• 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.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.1
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• pp.1-5
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• 2001

In this paper, a new method for calculating the penalty factors of all generators including the slack bus is presented. A simple transposition of the angle reference, from the conventional slack bus to another bus where no generation exists, enables the derivation of the loss sensitivity of the slack bus. Penalty factors are obtained without any physical assumption through a simple substitution of the bus loss sensitivities. Penalty factors calculated by proposed method are not dependent on reference bus and can also be directly substituted into the general ELD equation for computing the optimal dispatch. Equations for loss sensitivities, Penalty factors and ELD are calculated simultaneously in normal power flow computation. A case study on a test system has proved the effectiveness of the proposed' angle reference transposition' method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.11
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• pp.612-616
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• 2013

A circular CAV damper has been developed, based on the investigation of the pressure loss, and the flow-resisting moment by the damper blade. When a torsional spring is attached to the damper axle, and the setting angle is adjusted to around $82^{\circ}$, the volume rate across the damper is almost independent of the static pressure. Such a CAV characteristic appears at an opening angle between $40^{\circ}$ and $60^{\circ}$, where the normalized moment decreases linearly with the angle. In addition, by adjusting the setting angle, the volume rate can be controlled to within 10% error, regardless of the pressure loss.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.7
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• pp.967-974
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• 2001

Experimental investigations on the flow characteristics of downstream region of a butterfly valve, which is used in SI engine, have been conducted according to Reynolds number and valve angle. Measurement programs of the flowfield using x-type of hotwire anemometry include the mean and fluctuating velocity, turbulnet intensity, shear stress, power spectrum and pressure loss coefficient. Experimental results show that flow characteristics and independent of relatively high Reynolds number; 60,000 and 80,000. It is also seen that streamwise mean velocities have relatively large velocity gradient around the butterfly valve with increasing the valve opening angle and this trend appears even in the far downstream region. The distributions of turbulent intensity and shear stress show irregular behavior regardless of the valve opening angle and those of the case of the valve opening angle of 45°are the largest. The pressure loss coefficient of the body surface of the throttle valve increases mildly with the increase of Reynolds number and increases rapidly with the reduction of the valve opening angle.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.667-668
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• 2015

Synchronous Reluctance Motor (SynRM) has a simple structure with high efficient and without rotor conductor loss. Therefore, it is better than induction motor for electric vehicle (EV) on aspect of efficiency. SynRM usually operates on the constant torque region using maximum torque per ampere （MTPA）control which is adopted due to rotor structure limitation. Thus, the accurate current angle is crucial for motor control. However, finite element analysis (FEA) program is not sufficient exactly to regard how the iron loss and magnetic saturation influences on the current angle. Consequently, this paper proposed a method to calculate the current angle with consideration of iron loss.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.300-305
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• 2013

The torque was calculated with inductance and iron loss. Because the linkage flux can change the inductance, and q-axis current can change the iron loss. Therefore, precise estimation of torque can achieve with the inductance and iron loss detail calculations. So, in this paper, the d, q-axis inductance was verified through CVCT(Current Vector Control Test) and DCT(Direct Current Test). Also in the iron loss calculation, the prediction of all areas of current magnitude, phase angle and speed was very difficult. And LUT(Look-Up Table) was spent time and resource largely. Therefore, iron loss mathematization was proposed according to current magnitude, phase angle and speed. Also, characteristics of IPMSM were comprised of analyzed and experimental values.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.13-13
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• 1998

A simple model of the tip leakage flow models of the rotor downstream flow is developed, based on Lakshminarayana's theoretical concept on the tip clearance flow and the experimental data published in open literature. And new 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 through flow analysis. Combining these new models and 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.

• International Journal of Fluid Machinery and Systems
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• v.2 no.1
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• pp.13-20
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• 2009

The effects of positively bowed blade on the aerodynamic performance of annular compressor cascades with large camber angle were experimentally investigated under different incidences. The distributions of the exit total pressure loss and secondary flow vectors of compressor cascades were analyzed. The static pressure was measured by tapping on the cascade surfaces, and the ink-trace flow visualizations were conducted. The results show that the value of the optimum bowed angle and optimum bowed height decrease because of the increased losses at the mid-span with the increase of the caber angle. The C-shape static pressure distribution along the radial direction exists on the suction surface of the straight cascade with large r camber angles. When bowed blade is applied, the larger bowed angle and larger bowed height will further enhance the accumulation of the low-energy fluid at the mid-span, thus deteriorate the flow behavior. Under $60^{\circ}$ camber angle, flow behavior near the end-wall region of some bowed cascades even deteriorates instead of improving because the blockage of the separated flow near the mid-span keeps the low-energy fluid near the end-walls from moving towards the mid-span region, and as a result, a rapid augmentation of the total loss is easy to take place under large bowed angle. With the increase of camber angle, the choice range of bowed angle corresponding to the best performance in different incidences become narrower.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.113-131
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• 1998

The objective of the present study is to investigate the characteristics of the dividing flow in the laminar flow region. Using glycerine water solution(wt43%) for Newtonian fluid and the polymer of viscoelastic fluid(500wppm) for non-Newtonian fluid, this research investigates the flow state of the dividing tube in steady laminar flow region of the two dimensional dividing tube by measuring the effect of Reynolds number, dividing angle, and the flow rate ratio on the loss coefficient. In T- and Y-type tubes, the loss coefficients of the Newtonian fluid decreases in constant rate when the Reynolds number is below 100. The effect of the flow rate ratio on the loss coefficients is negligible. But when the Reynolds number is over 100, the loss coefficient with various flow rate ratios approach an asymptotic value. The loss coefficient of the non-Newtonian fluid for different the Reynolds number shows the similar tendency of the Newtonian fluid. And when the Reynolds number is over 300, the loss coefficient is approximately 1.03 regardless of flow rate ratio or the dividing angle. The aspect ratio does hardly influence the reattachment length and the loss coefficient of both Newtonian and non Newtonian fluid. The loss coefficient decreases as the Reynolds number increases. The loss coefficient of Newtonian fluid is larger than that of non-Newtonian fluid.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.7 s.112
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• pp.729-738
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• 2006

Knowledge of acoustic transmission loss of acoustic window material has a great importance for the sonar performance in ship. The purpose of this study was to investigate the measurement and analysis method for the acoustic transmission loss of the acoustic window materials for sonar dome. The measurement and analysis were carried out in water with GRP material. Transmission losses were calculated based on integrated direct and transmitted signals. The experimental setup enabled to vary the angle of incidence. Thus the transmission loss data could be expressed as the function of frequency and angle of rotation. In this paper, diffraction effect of incident angle, size of specimen with test material, transmission analysis method and multiple waves as incident acoustic signal were discussed.