• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.223-227
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• 2005

A PCV valve is a part to control the flow rate of Blowby gas in a PCV system. A PCV system re-burns Blowby gas with fuel in a combustion chamber. Some gas enters to a crankcase room through the gap between piston ring and engine cylinder wall. This gas si called 'Blowby gas'. This gas causes many problems. In environmental view, Blowby gas includes about $25\~35\%$ hydrocarbon{HC) of total generated HC in an automobile. Hydrocarbon is a very harmful pollutant element in our life. In mechanical view, Blowby gas has some reaction with lubricant oil of crankcase room. Then, this causes lubricant oil contamination, crankcase corrosion and a decrease fo engine efficiency. Consequently, Blowby gas must be eliminated from a crankcase room. In this study, we simulated internal flow characteristics in a PCV valve according to spool dynamic behavior using local remeshing method And, we programmed our sub routine to simulate a spool dynamic motion. As results, spool dynamic behavior is periodically oscillated by the relationship between fluid force and elastic force of spring. And its magnitude is linearly increased by the differential pressure between inlet and outlet. Also, as spool is largely moved, flow area is suddenly decreased at orifice. For this reason, flow velocity is rapidly decreased by viscous effect.

• 소성∙가공
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• 제14권6호
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• pp.559-564
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• 2005

INCONEL 718, nickel based superalloy, has good formability, high strength, excellent corrosion resistance and mechanical properties at high temperature. Owing to theses attractive properties, it is utilized in applications such as combustion system, turbine engines and nuclear reactors. In such applications, components are typically required to be tolerant of high stress impact loading. This may cause material degradation and lead to catastrophic failure during service operation. Accurate understanding of material's mechanical properties with various strain rates is required in order to guarantee the reliability of structural parts made of INCONEL 718. This paper is concerned with the dynamic material properties of the INCONEL 718 at various strain rates. The dynamic response of the INCONEL 718 at the intermediate strain rate is obtained from the high speed tensile test and at the high strain rate is from the split Hopkinson pressure bar test. The effect of the strain rate on dynamic flow stress, work hardening characteristics, strain rate sensitivity and elongation to the failure is evaluated with the experimental results. Experimental results from both the quasi-static and the high strain rate up to 5000/sec are interpolated in order to construct the Johnson-Cook model as the constitutive relation that should be applied to simulate and design the structural parts made of rNCONEL 718.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.65-69
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• 2012

산화제 과잉 예연소기의 연소시험을 통해 예연소기 각 부위에서 압력을 측정하였다. 측정결과는 FFT를 통해 주파수 해석이 이루어 졌으나 정압 센서의 한계로 인하여 250 Hz 이상의 주파수에는 자세한 연구가 이루어지지 못하였다. 정압 데이터 분석결과 30 Hz의 하모닉스가 연소압과 산소입구에서 관측되었다. 따라서 연소압의 변화는 O/F 변화로 인한 것으로 파악된다. 반면에 동압센서 신호를 살펴보면 정압센서에서 확연히 나타났던 주파수보다 훨씬 더 명확한 주파수가 보다 높은 Hz에서 관측되는 것을 알 수 있었다.

• 한국안전학회지
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• 제27권5호
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• pp.9-15
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• 2012

The ignition characteristics in a confined axisymmetric coflow $CH_4$ jet were investigated numerically with the Fire Dynamics Simulator(FDS). The $CH_4$ fuel stream was diluted with main combustion product gases, such as $O_2$, $N_2$, CO, $CO_2$, and $H_2O$, and the mixed fuel stream was heated up to the sufficient temperature where a supplying fuel stream can be ignited. For the calculation of chemical reaction in the simulation, a 2-step global finite chemistry model was considered. Boundary condition for confined wall was optimized by investigating the effects of wall temperature on the ignition characteristics of fuel stream. In addition, the effects of composition of diluents in the fuel stream and fuel stream temperature on the ignition of fuel steam were investigated. The ignition characteristics of $CH_4$ stream with diluents were very sensitive to the wall temperature, composition of diluents in the fuel stream and fuel stream temperature.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.267-273
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• 2004

본 논문에서는 강한 압력파동에 구속된 액체 추진제 연소응답의 지배인자를 규명하고 비정상 거동 특성을 평가한다. 외부 압력섭동에 의해 교란된 탄화수소 계열 액체 추진제의 비정상 거동을 수치계산하고 연소응답의 관점에서 분석한다. 2상 사이의 평형을 고려한 1차원 액적기화 모델을 적용하고 압력파동은 인위적인 조화함수식으로 설정한다 외부 기상의 압력과 온도, 액적의 초기 직경과 내부온도, 외부 압력파동의 진폭과 구동 주파수 등 액체 로켓의 주요 설계인자 및 작동변수의 영향을 고찰한다. 본 연구를 통해 외부 압력파동의 구동 주파수와 외부 기상압력은 연소응답의 크기와 위상을 결정하는 지배인자임이 규명된 반면 외부 기상온도, 액적의 초기 직경과 외부온도 및 압력파동의 진폭 등은 연소응답과 약한 상관관계를 갖거나 그 영향이 미미하다. 기화열 섭동의 위상 및 액적표면과 내부의 파동에너지 전파특성이 연소응답의 크기와 위상을 결정한다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.128-134
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• 2007

본 논문은 고압 축소형 액체로켓엔진 연소기의 연소 성능과 특성에 관한 것이다. 4개의 고압 축소형 연소기 모델에 대하여 연소시험을 수행하였다. 고압 축소형 연소기는 크게 분사기 헤드부, 재생냉각 방식의 연소실부, 그리고 강제 물냉각 노즐부로 구성되어 있고, 1개의 모델은 연소실을 냉각한 연료가 헤드부로 유입되는 재생냉각 방식의 연소기이다. 연소압력은 70 bar이며 재생냉각 방식의 연소기 모델은 연소시험 중 고주파 연소불안정이 발생하여 하드웨어가 손상되었다. 각각의 고압 축소형 연소기의 연소시험 결과, 성능 비교 및 정압, 동압 특성에 대해 기술하였다.

• Journal of Mechanical Science and Technology
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• 제17권12호
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• pp.2087-2098
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• 2003

The development of numerical mathematical model to calculate both the static and dynamic characteristics of a multi-shaft gas turbine consisting of a single combustion chamber, including advanced cycle components such as intercooler and regenerator is presented in this paper. The numerical mathematical model is based on the simplified assumptions that quasi-static characteristic of turbo-machine and injector is used, total pressure loss and heat transfer relation for static calculation neglecting fuel transport time delay can be employed. The supercharger power has a cubical relation to its rotating velocity. The accuracy of each calculation is confirmed by monitoring mass and energy balances with comparative calculations for different time steps of integration. The features of the studied gas turbine scheme are the starting device with compressed air volumes and injector's supercharging the air directly ahead of the combustion chamber.

• 한국연소학회지
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• 제15권2호
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• pp.12-18
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• 2010

A numerical analysis was performed to predict the thermo-fluid dynamic characteristics of hydrazine monopropellant reaction in the thruster combustor and nozzle. A 1-D porous model was introduced to simulate catalytic reaction by iridium in the combustor while 2-D axisymmetric analysis was applied to predict the nozzle flow. The chemical species and temperature variations were predicted by changing the injection pressure and mass flow rate and their results were validated by comparison with limited experimental data. The thrust variation with injection pressure could be estimated using the current 1-D combustor modeling.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.642-647
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• 2010

막냉각은 고온의 연소가스에 장시간 노출되어 있는 공기흡입식 추진기관의 연소실 내벽을 열적으로 보호하기 위해 사용하고 있으며, 슬롯형 냉각라이너를 이용한 막냉각 방법은 냉각특성을 향상시키기 위해 오랫동안 연구되어 왔다. 본 논문에서는 다중 슬롯형 냉각라이너의 연소영역과 냉각영역에서의 기체역학적 유동 및 열전달 계산에 대한 연구결과를 기술하였다.

• 한국분무공학회지
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• 제24권2호
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• pp.58-65
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• 2019

A 3D FEM (Finite Element Method) based Helmholtz solver has been commonly used to characterize fundamental acoustic behavior and investigate dynamic instability features in many combustion systems. In this approach, a geometrical simplification of the target system has been generally made in order to reduce computational time and cost because a real combustor and fuel nozzle have a very complicated flow passage. The feasibility of these simplifications is quantitatively investigated in a small aero gas turbine nozzle in term of acoustic characteristics. It is found that the simplification in a nozzle geometry during the 3D FEM analysis process has no great influence on the acoustic modeling results, while the calculation complexity can be improved for a similar modeling accuracy.