• Title, Summary, Keyword: 입구 부

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Design Study of Engine Inlet Duct for Measurement Improvement of the Flow Properties on AIP (AIP면 유동측정 정확도 향상을 위한 가스터빈엔진 입구덕트 설계 연구)

  • Im, Ju Hyun;Kim, Sung Don;Kim, Yong Ryeon
    • Journal of the Korean Society of Propulsion Engineers
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    • v.21 no.3
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    • pp.49-55
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    • 2017
  • In this study, gas turbine engine inlet duct was designed to satisfy uniform flow at aerodynamic interface plane (AIP). Haack-series was selected as nose cone profile and duct outer radius($r_o$) was designed to satisfy to match with area change rate between the nose cone and outer duct wall by the 1-D sizing. The design object of the inlet duct wall profile which has the gradual area change rate was uniform Mach number in the core flow region and minimum boundary later thickness at the both inner nose wall and outer duct wall. The flow characteristics inside the inlet duct was evaluated using CFD. The static pressure distribution at the AIP showed uniform pattern within 0.16%. Based on Mach number profile, the boundary layer thickness was 2% of channel height. Kiel temperature rake location was decided less than 100 mm in front of nose cone where the Mach number is less than 0.1 in order to maximize the temperature probe recovery rate.

Effects of Entrance Loss on Harbor Resonances (항만 부진동에 미치는 입구손실의 영향)

  • 박우선;정원무;채장원
    • Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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    • pp.184-187
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    • 1996
  • 기존의 항만 부진동현상 해석은 대부분 완전유체라는 가정하에 선형이론에 기초하여 개발된 수치 모델에 의해 수행되고 있다. 실제의 경우에는 해저면의 마찰, 고체경계면을 따른 에너지 손실, 단면의 급 축소 및 확대에 따른 에너지 손실 등이 존재하므로, 이와 같은 에너지의 손실을 고려하지 않고 선형해석을 수행하게 되면 실제와는 다른 과장된 결과를 얻게 된다. 특히, 항 입구의 폭이 좁은 경우에는 실제와는 다르게 증폭비가 대단히 크게 예측된다. (중략)

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Non-Allowable Regime in Scram-to-Ramjet Transitions (스크램제트에서 램제트로의 모드 천이로 인한 불허지역)

  • Ha, Jeongho;Ladeinde, Foluso;Kim, Taeho;Kim, Heuydong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.297-300
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    • 2017
  • A drastic pressure increment at the combustor inlet induced thermal choking is inevitable during scram-to-ramjet transitions. This phenomenon which is called by Non-Allowable Region(NAR) was observed on the excessive increment in the equivalent ratio. However, many studies were not investigated about factors which affects a variation of NAR. In the present study, a variation of NAR with regard to Mach number in the inlet of isolator is numerically and analytically analyzed. The conclusions from the investigation show that increasing the Mach number in the isolator inlet enlarged in the range of NAR.

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Photosynthesis and Growth of Southern-type Garlic (Allium sativum L.) in Response to Elevated Temperatures in a Temperature Gradient Tunnel (온도구배터널 내 상승온도에 의한 난지형 마늘(Allium sativum L.)의 광합성 및 생육 특성의 변화)

  • Oh, Seo-Young;Moon, Kyung Hwan;Song, Eun Young;Shin, Minji;Koh, Seok Chan
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.21 no.4
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    • pp.250-260
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    • 2019
  • This study assessed clove germination, shoot growth, photosynthesis and bulb development of southern-type garlic (Allium sativum L.) in a temperature gradient tunnel (TGT), to examine the impacts of increases in temperature on the growth of garlic and find a way to minimize them. The temperatures in the middle and outlet of the TGT were 3.2℃ and 5.8℃ higher, respectively, than the ambient temperature at the tunnel inlet. The germination of garlic cloves was late at temperatures of ambient+3℃ (in the middle of the TGT) and ambient+6℃ (at the outlet) than at ambient temperature (at the inlet). However, bolting and the timing of maximum leaf number per plant were faster at ambient+3℃ or +6℃ than at ambient temperature. Shoot growth was generally greater at ambient temperature. Bulb growth did not significantly differ according to cultivation temperatures, but fresh and dry weights were slightly higher at ambient temperature and ambient+3℃ in the late growth stage. The photosynthesis rate (A), stomatal conductance (gs), and transpiration rate (E) were higher at ambient+3℃ than at ambient temperature. Furthermore, at ambient+3℃, the net photosynthetic rate (Amax) was high, while the dark respiration rate (Rd) was low. At ambient temperature and ambient+3℃, bulb development was healthier, resulting in better productivity and more commercial bulbs, while at ambient+6℃, the bulbs were small and secondary cloves developed, resulting in low commercial value. Therefore, at elevated temperatures caused by global warming, it is necessary to meet the low-temperature requirements before clove sowing, or to delay the sowing time, to improve germination rate and increase yield. The harvest should also be advanced to escape high-temperature stress in the bulb development stage.

Preliminary Thermal-Hydraulic Analysis of the CANDU Reactor Moderator Tank using the CUPID Code (CUPID 코드를 이용한 CANDU 원자로 칼란드리아 탱크 내부유동 열수력 예비 해석)

  • Choi, Su Ryong;Lee, Jae Ryong;Kim, Hyoung Tae;Yoon, Han Young;Jeong, Jae Jun
    • Journal of Energy Engineering
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    • v.23 no.4
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    • pp.95-105
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    • 2014
  • The CUPID code has been developed for a transient, three-dimensional, two-phase flow analysis at a component scale. It has been validated against a wide range of two-phase flow experiments. Especially, to assess its applicability to single- and two-phase flow analyses in the Calandria vessel of a CANDU nuclear reactor, it was validated using the experimental data of the 1/4-scaled facility of a Calandria vessel at the STERN laboratory. In this study, a preliminary thermal-hydraulic analysis of the CANDU reactor moderator tank using the CUPID code is carried out, which is based on the results of the previous studies. The complicated internal structure of the Calandria vessel and the inlet nozzle was modeled in a simplified manner by using a porous media approach. One of the most important factors in the analysis was found to be the modeling of the tank inlet nozzle. A calculation with a simple inlet nozzle modeling resulted in thermal stratification by buoyance, leading to a boiling from the top of the Calandria tank. This is not realistic at all and may occur due to the lack of inlet flow momentum. To improve this, a new nozzle modeling was used, which can preserve both mass flow and momentum flow at the inlet nozzle. This resulted in a realistic temperature distribution in the tank. In conclusion, it was shown that the CUPID code is applicable to thermal-hydraulic analysis of the CANDU reactor moderator tank using the cost-effective porous media approach and that the inlet nozzle modeling is very important for the flow analysis in the tank.

A Study on Poisoning of the Reforming Catalysts on the Position of Anode in the Direct Internal Reforming Molten Carbonate Fuel Cell (직접 내부개질형 용융탄산염 연료전지의 음극판 위치에 따른 개질 촉매 피독에 관한 연구)

  • Wee, Jung Ho;Chun, Hai Soo
    • Applied Chemistry for Engineering
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    • v.10 no.5
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    • pp.652-659
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    • 1999
  • The trend of poisoning of reforming catalyst along with the position of anodic catalyst bed was studied. Keeping the conditions that steam to carbon ratio was 2.5, operating voltage was 0.75 V, current density was $140mA/cm^2$, the unit cell was operated during 24 hrs at a steady state. And then the cell was stopped, the catalysts packed in the position of inlet, middle and outlet were sampled individually and then the amount of carbon, Li and K poisoned were analysed. After 100 hrs operated, the catalysts at the same positions were analysed at the same manner. The result of this experiment was as followings. After 24 hrs operated, the poisoning amounts of Li and K in the catalyst were 0.27 wt% at inlet, 0.23 wt% at middle and the highest value 1.59 wt% at outlet. After 100 hrs, the amount of poisoning is the highest in the catalyst packed at the inlet of unit cell. The performance simulation of unit cell explained these trends of poisoning catalysts. The simulation told that the catalyst in the region of the inlet of unit cell treated the 90% of initial methane flow rate and the highest electrochemical reaction happened in this region. So the catalysts of this region were the most poisoned with carbon, Li and K and also the rate of poisoning is faster than that of the catalyst at other regions. The temperature at the region of outlet of unit cell was $30^{\circ}C$ higher than that of other regions, so more Li, and K vaporized than at other regions and little reforming reaction at this region made the catalysts poisoning rate low.

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Effects of Inlet Water Temperature and Heat Load on Fan Power of Counter-Flow Wet Cooling Tower (입구 물온도와 열부하가 냉각탑의 팬동력에 미치는 영향 분석)

  • Nguyen, Minh Phu;Lee, Geun Sik
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.3
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    • pp.267-273
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    • 2013
  • In order to provide effective operating conditions for the fan in a wet cooling tower with film fill, a new program to search for the minimum fan power was developed using a model of the optimal total annual cost of the tower based on Merkel's model. In addition, a type of design map for a cooling tower was also developed. The inlet water temperature and heat load were considered as key parameters. The present program was first validated using several typical examples. The results showed that for a given heat load, a three-dimensional graph of the fan power (z-axis), mass flux of air (x-axis, minimum fan power), and inlet water temperature (y-axis, maximum of minimum fan power) showed a saddle configuration. The minimum fan power increased as the heat load increased. The conventionally known fact that the most effective cooling tower operation coincides with a high inlet water temperature and low air flow rate can be replaced by the statement that there exists an optimum mass flux of air corresponding to a minimum fan power for a given inlet water temperature, regardless of the heat load.

Explicit Analysis of Flows in Box Culvert (사각형 암거흐름의 양해적 해석)

  • Yoo, Dong-Hoon;Uhm, Ho-Sik
    • Journal of Korea Water Resources Association
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    • v.36 no.3
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    • pp.481-494
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    • 2003
  • Flow through the culvert is very complex depending on the characteristics of hydraulic conditions. A design method using a monograph is normally employed due to the wide range of flow characteristics and the difficulty of calculating inlet water depth. The present study suggests the method for determining the inlet water depth of box culvert using Bernoulli's equation. By employing the explicit equation of inlet water depth, a standard design method of box culvert is developed for a wide range of flow characteristics. Explicit solution techniques are proposed to determine the width and height, slope and discharge of box culvert.

The experimental study for the effect of tooth-brushing on the laser irradiated dentin surface (ND-YAG 레이저가 조사된 상아질 표면에 칫솔에 의한 기계적 마모가 미치는 영향에 대한 실험적 연구)

  • Park, Dong-Sung
    • Restorative Dentistry and Endodontics
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    • v.27 no.6
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    • pp.555-560
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    • 2002
  • 치근부 민감성 (hypersensitivity)은 부분적으로 치근면에서의 개방된 상아세관이 존재하는 것에 기인한다고 생각되며 이러한 치근부의 개방된 상아세관은 치경부 병소 (cervical lesion)에 주로 존재하는데 이는 칫솔질에 의한 마모(toothbrush abrasion), 화학적 침식 (chemical erosion), 또는 abfraction 등의 결과로 나타난다고 한다. 이미 Nd-YAG 레이저를 이용한 실험에서 레이저를 조사한 상아질 표면의 상아 세관 구경이 감소되고 상아세관의 폐쇄가 많이 증가되는 양상을 관찰한 바 있다. 이 실험의 목적은 고출력레이저인 Nd-YAC 레이저를 이용한 상아질 표면처치의 임상사용가능성을 좀 더 상세히 평가하기 위해 상아질에 레이저를 처리한 후 기계적으로 마모시킨 경우 상아질 표면의 변화를 관찰하는 것이다. 50개의 발치된 치아의 상아질을 노출시켜 표면을 연마한 후 대조군에서는 37% 인산으로 산부식하여 상아 세관을 노출시킨 후 레이저를 조사하였고, 실험군에서는 대조군과 같은 조건으로 산과 레이저로 처리된 상아질 표면을 15, 45, 90 그리고 180분 동안 전동 칫솔로 기계적으로 마모시켜 그 표면을 주사전자현미경으로 관찰한 결과, 대조군, 칫솔질을 15, 45분간 시행한 실험군에서는 상아 세관 입구가 10% 이내에서 노출되었고 50 그리고 180분간 칫솔질을 시행한 실험군에서는 45 그리고 48%의 상아세관 입구의 노출이 관찰되었다. 그러므로 Nd-YAC레이저의 조사는 상아질 표면에서 축적 시간이 45분 이상에서 90분 이하인 기계적 마모에 의한 상아 세관 입구의 노출을 억제할 수 있을 것이라 사료된다.

An Experimental Study on the Flow Characteristics Inside an Open Two-Phase Natural Circulation Loop (개방된 2상 자연순환 회로내의 유동특성에 관한 실험적 연구)

  • 경익수;이상용
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.5
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    • pp.1313-1320
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    • 1993
  • Flow patterns inside the riser section and the effects of the heater inlet-and exit-restrictions, liquid charging level and the heater inlet subcooling on the flow characteristics inside an open two-phase natural circulation loop were studied experimentally. Three basic circulation modes were observed ; periodic circulation (A)(flow oscillations with incubation(no boiling) period), continuous circulations(stable operation mode with no flow oscillations), and periodic circulation (B) (flow oscillations with continuous boiling). The circulation rate increases and then decreases with the increase of the heating rate and the maximum circulation rate appears with the continuous circulation mode. The decrease of the inlet-restriction or the increase of the exitrestriction destabilizes the system. When the liquid charging level or the inlet subcooling decreases, the continuous circulation mode starts at the lower heating rate and the system is stabilized.