• 연구논문집
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• 통권27호
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• pp.87-99
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• 1997

Present paper describes on/off design performance of a 50KW turbogenerator gas turbine engine for hybrid vehicle application. For optimum design point selection, relevant parameter study is carried out. The turbogenerator gas turbine engine for a hybrid vehicle is expected to be designed for maximum fuel economy, ultra low emissions, and very low cost. Compressor, combustor, turbine, and permanent-magnet generator will be mounted on a single high speed (82,000 rpm) shaft that will be supported on air bearings. As the generator is built into the shaft, gearbox and other moving parts become unnecessary and thus will increase the system's reliability and reduce the manufacturing cost. The engine has a radial compressor and turbine with design point pressure ratio of 4.0. This pressure ratio was set based on calculation of specific fuel consumption and specific power variation with pressure ratio. For the given turbine inlet temperature, a rather conservative value of $1100^\circK$ was selected. Designed mass flow rate was 0.5 kg/sec. Parametric study of the cycle indicates that specific work and efficiency increase at a given pressure ratio and turbine inlet temperature. Off design analysis shows that the gas turbine system reaches self operating condition at N/$N_{DP}$ = 0.53. Bleeding air for turbine stator cooling is omitted considering low TIT and for a simple geometric structure. Various engine performance simulations including, ambient temperature influence, surging at part load condition. Transient analysis were performed to secure the optimum engine operating characteristics. Surge margin throughout the performance analysis were maintained to be over 80% approximately. Validation of present results are yet to be seen as the performance tests are scheduled by the end of 1998 for comparison.

• 대한기계학회논문집B
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• 제20권6호
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• pp.1921-1930
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• 1996

To design an optimum engine intake system, a flow model for the intake manifold was developed by the finite difference method. The flow in the intake manifold was one-dimensional, and the finite difference equations were derived from governing equations of flow, continuity, momentum and energy. The thermodynamic properties of the cylinder were found by the first law of thermodynamics, and the boundary conditions were formulated using steady flow model. By comparing the calculated results with experimental data, the appropriate boundary conditions and convergence limits for the flow model were established. From this model, the optimum manifold lengths at different engine operating conditions were investigated. The optimum manifold length became shorter when the engine speeds were increased. The effect of intake valve timings on inlet air mass was also studied by this model. Advancing intake valve opening decreased inlet air mass slightly, and the optimum intake valve closing was found. The difference in inlet air mass between cylinders was very small in this engine.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3154-3158
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• 2008

A liquid rocket engine performance has been analyzed as a function of combustion pressure with LOx/RP-1R. The present method is verified by comparing the specific impulse for various combustion pressure with given pump head model. The optimal combustion pressure is between 150 bar and 200 bar for given efficiencies. Both the optimal combustion pressure and the specific impulse increase for increased turbine efficiency. The optimal combustion pressure decreases and the specific impulse increases for increased combustion efficiency. The pump efficiency and the turbine inlet temperature have the same qualitative effect as the turbine efficiency.

• 에너지공학
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• 제26권1호
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• pp.23-27
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• 2017

유기랭킨사이클에서 팽창기는 전체 성능과 사이클 효율에 큰 영향을 미치는 중요 부품이다. 유기랭킨사이클에 적용되는 팽창기는 입구 압력과 온도가 팽창기 기계적 특성이나 작동유체 특성 등에 의해 제한받게 되는데, 유기랭킨사이클은 팽창기 입구압력과 온도에 따라 사이클 출력, 흡수 열량 및 효율 등이 변화하게 된다. 본 연구에서는 용적형 팽창기가 적용되는 작동유체 냉매 R134a인 유기랭킨사이클의 성능이 팽창기 입구조건에 따라 유기랭킨사이클의 성능이 어떻게 변화하는지 이론적으로 비교 분석을 수행하였다.

• 대한기계학회논문집
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• 제18권1호
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• pp.232-239
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• 1994

This paper presents an effective way of improving fuel consumption for a variable displacement engine. The improvement of fuel consumption can be accomplished by means of deactivating inlet and exhaust valves, reducing the number of effective cylinders of a four-cylinder gasoline engine that is mounted on a domestic compact automobile.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1809-1818
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• 2004

The dependence of the ignition timing in an HCCI engine on intake temperature and pressure, equivalence ratio, and fuel species is investigated with a zero-dimensional model combined with a detailed chemical kinetics. The accuracy of the model is evaluated by comparing measured and computed results in a propane-fueled HCCI engine. It is shown that the peak pressure values are reproduced within 10% and ignition timing within 5$^{\circ}$ CA. The heat loss through the walls is found to affect significantly on the ignition timing for different inlet conditions. It is also shown that for the propane-fueled engine, the tolerance in intake temperatures is 20-25K and the tolerance in intake pressure is about 1 bar for stable operation without misfire or too early ignition. Comparison of propane and heptane fuels indicates that the tendency to misfire when heptane is employed as the fuel is less than that when propane is employed with the same wall temperature conditions. However, the heptane-fueled engine may have a lower compression ratio to avoid too early ignition and hence lower efficiency. For the selected set of engine parameters, stable operations might be achieved for the heptane-fueled engine with twice as much tolerance in intake temperatures as for the propane-fueled engine.

• 한국분무공학회지
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• 제22권2호
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• pp.62-68
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• 2017

It is important to study on the combustion instability to develop liquid rocket engines for preventing lower combustion efficiency and destruction of combustion chamber. There are many researches on simplex injector with liquid pulsation to solve this problem. In real rocket engine system, however, they use coaxial injectors. Therefore, research on coaxial injector with liquid pulsation is essential. In this study, we investigate dynamic characteristics of gas centered swirl coaxial injector varying tangential inlet diameter. A mechanical pulsator was used to generate an excitation in the liquid flow, and the response characteristics of the injector were confirmed. As tangential inlet diameter increased, mass flow rates increased and spray angle decreased. As tangential inlet diamter decreased, gain decreased because the pressure fluctuation in the injector manifold rarely passed through the inlet. Additionally, it was confirmed that a sufficiently small tangential inlet served as a damper.

• Journal of Advanced Marine Engineering and Technology
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• 제36권1호
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• pp.109-117
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• 2012

본 논문은 매연여과장치(DPF)의 Inlet Pipe 길이를 5가지 경우로 변화시켜, 이 변화가 유동장에 미치는 영향을 살펴보았다. 실험 방법으로서는 PIV 계측과 상용코드를 사용하여 수치해석을 수행 하였으며, 그 결과 PIV와 CFD는 87%로 일치하는 상관성을 보였다. 또한 동일한 유속 조건일 때 Inlet Pipe 길이가 20mm일 때 안정적이고 높은 압력 값을 보여 매연여과율을 높일 수 있을 거라 사료된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.367-370
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• 2006

This paper deals with the modeling and simulation of the internal flowfield in a valveless airbreathing pulse detonation engine (PDE) currently under experimental development at the U.S. Naval Postgraduate School. The system involves no valves in the airflow path, and the isolation between the inlet and combustor is achieved through the gasdynamics in an isolator. The analysis accommodates the full conservation equations in axisymmetric coordinates, and takes into account variable properties for ethylene/oxygen/air system. Chemical reaction schemes with a single progress variable are implemented to minimize the computational burden. Detailed flow evolution during a full cycle is explored and propulsive performance is calculated. Effect of initiator mass injection rate is examined and results indicate that the mass injection rate should be carefully selected to avoid the formation of recirculation zones in the initial cold flowfield. Flow evolution results demonstrate a successful detonation transmission from the initiator to the combustor. However, strong pressure disturbance may propagate upstream to the inlet nozzle, suggesting the current configuration could be further refined to provide more efficient isolation between the inlet and combustor.

• 대한기계학회논문집
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• 제18권12호
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• pp.3326-3334
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• 1994

To theoretically predict knock occurrence in S. I. engine as a function of engine design and operating parameters, transient local temperature and pressure, mixture density of flame front in combustion period are calculated. We next determined normal combustion period and auto ignition period of end gas using the prediction method on occurrence of spark knock which we suggested. We predict knock occurrence in S. I. engine by comparing consecutively normal combustion period with the auto ignition period of end gas in combustion period. Engine design and operating parameters such as compression ratio, engine speed, spark timing, inlet temperature and pressure are taken into account in this calculations. The predicted result are well matched with the experimental results in turbocharged engine. Therefore, this method will provide the systematic guideline for designing engines in view of knocking limits.