• Title/Summary/Keyword: 질량평균

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Effects of Pressure-Side Winglet at an Elevation of Tip Surface on the Tip-Leakage Flow and Aerodynamic Loss Downstream of a Turbine Blade Equipped with Pressure-Side Squealer Tip (압력면익단소익이 터빈 동익 압력면스퀼러팁 하류의 팁누설유동 및 압력손실에 미치는 영향)

  • Cheon, Joo Hong;Lee, Sang Woo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.10
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    • pp.645-651
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    • 2016
  • Effects of pressure-side winglet width on the tip leakage flow and aerodynamic loss downstream of a turbine blade with a pressure-side squealer rim have been investigated for the tip gap-to-span ratio of h/s = 1.36%. The pressure-side squealer has a fixed height-to-span ratio of $h_p/s=3.75%$ and the pressure-side winglet, which is installed at an elevation of tip surface, has width-to-pitch ratios of w/p = 2.64%, 5.28%, 7.92% and 10.55%. The results show that with increasing w/p, aerodynamic loss in the passage vortex region decreases, whereas that in the leakage flow region increases. As a result, the mass-averaged loss coefficient all over the measurement plane tends to decrease minutely with the increment of w/p. It is concluded that the pressure-side winglet for the pressure-side squealer tip can hardly contribute to the tip-leakge loss reduction.

Pressure Drop due to Friction in Small Rectangular Channel (미소 사각 채널에서의 마찰 압력 강하)

  • Lim, Tae-Woo;Choi, Jae-Hyuk;Kim, Jun-Hyo;Choi, Yong-Suk
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.18 no.5
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    • pp.461-467
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    • 2012
  • An experimental study was carried out to measure frictional pressure drop in flow boiling to deionized water in a microchannel having a hydraulic diameter of $500{\mu}m$. Tests were performed in the ranges of heat fluxes from 100 to $400kW/m^2$, vapor qualities from 0 to 0.2 and mass fluxes of 200, 400 and $600kg/m^2s$. The frictional pressure drop during flow boiling is predicted by using two models; the homogeneous model that assumes equal phase velocity and the separate flow model that allows a slip velocity between two phases. From the experimental results, it is found that the two phase multiplier decreases with an increase in mass flux. Measured data of pressure drop are compared to a few available correlations proposed for macroscale and mini/microscale. The homogeneous model well predicted frictional pressure drop within MAE of 29.4 % for the test conditions considered in this work.

Development of Hybrid Fiber-reinforced High Strength Lightweight Cementitious Composite (하이브리드 섬유로 보강한 고강도 경량 시멘트 복합체의 개발)

  • Bang, Jin-Wook;Kim, Jung-Su;Lee, Bang-Yeon;Jang, Young-Il;Kim, Yun-Yong
    • Composites Research
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    • v.23 no.4
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    • pp.35-43
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    • 2010
  • The purpose of this paper is to develop a Hybrid Fiber-reinforced High Strength Lightweight Cementitious Composite (HFSLCC) incorporated with lightweight filler and hybrid fibers for lightness and high ductility. Optimal ingredients and mixture proportion were determined on the basis of the micromechanical analysis and the steady-state cracking theory considering the fracture characteristics of matrix and the interfacial properties between fibers and matrix. Then 4 mixture proportions were determined according to the type and amount of fibers and the experiment was performed to evaluate the mechanical performance of those. The HFSLCC showed 3% of tensile strain, 4.2MPa of ultimate tensile stress, 57MPa of compressive strength and $1,660kg/m^3$ of bulk density. The mechanical performance of HFSLCC incorporated with PVA fibers of 1.0 Vol.% and PE fibers of 0.5 Vol.% is similar to those of the HFSLCC incorporated with fibers of 2.0 Vol.%.

A Combustion Characteristic Analysis of Quercus Variabilis and Pinus Densiflora Fallen Leaves Using Radiation Heat Flux (복사열을 이용한 소나무와 굴참나무 낙엽의 연소특성 분석)

  • Park, Hyung-Ju;Kim, Eung-Sik;Kim, Jang-Hwan;Kim, Dong-Hyun
    • Fire Science and Engineering
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    • v.21 no.3
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    • pp.41-46
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    • 2007
  • The combustion characteristics of surface forest fire fuels was analysed using variable external irradiation level. The characteristics such as ignition time, ignition temperature, critical heat flux and mass loss rate were measured. Fuel samples were exposed to incident heat fluxes from 8 to $50\;kW/m^2$. For the measurement of various combustion characteristics, the size of specimen holder was $100\;mm{\times}100\;mm{\times}12\;mm$ and the fuel samples grinded by electric mill were the fallen leaves of Quercus variabilis and Pinus densiflora. As results, the occurrence of ignition is possible to the heat flux more than $9\;kW/m^2$. The fuel of Pinus densiflora keeps its high temperature longer than that of Quercus variabilis during the combustion process. The results of measurement shows that the maximun and average mass loss rate of Quercus variabilis larger than that of Pinus densiflora.

Drying Characteristics of Fine Polymers in an Inert Medium Fluidized Bed (매체유동층에서 미세 고분자의 건조특성)

  • Kim, Og-Sin;Lee, Dong-Hyun
    • Clean Technology
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    • v.17 no.3
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    • pp.209-214
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    • 2011
  • The effects of inlet gas velocity (0.26-0.31 m/s), inlet gas temperature (315-353 K) and the mass ratio (0.1-0.4) of fine polymer (crosslinked poly methyl methacrylate beads) to inert medium particles on the drying rate of fine polymer in a 0.15 m-ID ${\times}$ 1.0 m-high inert medium fluidized bed dryer have been investigated. Crosslinked PMMA beads of 20 ${\mu}m$ (group C) were used as fine polymer, and glass beads of 590 ${\mu}m$ (group B) were used as the inert medium. The drying rate increases with increasing inlet gas temperature and velocity. However, the drying rate decreases slightly as the mass ratio of fine polymer to inert medium particles increases. The particle size distribution of dried fine polymers was mono distribution.

Comparison of Body Fat Content and Lipid in Serum in Cultured Flounder in Korea and Japan (한국산과 일본산 넙치의 체지방량 및 혈청지질 비교)

  • Park, Mi-Yeon;Tsuchimoto, Mutsuyosi;Tachibana, Katuyasu
    • Korean Journal of Ichthyology
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    • v.19 no.3
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    • pp.193-200
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    • 2007
  • The samples of cultured flounder (Paralichtys olivaceus) were collected from Tongyeong and Yosu in Korea and Nagasaki in Japan and processed to analyses of body and serum. Body size and weight were not significantly different between Korea and Japan produced. But the body weight of average size of flounder produced from Nagasaki was the highest from the samples. The average of fish body was not significantly different from the samples. The water content of fish body was lower in samples from Nagasaki and fat content was higher in the samples from Nagasaki and followed by Yosu and Tongyeong. The percentage of body water, fat and protein contents was Nagasaki, Yosu and Tongyeong in the order of high values. Japanese flounder showed relatively high content of body fat and muscle. The cholesterol of serum was highest in the samples of Yosu. The triglyceride of serum was highest in the samples of Nagasaki. Lipoprotein was highest in the samples of Nagasaki and enriched fat content in LDL fraction.

Analysis of Flow Characteristic and Optimum Design for Subminiature Pressure Reducer Under High Pressure (고압 적용용 초소형 감압기 설계를 위한 유동 해석 및 최적 설계)

  • Lee, WonJun;Baek, JongTae;Yun, Rin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.8
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    • pp.497-503
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    • 2017
  • A theoretical study on oxygen flow is fundamental to comprehend the practical production of an oxygen respirator and its stability. In this study, an orifice-type pressure-reducing component was designed for the newly developed oxygen respirator, using the commercial CFD tool, COMSOL Multiphysics, which increases its operational time compared to the existing component. The orifice was optimized by changing the length by 3, 6, and 9 mm within the entire computational domain of the oxygen respirator. Based on an oxygen flow rate of 0.028 kg/s, the oxygen respirator equipped with the newly developed orifice satisfied the flow rate within 33% for a respirator inlet pressure of 300 bar, and within 32.7% for 50, 75, and 100 bar. In terms of component manufacturing, the orifice length was selected as 3 mm, which removes additional changes to the existing component.

Elemental concentrations of atmospheric particles in Cheonan during 2006 (2006년 천안시 대기 입자의 원소 성분 특성)

  • Oh, Se-Won
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.9 no.6
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    • pp.1782-1786
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    • 2008
  • To investigate the characteristics of elemental components of atmospheric particles in Cheonan, atmospheric particles were sampled using a high volume air sampler equipped with a 5-stage cascade impactor during 2006. 16 elemental concentrations in fine and coarse particles were determined using ICP-AES and ICP-MS. The total mass concentrations of fine and coarse particles were 33.23 and $20.66{\mu}g/m3$, respectively, and the total elemental concentrations were 1.27, $1.71{\mu}g/m3$, occupying 3.8 and 8.3% of the total mass. Fe, Al, Ti were the most abundant elements in both fine and coarse particles, and the total Pb concentration was 84.55ng/m3, below the National standard. Enrichment factor for Sc, Cr, Cu, Zn, As, Se, Sn, Pb in fine particles were above 1,000. This indicates that the elements in fine particles are mainly from the anthropogenic sources including automobiles.

A Study on the Combustion Characteristics of Phenol Foam (페놀 폼의 연소특성에 관한 연구)

  • Park, Hyung-Ju
    • Fire Science and Engineering
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    • v.24 no.1
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    • pp.122-127
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    • 2010
  • The combustion characteristics of phenol foam were analysed using variable external irradiation level (20, 25, 35, 50, and $70kW/m^2$) and in the mixture gas of oxygen/nitrogen. The oxygen index were carried out from the oxygen index tester (KS M ISO 4589-2) and ignition time, critical heat flux, and mass loss rate were carried out from the mass loss calorimeter (ISO 5660-1). As the results of this study, the critical heat flux and average mass loss rate were $28.99kW/m^2$ and $0.56{\sim}1.77g/m^2s$ respectively at the variable external irradiation level. And the limited oxygen index were 45.1% in mixture gas of oxygen/nitrogen. In conclusion, we knew that phenol foam had the best performance than other foam materials in fire safety from all data of this study.

A Study on Combustion Characteristic with Chamber Pressure in Hybrid Rocket (하이브리드 로켓에서의 압력에 따른 연소특성에 관한 연구)

  • Cho, Jung-Tae;Kim, Gi-Hun;Lee, Jung-Pyo;Kim, Hak-Chul;Park, Seon-Woo;Park, Joon-Hyng;Han, Hee-Soo;Hwang, Jae-Woong;Moon, Hee-Jang;Sung, Hong-Gye;Kim, Jin-Kon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.11a
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    • pp.243-246
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    • 2008
  • The combustion characteristic of solid fuel with chamber pressure were experimentally studied in hybrid combustion. This paper was experimental confirmed whether solid fuel affected not only oxidizer mass flux but also chamber pressure. Poly-Ethylene(PE) was used as fuel, GOX was used as oxidizer. Chamber pressure was controled by nozzle throat diameter 6mm and 9mm. In low oxidizer mass flux, solid fuel regression rate was affected not only oxidizer mass flux but also chamber pressure. As well, the regression rate increase as chamber pressure increase with same oxidizer mass flux.

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