• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1345-1351
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• 2013

Variable iron loss as function of current phase angle of Interior Permanent Magnet Synchronous Motor(IPMSM) was calculated through Curve Fitting Method(CFM). Also, a magnetic flux density distribution of iron core according to current phase angle was analyzed, and an iron loss calculation was performed including harmonic distortion. The experiment was performed by production of non-magnetizing model for the separation of mechanical loss, and the iron loss was calculated by the measurement of input using power analyzer and output power using dynamometer. Some error was generated between experimental results and calculation value, but an iron loss diminution according to current phase angle followed a same pattern. So, errors were generated by measurement, vibration, noise, harmonic distortion loss, etc.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2591-2596
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• 2007

The effect of incidence angle on the three-dimensional flow and aerodynamic loss in the downstream region of a high-turning turbine rotor blade has been investigated with a straight miniature five-hole probe. The incidence angle is changed to be +10, +5, 0, -10, -20, -30 and -40 degrees. The results show that the positive incidence reinforces the three-dimensional vortical flows within the turbine passage including the passage vortex, but the negative incidence weaken them significantly. A small increment in the positive incidence angle results in a remarkable aerodynamic loss increase, while increasing the incidence angle in the negative range leads to a very small change in the aerodynamic loss.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.30-34
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• 2001

In the present study, we studied the method of predicting the on-design and on-design point performance of axial flow fan with adjustable pitch blades. With the change of stagger angle of axial flow fan with adjustable pitch blade, flow rate and pressure can be changed. Because of this merit adjustable pitch fans are used in many industrial facility. When changing stagger angle or estimating the performance at a wide range of off-design condition, incidence angle changes greatly as the flow rate changes. Therefore, the deviation angle at the blade exit is estimated by the correlation considering the effects of blade design, incidence angle variation. In the loss model, we used known pressure loss model for blade boundary layer and wake, secondary flow, endwall boundary layer and tip leakage flow. The results of modified deviation angle model and experiment were compared for the usefulness of the modified model.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.11
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• pp.1591-1602
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• 1998

Simple spanwise distribution models of deviation angle and pressure loss coefficient due to the tip leakage flow are formulated for use in association with the streamline curvature method as a flow analysis. Combining these new models with the previous deviation and loss models due to secondary flow, a robust streamline curvature method is established for flow analysis of single-stage, subsonic axial turbines with wide ranges of turning angle, aspect ratio and blading type. At the exit from rotor rows, the flow variables are mixed radially according to a spanwise transport equation. The proposed streamline curvature method is tested against a forced vortex type turbine as well as a free vortex type one. The results show that the spanwise variations of flow angle, axial velocity and loss coefficients at rotor exit are predicted with good accuracy, being comparable to a steady three-dimensional Navier-Stokes analysis. This simple and fast flow analysis is found to be very useful for the turbine design at the initial design phase.

• Journal of Korean Foot and Ankle Society
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• v.21 no.4
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• pp.135-138
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• 2017

Purpose: The purpose of this study is to determine the correlation between the correction loss of hallux valgus angle and the severity of valgus angle of the second toe. Materials and Methods: We selected 312 cases from 268 surgical patients with hallux valgus deformity receiving distal chevron osteotomy. For a radiological evaluation, we analyzed the changes in the hallux valgus angles, first to second intermetatarsal angles, and valgus angle of the second toe post index operations. All patients were women; the mean age was 46 years. The mean follow-up period was 17 months. Results: The mean hallux valgus angle was $33.6^{\circ}$ preoperatively (range, $25.7^{\circ}{\sim}44.8^{\circ}$), $13.1^{\circ}$ (range, $8.4^{\circ}{\sim}16.4^{\circ}$) after 4 weeks of postoperative period, and $17.1^{\circ}$ (range, $9.4^{\circ}{\sim}28.5^{\circ}$) at their final follow-up. The mean valgus angle of the second toe was $8.4^{\circ}$ preoperatively (range, $2.0^{\circ}{\sim}25.8^{\circ}$) and $8.3^{\circ}$ (range, $1.7^{\circ}{\sim}24.9^{\circ}$) at the final follow-up. Preoperatively, there was a positive correlation between the valgus angle of the second toe and hallux valgus angle (r=0.747, p=0.001). The correction loss of hallux valgus angle had a significant correlation with the severity of valgus angle of the second toe (r=0.802, p=0.001). Conclusion: The existence of the second toe valgus deformity may present itself as a cause of correction loss of hallux valgus angle. The preoperative measurement of the second toe valgus angle may be a good predictor of correction loss; therefore, thorough preoperative warning on the possibility of correction loss should be conducted to maximize patient satisfaction after the procedure.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.6
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• pp.923-930
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• 2008

The butterfly valve is widely used in the industrial field as an on-off or a flow control valve. When the butterfly valve is used as a flow control valve. cavitation sometimes occurs in the range of high flow rate because of the small valve opening. Therefore. the pressure loss and the cavitation characteristics are investigated by use of a commercial CFD code. The results show that the possibility of cavitation occurrence in the cryogenic butterfly valve is very high in the case of valve opening angle below 10 degree and incident velocity over 6m/s. By increasing the inlet velocity at 10 degree of valve opening angle. the value of loss coefficient increased. However. by increasing the inlet velocity at 50 degree of valve opening angle. the value of loss coefficient decreased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.1
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• pp.12-24
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• 1998

The paper presents the mechanism of secondary flows and the associated total pressure losses occurring in turbine cascades with turning angle of about 127 and 77 degree. Velocity and pressure measurements are taken in seven traverse planes through the cascade passage using a prism type five hole probe. Oil-film flow visualization is also conducted on blade and endwall surfaces. The characteristics of the limiting streamlines show that the three dimensional separation is an important flow feature of endwall and blade surfaces. The larger turning results in much stronger contribution of the secondary flows to the loss developing mechanism. A large part of the endwall loss region at downstream pressure side is found to be very thin when compared to that of the cascade inlet and suction side endwall. Evolution of overall loss starts quite early within the cascade and the rate of the loss growth is much larger in the blade of large turning angle than in the blade of small turning angle.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.59-63
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• 2005

In this article, we apply the standard method of Lagrange multipliers to examine the algorithm in a recent IEEE publication which calculates the optimal generation for minimizing the system loss using loss sensitivities derived by angle reference transposition, and show that the two algorithms are mathematically the same.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.11
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• pp.779-786
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• 2019

Effects of chamfered perforated plate on pressure loss characteristics were studied with CFD analysis. Both inlet chamfer angle and outlet chamfer angle were considered. Perforated patterns were compared by pressure loss coefficient in certain porosity and Reynolds number. Reynolds number effects were studied for several chamfer angles and plate thickness. As the inlet chamfer angle was increased, the pressure loss coefficient was decreased until the certain angle and reversed to increase. In the outlet chamfered shape cases, the pressure loss coefficient was increased with chamfer angle. Effects of pattern shapes and Reynolds number on pressure loss characteristics were negligible with different chamfer angles and thickness studied in this paper.

• Journal of KSNVE
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• v.7 no.6
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• pp.945-952
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• 1997

This paper shows the feasibility of the suggestion that the angle distribution of incident sound to panels might be gaussian, instead of the conventional uniform distribution in the analysis of transmission loss of panels. To prove the suggestion, the problems with the diffuse sound field in a reverberation room are examined by case studies and the comparision of the prediction with the measurement of sound transmission loss of walls are performed. The results of the comparision show good agreement between the two values.