• 유체기계공업학회:학술대회논문집
• /
• 2001.11a
• /
• pp.69-75
• /
• 2001

A new method to calculate the aeroacoustic pressure of a centrifugal fan was developed The fan consists of an impeller, diffuser and circular casing. Due to the high rotating velocity and the small gap between the impeller and diffuser, the centrifugal fan makes very high noise level at BPF and its harmonic frequencies. The aeroacoustic pressure is calculated acoustic analogy In this paper, only dipole term is considered in the equation. The acoustics generated by moving impeller and stationary diffuser is calculated separately. The unsteady flow field data is calculated by the vortex method The predicted acoustic pressure agrees very well to the measured data. The difference of the two is smaller than 3dBA.

• International Journal of Fluid Machinery and Systems
• /
• v.1 no.1
• /
• pp.109-120
• /
• 2008

An innovative method of changing a centrifugal low specific speed pump performance and pressure fluctuation by applying outlet flaps to impeller exit has been investigated. The outlet blade edge section corresponds to the trailing edge of wing on the circular-cascade, which dominates the pump performance and pressure fluctuation. Computational fluid dynamics (CFD) analysis of the entire impeller and volute casing and an experimental investigation are conducted. The pressure fluctuation and the vibration of the shaft are measured simultaneously. Kurtosis is applied as a dimensionless parameter with which the unevenness of velocity distribution at impeller outlet is indicated. The influence of the flaps on the pressure fluctuation is explained by the kurtosis. This paper presents a theoretical method of predicting the pump performance related to the attachment of a flap at impeller outlet.

• Journal of Power System Engineering
• /
• v.20 no.6
• /
• pp.71-79
• /
• 2016

This paper introduces the design method of the centrifugal turbo fan and the process of developing the design program of it. The developed design program confirmed the applicability by experimental performance data. Here, we proposed new velocity coefficients and considered various losses such as impeller inlet loss, vane passage flow loss, casing pressure loss, recirculation loss power, and disk friction loss power. Especially, the inlet and outlet widths of the impeller were newly determined by reflecting the experimental results. As a result, this fan design program shows a good performance result regardless of the types of impeller and is expected to be a very useful design tool.

• Journal of Mushroom
• /
• v.9 no.4
• /
• pp.198-201
• /
• 2011

Cobweb disease symptoms were observed in a mushroom farm in Buye, Korea during a disease survey in 2008-2011. Five isolates of Cladobotryum sp. were obtained from the infected caps and stipes. These isolates of Cladobotryum sp. were identified as C. mycophilum based on their morphological, cultural characteristics and analysis of the ITS sequences. Early symptoms were noticed as round, fleshy, yellowish brown lesions on mushroom caps. Late symptoms progressed when the parasitic fungus formed white cobweb circular colonies on dead or damaged pinheads, spread on the surface of the casing, and covered entirely fruiting bodies. Optimal temperature and pH for mycelial growth on MEA is $23^{\circ}C$ and 6.0. Microscopically the spores of the fungus are large and most 2~3 celled produced on vertically branched conidiophores. Mushroom caps turned dark brown and shrunk due to soft rot. Testing of sensitivity to selected fungicides showed that isolate was highly resistance to Mancozeb and Thiophanate-methyl, moderately sensitivity to Iprodione, and highly sensitivity to Benomyl, Prochloraz-Mn and Carbendazim.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2004.04a
• /
• pp.281-286
• /
• 2004

The vacuum cleaner motor runs on very high speed for the suction power. Specially, the motive power is provided by the impeller being rotate on very high speed. And centrifugal fan consists of the impeller, the diffuser, and the circular casing. Due to the high rotating speed or the impeller and small gap distance between the impeller and diffuser, the centrifugal fan makes very high noise level at BPF and harmonic frequencies. In order to calculate the sound pressure of centrifugal fan, the unsteady flow data is needed. And Noise cause is dividing to fluid noise by exhaust flow of fan and vibration noise by rotational vibration of vacuum cleaner fan motor. Until now, measuring method has been used to measure vibration by the accelerometer; this method has been not measured for the vibration in some parts of brush and commutator because of motor construction and 3-D vibrating mode. This paper was purposed on the accurate analysis, using laser vibration analyzer,. By using this measured data of noise cause against the difficult part in old times, we would like to use for the design of silent fan motor.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.3 s.168
• /
• pp.46-51
• /
• 2005

The vacuum cleaner motor runs at very high speed for suction power. Specially, motor power is provided by the impeller being rotated at very high speed. The centrifugal fan consists of the impeller, the diffuser, and the circular casing. Due to the high rotating speed of the impeller and small gap distance between the impeller and the diffuser, the level of noise in the centrifugal fan is at BPF(Blade Passage Frequency) and its harmonic frequencies. In order to calculate the sound pressure of centrifugal fan, unsteady flow data are needed. The cause of noise is obtained by dividing the fluid noise by exhaust flow of fan and vibration noise by rotational vibration of vacuum cleaner fan motor. Until now, an accelerometer has been used to measure vibration. However, it can not measure vibration in some parts of brush and commutator because of motor construction and 3-D vibrating mode. This study was conducted to perform accurate analysis of vibration and aerodynamic sound for fan motor in a vacuum cleaner using a laser vibration analyzer. A silent fan motor can be designed using the data measured in this study.

• Journal of KSNVE
• /
• v.7 no.1
• /
• pp.99-106
• /
• 1997

Centrigugal fans are widely used due to their ability to achieve relatively high pressure ratios in a short axial distance compared to axial fans. Because of their widespread use, the noise generated by these machines causes one of serious problems. In general, centrigugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the periodic flow discharged radially from the impeller and the stator blades or the cutoff. But in vacuum cleaner fan the noise is dominated by not only the discrete tones of BPF but also broadband frequencies. In this study we investigate the mechanism of broadband noise and predict for the unsteady flow field and the acoustic pressure field associated with the centrifugal fan. DVM(discrete vortex method) is used to calculates the flow field and the Lowson's method is used to predict the acoustic pressures. From the results we find that the broadband noise of a circular casing centrifugal fan is due to the unsteady force fluctuation around the impeller blades related to the vortex shedding. The unsteady forces associated with the shed vortices at impeller and related to the interactions to the diffuser and the exit.

• The KSFM Journal of Fluid Machinery
• /
• v.5 no.2 s.15
• /
• pp.36-42
• /
• 2002

A new method to calculate the aeroacoustic pressure of a centrifugal fan that is used in a vacuum cleaner has been developed. The centrifugal fan consists of the impeller, the diffuser, and the circular casing. Due to the high rotating speed of the impeller and the small gap distance between the impeller and diffuser, the centrifugal fan makes very high noise levels at BPF and its harmonic frequencies. In order to calculate the sound pressure of a centrifugal fan, the unsteady flow field data is needed. This unsteady flow field is calculated by the vortex method. The sound pressure is then calculated by acoustic analogy. In this paper, only dipole term is considered in the equation. The noise generated by moving impeller and stationary diffuser is calculated separately. The predicted acoustic pressures agree very well with the measured data. The difference between the two is less than 4dB

• Journal of Practical Agriculture & Fisheries Research
• /
• v.17 no.1
• /
• pp.57-71
• /
• 2015

This study was conducted to develop the fertigation system with a peristaltic hose pump and brushless DC motor. The fertigation system was consisted of sensor, main controller, motor control unit, peristaltic pump, water supply pump, control panel, and filter. The peristaltic pump discharges liquid by squeezing the tube with rollers. Rollers attached to the external circumference of the rotor compresses the flexible tube. The fluid is contained within a flexible tube fitted inside a circular pump casing. The developed fertigation system has no mixing tank but instead injects directly a concentrated nutrient solution into a water supply pipe. The revolution speed of the peristaltic pump is controlled by PWM (Pulse width modulation) method. When the revolution speed of the peristaltic pump was 300rpm, the flow rate of the 3.2, 4.8, 6.3mm diameter tube was 202, 530, 857mL/min, respectively. As increasing revolution speed, the flow rate of the peristaltic pump linearly increased. As the inner diameter of a tube larger, a slope of graph is more steep. Flow rate of three roller was more than that of four roller. Flow rate of a norprene tube with good restoring force was more than that of a pharmed tube. As EC sensor probe was installed in direct piping in comparison with bypass piping showed good performance. After starting the system, it took 16~17 seconds to stabilize EC. The maximum value of EC was 1.44~1.7dS/m at a setting value of 1.4dS/m. The developed fertigation system showed ±0.06dS/m deviation from the setting value of EC. In field test, Cucumber plants generally showed good growth. From these findings, this fertigation system can be appropriately suitable for fertigation culture for crops.