• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.469-473
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• 2010

본 연구에서는 빠른 후퇴율을 갖는 용융성 고체연료를 사용한 연소 실험을 수행하여 연소 중 압력진동 특성을 분석하고 연소 불안정의 위해성을 검토하였다. 빠른 후퇴율을 가지는 용융성 고체연료는 기존의 폴리머계 연료에 비해 압력 진동의 진폭이 증가하였다. 그러나 연료 그레인 내부 직경의 증가가 연소실 압력 진동의 증폭을 제한하여 급격한 연소 불안정은 거의 일어나지 않았다. 축방향 인젝터를 사용하는 경우 연료 연소량의 큰 증가와 예연소실에서의 와류 진동이 큰 압력 진동을 유발하였다.

• 한국추진공학회지
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• 제5권4호
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• pp.50-56
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• 2001

본 연구는 음속/초음속 공기이젝터 시스템을 통하는 유동을 실험적으로 조사한 것으로, 이젝터 시스템의 2차정체실 압력-시간의 의존성을 조사하였다. 본 실험에서 적용된 1차구동 노즐은 총 6가지 형태로, 두 개의 음속노즐과 두 개의 초음속 노즐 그리고 페탈노즐 및 로브형 노즐이 사용되었다. 실험에서는 이젝터-디퓨저 벽면에서 압력을 측정하였으며, 2차 정실실의 체적이 이젝터 내부에 미치는 영향을 조사하기 위하여, 2차 정체실의 체적을 변화시켰다. 그 결과 2차정체실의 체적은 이젝터 시스템의 정상 작동에는 영향을 미치지 않았지만, 2차정체실에서의 압력-시간 의존성은 2차정체실의 체적에 큰 영향을 받는다는 것을 알았다.

• 대한기계학회논문집B
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• 제26권2호
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• pp.177-183
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• 2002

The field tests on the waterhammer were carried out in the pump pipeline system with an air chamber. The effects of the input variables and the design parameters for the air chamber were investigated by both the numerical calculations and the experiments. Because the waterhammer problems as a result of the pump power failure were the most important, these situations were carefully studied. Among the input variables used in the waterhammer analysis, the polytropic exponent, the discharge coefficient and the wavespeed had influence on the simulated results in that order, and were calibrated in comparison with the experimental results. As the initial air volume in a vessel increased, the period of waterhammer increased and the pressure variation decreased, resulting from the reduction of the rate of pressure change in the air chamber. Using smaller orifice in the bypass pipe, the pressure rise was suppressed in some degree and the pressure surge was dissipated more rapidly as time passed. The simulations were in fairly good agreement with the measured values until 1∼2 periods of waterhammer. Not only the maximum and minimum pressures in the pipe1ine but also those occurring times were reasonably predicted. The computer program developed in this study will be useful in designing the optimum parameters of an air chamber for the real pump pipeline system.

• Journal of Mechanical Science and Technology
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• 제17권10호
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• pp.1563-1571
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• 2003

A fast response NO analyzer was applied to investigate the relation between cycle-by-cycle NO emissions and combustion chamber pressure. NO emissions were sampled at an isolated exhaust manifold of 4-stroke spark ignition engine to avoid the interference of exhaust gas from other cylinders. The linear correlation analysis was performed with collected data of NO emissions and combustion chamber pressure with respect to the various air-fuel mixture ratios and engine loads. The sampled data sets were obtained during 200 cycles at each operating condition. The results showed that there was a typical pattern in NO emissions from an exhaust port through a cycle. It was possible to set a block of crank angle in which the linear correlation coefficient between NO emissions and combustion chamber pressure was high. As the engine load increased, NO emissions were more dependent on combustion chamber pressure after TDC. It was also analyzed that the correlation between two parameters with respect to air-fuel mixture ratio tended to increase as mixture went leaner. Furthermore, this correlation coefficient for the mixture near the lean limit seemed to be kept high even though combustion was unstable.

• 한국수소및신에너지학회논문집
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• 제28권3호
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• pp.315-321
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• 2017

A combustion chamber is designed and fabricated for studying the combustion characteristics of counterflow flames at elevated pressure and establishing the fundamental combustion database of counterflow flames. The combustion chamber design aims to allow the maximum operating pressure of 11 bar and be able to conduct flame visualization and the measurements of flame extinction limits, flame temperature and combustion emissions at elevated pressure. Preliminary tests for counterflow nonpremixed $CH_4-NH_3-N_2$/air flames at 1-3 bar have been conducted, and the results confirm the proper operation of the designed chamber.

• 한국분말재료학회지
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• 제17권5호
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• pp.379-384
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• 2010

In the present work, bismuth nanopowders with various particle size distributions were synthesized by controlling argon (Ar) gas flow rate and chamber pressure of a gas condensation (GC) apparatus. From the analyses of transmission electron microscopy (TEM) images and nitrogen gas adsorption results, it was found that as Ar gas flow rate increased, the specific surface area of bismuth increased and the average particles size decreased. On the other hand, as the chamber pressure increased, the specific surface area of bismuth decreased and the average particles size increased. The optimum gas flow rate and chamber pressure for the maximized electrochemical active surface area were determined to be 8 L/min and 50 torr, respectively. The bismuth nanopowders synthesized at the above condition exhibit 13.47 $m^2g^{-1}$ of specific surface area and 45.6 nm of average particles diameter.

• 한국정밀공학회지
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• 제28권4호
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• pp.526-533
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• 2011

This research is about the pulsatile pump system utilized in the perfusion bioreactor for the in vitro human tissue culture. A pulsatile pump system which can be applied to the culture of the vascular tissues including blood vessel is developed by using the idea of human heart's blood pumping into organs as followings: culture chamber, a pressurizing device which generates laminar pulsatile flow by controlling the x-sectional area of the culture media delivering tubing, a compliance chamber which supplies the pressuring device with a constant pressure, and a peristaltic pump which circulates the culture media in a circuit ranging from the culture chamber to the compliance chamber. The developed pulsatile pump system shows that a physiology of the human heart's blood pumping including pulsatile pressure waveform of systolic-diastolic pressure is well represented. Not only time domain but also frequency domain characteristics of pulsatile pump system which are necessary for the vascular tissue culture such as pulsatile pressure waveform's shape, the frequency, and the magnitude can be easily generated and manipulated by using the proposed system.

• Journal of Biosystems Engineering
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• 제29권3호
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• pp.225-232
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• 2004

A new type of garlic peeling chamber has been developed which separates and peels garlic cloves using high-Pressure water Jets. The cylindrically-shaped chamber was fabricated with stainless steel plate and has a number of drilled holes, which function as solid-stream spray nozzles, on its interior wall. The chamber was divided into upper and lower section so that water can be applied at different pressures from each section. Three chambers of similar design were tested to evaluate their performances according to various pressure levels. The strongest correlation was observed between the pressure difference(lower-upper) and the proportion of unseparated and completely-peeled garlic cloves. Hanji-type garlic required higher or pressure difference to separate cloves from garlic bulbs than nanji-type garlic. On the other hand, protective leaves(skin) from the cloves were peeled more easily in case of hanji-type garlic. As a result of three consecutive peeling operations, the proportion of completely-peeled garlic cloves changed in the order of 80.1, 82.6, 84.1% in case of hanji-type, and 19.6, 29.1, 40.2% in case of nanji-type garlic.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.10-13
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• 2010

75톤급 기술검증용 연소기 시제의 저압 연소시험을 수행하였다. 기술검증용 연소기의 설계 연소압력은 60 bar, 추진제 유량은 243.6 kg/s이다. 그러나 국내 연소시험설비의 여건상 연소압력 30 bar, 추진제 유량 121.8 kg/s의 저압 조건에서의 연소기 작동성 및 연소성능을 검증하기 위한 시험을 수행하였다. 모든 연소시험은 하드웨어의 손상 없이 성공적으로 수행되었다. 본 시험결과는 향후 75톤급 연소기의 설계점 조건에서의 연소성능을 예측하는 기본 데이터로 활용될 수 있을 것이다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.1084-1087
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• 2017

액체로켓에서 엔진의 시동은 산화제와 연료를 연소기에 매우 짧은 시간의 차를 두고 주입하여야 하며, 이때 주입시간의 간격, 점화기 작동 지연 등은 방대한 량의 추진제 혼합물에 에너지를 인가함으로서 대형 폭발로 이어질 수 있는 상황이 된다. 그러므로 각 추진제의 천이특성과 연소기 또는 가스발생기의 유입 시점을 측정하는 것은 매우 중요하며, 상대적으로 느린 응답 특성을 갖는 정압으로는 유입 시점을 관측하기에는 어려움이 많으므로 추진제 유로를 따라 동압을 측정하여 보다 정확한 유입시점을 찾을 수 있었다.