RATO(Rocket-Assisted Take Off) 시스템 적용을 위한 하이브리드 로켓 비단공형 연료 그레인 기초 연소특성 연구

김수진,고수한,김설희,김경모,이성근,한예찬,문희장 한국항공운항학회 2022 한국항공운항학회지 Vol.30 No.4

In an attempt to apply hybrid rocket to the RATO (Rocket-Assisted Take Off) system, combustion characteristics of the non-circular grain were figured out in this study. Having larger combustion area, it was reconfirmed that the non-circular grain has advantages over regression rate, characteristic velocity and chamber pressure in which all gave higher values. Experiments were performed to understand the effect of the non-circular grain geometry over time where local regression rates depending on grain location were analyzed. It was found that the regression rate of five distinct locations were different. Partial conclusion driven was that these differences are due to the heat transfer caused by dissimilar distances from the flame layer. Besides, as combustion duration increased, the fuel port became circular, and the regression rate converged to a single value over the whole grain.

침식연소가 방지되는 사출용 다발 원통형 그레인 가스발생기 개발

오석진(Seok-Jin Oh),차홍석(Hong-Seok Cha),장승교(Seung-Gyo Jang) 한국추진공학회 2011 한국추진공학회 학술대회논문집 Vol.2011 No.11

본 논문에는 유도탄 사출시스템의 사출성능 향상을 위해 침식연소 현상이 발생하지 않는 상태에서 가스발생기의 압력 기울기를 증가시키는 방법에 대해 기술하였다. 안정연소를 얻기 위해 그레인에 반경방향홀을 뚫는 방법과 그레인의 길이대 직경비를 줄이는 방법을 고안하여 이를 적용, 연소시험을 실시하였다. 시험결과 반경방향홀 그레인을 적용했을 경우 침식연소 방지효과는 좋았으나 사출성능을 저하시키는 쪽으로 성능이 변화하였다. 반면에, 다열형 그레인을 적용시 침식연소 방지효과와 함께 사출성능을 향상시키는데 유용한 것으로 나타났다. An achieving method of highly progressive pressure gradient is presented to enhance the missile ejection system‘s performance by using a gas generator in the condition of preventing erosive burning. To obtain and confirm a stable burning, a ground burning test was performed to evaluate the new methods of a radial-hole and a multi-row propellant grain. The test results show that a radial-hole grain takes good effect on erosive burning and not on ejection performance. On the other hand, a multi-row grain which reduces the legnth-to-diameter ratio(L/D) of grain is very effective to prevent the erosive burning and to enhance the ejection performance simultaneously.

침식연소가 방지되는 사출용 다발 원통형 그레인 가스발생기 개발

오석진(Seok-Jin Oh),차홍석(Hong-Seok Cha),장승교(Seung-Gyo Jang) 한국추진공학회 2012 한국추진공학회지 Vol.16 No.3

An achieving method of highly progressive pressure gradient is presented to enhance the missile ejection system‘s performance by using a gas generator in the condition of preventing erosive burning. To obtain and confirm a stable burning, a ground burning test was performed to evaluate the new methods of a radial-hole and a multi-row propellant grain. The test results show that a radial-hole grain takes good effect on erosive burning and not on ejection performance. On the other hand, a multi-row grain which reduces the length-to-diameter ratio(L/D) of grain is very effective to prevent the erosive burning and to enhance the ejection performance simultaneously.

Movability Number as the Parameter of Sediment Incipient Motion: A Mathematical Approach

Bhat Aamer Majid,Ahanger Manzoor Ahmad,Mohapatra Pranab Kumar 한국해양과학기술원 2023 Ocean science journal Vol.58 No.4

In fluvial sediment transport, the sediment threshold parameter Movability Number, which is the ratio of the shear velocity and the settling velocity of a sediment particle, is seen as a potential replacement for the traditional Shields parameter. Until now, the studies carried out on Movability Number have been mostly empirical or crudely analytical. In the current study, a mathematical modeling approach is attempted. Steady unidirectional flow is considered and the mode of entrainment is taken as that of rolling, with a compact sediment bed. The mathematical relationships developed here express the Movability Number as a function of either shear Reynolds number or dimensionless grain diameter. Comparisons are made with both experimental data and previous empirical formulae. The developed model is a novel approach to study the Movability Number, which bears satisfactory nearness to the previous studies. The deviation produced in terms of underestimation is due to the rolling mode of motion, which requires the least disturbing energy. The developed model can be improved by the consideration of turbulence in future studies.

조석의 침투류에 의한 패류 유생의 착저(着底)효과에 관한 기초적 연구

백상호,박광재,박영제,전제천,조기채,김이운 한국패류학회 2009 The Korean Journal of Malacology Vol.25 No.2

It is a research that free floating larva of Ruditapes philippinarum in compliance with infiltration flow of tidal accumulation and bottom-clinging system in high density also, It is a precondition this for the continuous augmentation of Ruditapes philippinarum resources. So in flow field of tidal the free floating larva produced the infiltration water tank that can possibly bottom-clinging and experiment the water tank which uses free floating larva, It evaluates that the acceleration effect of free floating larva by infiltration in objective. As a result, 1) The experiment on free floating larva's bottom sediment grain diameter came to be high recording as bottom-clinging rate at the static water field and even biologically it selects bottom-clinging substrate it will be able to confirm. 2) About occurrence of infiltration flow field is in case of that: the drift of a current 10cm/s , bottom sediment grain 1.21mm infiltration flow 0.3cm/s increase of 3~5 times was confirmed. 3) From free floating larva of Ruditapes philippinarum the choice of bottom sediment grain diameter depends in the biological factor and form the flow field the bottom-clinging acceleration effect was controled over physical stable condition. 4) In case of density of Ruditapes philippinarum free floating larva of sea area, bottom sediment grain diameter, flow condition which are very cleanly in the research that possibly could conjecture the free floating larva's bottom-clinging rate. It is a research that free floating larva of Ruditapes philippinarum in compliance with infiltration flow of tidal accumulation and bottom-clinging system in high density also, It is a precondition this for the continuous augmentation of Ruditapes philippinarum resources. So in flow field of tidal the free floating larva produced the infiltration water tank that can possibly bottom-clinging and experiment the water tank which uses free floating larva, It evaluates that the acceleration effect of free floating larva by infiltration in objective. As a result, 1) The experiment on free floating larva's bottom sediment grain diameter came to be high recording as bottom-clinging rate at the static water field and even biologically it selects bottom-clinging substrate it will be able to confirm. 2) About occurrence of infiltration flow field is in case of that: the drift of a current 10cm/s , bottom sediment grain 1.21mm infiltration flow 0.3cm/s increase of 3~5 times was confirmed. 3) From free floating larva of Ruditapes philippinarum the choice of bottom sediment grain diameter depends in the biological factor and form the flow field the bottom-clinging acceleration effect was controled over physical stable condition. 4) In case of density of Ruditapes philippinarum free floating larva of sea area, bottom sediment grain diameter, flow condition which are very cleanly in the research that possibly could conjecture the free floating larva's bottom-clinging rate.

한천의 대표입경을 이용한 조도계수 산정

이준호 ( Jun Ho Lee ),양성기 ( Sung Kee Yang ),김동수 ( Dong Su Kim ) 한국환경과학회 2013 한국환경과학회지 Vol.22 No.5

Roughness coefficient was computed for review of applicability based on measurement of the representative grain diameter reflecting channel characteristics of Han Stream. After field survey, collection of bed material, and grain analysis on the collected bed material, roughness coefficient was computed using representative grain and existing empirical equation for roughness coefficient. Value of roughness coefficient calculated using equation by Meyer-Peter and Muller (1948) was 0.0417 for upstream, 0.0432 for midstream, and 0.0493 for downstream. As a result of comparing the computed roughness coefficient to other empirical equations for review of applicability, the coefficient was larger in Strickler (1923) equation by 0.006. Smaller coefficient was shown by Planning Report for River Improvement Works. Equation by Garde and Raju (1978) was larger by 0.004, and equations by Lane and Carlson (1953) and by Meyer-Peter and Muller (1948) were larger by 0.001. Such precise roughness coefficient is extremely important when computing the amount of flood in rivers to prevent destruction of downstream embankments and property damages from flooding. Since roughness coefficient is a factor determined by complicated elements and differs according to time and space, continued management of roughness coefficient in rivers and streams is deemed necessary.

Effect of Pulsed Current GTA Welding Parameters on the Fusion Zone Microstructure of AA 6061 Aluminium Alloy

( T. Senthil Kumar ),( V. Balasubramanian ),( S. Babu ),( M. Y. Sanavullah ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 METALS AND MATERIALS International Vol.13 No.4

AA6061 aluminium alloy (Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of food processing equipment, chemical containers, passenger cars, road tankers, and railway transport systems. The preferred process for welding these aluminium alloys is frequently Gas Tungsten Arc (GTA) welding due to its comparatively easy applicability and lower cost. In the case of single pass GTA welding of thinner sections of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current processes. The use of pulsed current parameters has been found to improve the mechanical properties of the welds compared to those of continuous current welds of this alloy due to grain refinement occurring in the fusion zone. In this investigation, an attempt has been made to develop a mathematical model to predict the fusion zone grain diameter incorporating pulsed current welding parameters. Statistical tools such as design of experiments, analysis of variance, and regression analysis are used to develop the mathematical model. The developed model can be effectively used to predict the fusion grain diameter at a 95 % confidence level for the given pulsed current parameters. The effect of pulsed current GTA welding parameters on the fusion zone grain diameter of AA 6061 aluminium alloy welds is reported in this paper.

국내산 밀의 품종별 이화학적 특성과 쿠키 제조 적성

최영심(Young Sim Choi),이명호(Myung Ho Lee) 한국조리학회 2009 한국조리학회지 Vol.15 No.1