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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The KSFM Journal of Fluid Machinery
Journal Basic Information
Journal DOI :
Korean Fluid Machinery Association
Editor in Chief :
Volume & Issues
Volume 18, Issue 6 - Dec 2015
Volume 18, Issue 5 - Oct 2015
Volume 18, Issue 4 - Aug 2015
Volume 18, Issue 3 - Jun 2015
Volume 18, Issue 2 - Apr 2015
Volume 18, Issue 1 - Feb 2015
Selecting the target year
CFD Analysis to Estimate Drop Time and Impact Velocity of a Control Rod Assembly in the Sodium Cooled Faster Reactor
Kim, JaeYong ; Yoon, KyungHo ; Oh, Se-Hong ; Ko, SungHo ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 5~11
DOI : 10.5293/kfma.2015.18.6.005
In a pressurized water reactor (PWR), control rod assembly (CRA) falls into the guide tubes of a fuel assembly due to gravity for scram. Various theoretical approaches and numerical analyses have been performed because its shape is simple and its design was completely developed several decades ago. A control rod assembly for a sodium-cooled faster reactor (SFR) which is geometrically more complicated is being actively developed in Korea nowadays. Drop time and impact velocity of a CRA are important parameters with respect to reactivity insertion time and the mechanical robustness of a CRA and a guide duct. In this paper, computational method considering simultaneously the equation of motion for rigid body and the Navier-Stokes equations for fluid is suggested and verified by comparison with theoretical analysis results. Through this valuable CFD analysis method, drop time and impact velocity of initially designed SFR CRA are evaluated before performing scram tests with it.
Design of Magnetic Bearings for 200 HP Class Turbo Blower
Park, Cheol Hoon ; Yoon, Tae Gwang ; Park, Jun Young ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 12~18
DOI : 10.5293/kfma.2015.18.6.012
Recently, the development trend of turbomachinery is high capacity and high efficiency. Most of turbomachinery in the market are adopting ball bearings or air foil bearings. However, ball bearings have a limit for high speed product over
(product of the inner diameter of the bearing in mm (D) and the maximum speed in rpm (N)). Air foil bearings have a limit for high axial load for high power products over 200~300 HP(horse power). Magnetic bearing is one of the solutions to overcome the limits of high speed and high axial load. Because magnetic bearings have no friction between the rotor and the bearings, they can reduce the load of the motor and make it possible to increase the rotating speed up to
. Moreover, they can have high axial load capacity, because the axial load capacity of magnetic bearing depends on the capacity of the designed electromagnet. In this study, the radial and thrust magnetic bearings are designed to be applied to the 200 HP class turbo blower, and their performance was evaluated by the experiment. Based on the tests up to 26,400 rpm and 21,000 rpm under the no-load and load condition, respectively, it was verified that the magnetic bearings are stably support the rotor of the turbo blower.
The Analysis on Exergy Loss and its Reduction Methods in Steam Desuperheating and Depressurizing Process
Yi, Joong Yong ; Lee, Chan ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 19~26
DOI : 10.5293/kfma.2015.18.6.019
The present paper presented and applied an exergy analysis method to evaluate the magnitudes and the locations of exergy losses in the conventional desuperheating and depressurizing process of high pressure and temperature steam delivery system. In addition, for the reduction of exergy losses occurred in conventional process, the present study proposed new alternative processes in which the pressure reducing valve and the desuperheater of conventional process are substituted with steam turbine and heat exchanger, and their effects on exergy loss reduction and exergy efficiency improvement are theoretically investigated and compared. From the present analysis results, the total exergy loss caused in conventional desuperheating and depressurizing process accounted for 66.5% of exergy input and 85% of the total exergy loss was due to the mixing between steam and cold water(e.g desuperheating). However, it was shown from the present analysis results that the present alternative processes can additionally reduce exergy loss by maximum 92.7% of the total exergy loss in conventional process, and can also produce additional and useful energy, the electricity of 220.6 kWh and the heat of 54.3 MJ/hr.
Micro Energy Harvesting System Based On Reverse Electro Wetting On Dielectric (REWOD)
Cho, Jin Hyun ; Kim, Gil Yeon ; Choi, Sang Beak ; Jeon, Tae-joon ; Kim, Sun Min ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 27~30
DOI : 10.5293/kfma.2015.18.6.027
In this study, we attempted to harvest energy using water droplet based on Reverse Electro Wetting On Dielectric (REWOD) phenomenon between water droplet and dielectric surface without external bias. REWOD device can be fabricated via simple coating process, which is highly economic and easy. We believe that our system is well-suited for IoT(Internet of Things) embedded electronics that require low but consistent electricity. Moreover, our device can be integrated with window to generate electricity upon raindrops.
Establishment of Multi-Stage Turbocharger Layout for HALE UAV Engine and Its Performance Assessment
Kang, Young Seok ; Lim, Byung Jun ; Kim, Jong Kuk ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 31~36
DOI : 10.5293/kfma.2015.18.6.031
A multi-stage turbocharger system has been constructed for HALE UAV internal combustion engine. To boost rarefied intake air up to sea level condition, the turbocharger system should consist of 3 stages including heat exchanger located after compressor outlet to drop compressed air temperature. One dimensional system analysis has been conducted by matching required power between compressor and turbine and adequate turbochargers have been searched for from commercially available models targeting for automobiles. By applying commercial automobile turbochargers to the multi-stage turbocharger system, it is expected that considerable amount of research resources will be saved.
Conjugate Heat Transfer Analysis of High Pressure Turbine with Secondary Flow Path and Thermal Barrier Coating
Kang, Young-Seok ; Rhee, Dong Ho ; Cha, Bong Jun ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 37~44
DOI : 10.5293/kfma.2015.18.6.037
Conjugate heat analysis on a high pressure turbine stage including secondary flow paths has been carried out. The secondary flow paths were designed to be located in front of the nozzle and between the nozzle and rotor domains. Thermal boundary conditions such as empirical based temperature or heat transfer coefficient were specified at nozzle and rotor solid domains. To create heat transfer interface between the nozzle solid domain and the rotor fluid domain, frozen rotor with automatic pitch control was used assuming that there is little temperature variation along the circumferential direction at the nozzle solid and rotor fluid domain interface. The simulation results showed that secondary flow injected from the secondary flow path not only prevents main flow from penetrating into the secondary flow path, but also effectively cools down the nozzle and rotor surfaces. Also thermal barrier coating with different thickness was numerically implemented on the nozzle surface. The thermal barrier coating further reduces temperature gradient over the entire nozzle surface as well as the overall temperature level.
Development of a Submerged Propeller Turbine for Micro Hydro Power
Kim, Byung-Kon ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 45~56
DOI : 10.5293/kfma.2015.18.6.045
This paper aims to develop a submerged propeller turbine for micro hydropower plant which allows to sustain high values of efficiency in a broad range of hydrological conditions (H=2~6 m,
). The two aspects to be considered in this development are mechanical simplicity and high-efficiency operation. Unlike conventional turbines that have spiral casing and gear box, this is directing driving and no spiral casing. A 10 kW class turbine which has the most high potential of the power generation has been developed. The most important element in the design of turbine is the runner blade. The initial blade is designed using inverse design method and then the runner geometry is modified by classical hydraulic method. The design process is carried out in two steps. First, the blade shape is fix and then other components of submerged propeller turbine are designed. Computational fluid dynamics analyses based on the Navier-Stokes equations have been used to obtain overall performance data for the blade and the full turbine, respectively. The results generated by performance parameters(head, guide vane opening angle and rotational speed) variations are theoretically analysed. The evaluation criteria for the blade and the turbine performances are the pressure distribution and flow's behavior on the runner blades and turbine. The results of simulation reveals an efficiency of 91.5% and power generation of 10.5kW at the best efficiency point at the head of 4m and a discharge of
A Study on Comparison of the Characteristic Test of Discharge Water Flowmeters (Electromagnetic Flowmeter, Parshall Flume)
An, Yang-ki ; Kim, Jee-young ; Kim, Kum-hee ; Jang, Hee-soo ; Jung, Jung-pil ; Choi, Jong-woo ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 57~62
DOI : 10.5293/kfma.2015.18.6.057
The test of comparing liquid flow calibration system (approved by KOLAS) for accuracy and structure change test was performed in the test bed in order to evaluate the typical characteristics of the electromagnetic flow meters and parshall flume that are generally used in the water discharging facilities. The results of the accuracy comparing test with liquid flow calibration system showed the error of less than 2%. Pharshall plume got error up to -8.3% (low flow) from the flow rate test, but less than 4% from the accumulated flow test because of offset error at high flow rate and low flow rate. Evaluation of structual change test was tested with only parshall flume using structure and it consisted of installation angle (parshall flume and level sensor) and position change. Installation angle, water level sensor angle and position changing test for parshall flume had errors of 3.1%~-9.2%, 0.4%~-5.6% and 0.2%~1.3% respectively. Especially, the error showed the largest increase when the water level sensor measured the point of decreased flow by the structure change. Therefore, error factors (change of straight pipe length, installation of obstacle or effect of foreign substances on water level sensor) that can often occur in the field should be derived and the research for optimized installation method should be carried out continuously.
Analysis of the Dynamic Characteristics on Aerodynamic Loads of Wind Turbine Blade with New Airfoil KA2
Kang, Sang-Kyun ; Lee, Ji-Hyun ; Lee, Jang-Ho ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 63~70
DOI : 10.5293/kfma.2015.18.6.063
This paper proposes a novel airfoil named "KA2" for the blade of the wind turbine systems. Dynamic loads characteristics are analyzed and compared using aerodynamic data of ten airfoils including the proposed airfoil. The blade is divided into the sixteen elements in the longitudinal direction of the blade for applying the Blade Element Method Theory (BEMT) method, and in each element, torque, thrust, and pitching moment are calculated using turbulent time varying wind speed and aerodynamic data of each wing. Additionally, each force and torque is accumulated in the whole region of the blade for the estimation of representative values. The magnitude of such forces is comparatively analyzed for different airfoils. The angle of attack is constant below the rated wind speed due to the fact that the tip speed ratio is kept at the constant value, and it increases in the region of over rated wind speed as the tip speed ratio decreasing with constant rated rpm and increasing wind speed. Such increase in the angle of attack causes the changes of the force acting on the airfoil with different characteristics of lift and drag in the stall region of each different airfoil. Even though the mean wind speed is in the rated speed in a given time, because of the turbulence, it has either the over rated or under rated speed most of the time. Furthermore, the dynamic properties of each force are analyzed in this rated wind speed in order to objectively understand the dynamic properties of the blades which are designed based on the different airfoils. These dynamic properties are also compared by the standard deviation of time varying characteristics. Moreover, the output characteristics of the wind turbine are investigated with different airfoils and wind speeds. Based on these investigations, it was revealed that the proposed airfoil (KA2) is well applicable to the blade with passive pitch control system.
Analysis of Noise Characteristic of Uneven Pitch Regenerative Blower
Lee, Kyoung-Yong ; Jung, Uk-Hee ; Kim, Jin-Hyuk ; Kim, Cheol-Ho ; Choi, Young-Seok ; Ma, Jae-Hyun ; Jeong, Kyung-Ho ; Park, Woon-Jean ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 71~75
DOI : 10.5293/kfma.2015.18.6.071
The flow and noise characteristics of the regenerative blower are evaluated experimentally. To decrease the noise of regenerative blower at a high frequency, we arrange the impeller vanes unevenly by special formula. The uneven pitch formular consists of the combination of trigonometric function. The magnitude of degree between each vanes and the control parameters of trigonometric functions are main design parameters for the uneven pitch. The flow characteristics of even and uneven impellers are tested by the fan tester and compared each results. The efficiency of a blower is calculated by the axial power using a dynamo system. The noise property of designed impeller is measured in an anechoic room. In this study, we certify that the uneven pitch impeller is effective in the noise reduction at a high frequency.
Relationship between Cavitation Incipient and NPSH Characteristic for Inverter Drive Centrifugal Pumps
Rakibuzzaman, Md ; Suh, Sang-Ho ; Kim, Hyoung-Ho ; Jung, Young-Hoon ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 76~80
DOI : 10.5293/kfma.2015.18.6.076
The purpose of this study is to understand the cavitation phenomena in centrifugal pumps through computational fluid dynamics method. NPSH characteristic curve is measured from different flow operating conditions. Steady state, liquid-vapor homogeneous method with two equations transport turbulence model is employed to estimate the NPSH curve in centrifugal pumps. The Rayleigh-Plesset cavitation model is adapted as source term for inter-phase mass transfer in order to understand cavitation phenomena in centrifugal pumps. The cavitation incipient curve is clearly estimated at different flows operating conditions. A relationship is made between cavitation incipient and NPSH curve. Also the effects on water vapor volume fraction and pressure load distributions on the impeller blade are also described.
Evaluation of Energy Savings for Inverter Driving Centrifugal Pump with Duty Cycles
Kim, Kyungwuk ; Suh, Sang-Ho ; Rakibuzzaman, Rakibuzzaman ;
The KSFM Journal of Fluid Machinery, volume 18, issue 6, 2015, Pages 81~85
DOI : 10.5293/kfma.2015.18.6.081
The purpose of this study is to evaluate energy savings for inverter driving multi-stage centrifugal pump. Variable speed driving pump system has high efficiency compared with constant speed driving pump system. Because of difficulty to estimate operating efficiency of variable speed driving pump system, energy saving rates are used to replace operating efficiency. energy saving rates are calculated from pump input power and pump duty cycle. But another researches have used pump duty cycles of each season for energy saving rate. In this study, for estimating energy saving rate more high accuracy, pump duty cycles are measured for 1 year. pump duty cycles, depending on the season and be classified according to the weekday/weekend or during the week day. By this pump duty cycles, Energy saving rate is calculated appropriately.