착륙선용 전기펌프 사이클 엔진의 임펠러 형상 설계에 대한 고찰

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 항공우주공학과, 2021. 2. 윤영빈.With the growing interest in lunar exploration around the world and many landing missions being raised, it can be expected that demand for high-performance lander engines that play a key role in landing will increase. Meanwhile, with the advent of the New Space era, the economic feasibility of launch vehicle is emerging as an important topic. As a result, the electric pump system, which has the advantage of being easy to produce, easy to control, and cheap, is in the spotlight. As a result, research on electric pump cycle is becoming more active, but most of them are devoted to simulation research. Authors research group also manufactured electric pumps with different impeller shapes, but the performance measurement was not done. In this research, experimental study on the effect of the geometric shape of the pump on the propulsion system using the electric pump system was done. Sample lunar landing mission using an engine equipped with an electric pump was established to set evaluation criteria. In addition, it was investigated that lunar lander with electric pumps could significantly reduce dry mass of lander system, indicating that this mission configuration is affordable. The characteristics of pump systems were then measured experimentally. A closed loop test rig was built to measure the performance of the pump. The hydraulic performance, efficiency, and suction performance of different impellers are measured and compared. The comparison showed that the pressure rise of the small discharge angle impeller was low, but it showed higher efficiency and better suction performance. Finally, performance of electric pump at given mission was predicted and design trade-off was discussed.세계적으로 달 탐사에 대한 관심이 뜨거워지며 착륙 임무가 다수 제기됨에 따라, 착륙에 핵심적인 역할을 수행하는 고성능 착륙선 엔진에 대한 수요가 늘어날 것이라 예상할 수 있다. 한편, New space 시대가 도래함에 따라 발사체의 경제성이 중요한 화두로 떠오르고 있다. 이에 따라 생산이 간편하며, 제어가 쉽고 가격이 저렴하다는 장점이 있는 전기펌프 시스템이 새로이 각광을 받고 있다. 이에 전기펌프 시스템에 관한 연구가 활발해지고 있으나 대부분 시뮬레이션 연구에서 그치고 있다. 본 연구 그룹에서도 서로 다른 임펠러 형상으로 전기펌프를 제작한 바 있으나 이들 펌프의 성능 측정은 이루어지지 못했다. 본 연구에서는 이미 보유한 전기펌프 시스템을 이용하여 펌프의 기하학적 형상이 추력기 시스템에 미치는 영향을 실험적으로 연구하였다. 먼저, 실험적 분석의 기준을 세우기 위해 전기펌프가 적용된 엔진을 활용한 달 착륙 임무를 구성하였다. 추가로, 전기펌프를 적용한 달 착륙선이 가압식 사이클을 적용하는 경우보다 착륙선의 건조중량을 크게 줄일 수 있어 이러한 임무 구성이 가능성 있음을 보였다. 이후 보유한 전기펌프 시스템의 특성을 실험적으로 측정하였다. 펌프의 성능을 측정하기 위해 closed loop 방식의 test rig를 구축하였다. 서로 다른 임펠러의 수력학적 성능, 효율, 흡입성능을 측정하여 비교하였다. 비교 결과 토출각이 작은 임펠러의 경우 더 낮은 압력상승을 보였으나 더 높은 효율과 더 좋은 흡입성능을 보였다. 최종적으로 임무 설계 지점에서의 펌프 성능을 예측하고 전기펌프 방식 엔진을 설계할 떄 고려해야 할 tradeoff 관계를 살펴보았다.1. Introduction 1 1.1 Background 1 1.2 Previous work 5 1.3 Research objective 11 2. Mission Design 12 2.1 Background 12 2.2 Mission configuration 15 2.3 Feed system configuration 21 2.4 Analysis result 22 3. Pump Experiment 24 3.1. Experiment setup 24 3.1.1 Pump system 25 3.1.2 Test facility 26 3.1.3 Experimental method 29 3.2 Experimental result 34 3.2.1 Hydraulic performance 34 3.2.2 Cavitation performance 39 4. Discussion 43 4.1 Design point prediction 44 4.2 Design consideration 46 5. Conclusion 47 Reference 48 초록 51Maste

Anthropological Study on the Pelvis of the Korean Fetus

The author has measured 38 items on the pelves of 365 Korean fetuses. ranging from the 4th to the 10th fetal months, and computed 23 indices. The following conclusions have been drawn. 1. The dimensions of the greater pelvis increase about 4 times during the period from the 4th to the 10 th fetal months and the growth rate of the anteroposterior diameters is higher than that of the longitudinal and the transverse diameters. 2. The form of the greater pelvis is high longitudinally , narrow transversely and flattened anteropostriorly as compared with the adult pelvis. 3. The dimensions of the lesser pelvis increase about 3.5 times during the period from the 4th to the 10th fetal months and the growth rate of the longitudinal diameters is higher than that of the transverse and the antero-posterior diameters. 4. The form of the lesser pelvis is low longitudinally , narrow transversely , thick antero-posteriorly and cylindrical as compared with the adult pelvis. 5. The dimensions of the obturator foramen and the acetabulum increase over 4 times during the period from the 4th to the 10th fetal months. 6. There are no differences in the fetal pelvis between both sexes and the sex differences in pelvis occur after birth. 7. There are no differences in all of the items between both right and left sides

Effect of dexamethasone and some drugs on shope rabbit papilloma

의학과/석사[한글] [영문] In 1933 Shope described an infectious papilloma of wild cottontail rabbits. Shope rabbit papilloma is a virus-induced epidermal neoplasm indigenous to western cottontail rabbits and readily transmissible to domestic rabbits by inoculation with a cell-free extract of wild cottontail papilloma. Shope papilloma induced in the domestic rabbits may spontaneously, remain benign, or progress to carcinoma. Kidd et al. (1936) noted that the regression is not correlated with the titer of virus neutralizing antibody. The possibility that papilloma regression is brought about by a mechanism analogous to that operating in allograft rejection was suggested by kidd et al. (1938) with the view of the histological resemblance between papilloma regression and rejection of allografted tissue. That regression is mediated by an immu mechanism is strongly indicated by the findings of Evans et al.(1962) that the proportion of rabbits showing regression is substantially increased by vaccination of rabbits with rheir own papilloma tissue or with papilloma tissue from another rabbits. Mcmichael (1967) demonstrated that suppression of regression was achieved by use of large doses of corticosteroid. The effect of 5-fluorouracil on human warts was mentioned as being effective by Goldman et al.(1963). In Korea resinous extract from Paulownia coreana has long been used empirically in the treatment of human warts. In this investigation effects of dexamethesone administration on the development and the spontaneous regression of Shope papilloma in domestic rabbits were studied. At the same time, observations were made to evaluate the comparative effectiveness of topical application of 5% 5-fluorouracil ointment resinous extract from Paulownia cireana on Shope papilloma in the domestic rabbits. The results are summarized as follows : 1. Administration of dexamethasone significantly reduced the spontaneous regression of Shope papilloma in donestic rabbits by 12 weeks after virus inoculation. 2. Topical application of 5% 5-fluorouracil ointment on Shope papilloma cured the tumors by 4 weeks of drug application. However, similar treatment with resinous extract from Paulownia coreana was without any demonstrable effects. 3. Marked losses of body weight became manifest in dexamethasone treated rabbits. 4. Reinoculation of Shope papilloma virus into 2 rabbits whose papilloma had regressed 3 months ago failed to produce papillomas.restrictio

Traveling Salesperson Problem with capacity constraint

Maste

Change Control of Versions using Semantic Primitive Relations

버전통제 시스템의 자동화는 공학적 설계자료를 위한 데이타베이스의 관리자에게는 필수적인 기능이나 자동화에 따르는 위험부담으로 인해 쉽지 않은 문제이다. 현재까지 제시된 시스템들에서 볼 수 있는 한계는 동태적 모형화 도구의 미흡으로 변경통제에 필요한 충분한 정보가 데이타모형 내에 정의되지 못하는 점이다. 그 결과, 제한된 범위에서만 자동화가 가능하거나 시스템 환경의 변화에 대응하기 곤란한 자동화 시스템이 된다. 본 고에서는 동태적 모형화 도구로 의미론적 관계소를 이용한 버전의 변경통제 방안을 제시하고자 한다. 그 결과로 제시되는 데이타모형은 일종의 객체기반 타입 모형(‘OBTM’)이다. 메타-객체인 의미론적 관계소와 그에 대한 메타-지식은 선언적 모형정의를 가능케 함은 물론 시스템의 효용성을 높여 줄 수 있다. 또한 OBTM에 포함된 메타모형은 데이타모형의 가시성과 확장성을 보장해 줄 수 있다

Statistical Observation on the Intestinal Obstruction

1. The author conducted analytical examinations of 176 cases of intestinal obstruction, which have been treated for the past three years at the department. 2. This study has been conducted based on such clinical records as sex, age. chief complaints, symtoms, causes , localities of obstruction, surgical procedures, results of operation, etc. 3. The most frequent cause was adhesion resulting from surgical operation. This shows a marked contrast as compared with the most frequent or the second most frequent causes , i.e. incarcerated hernia, in European countries. It is the authors opinion that careful attention must be paid to adhesion following operation. 4. Congenital anomalies in the intestinal tracts in infants including intussusception were not infrequent. 5. It has been concluded that careful review of nutritional problems following resection of long intestinal segment is necessary. 6. Intestinal obstructions resulting from mesenteric thrombosis were also frequent

Ion impact-induced secondary electron emission from MgO

Thesis(master`s)--서울대학교 대학원 :화학생물공학부,2006.Maste

Clinical Observation of the 100 Cases of Biliary Tract Obstruction

1. The authors reported the findings regarding 100 cases of biliary tract obstruction which underwent surgical treatment at the department prior to september 1962. 2. The occurrence ratio between male and female was 1: 1. 2. This ratio shows a marked difference as compared with 1 : 4 in foreign countries. 3. The chief complaints were in most cases epigastric pains. This has led the authors to conclude that special concern must be paid to what is called Kasoomari"( gastric pain). 4. That a large percentage (73%) of the patients was suffering from jaundice means that patients in general receive treatment when their troubles have been aggravated to a considerable extent. 5. 71 of the 100 biliary tract obstruction cases were due to gall stones. Butters cancer was not infrequent. 6. 74% had stones in the bile duct and gall bladder and in 55% of cases stones were found only in the bile duct. 7. The authors reported one case of myocardiac changes shown in the electrocardiogram in the acute stage of cholecystitis