysis to develop a conical-type that generates fine bubble, and which is free from nozzle blockage. We complement the air-diffuser design by numerically analyzing the internal air-flow pattern within the diffuser. Then, by applying the diffuser to a mockup bioreactor, we experimentally and numerically study the bubble behavior observed in the diffuser and the 2-phase fluid flow in the bioreactor. The results obtained include statistics of the cord length and increased velocity, and we investigate the mechanisms of the fluid-flow characteristics including bubble clouds. Throughout the study, we systemize the design procedures for the design of efficient air diffusers, and we visualize the fluid-flow patterns caused by bubble generation within the mockup bioreactor. These results will provide a meaningful basis for further study as well as the detection of oxygen transfer and fluid-flow characteristics in real-scale bio-reactors using sets of air diffusers.
Flow Characteristics of Central-Driven Ejector with Design Parameters
Park, Sang Kyoo ; Yang, Hei Cheon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 39, issue 8, 2015, Pages 645~651
DOI : 10.3795/KSME-B.2015.39.8.645
The objective of this study is to experimentally investigate the effect of design parameter on the mass ratio of a central-driven ejector. The design parameters are the primary nozzle area and distance ratios, diffuser exit-area ratio and mixing-tube length ratio. The experimental setup was an open-loop continuous circulation system which has a movable nozzle ejector, an electric motor-pump, a water tank, a control panel and high-speed camera unit. We calculated the mass ratio using the measured primary and suction-flow rates with the experimental parameter of primary water-flow rate or pressure. The results showed that the mass ratio increased with the primary nozzle distance ratio and mixing tube length ratio, while the mass ratio decreased with the primary nozzle-area ratio and diffuser exit-area ratio.
Investigating the Power-Performance Prediction on an H- and Helical-type Tidal Current Turbine Using CFD Method
Kim, Bum Suk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 39, issue 8, 2015, Pages 653~660
DOI : 10.3795/KSME-B.2015.39.8.653
In this study, we conduct power performance and load analyses of two different types of vertical-axis tidal-current turbines using the computational fluid dynamics (CFD) method. To analyze the power output and loads, we perform transient CFD simulations considering the cavitation model using ANSYS CFX. The averaged power output of an H-type rotor was 7.47 kW and 67.6 kW in normal and extreme operating conditions, respectively, which did not satisfy the initial design conditions. However, in the case of the helical-type rotor, the power output under normal and extreme conditions were close to the expected values. The cavitation, which may cause instantaneous power fluctuation, occurred repeatedly at the suction side of the rotors. In order to guarantee a more stable power supply and to prevent fatigue failure, we require a design that minimizes cavitation.
Rotor-Blade Shape Design and Power-Performance Analysis for Horizontal-Axis Tidal Turbine Using CFD
Jung, Ji Hyun ; Kim, Bum Suk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 39, issue 8, 2015, Pages 661~668
DOI : 10.3795/KSME-B.2015.39.8.661
We present a design methodology for horizontal-axis tidal turbine blades based on blade element momentum theory, which has been used for aerodynamic design and power-performance analysis in the wind-energy industry. We design a 2-blade-type 1 MW HATT blade, which consists of a single airfoil (S814), and we present the detailed design parameters in this paper. Tidal turbine blades can experience cavitation problems at the blade-tip region, and this should be seriously considered during the early design stage. We perform computational fluid dynamics (CFD) simulations considering the cavitation model to predict the power performance and to investigate the flow characteristics of the blade. The maximum power coefficient is shown to be about 47 under the condition where TSR = 7, and we observed cavitation on the suction and pressure sides of the blade.
Effect of Height Variation of Recirculating Casing Treatment on the Performance of a Turbocharger Compressor
Nguyen, Van Hap ; Zhou, Tianjun ; Lee, Geun Sik ;
Transactions of the Korean Society of Mechanical Engineers B, volume 39, issue 8, 2015, Pages 669~675
DOI : 10.3795/KSME-B.2015.39.8.669
In this study, we investigate the performance variations of an automotive turbocharger compressor with respect to the height variation of the recirculating casing treatment (RCT). We use three RCT heights, namely 1.2 mm, 1.5 mm, and 1.8 mm. We vary the compressor speed from 90,000 to 150,000 rpm, and the flow rate from 0.015 kg/s to 0.08 kg/s. The calculation results of the total pressure ratio and isentropic efficiency showed good agreement with the performance data provided by the manufacturer within a 0.7 percent error. The results showed that the RCT heights of 1.2 mm, 1.8 mm, and 1.5 mm, in that order, exhibited a more uniform pressure distribution, higher pressure ratio, and wider operational range. As the number of revolutions per minute increased, we obtained typical characteristics of a compressor map having a narrower operational range in the region of higher pressure ratio.
Relative Viscosity of Emulsions in Simple Shear Flow: Temperature, Shear Rate, and Interfacial Tension Dependence
Choi, Se Bin ; Lee, Joon Sang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 39, issue 8, 2015, Pages 677~682
DOI : 10.3795/KSME-B.2015.39.8.677
We simulate an emulsion system under simple shear rates to analyze its rheological characteristics using the lattice Boltzmann method (LBM). We calculate the relative viscosity of an emulsion under a simple shear flow along with changes in temperature, shear rate, and surfactant concentration. The relative viscosity of emulsions decreased with an increase in temperature. We observed the shear-thinning phenomena, which is responsible for the inverse proportion between the shear rate and viscosity. An increase in the interfacial tension caused a decrease in the relative viscosity of the decane-in-water emulsion because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress.
The Co-Combustion Characteristics of Coal and Wood Pellet in a 25W Lab-scale Circulating Fluidized Bed Reactor
Kim, Jin Ho ; Yang, Sang Yeol ; Kim, Gyu Bo ; Jeon, Chung Hwan ;
Transactions of the Korean Society of Mechanical Engineers B, volume 39, issue 8, 2015, Pages 683~691
DOI : 10.3795/KSME-B.2015.39.8.683
Circulating Fluidized Bed(CFB) combustion has the several advantages which are the fuel flexibility, the economy, the efficiency and the environment. It is necessary to apply a renewable energy to produce electricity due to the Renewable Portfolio Standard(RPS) mandates recently. So, in this study, co-combustion with a coal and a wood pellet was investigated to evaluate the combustibility and the environment as function of blending ratio of them in a Lab-scale CFB reactor. To investigate the characteristics of the co-combustion, the blending ratio which is the weight of wood pellet by the total calorific value of the supplied, was considered. Bed material was a river sand(No. 7). As increasing the blending ratio, the exhausted gas emissions such as CO, NOx, HC and SOx were decreased. But in case of wood pellet over 30%, CO, HC and SOx emission were increased. And the gas temperatures at the downstream were decreased.
Numerical study to Determine Optimal Design of 500W Darrieus-type Vertical Axis Wind Turbine
Lee, Young Tae ; Lim, Hee Chang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 39, issue 8, 2015, Pages 693~702
DOI : 10.3795/KSME-B.2015.39.8.693
This paper presents the performance characteristics of a Darrieus-type vertical-axis wind turbine (VAWT) with National Advisory Committee for Aeronautics (NACA) airfoil blades. To estimate the optimum shape of the Darrieus-type wind turbine in accordance with various design parameters, we examine the aerodynamic characteristics and separated flow occurring in the vicinity of the blade, the interaction between the flow and blade, and the torque and power characteristics that are derived from it. We consider several parameters (chord length, rotor diameter, pitch angle, and helical angle) to determine the optimum shape design and characteristics of the interaction with the ambient flow. From our results, rotors with high solidity have a high power coefficient in the low tip-speed ratio (TSR) range. On the contrary, in the low TSR range, rotors with low solidity have a high power coefficient. When the pitch angle at which the airfoil is directed inward equals
and the helical angle equals
, the Darrieus-type VAWT generates maximum power.
Numerical Study on Variations in the Sealing Performance of Air Curtains in Large-Scale Factory Opening Considering Various Design Factors
Moon, Jongmin ; Rhee, Gwang Hoon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 39, issue 8, 2015, Pages 703~711
DOI : 10.3795/KSME-B.2015.39.8.703
In large-scale factories, there are usually openings in the building to increase the efficiency of workers. However, if the factory is heated during winter, openings significantly increase the heating load. Therefore, there is a need for air curtains to be installed at the top of openings in factories to reduce the heating load due to the cold air entering from outside. The main design variables of these air curtains are the discharge angle, speed, and temperature, etc. While there have already been many studies focusing on these design variables, the distance from the opening and the width of the discharge have not been studied even though they also affect the sealing performance. As a result, when the distance from the opening decreases and the width of the discharge increases, we realize an optimum air curtain performance. However, if the distance from the opening is about 1.5 m, by adjusting the discharge angle and the distance from the opening, the sealing performance of the air curtain is improved by 13.7％.