• 한국유체기계학회 논문집
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• 제1권1호
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• pp.81-89
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• 1998

In this study, the effects of the impeller shapes on the pump performances of the non-clogging and the screw-type centrifugal pumps are experimentally studied. The characteristics of total head, efficiency and power of the non-clogging pump increase as the number of vanes increases. The screw-type centrifugal pump with the linear-shape vane shows a little better performance than that of the screw-type centrifugal pump with the curved-shape vane. The differences in the characteristics of total head, efficiency and power are, however, insignificant. Therefore, it is advisable that, considering the convenience of pump manufacturing, the screw-type centrifugal pump with the linear-shape vane should be used. This study also compares the pump characteristics of the non-clogging pump and screw-type centrifugal pump. The characteristics of total head and efficiency of the non-clogging pump are better than those of the screw-type centrifugal pump. The screw-type centrifugal pump requires more shaft power than the non-clogging pump.

• 한국유체기계학회 논문집
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• 제19권6호
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• pp.34-42
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• 2016

The organic Rankine cycle (ORC) has been used to convert thermal energy to mechanical energy or electricity. The available thermal energy could be waste heat, solar energy, geothermal energy, and so on. However, these kinds of thermal energies cannot be provided continuously. Hence, the ORC can be operated at the off-design point. In this case, the performance of the ORC could be worse because the components of the ORC system designed based on a design point can be mismatched with the output power obtained at the off-design point. In order to improve the performance at the off-design point, a few components were replaced including generator, bearing, load bank, shaft, pump and so on. Experiments were performed on the same facility without including other losses in the experiment. The experimental results were compared with the results obtained with the previous model, and they showed that the system efficiency of the ORC was greatly affected by the losses occurred on the components.

• 한국유체기계학회 논문집
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• 제6권3호
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• pp.28-35
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• 2003

This paper presents analysis results for the effect of power control strategies on the part load performance of gas turbine based power generation systems utilizing exhaust heat of the gas turbine such as combined cycle power plants and regenerative gas turbines. For the combined cycle, part load efficiency variations were compared among different single shaft gas turbines representing various technology levels. Power control strategies considered were fuel only control and IGV control. It has been observed that gas turbines with higher design performances exhibit superior part load performances. Improvement of part load efficiency of the combined cycle by adopting air flow modulation was analyzed and it was concluded that since the average combined cycle performance is affected by the range of IGV control as well as its temperature control principle, a control strategy appropriate for the load characteristics of the individual plant should be adopted. For the regenerative gas turbine, it is likewise concluded that maintaining exhaust temperature as high as possible by air flow rate modulation is required to increase part load efficiency.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.677-680
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• 2003

The control of the SRM(Switched Reluctance Motor) is usually based on the non-linear inductance profiles with positions. So determination of optimal switching angle is very different. we present self-tuning control of SRM for maximum torque and efficiency with phase current and shaft position sensor During the sample time, micro-controller checks the number of pre-checked pulse. After micro-controller calculates between two data, it move forward or backward turn-off angle. When the turn-off angle is fixed optimal turn-off angle, turn-on angle moves forward or backward by a step using self-tuning control method. And then, optimal turn-off angle is searched once again. As such a repeating process, turn-on/off angle is moves automatically to obtain the maximum torque and efficiency. The experimental results are presented to validate the self-tuning algorithm.

• 전력전자학회논문지
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• 제23권2호
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• pp.112-120
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• 2018

This work presents a hybrid generator, which is a combination of a permanent magnet (PM) and winding structure with a PM exciter. The field winding of the proposed hybrid generator is fed by the PM exciter and the embedded current controller, which is installed in the generator shaft. In the no-load condition, the output voltage of the generator is produced by the PM flux of the generator without any field winding current. The field winding current produces an insufficient flux to retain the output voltage of the generator when the load is injected. The total efficiency can be increased from the PM exciter and PM flux of the generator. The field current has to be controlled inside the proposed generator. The generated power from the PM exciter is used to excite the field flux of the generator. The embedded current controller is commanded by the external voltage controller using the infrared wireless method. The 10 kW prototype hybrid PM generator is designed and tested to verify the effectiveness of the proposed system. The experimental results are compared with those of the winding generator with PM exciter.

• 한국자동차공학회논문집
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• 제23권1호
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• pp.112-121
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• 2015

In this paper, powertrain of output split type plug-in hybrid electric vehicle is analyzed for the operation range of speed, torque, and power. First, it is assumed that the efficiency of motor is 100%. And, the speed and torque equations are derived based on the lever analogy. With the above equations, the simulations are performed for the powertrain of output split type plug-in hybrid electric vehicle. From the simulation results, it is found that the output torques of EV1 and series modes are larger than the EV2 and power split modes' ones. It means the EV1 and series modes can be used for the rapid acceleration. But the EV1 and series modes can be used only the velocity of under the 120 km/h. It is because the motor reaches its maximum speed when the velocity is over the 120 km/h for the EV1 and series modes. When the engine is turned on, the engine power is transmitted through the two motors. But, the power split mode shows the power split of engine at the output shaft, and it has the point of zero motor power. Thus, the transmission efficiency of the power split mode can be higher than the series mode's one, it the motor efficiency is considered.

• 대한토목학회논문집
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• 제26권6C호
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• pp.407-419
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• 2006

현장타설말뚝이 주면저항력에 의해서만 지지되는 상황은 천공홀 바닥을 청소할 수 없어서 선단부 지지력의 반현 여부를 확신할 수 없을 때이다. 반대로, 신선한 기반암이 낮은 강도의 상부 재료 하부에 있는 경우는 암반에서의 선단지지력만으로 상부 하중을 지탱할 수 있으며, 상부 재료에서는 지지력 발현을 기대하지 않아도 된다. 그러나 신선암에서 일정 깊이 천공을 실시한 경우, 현장타설말뚝은 주면저항력과 선단지지력 모두를 기대할 수 있다. 암반에 근입된 현장타설말뚝의 거동에 관한 이론적 연구와 현장 시험을 통하여 작용 하중의 대부분이 통상 주면저항력에 의해서 지지되게 된다는 사실이 알려져 있다. 암-콘크리트 접촉면에서의 수직응력은 두 가지 기구에 의해 증가하게 된다. 먼저, 말뚝 상부에 작용하는 압축하중에 의해서 콘크리트는 탄성 다이레이션이 발생하고 두 번째로 거친 천공홀 표면에서 전단 변위를 통해서 접촉면의 역학적 다이레이션이 발생되게 된다. 수직 변위에 대한 근입부 주변 물질의 강성도가 일정하면, 작용하중이 증가함에 따라서 수직응력은 증가하게 되며 따라서, 전단강도의 증가 현상이 발생하게 된다. 본 연구에서는 수치해석을 통하여 암반에 근입된 현장타설말뚝의 주면부 거동특성을 조사하였다. 또한, 두부의 하중-침하량(선단부 침하량+말뚝의 탄성변형량) 관계가 비선형성을 띠는 원인 및 파괴기구를 충분히 조사함으로써 암반에 근입된 현장타설말뚝의 주면저항력에 영향을 미치는 요소들을 모두 고려하여 국내 풍화암 및 연암에 근입되는 현장타설말뚝의 설계차트를 제시하고 이를 검증하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제29권7호
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• pp.750-757
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• 2005

The objective of this study is an understanding of the effect of inlet flow angle on the output power performance of a Francis hydraulic turbine, An optimum induced angle at the inlet of the turbine is one of the most important design parameters to have the best performance of the turbine at a given operating condition, In general. rotating speed of the turbine is varied with the change of water mass flowrate in a volute, The induced angle of the inlet water should be properly adjusted to the operating condition to have maximum energy conversion efficiency of the turbine, In this study. a numerical simulation was conducted to have detail understanding of the flow phenomenon in the flow path and output power of the model Francis turbine. The indicated power produced by the model turbine at a given operating condition was found numerically and compared to the brake power of the turbine measured by experiment at KIER. From comparison of two results, turbine efficiency or energy conversion efficiency of the model turbine was estimated. From the study, it was found that the rotating power of the turbine linearly increased with the rotating speed. It means that the higher volume flow rate supplied. the bigger torque on the turbine shaft generated. The maximum brake efficiency of the turbine is around 46$\%$ at 35 degree of induced angle. The difference between numerical and experimental output of the model turbine is defined as mechanical efficiency. The maximum mechanical efficiency of the turbine is around 93$\%$ at 25$\∼$30 degree of induced angle.

• Journal of Advanced Marine Engineering and Technology
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• 제41권4호
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• pp.310-315
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• 2017

최근 건조되는 선박은 연료소비량을 절감하고 안락한 운항을 위해서 고효율 프로펠러를 부착하고 있다. 이와 같이 고효율 프로펠러가 탑재됨에 따라 이전의 프로펠러 특성을 고려한 프로펠러 감쇠방법을 이용하여 해당 축계의 비틀림진동 해석을 할 경우에는 해석 오차가 많이 발생되고 있다. 이러한 오차는 고효율 프로펠러의 개발이 지속됨에 따라 더욱 커질 것으로 예상된다. 본 논문에서는 비틀림진동 해석에 적용되고 있는 각종 프로펠러 감쇠 적용방법들에 따른 해석 편차를 검토하였다. 또한 고효율 직결식 10MW급 프로펠러를 적용한 선박들을 대상으로 프로펠러 감쇠 적용방법에 따른 해석치와 계측 결과를 비교 검토하여 현 시점에서 사용상 적절한 프로펠러 감쇠방법을 제시하였다.

• 한국터널지하공간학회 논문집
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• 제16권2호
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• pp.203-211
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• 2014

본 논문은 shield TBM의 버럭 배토장비인 screw conveyor의 최적 버럭 배토효율에 관한 연구이다. screw conveyor의 배토효율에 영향을 미치는 주요 Parameter인 screw 형태(Shaft식, Ribbon식), screw conveyor와 screw 각도의 영향을 분석하기 위하여 축소모형시험을 실시하였다. 축소모형시험을 통해 구한 버럭 배토 효율과 기존 이론식을 통해 구한 최적의 버럭 배토효율을 비교 분석하여 최적의 screw 형태, screw conveyor와 screw각도를 도출 할 수 있었다. 결론적으로 축소모형시험을 통하여 screw conveyor 설계인자들에 대하여 제시하였다. 또한 이 연구 결과는 향후 shield TBM 기술을 발전시키는데 유용할 것으로 기대된다.