• International Journal of Aerospace System Engineering
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• v.9 no.2
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• pp.1-9
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• 2022

The NEA release mechanism is used to provide restraint and release functions with low shock for critical deployment operations on solar arrays after launch. The GK3 solar array consists of 2 wings and 6 hold down points per panel. The NEA SSD9103S1 is a part of the GK3 solar array hold-down and release mechanism. Each NEA unit is equipped with two Z-diodes which provide power to a NEA unit connected in series after actuation of the fuse wire. This paper presents the hot firing test results of a quadrature NEA SSD9103S1 configuration. One output powers a maximum of 4 NEA SSD9103S1 units simultaneously. The necessary actuation pulse duration has been determined to meet margin requirement for thermal energy of minimum 4. Actuation thermal energy difference is about 6.6% between each half of two fired serial NEAs. Thermal energy margin at worst case is minimum 5.9 in case of an actuation pulse duration of 500 ms. Two series Zener impedance depend on current applied has been characterized by an additional actuation after all fuse wires are open circuit. Total number of actuation commands to the GK3 NEA unit reduce drastically from 24 in case of single NEA configuration down to 8 in case of parallel and quadrature NEA configurations. It can be accommodated by the existing HP2U Pyro design without any impact.

• Journal of the korean Society of Automotive Engineers
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• v.7 no.1
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• pp.12-17
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• 1985

주위기체와 다른 기체를 간헐적으로 또는 단발로 분사한 경우, 분류내의 분사체의 농도는 시간에 따라 급격히 변화한다. 수ms인 전자식기체 채취밸브를 이용해서 기체를 채취하고, 가스마토그 라프 등에 의해 가스분석을 행하는 방법이 있고 주로 피스톤식 내연기관의 연소실내 농도의 측 정에 이용되고 있다. 이 방법은 밸브 열립시간을 단축시켜도 약 1ms가 한도이고 시간분해능력도 1ms정도가 최단시간이다. 또 동일한 장소에서 농도의 시간경과를 얻는 데에는 각각의 시간에 대해서 기체의 채취와 분석을 행하지 않으면 안되어 실제시간의 농도측정이 불가능하다는 결점이 있다. 최근 레이저 응용기술의 진보에 의해 라만산란, 레리산란, CARS법 등의 농도순간측정이 가능해지고 있고, 점차 현실화되어가고 있다. 이들의 방법은 국소의 순간농도뿐만 아니라 온도의 동시측정도 가능하게 하는 특징을 갖고있다. 그러나 레이저에 의한 측정장치는 현시정에서는 아직 가격이 고가이고 광학계의 설치 등, 실험상의 조작이 복잡한 것 등의 결점을 갖고 있다. 본 고에서는 최근 진전이 현저하고 실용화에 대한 확신을 갖고 있는 열선농도Probe에 의한 순간농 도의 측정방법을 소개하고자 한다.

• The KSFM Journal of Fluid Machinery
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• v.11 no.6
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• pp.54-63
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• 2008

A study on the flow characteristics in a 4-stage axial compressor and the behavior of rotating stall was experimentally performed at the third-stage rotor and stator rows in order to investigate its performance and instability of the compression system. The pressure losses generated due to the leakage flow at a tip clearance and a shroud seal clearance and the wake flow near the trailing edge of a blade were taken into consideration to estimate the causes of performance drop of the low speed research compressor(LSRC) in Seoul national university. In addition, the measurement of rotating stall was conducted with hot-wire probes and the existence and propagation of stall cell could be confirmed through fast Fourier transform and cross-correlation analysis.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2597-2602
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• 2007

In this paper, the performance analysis is experimentally carried out in order to select the best cooling fan and shroud considering both cooling performance and noise reduction. 4 cooling fans have been tested in the fan tester and the real excavator. In order to obtain the performance of the cooling fans, flow capacity has been estimated by measuring flow velocity using a hot wire anemometer, and noise radiation has been also measured to estimate the fan noise. Characteristics of a box-type and a streamlined shroud have been examined by changing the immersion depth of cooling fans. Based upon the results, the best cooling fan is selected. Finally, the criterion to select the best cooling fan has been set up.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2868-2872
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• 2007

In this study, a passive control using a boat-tail device is conducted for a three-dimensional car model in ground proximity. We consider various boat-tails and investigate the mechanism of drag reduction by them. By varying the length and slant angle of boat-tail, we obtain drag reductions up to 40%. From the oil-surface flow visualization and hot-wire measurement, the drag reduction by the boat-tail is characterized by the shear-layer instability and reattachment on the boat-tail, forming a small separation bubble at the upstream part of boat-tail surface, resulting in the delay of main separation and drag reduction. At high slant angles, the flow fully separates and drag is nearly same as that of no control.

• Journal of Power System Engineering
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• v.13 no.2
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• pp.49-55
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• 2009

Recently, a study on condensers for refrigerators has focused on new model which will cost less and will be more efficient. Some widely used condensers for domestic refrigerators are wire-and-tube type condenser, hot-wall type condenser, and spiral type condenser. Some companies which use the spiral type condenser at the moment try to develop a new tube-and-plate type condenser which will cost less and will be as efficient as the spiral type. As a standard condenser type, tube-and-plate type condenser is used in this study. A two-dimensional numerical model for the tube-and-plate type condenser is proposed, and the flow and heat transfer characteristics for several types of condensers are investigated.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.58.2-58.2
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• 2010

본 연구에서는 n-type wafer에 비정질 실리콘을 증착한 이종접합 태양전지를 열처리 방법을 이용하여 열처리의 효과를 분석함으로써 이종접합 태양전지에 효율적인 열처리 효과에 대하여 연구하였다. P, N-layer는 PECVD(Plasma-enhanced chemical vapor deposition) I-layer는 HWCVD(Hot wire chemical vapor deposition), ITO는 RF 마그네트론 스퍼터링법으로 동일한 조건에서 제작하였고 rapid thermal process를 이용하여 진공 중에서 $150^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$, $250^{\circ}C$까지 열처리를 하였다. 열처리 전과 후 QSSPC로 minority carrier life time, 자외 가시선 분광분석 장치로 투과 반사도를, Ellipsometer로 흡수 계수 등의 변화를 조사하였다. 열처리 후 Minority carrier life time, Voc 및 광변환 효율이 증가하였다.

• Wind and Structures
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• v.9 no.6
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• pp.419-440
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• 2006

This article synthesizes the literature on the meteorology, experimental simulation, and wind engineering ramifications of intense downburst outflows. A novel design of a large-scale test facility and experimental evidence of its validity are presented. A two-dimensional slot jet is used to simulate only the outflow region of a downburst. Profiles of mean velocity and turbulence quantities are acquired using hot-wire anemometry. Comparison with the literature provides empirical evidence that supports the current approach. A geometric analysis considers the validity of applying a two-dimensional approximation for downburst wind loading of structures. This analysis is applicable to power transmission lines in particular. The slot jet concept can be implemented in a large boundary layer wind tunnel to enable large-scale laboratory experiments of thunderstorm wind loads on structures.

• Wind and Structures
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• v.10 no.4
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• pp.315-346
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• 2007

A preceding companion article introduced the slot jet approach for large-scale quasi-steady modelling of a downburst outflow. This article extends the approach to model the time-dependent features of the outflow. A two-dimensional slot jet with an actuated gate produces a gust with a dominant roll vortex. Two designs for the gate mechanism are investigated. Hot-wire anemometry velocity histories and profiles are presented. As well, a three-dimensional, subcloud numerical model is used to approximate the downdraft microphysics, and to compute stationary and translating outflows at high resolution. The evolution of the horizontal and vertical velocity components is examined. Comparison of the present experimental and numerical results with field observations is encouraging.

• Journal of ILASS-Korea
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• v.20 no.2
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• pp.70-75
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• 2015

Swirl flow in the gun type burner has an impact on the stabilization of the flame, improvement of the combustion efficiency. The swirl flow is created by the spinner which is inside the airtube that guide the combustion air. Gun type burner has generally the inner devices composed electronic spark plug, injection nozzle, combustion device adaptor, and spinner. These inner components change the air flow behavior passing through airtube. So, this study conducted the measurement using by hot-wire anemometer and analyzed effect of the swirl number of spinner on the exhaust air of gun type burner. Turbulence characteristics come up in this study was mean velocity, turbulence intensity, kinetic energy, shear stress and flattness factor of the air flow with the change of the distance of axial direction and tangential direction from the exit of the airtube.