• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.6
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• pp.834-844
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• 2000

In this study, an off-design performance analysis procedure is developed based on Two-zone model and TEIS model. In Two-zone model, there are both primary zone and secondary zone for an isentropic core flow and an average of all non-isentropic streamtubes respectively. The level of the core flow diffusion in an impeller is calculated by using TEIS model which regards the impeller as two successive rotating elements in series. At impeller exit, the mixing process occurs with an increase in entropy, that is to say, a decrease in total pressure. In loss models including Two-zone and TEIS model, some empirical parameters have a great influence on overall performance curve. So these parameters' influences on the overall performance curve are investigated and compared with experimental data.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.6
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• pp.695-702
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• 1999

A cross-flow fan which constitutes a fan-duct system with a stabilizer and a scroll-casing is widely used in many air-ventilating and air-conditioning devices. The cross-flow fan system has many design parameters which have crucial influence on the performance and the noise characteristics of the devices, which means many difficulties during the design stage of the devices and the general design guide has not sufficiently established yet. This study presents the experimental results of the parameter investigation of some chosen design parameter values, which are the shapes of the stabilizers, the profiles of the scroll casing part, and the diffusion angles of the flow exit. The results are expressed by the varying performance characteristics with the values of the parameters. They are found to have considerable effects on the system performance and should be considered with care in the design stage. Finally some helpful guides for the design and manufacturing of the cross-flow fan system are proposed.

• International Journal of Fluid Machinery and Systems
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• v.10 no.3
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• pp.218-226
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• 2017

Severe radial thrust under off-design operating conditions can be a harmful factor for centrifugal pumps. In the present work, effects of geometry of a double volute casing on the hydrodynamic performance of a centrifugal pump have been investigated focusing on off-design conditions. Three-dimensional steady Reynolds-averaged Navier-Stokes analysis was carried out by using shear stress transport turbulence model. Numerical results for the hydrodynamic performance of the centrifugal pump were validated compared with experimental data. The hydraulic efficiency and radial thrust coefficient were used as performance parameters to evaluate the hydrodynamic characteristics of the centrifugal pump. The cross-sectional area ratio of the volute casing, the expansion coefficient of the rib structure, the distance between the rib starting point and volute entrance, and radius and width of the volute entrance, and length of the rib structure, were selected as geometric parameters. Results of the parametric study show that the performance parameters are significantly affected by the geometric variables and operating conditions. Optimal configurations of the double volute casing based on the design of experiments technique show outstanding performance in terms of the efficiency and radial thrust coefficient.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.346-352
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• 2002

This paper is the experimental study to estimate the influence of various design parameters on the performance of mufflers with perforated tubes and through-flow partitions. Muffler types considered in the present work include through-flow chamber, through-flow chamber with partition, and cross-flow chamber. The influences of the design parameters on the performance of the mufflers can be outlined as follows. In the case of the through-f]ow type mufflers, increasing the tube thickness and the hole diameter of the perforated tubes does not change the maximum value of the transmission loss but decrease the cutoff frequency. In the case of the through-flow with partitions type mufflers, it is shown that combining a fe w short chambers and long chambers can modify the frequency locations of the resonance frequencies to optimize the performance of the mufflers. For the case of the cross-flow type mufflers, it is shown that the transmission loss of the mufflers is mainly affected by the lower porosity when the porosities are different in both sides of the plug. Overall, it is shown that performance of the through-flow type with partition type mufflers is excellent in the lower frequency region, where the cross-flow type mufflers have better performance in the higher frequency region.

• Journal of the Korean Solar Energy Society
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• v.32 no.4
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• pp.59-64
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• 2012

The correlation between hydrologic performance design parameters of small hydro power(SHP) sites and rainfall condition have been analyzed for major river systems. The model, which can predict flow duration characteristic of stream, was developed to estimate the inflow caused from rainfall. And another model to predict hydrologic performance for SHP plants is established. Based on the models developed in this study, the hydrologic performance characteristics for SHP sites have been analyzed. The results show that the hydrologic performance characteristics of SHP sites have some difference between the river systems. Especially, the specific design flowrate and specific output of SHP sites located on North Han river and Nakdong river systems have large difference compared with other river systems. It was found that the hydrologic performance design parameters such as specific design flowrate and specific output were affected by rainfall condition in basin area of SHP sites.

• The KSFM Journal of Fluid Machinery
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• v.18 no.1
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• pp.20-28
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• 2015

The pump-turbine impeller is the key component of pumped storage power plant. Current design methods of pump-turbine impeller are private and protected from public viewing. Generally, the design proceeds in two steps: the initial hydraulic design and optimization design to achieve a balanced performance between pump mode and turbine mode. In this study, the 3D inverse design method is used for the initial hydraulic impeller design. However, due to the special demand of high performance in both pump and reverse mode, the design method is insufficient. This study is carried out by modifying the geometrical parameters of the blade which have great influence and need special consideration in obtaining the high performance on the both modes, such as blade shape type at low pressure side (inlet of pump mode, outlet of turbine mode) and the blade lean at blade high pressure side (outlet of pump mode, inlet of turbine mode). The influence of the geometrical parameters on the performance characteristic is evaluated by CFD analysis which presents the efficiency and internal flow results. After these investigations of the geometrical parameters, the criteria of designing pump-turbine impeller blade low and high sides shape is achieved.

• Earthquakes and Structures
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• v.13 no.4
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• pp.397-407
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• 2017

With the growing demand for metallic dampers in engineering practice, it is urgent to establish a reasonable approach to evaluating the mechanical performance of metallic dampers under seismic excitations. This paper introduces an effective method for parameter identification of the modified Bouc-Wen model and its application to evaluating the fatigue performance of metallic dampers (MDs). The modified Bouc-Wen model which eliminates the redundant parameter is used to describe the hysteresis behavior of MDs. Relations between the parameters of the modified Bouc-Wen model and the mechanical performance parameters of MDs are studied first. A modified Genetic Algorithm using real-integer hybrid coding with relative fitness as well as adaptive crossover and mutation rates (called RFAGA) is then proposed to identify the parameters of the modified Bouc-Wen model. A reliable approach to evaluating the fatigue performance of the MDs with respect to the Chinese Code for Seismic Design of Buildings (GB 50011-2010) is finally proposed based on the research results. Experimental data are employed to demonstrate the process and verify the effectiveness of the proposed approach. It is shown that the RFAGA is able to converge quickly in the identification process, and the simulation curves based on the identification results fit well with the experimental hysteresis curves. Furthermore, the proposed approach is shown to be a useful tool for evaluating the fatigue performance of MDs with respect to the Chinese Code for Seismic Design of Buildings (GB 50011-2010).

• Steel and Composite Structures
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• v.41 no.5
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• pp.713-730
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• 2021

The seismic performance of rigid steel frames is widely investigated, but that of semi-rigid (SR) steel frames are not studied extensively, especially for near-field earthquakes. In this paper, the performances of five and ten-story steel SR frames having different degrees of semi-rigidity are evaluated at four performance points in the four different deformation states, namely, the elastic, elasto-plastic, plastic, and near collapse states. The performances of the SR frames are measured by the response parameters including the maximum values of the top floor displacement, base shear, inter-story drift ratio, number of plastic hinges, and SRSS of plastic hinge rotations. These response parameters are obtained by the capacity spectrum method (CSM) using pushover analysis. The validity of the response parameters determined by the CSM is evaluated by the results of the nonlinear time history analysis (NLTHA) for both near and far-field earthquakes at different PGA levels, which are consistent with the performance points. Results of the study show that the plastic hinges of SR frame significantly increase in the range of plastic to near-collapse states for both near and far-field earthquakes. The effect of the degree of semi-rigidity is pronounced only at higher degrees of semi-rigidity. The predictions of the CSM are fairly well in comparison to the NLTHA.

• Journal of the Korea Concrete Institute
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• v.12 no.4
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• pp.3-14
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• 2000

Structural performance of the walls subjected to lateral load reversals depends on various parameters such as loading history, sectional shape, reinforcement, lateral confinement, aspect ratio, axial compression, etc. Thus, the performance of the shearwall for wall-type apartment should be evaluated properly considering above parameters. This study investigates the effect of sectional shape on the structural performance of the wall. Sectional shape of the specimen is rectangular, barbell and T. Based on this experimental results, all specimens behaved as ductile fashion and failed by concrete crushing of the compression zone. Deformation index of those specimens evaluated better than 3 of ductility ratio, and 1.5% of deformability specified by seismic provision. Moreover, the performance of the rectangular shaped specimen, whose compression zone was confined with U-bar and cross tie, was as good as the barbell shaped specimen. Therefore, if we considered construction practice such as workmanship and detailing, shearwall with rectangular section may be more economical lateral load resisting system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.11
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• pp.909-915
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• 2009

In this paper, a study of performance improvement for a centrifugal vertical pump having specific speed of 330 is introduced. The existing model has high efficiency but needs better NPSH required performance. Such that new pump model is designed to obtain larger suction specific speed. 6 design parameters considered to affect pump performance are selected for impeller design. Key design parameters are investigated using by design of experiments and CFD, and impeller inlet diameter is increased to get better suction performance. The amount of inlet diameter increase is determined by using cavitation analysis. The results show that new design model has higher efficiency and better NPSH required performance than the existing model.