• Title/Summary/Keyword: 전단 혼합특성

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Combustion Characteristics of the Methane-Oxygen Bipropellant Injected by a Shear-coaxial Injector (전단동축형인젝터를 통해 분사된 메탄-산소 이원추진제의 연소특성)

  • Hong, Joon Yeol;Bae, Seong Hun;Bae, Dae Seok;Kim, Jeong Soo
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2017.05a
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    • pp.787-790
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    • 2017
  • This study is a preliminary research on characterization of methane - oxygen combustion used in bipropellant thruster. The limit of combustion stability and flame shape of methane - oxygen non-premixed flame injected by shear coaxial injector in the model combustion chamber Experimental studies have been carried out. A direct image of the flame was photographed using a DSLR camera, and combustion characteristics and flame length were quantified through image post-processing. As a result, it was confirmed that the stabilized flame was generated at the stoichiometric ratio as the oxidizer Reynolds number ($Re_o$) was increased, and the length of the turbulent flame was increased under the same injector diameter condition.

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Performance Test of a Small Simulated High-Altitude Test Facility for a Gas-turbine Combustor (가스터빈 저온/저압 점화장치 구성 및 운영조건 확인 시험)

  • Kim, Tae-Woan;Lee, Yang-Suk;Ko, Young-Sung;Lim, Byeung-Jun;Kim, Hyeong-Mo;Kim, Sun-Jin
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.11a
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    • pp.153-156
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    • 2008
  • Ignition and combustion performance of a gas-turbine engine were changed by various high-altitude condition. A goal of this study is to make the small test facility to simulate high-altitude condition. To perform the low pressure condition, a diffuser was used in various diffuser front of primary nozzle pressure. To perform the low temperature, heat exchanger was used in various mixture ratio of cryogenic air and ambient temperature air. The experimental result shows that high-altitude conditions can be controled by diffuser front of primary nozzle pressure and mixture ratio of cryogenic air and ambient temperature air.

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A Study on the Design of Ku-band Mixer Using a HEMT (HEMT를 이용한 Ku-band 혼합기의 설계에 관한 연구)

  • 성혁제;구자건
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.18 no.7
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    • pp.944-950
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    • 1993
  • Diodes and GaAs have been commonly used in a mixer design until recently. However, diodes are not preferred to use at the front-end of DBS receiver due to the conversion loss large noise. HEMT has larger conversion gain and better noise characteristics comparing with GaAs MESFET. This paper describes the design procedure, structure, and performance of a mixer, utilizaing HEMT designed by OKI Co. . A mixer configuration in which the local oscillator(LO) signal is applied to the gate is used. When the LO power is 0.01 dBm, the conversion gain of 3.7dB is obtained at IF and the 3 dB bandwidth is 400MMz.

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Characteristic Study on Effect of the Vent Mixer to Supersonic Fuel-Air Mixing with Stereoscopic-PIV Method (3차원 PIV 기법을 사용한 벤트혼합기가 초음속 연료-공기 혼합에 미치는 특성 연구)

  • Kim, Chae-Hyoung;Jeung, In-Seuck;Choi, Byung-Il;Kouchi, Toshinori;Masuya, Goro
    • Journal of the Korean Society of Propulsion Engineers
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    • v.16 no.4
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    • pp.50-56
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    • 2012
  • Vent mixer can provide main flow directly into a recirculation region downstream of the mixer to enhance fuel-air mixing efficiency. Based on experimental results of three-dimensional velocity, vorticity and turbulent kinetic energy obtained by a stereoscopic PIV method, the performance of the vent mixer was compared with that of the step mixer which was used as a basic model. Thick shear layers of the vent mixer induced the increase of the penetration height. The turbulent kinetic energy mainly distributed along a boundary layer between the main flow and the jet plume. This turbulent field activates mass transfer in a mixing region, leading to the mixing enhancement.

Synthesis and Characteristics of Hectorite Clay by Hydrothermal Process (헥토라이트 점토의 수열합성 및 특성)

  • 이석기;구광모;이정훈;이병교
    • Journal of the Korean Ceramic Society
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    • v.37 no.12
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    • pp.1192-1197
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    • 2000
  • Si-Mg 첨가물, LiOH, NaOH로부터 제조한 슬러리의 수열반응으로 헥토라이트 점토를 합성하였다. 수열합성의 온도와 반응시간에 따른 합성헥토라이트 점토의 화학적 조성과 결정형태를 조사하였고, 합성헥토라이트 0.2~1.0% 수분산액의 투과도와 입경을 UV-VIS 분광광도계와 투과전자현미경으로 각각 측정하였다. 합성헥토라이트 수분산액의 투과도와 유동성은 25$0^{\circ}C$, 6시간의 합성조건과 Si/Mg/Li/Na=8.0/5.4/0.6/0.6의 조성에서 최대치를 나타내었고, Mg/Si=5.4/8.0의 슬러리 조성으로부터 합성된 헥토라이트(Hec-6)가 최적의 투명성과 용액점도를 나타내었다. 또한 Hec-6의 수분산액은 높은 전단력에서 낮은 점도의 졸상으로 전화됨으로서 요변성을 나타내었고, 1.0% Hec-6/sodium carboxymethyl cellulose(50/50) 혼합용액은 전단력이 1.0 s$^{-1}$ 이상에서 1.0% Hec-6 수분산액보다 더욱 높은 점도를 나타냄으로서 점도의 상승효과가 나타났다.

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Study on the Broadband RF Front-End Architecture (광대역 RF 전단부 구조에 관한 연구)

  • Go, Min-Ho;Pyo, Seung-Chul;Park, Hyo-Dal
    • The Journal of the Korea institute of electronic communication sciences
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    • v.4 no.3
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    • pp.183-189
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    • 2009
  • In this paper, we propose RF front-end architecture using hybrid conversion method to receive broadband signal. The validity is verified by design, fabrication and experiment. The proposed RF front-end architecture due to up-conversion block improves the deficiency of performance deterioration to be generated through harmonic signal and image signal conversion in the conventional RF front-end, and improves the deficiency of the complexity that is from to adopt a multiple local oscillators for the generation of wideband LO signal in the conventional RF front-end by applying the principle that tuning bandwidth is multiplied at sub-harmonic mixer. Manufactured circuits satisfy the deduced design specification and target standard with gain above 80 dB, noise figure below 6.0 dB and IIP3 performance above -5.0 dBm for the condition of the minimum gain in RF front-end.

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Shearing Properties of Fiber-Reinforced Soil (섬유혼합 보강토의 전단특성)

  • 조삼덕;김진만
    • Proceedings of the Korean Geotechical Society Conference
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    • 1993.10a
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    • pp.23-28
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    • 1993
  • Shearing properties of soil reinforced with discrete randomly oriented inclusions depend on soil density, particle size, grading, fiber length, tensile strength and stiffness of fiber, mixing ration of fiber, confining stress, etc.. In this paper the effects of those various factors on shear strength of the fiber-reinforced soil was evaluated through triaxial tests and uniaxial tests. Tests were performed on two sandy soils and one silty soil with inclusions in varing lengths, contents and tensile strengths and tested at different confining stresses in triaxial test. From the experimental results, it was investigated if there is an optimal range of fiber lengths and fiber contents for the tested soils.

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A Study on the properties of flexural behavior according to reinforcing method of Composite Beams of different types of structure (이질 구조부 보강방법에 따른 혼합구조보의 휨거동 특성에 관한 연구)

  • Lim, Byung Ho;Park, Jung Min;Kim, Wha Jung
    • Journal of Korean Society of Steel Construction
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    • v.13 no.4
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    • pp.419-431
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    • 2001
  • This study was to investigate structural behavior of composite structure beams composed of end-RC. center-Steel according to respective reinforcing method for connection zone composed of different materials (SRC) while attaching main bars on steel-flange by welding. The main reinforcing methods are as follows ; non-reinforcing, vertical shear reinforcing (type-stirrup), inclined reinforcing(type-x), horizontal reinforcing(type-web, 0.3L), double horizontal reinforcing (type-web, 0.3L), vertical reinforcing (type-flange, 0.3L). Consequently, It showed little difference in structural properties like ductility and strength according to the attaching method of main bars. For Maximizing the structural properties of composite beam, the most effective methods were vertical reinforcing one and double horizontal reinforcing one.

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Numerical simulation of flow characteristics and pollutant transport at river confluence (하천 합류부의 흐름특성 및 오염물의 혼합거동 모의)

  • Yun, Se Hun;Seo, Il Won
    • Proceedings of the Korea Water Resources Association Conference
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    • 2022.05a
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    • pp.91-91
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    • 2022
  • 하천 합류부에서 수체의 흐름은 매우 역동적으로 변화하며 합류부의 복잡한 3차원 흐름과 난류 구조는 2차류(secondary currents)의 강도변화, 전단층(shear layer)의 뒤틀림 그리고 재순환구역(recirculation zone)의 발생 등 합류부에서의 독특한 특징을 형성한다. 이러한 특징들의 변화는 수체의 흐름구조 뿐만 아니라 하천으로 유입된 오염물의 거동에도 영향을 준다. 기존의 합류부 연구들은 주로 본류와 지류의 합류각이나 유량비에 차이를 두어 합류부의 특징 변화를 모의하였다. 하지만 실제 자연하천에서 홍수방지를 위한 수심확보, 건축자재의 골재수집 등 다양한 목적으로 수행되는 본류의 준설작업으로 인해 발생하는 본류와 지류의 하상면 단차 또한 합류부의 특성에 영향을 미치는 주요한 인자 중 하나이다. 단차가 커짐에 따라 증가하는 지류수체의 낙차는 이차류의 강화를 야기하며 이는 합류부에서의 유속구조를 변화시켜 흐름을 가속시키거나 지체시키며 오염물의 혼합에 영향을 미친다. 본 연구에서는 3차원 수치모의를 통해 90도로 합류되는 수로에서의 흐름구조와 오염물의 혼합에 단차비와 유량비가 미치는 영향을 모의하였다. 유동장 해석을 위해 3차원 RANS (Reynolds-averaged Navier-Stoke) 방정식을 사용하였으며 난류해석은 k-𝜔 SST 모델을 이용하였다. 본류의 경우 11.4m의 수로 연장을 갖고, 하폭은 0.3m이며 수심은 단차의 크기에 따라 변화한다. 지류의 경우는 수로연장 1m, 하폭 및 수로깊이는 0.1m이다. 수치결과의 검증을 위해 이주하(2013)이 수행한 실내 합류수로의 실험결과를 이용하였다. 모의결과를 통해 파악한 합류부의 흐름특성을 이용하여 적절한 2차원 분산계수를 산정한다. 자연하천에서 오염물의 혼합거동을 효과적으로 모의하기 위해 수심 평균된 2차원 이송-분산모형을 이용하는데 이때 적절한 분산계수의 산정이 필수적이다. 본 연구에서는 합류 후 흐름방향에 따라 분산특성이 상이한 구간을 구분하여 분산계수를 산정하였으며 이를 통해 오염물의 거동을 정확하게 모의하였다.

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Characteristics of Waste Lime and Soil Mixture for Reusing of Roadbed Embanking Material (도로노반 성토재로의 재활용을 위한 폐석회 혼합토의 특성연구)

  • Hong, Seung-Seo;Kim, Young-Seok;Lee, Yong-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.11 no.12
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    • pp.5157-5164
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    • 2010
  • Currently about 3.2 millon tons of waste lime are accumulated and annually 100,000 tons are producted. This study was carried out to investigate the characteristics of soil mixed with waste lime for reusing of roadbed embanking material. Waste lime used in this study is producted as a by-product in the manufacturing process of making $Na_2CO_3$ from local chemical factory in Incheon. In this study, the feasible reuse of waste lime mixed with granite weathered soil, clay, crushed rock was investigated through laboratory tests including specific gravity test, sieve analysis, hydrometer analysis, atterberg limit test, compaction test, unconfined compressive test, CBR test, permeability test, shear test, and abrasion test. The mixing rate is granite weathered soil, clay, crushed rock 80 % respectively and waste lime 20 % by weight. From the test results, it is shown that the waste lime and soil mixtures satisfy the criteria as road embanking material specification.