• 대한기계학회논문집
• /
• 제15권2호
• /
• pp.618-629
• /
• 1991

The purpose of this experiment is to understand the distribution of coal particles inside CWM droplet which is believed to be a very important factor controlling the flame stability. CWM slurry is atomized by an air assisted twin fluid nozzle. An experimental rig is designed and fabricated. The mean size of coal particle distribution in CWM slurry, atomizing air pressure, coal particle loading in slurry and sampling position inside spray are main experimental variables. The atomized CWM droplets are sampled on the thin white layer of magnesium oxide by the emergency sampling shutter. The sampled coal particles on magnesium oxide layers are collected into test tubes and dispersed completely by Ultra-Sonicator. The size distribution of coal particles inside droplets are measured by Coulter Counter. The presence of coal particle inside the impressions of droplets on magnesium oxide layer are investigated by photo technique. There are quite many droplets which do not have any coal particles. Those are just water droplets, not CWM droplets. The population ratio of droplets without coal particles to toal number of droplets is strongly affected by the mean size of coal particle distribution in slurry and this ration becomes bigger number as the mean size of coal particles be larger. The size distribution of coal particles inside CWM droplets is not even and depends on the size of droplet. Experimental results show that the larger CWM droplets has droplets has bigger mean value of particle size distribution. This trend becomes more evident as the atomizing air pressure is raised and the mean size of coal particles in CWM slurry is bigger. That is, the distribution of coal particles inside CWM dropolets is very much affected by the atomizing air pressure and the mean size of pulverized coal particles in CWM slurry.

• 대한기계학회논문집A
• /
• 제34권1호
• /
• pp.49-54
• /
• 2010

탄성변형 접촉 조건을 가지는 이중냉각 핵연료봉과 이를 지지하는 지지구조체 사이에서 발생하는 프레팅 마멸거동을 모사 시험편을 이용하여 실험적으로 분석하였다. 이중냉각 핵연료봉은 기존의 핵연료에 비해 외경이 증가하므로 새로운 형상을 가지는 지지구조체의 적용이 필수적이며 이에 대한 진동 특성 및 마멸 저항성에 대한 평가가 필수적이다. 본 연구에서는 현재까지 제안된 다양한 형상 중에서 대표적으로 엠보싱 형상을 가지는 지지구조체의 모사 시험편을 이용하여 이중냉각 핵연료봉의 내마멸 특성을 분석하였다. 개발된 지지구조체 특성 시험장비를 이용하여 모사된 지지구조체 시험편의 특성시험을 수행하였으며 이를 해석에 의한 결과와 비교하였다. 또한 기존의 핵연료 내마멸시험과 동일한 조건 및 장비를 이용하여 프레팅 마멸시험을 수행하여 이중냉각 핵연료봉의 프레팅 마멸거동을 관찰하였다. 본 논문에서는 실험결과로부터 지지구조체 특성과 프레팅 마멸거동 사이의 상관관계에 대하여 자세히 논하였다.

• Tribology and Lubricants
• /
• 제36권1호
• /
• pp.27-33
• /
• 2020

Self-equalizing tilting pad thrust bearings are usually employed in turbomachines to achieve high stability and reliability. A tilting pad bearing can incorporate self-equalizing links to handle the misalignment between the bearing and the thrust collar. In this popular design method, the pads sit on the upper-level plates and the lower-level plates stay on the retainer base. With misalignment, the pads that are heavily loaded are pushed down. Consequently, the link pushes up the pads on the opposite side, keeping the bearing surface parallel to the thrust collar surface. The self-equalizing link is used to handle the misalignment from the thermal and mechanical effects. In this study, the experimental investigation deals with the performance of self-equalizing tilting pad thrust bearings. The test rig for evaluating the performance of bearing is developed which can control the misalignment angle. Simultaneous measurements are taken for the force acting on each pad. Pad metal temperature and oil film thickness are functions of the shaft speed, bearing load, misalignment angle, and design of leveling plates. The effect of misalignment on bearing performance is discussed. The results demonstrate that the load on each pad depends on the test conditions(especially misalignment angle), and the load influences the performance of bearings.

• 한국산학기술학회논문지
• /
• 제12권5호
• /
• pp.2005-2010
• /
• 2011

최근 배기 규제가 자동차 엔진에 국한되지 않고 노외용 소형엔진 부분에서도 세계적으로 강화됨에 따라, 배기규제에 대응하기 위하여 기존 노외용 소형엔진의 기화기 방식에서 벗어나 전자연료 분무방식으로의 전환이 필요하게 되었다. 본 연구에서는 400cc 가솔린 엔진용 인젝터의 연료공급 특성을 실험적으로 분석하였으며, 이를 토대로 소형엔진에 적합한 인젝터를 선정하였다. 분무질량분포 측정장치를 통하여 3홀 및 6홀인젝터의 분무질량분포 특성을 분석하였다. 가시화 실험 장치를 통하여 각 인젝터의 분무각, 분무도달거리 및 분무폭을 분석하였다. 분무질량분포 실험 및 분무 가시화 실험을 통하여 분무특성이 우수하고 안정적인 분무를 형성하는 6홀 인젝터를 소형엔진용으로 선정하였다.

• 한국산학기술학회논문지
• /
• 제13권9호
• /
• pp.3889-3894
• /
• 2012

국내 여객을 취급하는 철도역사의 승강장은 간선철도노선의 저상승강장(500mm)과 광역전철구간의 고상승강장(1135mm)으로 구분 운용되고 있다. 저상승강장 전용 중 고속 열차가 수도권 전철구간(고상승강장)과 본선구간(저상승강장)에서 혼용 운영될 경우를 대비하고 안전운전 및 승객편의를 함께 고려하기 위해 저상 고상 승강장 겸용 승강시스템의 개발은 필수적이다. 한편 현재 개발 중인 시스템(스텝)에 대한 국내의 내구성 및 신뢰성 시험 기준은 존재하지 않는다. 따라서 본 연구에서는 저상/고상 승강장 겸용 텔레스코픽 슬라이드방식 승강문 스텝의 개발을 위한 연구 일환으로서, VPD관점에서 내구성 해석을 수행하고 신뢰성 보증시험에 준한 무고장 시험시간동안 실물 리그시험을 통하여 이의 내구성 기준 및 보증수명을 검토하였다.

• 대한기계학회논문집A
• /
• 제34권12호
• /
• pp.1865-1870
• /
• 2010

이 논문에서는 뉴럴네트워크 모델에 기초하여 셀프 센싱이 가능한 IPMC 액추에이터를 개발하고자 한다. IPMC의 양면에 있는 두 개의 지정된 점에서 측정된 입력 전압과 입력 신호들을 뉴럴네트워크 모델의 입력 신호로 사용한다. CCD 레이저 변위 센서는 제시된 뉴럴네트워크 모델의 학습된 출력값으로 사용되는 IPMC 끝의 변위를 정확히 측정하기 위해 설치된다. 결과적으로 뉴럴네트워크 모델은 수집된 입력/출력 학습데이터에 의해 최대한으로 활용된 IPMC의 끝의 변위를 평가하기 위해 만들어진다. IPMC 액추에이터를 위해 설계된 모델의 효율성은 결과들을 모델링함으로서 증명되어진다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.17-22
• /
• 2007

Low-cycle environmental fatigue tests of cast austenitic stainless steel CF8M at the condition of fatigue strain rate 0.04%/sec were conducted at the pressure and temperature, 15MPa, $315^{\circ}C$ of a operating pressurized water reactor. The used test rig was limited to install an extensometer at the gauge length of the cylindrical fatigue specimen inside the small autoclave. So the magnet type LVDT's were used to measure the fatigue displacement at the specimen shoulders inside the high temperature and high pressure water autoclave. However, the displacement and strain measured at the specimen shoulders is different from the one at the gauge length for the geometry and the cyclic strain hardening effect. FEM calculated the displacement and the strain of the gauge length from the data measured at the shoulders. Tensile test properties in elastic and plastic behavior of CF8M material were used in the FEM analysis. A series of low cycle fatigue tests simulating the cyclic strain hardening effect verified that the FEM calculation was well agreed with the simulated tests. The process and method developed in this study would be so useful to produce reliable environmental fatigue curves of CF8M stainless steel in pressurized water reactors.

• 비파괴검사학회지
• /
• 제16권1호
• /
• pp.29-33
• /
• 1996

핵연료봉의 결함 탐상을 위하여 차동환상형 와전류시험 탐촉자를 설계 및 제작하여, 핵연료봉 시험을 위한 최적 시험 조건을 구하였다. 관통결함, 내부결함, 외부결함을 낸 표준시편에 대하여 와전류시험을 수행함으로써 시험 주파수와 출력 신호의 위상 및 크기에 대한 상관 관계를 구하였다. 이를 토대로 하여 고리원자력 1호기에서 연소한 핵연료봉 G33-N2에 대하여 와전류시험을 수행하여 관통결함 신호를 얻었다. 와전류시험에서 관통결함으로 예측된 위치에서 금속조직시험을 수행하여 얻은 결과는 와전류시험 결과와 잘 일치하였다. 따라서 와전류시험법은 조사핵연료봉의 피복관에 대한 건전성을 평가하는 도구로써 그 신뢰성이 양호함을 실증하였다.

• Tribology and Lubricants
• /
• 제33권4호
• /
• pp.134-140
• /
• 2017

With the increase in adoption of tilting pad journal bearings (TPJBs), various failure mechanisms related to TPJBs have been reported, of which pad wear is a frequently reported one. Pad wear causes change in geometry of the bearing, which can sometimes result in the failure of the entire system. The objective of this research is to investigate the influence of pad wear on the pad temperature, which is one of the widely used condition monitoring methods for TPJBs. For the theoretical investigation, thermohydrodynamic (THD) analysis was conducted by solving the generalized Reynolds equation and the 3D energy equation. The results of the analysis show that the temperature of the loaded pad increases while that of the unloaded pad decreases, when there is wear on the loaded pads. In addition, the minimum film thickness decreases with an increase in the wear depth. A validation test was conducted with a test rig, which mimics the axial turbine when a test rotor is supported by two TPJBs. The test bearing consists of five pads with a diameter of 60 mm, and a resistance temperature detector (RTD) is installed in the pad for temperature monitoring. The test was performed by replacing the two loaded pads with the worn pad. The test result for the TPJB with wear depth of $30{\mu}m$ show that the temperatures of the loaded pads are $8^{\circ}C$ higher and that of the unloaded pad is $2.5^{\circ}C$ lower than that of the normal TPJB. In addition, the predicted pad temperature shows good agreement with the measured pad temperatures.

• 한국항공운항학회지
• /
• 제15권4호
• /
• pp.9-16
• /
• 2007

Tilt rotor aircraft can take off and land vertically and cruise faster than any other helicopter. A scaled flight demonstration model of a tilt rotor aircraft has been developed by KARI. Because the flight characteristics of tilt rotor are not well known, the developed scaled model would be helpful to evaluate flight control algorithm of a full scale aircraft. The tethered hover test has been performed in order to improve hover flight characteristics of tilt rotor aircraft prior to flight test of the small scaled model. During the tethered hover test, the performance of rotor speed governor, rate SAS (Stability Augmentation System) and control surface mixers have been evaluated. We expect that the results of real flight hover test would be quite same as tethered hover test. Therefore the tethered hover test results will reduce the risk of flight test properly by fixing some of hidden problems which might occur during the flight test. This paper presents the results of tethered hover test in detail and shows how it could be final ground test before flight test. The control mixer gain and rate SAS feedback gains were modified in order to get higher controllability and stability during the tethered hover flight. The rotor governor showed that it could keep rotor RPM constant with very small deviation even during severe pilot collective input change. The tethered hover test results gave pilot and engineers confirmation and experience about the scheduled flight test.