• Clean Technology
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• v.25 no.2
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• pp.161-167
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• 2019

Several types of reactors have been used during the past decade to perform fast pyrolysis of biomass. Among the developed fast pyrolysis reactors, fluidized bed reactors have been widely used in the fast pyrolysis process. In recent years, experimental studies have been conducted on the characteristics of biomass fast pyrolysis in a spouted bed reactor. The fluidization characteristics of a spouted bed reactor are influenced by particle properties, fluid jet velocity, and the structure of the core and annulus. The geometry of the spouted bed reactor is the main factor determining the structure of the core and annulus. Accordingly, to optimize the design of a spouted bed reactor, it is necessary to study the pyrolysis characteristics of biomass. However, no detailed investigations have been made of the fast pyrolysis characteristics of biomass in accordance with the geometry of the spouted bed reactor. In this study, fast pyrolysis experiments using Jatropha curcas L. seed shell cake were conducted in a conical spouted bed reactor to study the effects of reaction temperature and reactor cone angle on the product yield and pyrolysis oil quality. The highest energy yield of pyrolysis oil obtained was 63.9% with a reaction temperature of $450^{\circ}C$ and reactor cone angle of $44^{\circ}$. The results showed that the reaction temperature and reactor cone angle affected the quality of the pyrolysis oil.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.5
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• pp.414-420
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• 2010

This paper presents a validation of the accuracy of a reduced order model(ROM) and the efficiency of the design optimization using a Proper Orthogonal Decomposition(POD) to transonic wing/fuselage system. Three dimensional Euler equations are solved to extrude snapshot data of the full order aerodynamic analysis, and then a set of POD basis vectors reproducing the behavior of flow around the wing/fuselage system is calculated from these snapshots. In this study, reduced order model constructed through this procedure is applied to several validation cases, and then it is confirmed that the ROM has the capability of the prediction of flow field in the space of interest. Additionally, after the design optimization of the wing/fuselage system with the ROM is performed, results of the ROM are compared with results of the design optimization using response surface model(RSM). From these, it can be confirmed that the design optimization with the ROM is more efficient than RSM.

• Journal of Ocean Engineering and Technology
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• v.27 no.3
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• pp.67-72
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• 2013

In this study, numerical analyses that considered the dynamic interaction effects between the flow and a turbine were carried out to investigate the power output performance of an H-type Darrieus turbine rotor, which is one of the representative lifting-type vertical-axis tidal-current turbines. For this purpose, a commercial CFD code, Star-CCM+, was utilized for an example three-bladed turbine with a rotor diameter of 3.5 m, a solidity of 0.13, and the blade shape of an NACA0020 airfoil, and the optimal tip speed ratio (TSR) and corresponding maximum power coefficient were evaluated through exhaustive simulations with different sets of flow speed and external torque conditions. The optimal TSR and maximum power coefficient were found to be approximately 1.84 and 48%, respectively. The torque and angular velocity pulsations were also investigated, and it was found that the pulsation ratios for the torque and angular velocity were gradually increased and decreased with an increase in TSR, respectively.

• Journal of Ocean Engineering and Technology
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• v.27 no.3
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• pp.73-78
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• 2013

CFD (computational fluid dynamics) analyses that considered the dynamic interaction effects between the flow and a turbine were performed to evaluate the power output characteristics of two representative vertical-axis tidal-current turbines: an H-type Darrieus turbine and Gorlov helical turbine (GHT). For this purpose, a commercial CFD code, Star-CCM+, was utilized, and the power output characteristic were investigated in relation to the scale ratio using the relation between the Reynolds number and the lift-to-drag ratio. It was found that the power coefficients were significantly reduced when the scaled model turbine was used, especially when the Reynolds number was lower than $10^5$. The power output characteristics of GHT in relation to the twisting angle were also investigated using a three-dimensional CFD analysis, and it was found that the power coefficient was maximized for the case of a Darrieus turbine, i.e., a twisting angle of $0^{\circ}$, and the torque pulsation ratio was minimized when the blade covered $360^{\circ}$ for the case of a turbine with a twisting angle of $120^{\circ}$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.335-342
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• 1986

The feasibility of simultaneous measurement of gas-liquid tow-phase flowrate and quality with a sharp-edged orifice has been investigated. Instantaneous pressure drop curves were monitored for various combinations of gas and liquid flowrates in the bubbly flow regime and some statistical properties of the curves were calculated. The time-averaged value of pressure drop increases with increasing gas and liquid flowrate, whereas the mean amplitude and the intensity of fluctuation monotonically increase as void fraction becomes larger in the flow regime. The statistical furctions for the instantaneous curves indicate a consistent pattern throughout the flow regime and the probability density function, which as a single-peaked and symmetrical distribution, is well predicted by the Gaussian distribution function. The results indicate that simultaneous determination of two-phase flowrate and quality may be possible based upon the statistical analysis of instaneous pressure drop curves measured in a sharp-edged orifice.

• The KSFM Journal of Fluid Machinery
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• v.3 no.1 s.6
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• pp.43-50
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• 2000

Upgrade development of a high pressure ratio centrifugal compressor in marine engine turbochargers is presented. A new matched operating point at increased speed of rotation was determined through system cycle analysis using the exisitng test data of turbine performance. Under some severe restrictions for geometric parameters, the state-of-the-art methods of both aerodynamic design and CFD analysis were applied, in which only an impeller, a vaned diffusor and some part of casing wall were modified. Prototype hardware was fabricated and assembled for system performance tests. Excellent performance in pressure ratio and efficiency was obtained over whole speed region. Reduced surge and choke margin was, however, observed at design speed of rotation.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.10a
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• pp.47-58
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• 2005

Rice straw is one of the main renewable energy sources in Korea, and bio-oil is produced from rice straw with a lab. scale plant equipped mainly with a fluidized bed and a char removal system. We investigated how the reaction temperature affected the production of bio-oil and the efficiency of a char removal system. To elucidate how the temperature depended on the production of bio-oil, experiment were conducted between $450^{\circ}C\;and\;600^{\circ}C$ with a feed rate of about 300g/h. The mass balance was established in each experiment, and the produced gas and oil were analyzed with the aid of GCs and a GC-MS system. The char removal system is composed of a cyclone and a hot filter. In the experiments, we observed that the optimum reaction temperature range for the production of bio-oil is between $450^{\circ}C\;and\;500^{\circ}C$.

• Composites Research
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• v.27 no.1
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• pp.31-36
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• 2014

This paper presents the slip behavior of composite fabrics by high speed resin flow in high pressure resin transfer molding. In order to observe the fiber deformation behavior, we constructed the measuring equipment for friction coefficient between fiber and mold, and the monitoring system for deformation of fiber preform in high-pressure RTM process. Coulomb friction coefficient and hydrodynamic friction coefficient between fiber preform and mold were measured and the external force induced by fluid flow causing the deformation of fiber preform was measured. Friction force calculated by friction coefficient and the external force upon fiber deformation were compared, which showed that preform deformation occurred when the external force was bigger than the friction force. The slip behavior of the fiber preform was mainly influenced by the volume fraction of fiber preform and the friction coefficient.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.6
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• pp.347-355
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• 2016

This study presents a Lattice Boltzmann Method (LBM) coupled with a momentum-exchange approach/fictitious domain (MEA/FD) method for the simulation of particle suspensions. The method combines the advantages of the LB and the FD methods by using two unrelated meshes, namely, a Eulerian mesh for the flow domain and a Lagrangian mesh for the solid domain. The rigid body conditions are enforced by the momentum-exchange scheme in which the desired value of velocity is imposed directly in the particle inner domain by introducing a pseudo body force to satisfy the constraint of rigid body motion, which is the key idea of a fictitious domain (FD) method. The LB-MEA/FD method has been validated by simulating two different cases, and the results have been compared with those through other methods. The numerical evidence illustrated the capability and robustness of the present method for simulating particle suspensions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.9
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• pp.817-824
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• 2010

An improved spray model of a pressure-swirl atomizer was developed and the grid dependency of the model was investigated. Since the Lagrangian-Eulerian approach was adopted for tracking droplets, very small grids could not be used. However, in order to detect swirl flow accurately, small grids were needed because of the consideration of swirl injection. In order to overcome these limitations, numerical studies were performed by using various grids with cell sizes ranging from 10.0 $\times$ 10 mm to 0.625 $\times$ 0.625 mm. From these calculated results, it was observed that the most efficient grid cell size was 1.25 $\times$ 1.25 mm.