• Tuberculosis and Respiratory Diseases
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• 제43권2호
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• pp.201-209
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• 1996

연구배경: Auto-PEEP 혹은 intrinsic PEEP은 호기말에 폐용적이 전체 호흡기계의 이완 용적으로 돌아오지 않음으로써, 증가된 호흡기계의 탄성반도압만큼 호기말 폐포내압(alveolar pressure) 이양의 값을 보이는 것을 말한다. Auto-PEEP 이 존재하는 만성폐쇄성폐질환 환자에게 externa1 PEEP을 적용하면 환자의 호흡 일을 줄일 수 있어서, 질환의 급성악화시 혹은 기계호흡으로부터의 이탈시 환자의 자발호흡을 보조하기 위한 요법으로 제시되고 있다. 이에 기계호흡중인 환자에서 auto-PEEP의 존재가 호흡 일에 미치는 영향을 알아보고, externa1 PEEP의 사용이 auto- PEEP에 의해 증가된 호흡 일을 줄이는지를 알아보기 위해 본 연구를 시행하였다. 방법: 호흡부전으로 기계호흡을 하고 있는 환자 15명을 대상으로 연구가 이루어 졌으며, 이들 7명에서 auto-PEEP이 관찰되었고(auto-PPEP군) 8명에서 auto-PEEP이 auto-PEEP군). 양군 간의 환자의 호흡역학적 지표의 차이를 조사하였으며, auto-PEEP이 존재하는 환자들에 대해 3cm $H_2O$의 external PEEP을 적용한 뒤 호흡역학적 지표들의 변화를 조사하였다. 호흡역학적 지표는 상시호흡량(tidal volume, 이하 $V_T$), 분당 호흡수, 분당환기량 (minute ventilation 이하 $V_E$), 최고흡기유량(peak inspiratory flow rate, 이하 PIFR), 최고호기유행peak expiratory flow rate, 이하 PEFR), 최고흡기압(peak inspiratory pressure, 이하 PIP), $T_I/T_{TOT}$, auto-PEEP, 폐 동적탄성 (dynamic compliance of lung, 이하 Cdyn), 호기 기도저항(expiratory airway resistance, 이하 RAWe), 평균 기도저항(mean airway resistance, 이하 RAWm), $P_{0.1}$, 환자에 의해 수행되는 호흡 일 (work of breathing performed by patient, 이하 호흡 일), pressure-time product(이하 PTP)등이었다.

• 대한기계학회논문집
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• 제8권3호
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• pp.201-209
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• 1984

본 연구는 Kim과 Chiu가 사용한 연속체 관점에서 유도된 액체-기체상의 2상유 동모델(Two Phase Flow:TPF)을 이용하여 초기 집단연소수(group combustion number)의 크기, 즉 액적들의 초기 분포상태에 따른 연소상태를 예측 분류한다. 또한 이때 예 측된 대표적인 연소상태에서 형성되는 화염의 성질을 비교 검토한다.

• 한국항공우주학회지
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• 제43권10호
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• pp.868-874
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• 2015

가변추력은 대기가 없는 행성에 착륙하거나, 우주공간에서의 도킹에 필수적인 것으로 알려져 있다. 추력을 조절하기 위해 질유량 조절이 가능한 분사기를 사용하는 방법이 대표적으로 알려져 있다. 이에 따라 본 연구에서는 추력조절을 위하여 이중매니폴드 분사기를 사용하여 질유량을 조절하였다. 이중매니폴드 분사기의 주요 변수 중 하나로 판단되는 접선방향 유입구의 개수의 변화에 따른 분사특성을 확인하기 위하여 분무각, 분무패턴을 포함하는 외부유동을 측정하였으며 내부유동 특성 파악을 위한 film thickness를 확인하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권10호
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• pp.500-505
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• 2002

In this paper, fluorescent discharge type ozonizer has been designed and manufactured. Ozone discharge and generation characteristics have been investigated in accordance with a sort of internal electrodes, output voltage of power supply, air flow rate and discharge power. Air has been used as the supplied gas of the ozonizer In this paper, when disuse fluorescent lamp was used as an internal electrode. Air flow rate was varied from 2[1/min] to 10[1/min]. The maximum ozone concentration and yield were 3495[ppm] and 23.4[g/kWh] respectively at 2[1/min] air flow rate and 35.2[W] input power. Illumination was appeared as 5[lx] within 15[cm] from external electrode. Whorl fluorescent discharge type ozonizer was used, air flow rate was also varied from 2[1/min] to 10[1/min]. At this moment, the maximum ozone concentration and yield were 2824[ppm] and 21.7[g/kWh] respectively at 2[1/min] air flow rate and 30.5[W] input power. Illumination was also appeared as 5[lx] within 15[cm] from external electrode like used fluorescent lamp.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2000년도 춘계 학술발표회 논문집
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• pp.43-50
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• 2000

The flow field of a 1 Ton/Day entrained-flow gasifier constructed in KIER was numerical simulate in this paper. The standard $k-{\varepsilon}$ turbulence model and simple procedure was used with the Primitive-Variable methods during computation. In order to find the influence factors of the flow field which may have great effects on coal gasification process inside gasifier, difference geometry parameters at various operating conditions were studied by simulation methods. The calculation results show that the basic shape of the flow field is still parabolic even the oxygen gas is injected from the off-axis position. There exist an obvious external recirculation zone with a length less than 1.0m and a small internal recirculation region nears the inlet part. The flow field inside the new gasifier is nearly similar as that of the old 0.5T/D gasifier at same position if the design of burner remains unchanged.

• 대한기계학회논문집B
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• 제31권3호
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• pp.264-272
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• 2007

The aim of this study is to investigate the effects of nozzle orifice shapes and the nozzle length-to-diameter ratio(L/D) on the nozzle cavitation formation inside the orifice and the external flow pattern. The nozzle used in this work was tested the taper orifice nozzle and the rectangular orifice nozzle which was made from the transparent acrylic acid resin. For studying the effect of the nozzle L/D ratio, it was used to three L/D ratios of 3.33, 10, and 20. The cavitation flow of nozzle was visualized by using the ICCD camera and optical system. This work revealed that the flow rate and discharge coefficient($C_d$) of the taper orifice nozzle was larger than those of the rectangular orifice nozzle at the same injection pressure. The cavitation flow was observed in the nozzle orifice at the low injection pressure and the breakup of liquid jet was promoted as the L/D ratio is decreased. The cavitation of biodiesel fuel was formed at the lower injection pressure than that of diesel fuel because of higher viscosity and density.

• Advances in aircraft and spacecraft science
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• 제5권3호
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• pp.349-362
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• 2018

A non-linear numerical simulation technique for predicting the unsteady performances of an airbreathing engine is developed. The study focuses on the simulation of integrated propulsion systems, where a closer coupling is needed between the airframe and the engine dynamics. In fact, the solution of the fully unsteady flow governing equations, rather than a lumped volume gas dynamics discretization, is essential for modeling the coupling between aero-servoelastic modes and engine dynamics in highly integrated propulsion systems. This consideration holds for any propulsion system when a full separation between the fluid dynamic time-scale and engine transient cannot be appreciated, as in the case of flow instabilities (e.g., rotating stall, surge, inlet unstart), or in case of sudden external perturbations (e.g., gas ingestion). Simulations of the coupling between external and internal flow are performed. The flow around the nacelle and inside the engine ducts (i.e., air intakes, nozzles) is solved by CFD computations, whereas the flow evolution through compressor and turbine bladings is simulated by actuator disks. Shaft work balance and rotor dynamics are deduced from the estimated torque on each turbine/compressor blade row.

• 멤브레인
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• 제17권4호
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• pp.318-328
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• 2007

본 연구에서는 호소수의 정수처리공정 중 폴리술폰계 중공사막을 이용한 침지형(흡인압)과 외압형을 동시에 적용한 분리막 공정으로 압력 및 공경에 따른 투과플럭스의 변화에 관한 성능을 평가하고자 하였다. 침지형(흡인압) 공정의 압력에 따른 최대 투과 플럭스는 공경이 $0.3{\mu}m$에서 평균 282 LMH, $0.05{\mu}m$에서는 234 LMH를 나타내었으며 외압형(외압) 공정의 압력에 따른 최대 투과 플럭스는 공경이 $0.3{\mu}m$에서 평균 443 LMH, $0.05{\mu}m$에서는 522 LMH를 나타내었다. 또한, 흡인압과 외압을 동시에 적용한 공정의 압력에 따른 최대 투과 플럭스는 공경이 $0.3{\mu}m$에서 평균 674 LMH $0.05{\mu}m$에서는 648 LMH를 나타내었다. 따라서, 호소수를 이용한 정수처리공정에서 분리막으로 흡인압과 외압을 동시에 이용할 경우 단위 면적당 생산수를 최대로 할 수 있을 것으로 사료된다.

• 한국수소및신에너지학회논문집
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• 제15권1호
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• pp.54-61
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• 2004

Temperature characteristics in a stack of molten carbonate fuel cell (MCFC) have been investigated with simulation based on the computational fluid dynamics (CFD) codes and experimental way. The MCFC has generally two stack structures when the natural gas is used as fuel; one is the external reforming type and the other is internal reforming type. Computer simulation at the external reforming stack suggests that the maximum temperature in the stack depends on the gas flow length. The 2 kW MCFC stack with 25 cm gas flow length showed about $675^\circ{C}$ of maximum temperature.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 추계학술대회 논문
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• pp.138-143
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• 1996

The 3-dimensional complex parts which construct automobile and aerospace parts are very difficult to polish by traditional polishing method. Abrasive flow machining is useful to polish an internal or external surface of the 3-dimensional shape part. In this paper media flow between workpiece and tooling part has been simulated and the charateristics of abrasive flow machining process have been analyzed according to various machining conditions by calculating the material removal and surface roughness.