• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.1
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• pp.1-8
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• 2008

Numerical optimization for design of a blade stacking line of a low speed axial flow fan with a fast and elitist Non-Dominated Sorting of Genetic Algorithm(NSGA-II) of multi-objective optimization using three-dimensional Navier-Stokes analysis is presented in this work. Reynolds-averaged Navier-Stokes(RANS) equations with ${\kappa}-{\varepsilon}$ turbulence model are discretized with finite volume approximations and solved on unstructured grids. Regression analysis is performed to get second order polynomial response which is used to generate Pareto optimal front with help of NSGA-II and local search strategy with weighted sum approach to refine the result obtained by NSGA-II to get better Pareto optimal front. Four geometric variables related to spanwise distributions of sweep and lean of blade stacking line are chosen as design variables to find higher performed fan blade. The performance is measured in terms of the objectives; total efficiency, total pressure and torque. Hence the motive of the optimization is to enhance total efficiency and total pressure and to reduce torque.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.601-606
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• 2004

Vibration spectrums of the test loop according to flow conditions were analyzed in order to identify the sources of vibration at peak frequencies. While a flow condition of the sweep test was changed by varying pump rotational speed from 450 rpm to 1500 rpm by the step 150 rpm, midspan acceleration of the test section in width-direction and dynamic pressure perturbation in the test section were measured. Other sources of vibration due to the flow structure interactions, such as acoustic resonance, blade pulsing frequency and bellows wrinkles, were investigated. Pressure perturbation in the section and acoustic resonance due to branch pipe give major effects to the vibration of the test section in high frequency range of 1.5 kHz to 2.8 kHz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.386-391
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• 1998

The effect of the changes in parameter angles(precone, droop, sweep) on the lead-lag damping was focused on. Experiment was made with hingeless 4-blade rotors and NACA 0012 airfoil. For the measurement of the rotating natural frequencies and lead-lag damping, non-rotating swash plate was oscillated at the regressing lag mode frequency and the data were acquired after the excitation was cut off. Analysis was made using a finite element formulation based on Hamilton's principle. The main blade is assumed as elastic beams. Quasi-steady strip theory is used to obtain aerodynamic forces, and non-circulatory forces are also included.

• International Journal of Fluid Machinery and Systems
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• v.1 no.1
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• pp.148-154
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• 2008

The Wells turbine rotor consists of several symmetric airfoil blades arranged around a central hub, and the stagger angle is 90 degrees. These characteristics simplify the total construction of OWC type wave energy converters. Although the Wells turbine is simple, the turbine produces a complicated flow field due to the peculiar arrangement of blades, which can rotate in the same direction irrespective of the oscillating airflow. In order to understand these flows, flow visualization is carried out with an oil-film method in the water tunnel. This research aims to analyze the mechanism of the 3-D flows around the turbine with the flow visualization. The flow visualization explained the influence of attack angle, the difference between fan-shaped and rectangular wings, and the sweep angle.

• The Journal of the Acoustical Society of Korea
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• v.39 no.5
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• pp.379-389
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• 2020

In this study, the flow and noise performances of high-speed fan motor unit for cordless vacuum cleaner is improved by optimizing the impeller which drives the suction air through flow passage of the cordless vacuum cleaner. Firstly, the unsteady incompressible Reynolds averaged Navier-Stokes (RANS) equations are solved to investigate the flow through the fan motor unit using the computational fluid dynamics techniques. Based on flow field results, the Ffowcs-Williams and Hawkings (FW-H) integral equation is used to predict flow noise radiated from the impeller. Predicted results are compared to the measured ones, which confirms the validity of the numerical method used. It is found that the strong vortex is formed around the mid-chord region of the main blades where the blade curvature change rapidly. Given that vortex acts as a loss for flow and a noise source for noise, impeller blade is redesigned to suppress the identified vortex. The response surface method using two factors is employed to determine the optimum inlet and outlet sweep angles for maximum flow rate and minimum noise. Further analysis of finally selected design confirms the improved flow and noise performance.

• Journal of the Korean Institute of Gas
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• v.24 no.3
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• pp.47-53
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• 2020

In this study, the optimization design data was presented by analyzing the performance and durability of the cooling fan by one-way fluid-structure interaction analysis of the cooling fan shape used in the engine generator. For this purpose, a steady-state analysis was performed on the flow field inside the cooling fan, and the durability was analyzed by using the steady-state calculation results as input data for structural analysis. Six types were modeled for fluid analysis by changing the blade and sweep angle of the cooling fan, and the ratio of mass flow rate and torque was best in A type, but B type with relatively large mass flow rate was the best. It was judged to have flow performance. As a result of examining the structural analysis by setting the four blade thickness of the B type selected through the fluid analysis, it was judged that B Type-3 is the most suitable when considering the fatigue safety factor.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.2
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• pp.118-126
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• 2011

The characteristics of the responses obtained in thermosonic tests are investigated in this study to improve the performance of a thermosonic test system. Thermosonic tests are conducted with an acoustic horn with high power capability to investigate the characteristics of the vibration produced in turbine blades with complex geometry. The influences of the excitation signal that is input to the horn and the coupling methods between a clamp and the acoustic horn on the characteristics of the vibration excited in a component are presented. As a result, an excitation method with a fast narrow band chirp test (sweep test) and a stud coupling is proposed as an excitation method for thermosonic testing. This method can be applied to different types of turbine blades and also to other components.

• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.558-563
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• 2014

To study the effects of fabrication methods on the performance and durability of polymer electrolyte membrane fuel cells (PEMFCs), membrane-electrode assemblies (MEAs) were fabricated using a Dr blade method, a spray method, screen print method and screen print + spray method. The performance of single cells assembled with the prepared MEAs were initially measured and compared. Electrode accelerated stress testing (AST) involving a potentiostatic step-wave with 10 s at 0.6 V followed by 30 s at 0.9 V was applied to test durability of MEAs. Before and after 6,000cycles of the AST, I-V curves, impedance spectra, cyclic voltammograms, linear sweep voltammetry (LSV) and transmission electron microscope (TEM) were measured. Under the operating conditions, the Dr Blde MEA exhibited the highest initial performance. After electrode accelerated stress testing, screen print + spray MEA showed lowest degradation rate.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.11
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• pp.903-910
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• 2014

Electric fans, which consist of axial blades, are operated by the induction motor. In this paper, the objective of this study is the performance improvement of the base model fan using the design optimization. In order to aerodynamic analysis, computational simulations are performed using commercial tool ANSYS-CFX ver. 14.5. And k-${\omega}$ SST turbulence model is used for the CFD analysis. The design variables are set up as sweep and lean angles. Volumetric flow rate and torque of the fan blades are fixed to objective function. The optimized model is shown the increment of the volumetric flow rate and the reduction of the torque compared with the base model. The experimental procedure is followed KS C 9301. CFD results and experimental results are fairly well matched.