• Proceedings of the Acoustical Society of Korea Conference
• /
• 1994.06a
• /
• pp.716-721
• /
• 1994

The goal of this study is to develop treatment methods for improving the noise quality of Home Appliance Drain Pumps. Developed treatment methods covers the various methods including the control of the water level through the developed electronic circuity and the various modifications over the design of impeller and fan units. In the first part of the studies Dominant noise sources of the pumps are analyzed. Specific noise problems of the pumps are classified on the basis of mechanic and magnetic origins. Factors including the pressure variations at suction head, magnetic interactions with structure, specific fan noises are studied sequentially. The second part of the studies are considered for development and application of treatment methods. Results denoted the basic problems and ways to improve the noise quality by treating the dominant soureces of drain pumps.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.7
• /
• pp.895-906
• /
• 2000

A three dimensional linear frequency-domain lifting surface panel method was used for the aerodynamic analysis of axial flow type micro-fans. As proven by the duct modeling, the tip clearance of the micro-fans tested is large enough to ignore the calculated effect of the duct system. As the numerical results and experimental data agreed well in the operating point region, the method was applicable in the parametric studies to determine the design parameters of axial flow fans. Experiments on micro-fans were carried out based on KS B 6311. The newly designed micro-fan showed improvements in both static pressure rise and volumetric flow rate compared to the existing fans at a given operating condition. No detection of surging and the smooth characteristic curve proved the improvement in performance. To reduce the fan noise in the fan design, it was necessary to make use of the frequency spectrum analysis data. Measurement of sound pressure level for micro-fans was conducted based on KS B 6361 and KS A 0705. The peak - which occurs at blade passage frequency and its higher harmonics due to the fan noise - was not detected. This justifies the design methodology of the blade.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.826-829
• /
• 2005

The State of the art of low noise fan design requires the consideration of optimal sound quality. The influential design parameters of the noise level by the centrifugal fan were selected that based on a preliminary test. The centrifugal fans were designed according from the experiment plan method by specify the selected design parameters. The experiments with the machined mock-up's of centrifugal impellers revealed the major design parameters having impacts upon the indices of sound quality (e.g. loudness, sharpness, roughness and fluctuation strength) at the same performance condition. With a response surface method. the major design parameters selected were analyzed to estimate their contributions upon the sound quality of the centrifugal fan and the optimal values were drawn for the consideration of the sound quality by using each level and its regression equation. In addition, the validity of the regression equations were numerically verified by means of the coefficient of determination. Furthermore, the mechanism of how the centrifugal fans influence the determinants of sound quality was suggested.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.5
• /
• pp.206-211
• /
• 2014

The objective of the present study was to identify ventilation problems, and also to suggest new axial fan systems for the improvement of IAQ in the underground parking lots. Numerical results for air mean-velocity, local mean age, and sound power level are presented along with some of fan angles. The results showed the influence of airflow patterns on the fan performances installed in the underground parking lots. Discharge air volume is increased with the angle of the blade. And also, the main factors affecting the noise of the ventilation fan was found to be a rotational speed.

• International Journal of Aeronautical and Space Sciences
• /
• v.15 no.1
• /
• pp.97-101
• /
• 2014

With the increase in global air travel, aircraft noise has become a major public issue. In modern aircraft engines, only a small proportion of the air that passes through the whole engine actually goes through the core of the engine, the rest passes around it down the bypass duct. A successful method of reducing noise further, even in ultra-high bypass ratio engines, is to absorb the sound created within the engine. Acoustically absorbent material or acoustic liners have desirable acoustic attenuation properties and thus are commonly used to reduce noise in jet engines. The liners typically are placed upstream and downstream of the rotors (fans) to absorb sound before it propagates out of the inlet and exhaust ducts. Noise attenuation can be dramatically improved by increasing the area over which a noise reducing material is applied and by placing the material closer to the noise source. In this paper we will briefly discuss acoustic liner applications in modern turbofan engines.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.19 no.1
• /
• pp.83-89
• /
• 2009

Generally, automobile cooling fan is used to lower the temperature of radiator. The cooling fans are manufactured by plastic injection molding process. The center of gravity of cooling fan is often deviated from the center due to the use of deteriorated materials. As the unbalanced of the cooing fan can generate noise, it is required to measure the degree of deviation of center of gravity in the cooling fan. In this work, automatic fan balancer which can effectively detect the magnitude and position of the unbalanced cooling fan is proposed and several experiments are carried out to verify the feasibility of the proposed algorithm.

• Journal of KSNVE
• /
• v.8 no.1
• /
• pp.112-121
• /
• 1998

In this report, Experimental analysis for main factors and analyzing methods of electro-magnetic noise and no loading noise was conducted because of noise of AC generator, which is peripheral equipment by reduction of engine noise that would be the main cause of vehicle radiation noise. In addition, This is intended to suggest the noise reduction development basis of AC generator for actual fan and electro-magnetic noise by making-analyzing-testing it's sample.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.6
• /
• pp.761-768
• /
• 1999

This paper is studied to find the optimum condition of double-inlet Sirocco fan installed in an indoor PAC for low noise operation by the Taguchi method. The goal of this study is to obtain the best combination of each control factor which results in a desired flowrate of Sirocco fan with minimum variability. In this study, the parameter design of the Taguchi method is adopted for robust design by the dynamic characteristic analysis using orthogonal arrays and S/N ratios. The flowrate measurements are conducted by using a multiple-nozzle-type fan tester according to the orthogonal array L9($3^4$). The results of this study can be summarized as follows ; (i) The optimum condition of control factor is a set of where A is an inner to outer diameter ratio($D_1/D_2$), B is a width to outer diameter ratio($L/D_2$), C is a blade attachment angle(${\theta}$) and D is a number of blade(Z), (ii) The flowrate under the optimum condition satisfies the equation $y=0.0384{\cdot}M$ where M is a signal factor, namely number of revolution. The flowrate performance improves about 7.3% more largely as compared with the current condition, which results in about 35RPM reduction of number of revolution for the target flowrate $18.5m^3/min$, and (iii) The sensitivity analysis shows that the major factors in contribution to flowrate performance are A, B, and D ; the percentage contributions of each control factor are 44.01%(Z), 26.77%($D_1/D_2$) and 20.42%($L/D_2$).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.2
• /
• pp.205-213
• /
• 2011

The characteristics of noise generation in the suction nozzle of a vacuum cleaner are analyzed numerically and experimentally. First, the flow resistance induced by each element in the suction nozzle of a vacuum cleaner with a double-blade rotary fan is investigated numerically and its relation with flow-induced noise and suction performance is examined in an anechoic room. The flow resistance and vorticity in the suction nozzle are calculated, and it is found that they are closely related to flow-induced noise and that the upper limit of noise reduction is only 4 dBA. This upper limit can be achieved by changing the design of the brush nozzle. Two methods for noise reduction by enlargement of flow-inlet area and by optimization of the number of blades are tested. Finally, the effects of each method are verified experimentally.

• The KSFM Journal of Fluid Machinery
• /
• v.1 no.1 s.1
• /
• pp.32-40
• /
• 1998

Aerodynamic performance of a cooling fan of driving motor was enhanced modifying the vane-shroud configuration. Performance of a target model was evaluated to obtain baseline data. The aerodynamic performance and sound pressure level were tested and measured with different numbers of vane of increased length. The tested models show high and stable performance and low values of specific noise level. The long vane-shroud structure induces more stable through flow and decreases the tip leakage flow, which contributes to the increases of performance and efficiency. The sound pressure level increases for the modified model, however, specific noise level decreases.