• 한국추진공학회지
• /
• 제4권1호
• /
• pp.22-29
• /
• 2000

본 연구에서는 750㎾급 수평축 풍력발전용 복합재 회전날개를 설계, 제작하여 구조시험을 수행하였다. 시험시 발생된 후연부위의 국부좌굴과 날개 끝 부위에서 과도하게 증가하는 처짐문제를 해결하기 위하여 개선설계를 수행하였다. 설계개선 내용으로는 스파의 두께를 점차적으로 변화시켜 과도한 처짐을 감소시켰으며, 웨브의 길이를 연장하여 국부좌굴현상을 방지하도록 하였다 개선설계결과는 유한요소해석을 수행하였으며 회전날개 구조의 안전성 및 안정성이 확인되었다.

• 한국추진공학회지
• /
• 제16권3호
• /
• pp.57-68
• /
• 2012

본 연구에서는 한국의 차세대 중형항공기에 사용될 고속형 터보프롭 항공기용 고효율 복합재 프로펠러 블레이드의 설계를 수행하였다. 와류 이론과 블레이드 깃 요소 이론을 활용하여 기본 공력설계 및 성능 해석을 수행하였고 공력설계 결과는 상업용 전산유체해석 프로그램인 ANSYS를 이용한 해석을 통해 확인 되었다. 프로펠러 구조 설계 시 카본/에폭시 복합재료가 적용되었으며, 경량화와 구조 안정성 개선을 위하여 스킨-스파-폼 샌드위치 구조 형식를 채택하였다. 제안된 프로펠러 블레이드는 공력 및 구조 해석과 시제품 프로펠러 블레이드의 구조 시험을 통하여 높은 효율과 안전한 구조임이 검토되었다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
• /
• pp.253-258
• /
• 2012

본 연구에서는 한국의 차세대 중형항공기에 사용될 터보프롭 항공기용 고효율 복합재 프로펠러 블레이드의 설계를 수행하였다. 와류 이론과 블레이드 깃 요소 이론을 활용하여 기본 공력설계 및 성능 해석을 수행하였고 공력설계 결과는 상업용 전산유체해석 프로그램인 ANSYS를 이용한 해석을 통해 확인하였다. 프로펠러 구조 설계 시 카본/에폭시 복합재료가 적용되었으며, 경량화와 구조 안정성 개선을 위하여 스킨-스파-폼 샌드위치 구조 형식를 채택하였다. 제안된 프로펠러 블레이드는 공력 및 구조 해석과 시제품 프로펠러 블레이드의 구조 시험을 통하여 높은 효율과 안전한 구조임이 검토되었다.

• 한국농공학회지
• /
• 제11권1호
• /
• pp.1580-1597
• /
• 1969

1. The field test of our experiment comparing the traditional syckle and the new manually pulled cutter showed that the working efficiency of the manually pulled cutter is about two times higher than that of the syckle. The operator can standerect while using the manually pulled cutter, thus reducing fatigue. Because of the reduction in body fatigue, the operator is able to work more total hours, making the manually pulled harvester three times more efficient than the syckle. 2. The optimum angle for the V-shaped cutter blade varies according to the number of the hiller, but in manufacturing the cutter, the range must be controlled between $35^{\circ}{\sim}45^{\circ}$. 3. The radius of curvature of the V-shaped blade is closely related to the blade angle. The best results were obtained when the radii of curvature were r=32cm with $35^{\circ}$ angle, r=153mm with $45^{\circ}$ angle, and r=220mm with $40^{\circ}$ angle. 4. The hardness distribution test of the blade showed great differences between foreign made and domestic made blades. The heat treatment method must be greatly improved for superior hardness distribution. 5. Although the efficiency of the manually pushed cutter is equal to that of the manually pulled cutter, the manually pushed cutter is not only more expensive to produce but also has a much more complicated structure than the manually pulled cutter. Because of our rural economic conditions, the power harvester which is utilized in foreign countries can not yet be introduced here. Thus, the manually pulled cutter should be popularized in our rural areas until economic conditions will allow us to introduce power harvesters. 6. The use of the manually pulled cutter will make it possible for an operator to harvest an area in only one-third of the time that it would take to harvest the same area with a traditional syckle, and it will make it possible for an operator to earn about 8,000 won for harvesting 10 Jung-bo: such benefits will help in increasing farm income and will contribute to farm modernization.

• 한국추진공학회지
• /
• 제4권3호
• /
• pp.29-37
• /
• 2000

풍력 터빈회전날개의 설계시 구조적 형상을 결정하는 예비설계 단계에서 종전에는 여러 가지 다양한 경우의 설계를 수행하여 이중 적합한 경우를 채택하는 시행착오 방법은 많은 설계시간을 요하였으나, 본 연구에서는 이 같은 설계시의 비효율적 요소를 배제하고자 적층판 이론을 기초로 한 설계 프로그램을 이용하는 설계기법을 계발함으로서 설계절차를 개선하였다. 개선된 설계절차에 따라 국제표준 설계규격 IEC1400-1에서 규정한 각 경우의 하중해석과 응력, 변형율 및 변형한계를 설정한 후, 단순화한 복합재 회전날개 구조에 혼합법칙과 주 응력 설계기법을 이용하여 복합재 구조의 형상을 정하였다. 설계된 구조는 본 연구를 통해 개발된 적층판 이론을 기초로 한 프로그램을 이용하여 강도 및 좌굴에 대한 구조의 안정성을 확인하여 상세설계 과정시 소요되는 시간을 최소화하였다. 설계된 구조는 표피 등을 고려하여 수정 설계한 후 유한요소법을 이용하여 응력, 변형율, 변위, 고유 진동수, 좌굴안정성, 피로수명 등을 해석하여 국제 표준규격의 만족 여부를 확인하였다.

• 한국유체기계학회 논문집
• /
• 제17권4호
• /
• pp.30-39
• /
• 2014

The cross flow turbine is economical because of its simple structure. For remote rural region, there are needs for a more simple structure and very low head cross flow turbines. However, in this kind of locations, the water from upstream always flows into the turbine with some other materials such as sand and pebble. These materials will be damage to the runner blade and shorten the turbine lifespan. Therefore, there is a need to develop a new type of cross flow turbine for the remote rural region where there is availability of abundant resources. The new design of the cross flow turbine has an inlet open duct, without guide vane and nozzle to simplify the structure. However, the turbine with inlet open duct and very low head shows relatively low efficiency. Therefore, the purpose of this study is to optimize the shape of the turbine inlet to improve the efficiency, and investigate the internal flow of a very low head cross flow turbine. There are two steps to optimize the turbine inlet shape. Firstly, by changing the turbine open angle along with changing the turbine inlet open duct bottom line (IODBL) location to investigate the internal flow. Secondly, keeping the turbine IODBL location at the maximum efficiency achieved at the first step, and changing the turbine IODBL angle to improve the performance. The result shows that there is a 7.4% of efficiency improvement by optimizing turbine IODBL location (open angle), and there is 0.3% of efficiency improvement by optimizing the turbine IODBL angle.

• 한국농공학회지
• /
• 제17권1호
• /
• pp.3627-3641
• /
• 1975

The Government is trying to increase total food grain yield to meet national self sufficiency by means of increasing unit yield as well as extending crop land, and this year he set the target of 321,000 hectare of forest to clear for cropping. This study was carried to investigate the most efficient method of clearing hillock by bulldozer, and successful method to develope yielding potential of newly cleared land in short term. Since the conventional land clearing method is just earth leveling and root removing neglecting top soil treatment, the growth of crop was poor and farmer tends not to care the land. The top-soil-furrowing method is applied through out this study, that is advantageous especially for the land having shallow top soil and low fertility like Korean forest. In this study, various operating method were tried to find out most efficient method separately in connection with the land slope less than 25 percent and over, and several fertilizing methods to develop yielding potential. The results are as follows; 1) For the natural land slope utilization method, applicable to the land having less than 25 percent slope, reverse operating was more efficient than using forward gear of bulldozer. The operating time was 3 hour 32 minutes and 36 seconds using forward gear was 2 hour 32 minutes and 30 seconds for reverse gear operation per 1,000 square meter. 2) Bulldozer having angle blade adjustment needed 7hr 15min. for constructing of terrace per 10a compaire with the one having angle & tilt adjustment needed 6hr 4min for same operations. Specially there is significant difference for operation time of first period (earth cutting) such as bulldozer having angle blade adjustment needed 3hr 56min compaired with the one having angle & tilt adjustment 3hr 59min. In construction of terrace, the bull-dozer having tilting and angle blade adjustment was most suitable and performed efficiently. 3) For the fertilizer application treatment, the grass (Ladino clover) yield in first year was almost same as ordinary field's in the plot applied(N.P.K+lime+manure) while none fertilizer plot showed one tenth of it, and (N.P.K.+lime) applied plot yielded on third. 4) The effect of different land clearing method to yield showed significant difference between each treatment especially in the first year, and the conventional method was the lowest. In the second year, still conventional terracing plot yielded only half of ordinary field while the other plots showed as same as ordinary field's. 5) The downward top soil treatment plot showed most rapid improvement in soil structure during one year physio chemically, it showed increase in pH rate and organic composition, and the soil changed gradually from loam to sand-loam and the moisture content increased against the pF rate, and it gives good condition to grow hay due to the increase of field water capacity with higher available water content. 6) Since the soil of tested area was granite, the rate of soil errosion was increased about 2 to 5 percent influencing in soil structure more sand reducing clay content, and an optimum contour farming method should be prepared as a counter measure of errosion.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 추계학술대회 논문집
• /
• pp.443-448
• /
• 2014

Recently, car-ferry passenger ships of navigating the coast area in the inside of our country are on an increasing trend of main engine power and the height of upper structure, which is increased to ship's speed and loading of large vehicles. The most ship with high-speed main engine is happened to excessive vibration by propeller induced excitation force on account of connecting the vibration of hull's girder and the upper structure by decreasing the shear stiffness and natural frequency for increasing the height of passenger deck. In this paper, By exchanging the propeller of alteration the number of blades, it could be keep to ship's speed and it's decreased the vibration of hull part that is located passenger deck on the upper deck, which is identified by countermeasure of protection against vibration to procure the safety ship's navigation through measuring the vibration of hull structure.

• 한국안전학회지
• /
• 제25권4호
• /
• pp.1-6
• /
• 2010

Wind power system is composed by 3 major parts, rotor blade, nacelle and tower. Especially, the nacelle cover has an important role to prevent the component of nacelle and rotor from an extreme external circumstance. Therefore it is necessary to analyze and evaluate the stress distribution and deformation for them in the design level. There are two major points in nacelle cover analysis. The one is nacelle cover itself and the other is cover support structure. According to GL specification, this study shows the result that CFRP nacelle cover of wind turbine satisfies the strength and deformation through numerical analysis using the commercial finite element analysis program.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2011년도 제37회 추계학술대회논문집
• /
• pp.501-504
• /
• 2011

본 연구에서 터보프롭 항공기의 프로펠러 블레이드에 대한 구조 설계 연구를 수행하였다. 프로펠러는 고속으로 비행할 수 있는 추력을 얻기 위해 구조적으로 높은 강도가 요구된다. 본 연구에서는 로펠러 구조 설계 시 고강도 및 고강성의 특성을 지닌 카본/에폭시 복합재료가 적용되었으며, 경량화를 위하여 스킨-스파-폼 샌드위치 구조 형태를 채택하였다. 구조 설계 하중은 블레이드에 작용하는 공력하중과 원심 하중을 분석하여 결정하였으며, 스파 플렌지는 굽힘 하중을 담당하고 스킨은 전단 하중을 담당하도록 복합재료 설계 개념을 반영하였다. 구조 안전성을 평가하기 위하여 상용 유한 요소 해석 코드인 나스트란을 활용하여 구조 해석을 수행하였다. 최종 공력 및 구조 설계 결과 분석을 통하여 설계된 프로펠러 블레이드의 효율이 우수하며 안전한 구조인 것으로 검토되었다.