• 한국지역사회생활과학회지
• /
• 제24권3호
• /
• pp.391-397
• /
• 2013

This study was conducted to define the characteristics of the fan according to the bed depth of rough rice for the silo used in South Korea. In this study, the characteristics like air flow resistance and air flow rate of the fan were investigated for an independent blowing system with 1 fan and the serial blowing system with 2 fans. In the experiment, the depth of rough rice was determined by 0, 1, 2, 3.2 and 4.5 m for an independent blowing system and the depth of rough rice was 4.5 m for the serial blowing system. The air flow resistances of the blowing fan and the suction fan in an independent blowing system were 55 mmAq and 88 mmAq respectively. In addition, the air flow resistance of the serial blowing system was 61% lower than the blowing fan and 28% lower than the suction fan of the independent blowing system. The air flow rates of the blowing fan and the suction fan in the serial blowing system were 516 $m^3/min$, 570 $m^3/min$, respectively. The former was 22% higher than the blowing fan while the latter was 29% higher than the suction fan in the independence blowing system. In other words, the serial blowing system was superior to the independent blowing system in blowing characteristics because the air flow rate was lower and air flow resistance was higher than the independent blowing system. However, the fan power consumption of the serial blowing system was more than 100% comparing with the independent blowing system.

• 한국산업융합학회 논문집
• /
• 제3권3호
• /
• pp.245-250
• /
• 2000

This study was carried out to investigate blowing performance for blowing type in space heater. This paper present that power requirement, static pressure, total pressure and static pressure efficiency were increased in proportion to air flow rate. And in the Korean space heater, side ward blowing type was effected than downward blowing type.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집D
• /
• pp.553-558
• /
• 2001

To find the effective combinations of blowing ratio and injection angle for a straight slot film cooling, film cooling characteristics was investigated using both flow visualization experiment and numerical simulation. Injection angles from $15^{\circ}\;to\;50^{\circ}$ and blowing ratios from 0.2 to 3.0 were selected for the simulation. Comparison between experimental and numerical results shows a good agreement, for the case of the injection angle of $30^{\circ}$ and blowing ratio ranging from 0.55 to 2.0. Film cooling effectiveness was found to be an increasing function of blowing ratio. The effects of injection angle became prominent as the blowing ratio increases. An interesting phenomenon was found for the injection angle of $15^{\circ}$ : the lowest film cooling effectiveness for the blowing ratio smaller than 1.0, but the highest film cooling effectiveness for the blowing ratio greater than 2.0 within wide range of downstream region. There exist optimum injection angles corresponding to maximum film cooling effectiveness : injection angle of $25^{\circ}$ for the blowing ratio from 0.2 to 2.0, and injection angle of $15^{\circ}$ for the blowing ratio of 3.0. Present study provides a design combination among film cooling effectiveness, blowing ratio, and injection angle.

• 한국유체기계학회 논문집
• /
• 제14권4호
• /
• pp.19-24
• /
• 2011

An experimental study was conducted to examine the effectiveness of a suction-blowing fan that could not only remove polluted air by suction but also create the air-curtain by blowing. In order to create the air-curtain, rotors were installed on the surface of the shroud. These blows fresh air into the polluted region. The fresh air is spouted backward 45o on the basis of the axial direction using a double-ducted bellmouth. In the same suction operating condition, the suction region was extended by increasing the blowing velocity. However, the increasing rate of suction region was reduced when the blowing velocity was increased steadily. Thus, an efficient blowing velocity should be determined depending on the suction operating condition. In addition, the blowing requires additional input power. In a fixed suction operating condition, the input power was linearly increased in proportion to the blowing flowrate. When the suction-blowing fan was operated in the same input power as the suction fan, the suction region was increased more than 30% based on the 0.6m/sec velocity.

• 한국항공우주학회지
• /
• 제35권12호
• /
• pp.1059-1066
• /
• 2007

타원형 단면 에어포일의 블로잉 제트에 의한 유동박리 제어효과에 대한 연구를 레이놀즈수 Rec=7.84×105에서 실험적 방법으로 수행하였다. 블로잉 제트는 에어포일 내부의 공기실에 있는 압축공기를 앞전 혹은 뒷전에 위치한 좁은 제트슬롯을 통하여 분출시켰다. 실험결과 블로잉은 날개면 압력회복으로 수직력을 증가시킴으로써 박리 유동을 제어할 수 있음을 보였다. 블로잉에 의한 수직력의 상승은 상대적으로 높은 받음각에서 더욱 효과가 컸으며 낮은 받음각에서는 감소되었다. 현 연구조건에서 수직력을 상승시키는데 가장 효과적인 블로잉 방식은 앞전에서의 90° 방향의 간헐제트이었다. 특히, 간헐제트가 부여된 경우 실속 받음각을 약 2°-3° 지연시킬 수 있었다. 연속제트와 간헐제트 모두 에어포일의 공력특성과 성능을 향상시킴으로써 유동박리 제어에 직접적이고 유효한 방법임을 입증하였다.

• 대한기계학회논문집B
• /
• 제28권1호
• /
• pp.31-40
• /
• 2004

Direct numerical simulations were performed to analyze the effects of time-periodical blowing through a spanwise slot on a turbulent boundary layer. The blowing velocity was varied in a cyclic manner from 0 to 2A$^{+}$(A$^{+}$ =0.25, 0.50 and 1.00) at a fixed blowing frequency of f$^{+}$=0.017. The effect of steady blowing (SB) was also examined, and the SB results were compared with those for periodic blowing (PB). PB reduced the skin friction near the slot, although to a slightly lesser extent than SB. PB was found to generate a spanwise vortical structure in the downstream of the slot. This vortex generates a reverse flow near the wall, thereby reducing the wall shear stress. The wall-normal and spanwise turbulence intensities under PB are increased as compared to those under SB, whereas the streamwise turbulent intensity under PB is weaker than that under SB. PB enhances more energy redistribution than SB. The periodic response of the streamwise turbulence intensity to PB is propagated to a lesser extent than that of the other components of the turbulence intensities and the Reynolds shear stress.

• 대한기계학회논문집B
• /
• 제28권1호
• /
• pp.41-51
• /
• 2004

A direct numerical simulation is performed to analyze the effects of a localized time-periodic blowing on a turbulent boundary layer flow at R $e_{+}$=300. Main emphasis is placed on the blowing frequency effect on near-wall turbulent flow structures at downstream. Wall-normal velocity on a spanwise slot is varied periodically at different frequencies (0.004$\leq$ $f^{＋}$$\leq$0.080). The amplitude of periodic blowing is $A^{＋}$=0.5 in wall nit, which corresponds to the value of $v_{rms}$ at $y^{＋}$=15 without blowing. The frequency responses are scrutinized by examining the phase or time-averaged turbulent statistics. The optimal frequency ( $f^{＋}$=0.03) is observed, where maximum increase in Reynolds shear stress, streamwise vorticity fluctuations and energy redistribution occurs. The phase-averaged stretching and tilting term are investigated to analyze the increase of streamwise vorticity fluctuations which are closely related to turbulent coherent structures. It is found that the difference between PB and SB at a high blowing frequencies is negligible.e.e.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집B
• /
• pp.746-751
• /
• 2001

We used a cylindrical model which simulates turbine blade leading edge to investigate the effects of free-stream turbulence intensity and blowing ratio on film cooling of turbine blade leading edge. Tests are carried out in a low-speed wind tunnel on a cylindrical model with three rows of injection holes. Mainstream Reynolds number based on the cylinder diameter was $7.1\times10^4$. Two types of turbulence grid are used to increase a free-stream turbulence intensity. The effect of coolant blowing ratio was studied for various blowing ratios. For each blowing ratios, wall temperatures around the surface of the test model are measured by thermocouples installed inside the model. Results show that blowing ratios have small effect on spanwise-averaged film effectiveness at high free-stream turbulence intensity. However, an increase in free-stream turbulence intensity enhances significantly spanwise-averaged film effectiveness at low blowing ratio.

• 대한기계학회논문집B
• /
• 제27권9호
• /
• pp.1342-1350
• /
• 2003

A direct numerical simulation of a spatially-developing turbulent boundary layer is performed to examine the characteristics of wall pressure fluctuations after the sudden application of wall blowing or suction. The uniform blowing or suction is given by the wall-normal velocity through a spanwise slot at the wall. The response of wall pressure fluctuations to uniform blowing or suction is analyzed by computing the turbulence statistics and frequency spectra. It is found that wall pressure fluctuations are more affected by blowing than by suction. The large elongated structure of wall pressure fluctuations is observed near the maximum location of $(p_w)_{rms}$ for blowing. The convection velocities for blowing increase with increasing the streamwise location after the slot. For both blowing and suction, the small scale of wall pressure fluctuations reacts in a short downstream distance to the spanwise slot, whereas the large scale recovers slowly in a farther downstream.

• 한국지능시스템학회논문지
• /
• 제18권4호
• /
• pp.482-487
• /
• 2008

침수의 경우에, 수중 비행체(UFV : Underwater Flight Vehicle)는 발라스트 탱크들의 내부를 고압 공기로 비워 내어 부상을 수행한다. 동시에, 침수와 부상 순차에 의한 오버슈트 심도를 감소시키기 위해서 제어판과 추진기를 병행하여 사용한다. 그런데, 기존의 전체 고압 공기 blow-off 방법은 가벼운 침수일지라도 부상 후에는 몸체를 수면에 드러나게 한다. 이는 불필요한 임무 실패 또는 몸체 노출의 결과를 가져온다. 따라서, 부상 제어에 의해 오버슈트 심도를 감소시킴과 동시에 몸체를 수면 근처에 유지시키는 것이 필요하다. 이 문제를 해결하기 위해서 심도 제어에 있어서의 전문가 지식을 확장하는 분해법 및 FBFE(Fuzzy Basis Function Expansion)을 사용하는 적응법에 기초한 적응 부상 제어 알고리즘이 제안되었다. 제안된 알고리즘의 성능을 검증하기 위해 UFV 부상 제어가 수행되었다. 시뮬레이션 결과는 제안된 알고리즘이 UFV 부상제어 시스템에 존재하는 문제점들을 온라인으로 효과적으로 해결하고 있음을 보여준다.