• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.1
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• pp.43-50
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• 2009

The characteristics at the intermediate operation point of the turbopump-gas generator(TP-GG) coupled test were investigated by analytical method. The pump outlet pressure, gas generator mixture ratio, gas generator pressure, and temperature were examined considering risk minimization of test. The engine system shows different behavior from the TP-GG coupled test at the intermediate operation point since the combustion pressure feeds back to the flow rate in the lines. The advanced valve changes in the combustor line helps less risky mode transition.

• Journal of Drive and Control
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• v.15 no.2
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• pp.1-8
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• 2018

This study is a first step toward reducing surge pressure, and it has another purpose, which is to developing an analysis model which can closely analyze a hydraulic circuit and be used in design. For development of analysis model, SimulationX, a commercial program, is used. The study progress methods are as follows. By analyzing the structure and operating mechanisms of each part of the hydraulic system of the pump truck and referring its parameters, develop a single component model. Assemble the developed single component model, and make an overall analysis the model. By comparing the similarities between the developed model and the actual system's test results, validate the reliability of the analysis model.

• Journal of computational fluids engineering
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• v.21 no.1
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• pp.50-57
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• 2016

In various industries related with construction and military machinery, a large amount of power is normally required because such machinery operations, such as digging or breaking, take place under difficult working conditions in a rough environment. Thus, a hydraulic system needs to be applied as the major power transfer system. To produce and supply hydraulic power depending on the various load conditions, a hydraulic piston pump is utilized as a typical power source for a hydraulic system. In the present study, numerical simulations were conducted using the commercial program, Ansys CFX 14.5. To lubricate the moving parts as the pump starts to operate, a small amount of oil leaks out through the clearance between the orifice in the piston-shoe and the recess at the swash-plate. Taking this into consideration, a cylindrically shaped computational domain was modeled to maintain the same equivalent leakage area. To validate the numerical method applied herein, the numerical results of the flow rate at the discharge port were compared with the experimental data, and a good agreement between them was shown. Using the verified method, the effects of the discharge pressure and the angle of the swash-plate were also evaluated under several load conditions. The results of the present study can be useful information for a hydraulic piston pump used in many different manufacturing industries.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.130-137
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• 2019

In this study, a centrifugal seawater cooling pump was analyzed to investigate its cavitation behavior over different operating flow rates. 3D two-phase simulations were carried out with ANSYS-CFX commercial code. The $k-{\varepsilon}$ turbulence and Rayleigh-Plesset cavitation models were employed in the simulations. A head drop characteristics curves for three discharge rates was built based on numerical predictions. At higher flow rates, the impeller was more vulnerable to bubble cavitation. The 3 % head drop points of the pump working at 0.7Q, Q, and 1.3Q (Q: design flow rate) corresponded with NPSHa 1.21 m, 1.83 m, and 3.45 m, respectively. The volume of vapor bubbles was estimated and cavitation locations were anticipated to visualize the development of the cavity within the impeller. Moreover, the distribution of pressure coefficient and a blade loading chart are specifically presented, bringing out the harmful impacts of cavitation on the pump operation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.406-414
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• 2004

In Gerotor pump, the pressure pulsations which occur due to the pump geometry result in vibration and noise of pump elements as well as cavitation in hydraulic system when the chambers of gerotor enter the delivery port and leave the suction port. Therefore it is important to study on the pressure pulsations before design and analysis of characteristics in Gerotor pump. In this paper, to reduce the unnecessary pressure pulsations, the port plate of Gerotor pump is designed based on the notch of the vane pumps and the relief grove of the piston pumps. The theoretical analysis of the pressure pulsations is performed in consideration of design parameters of the port plate which include each port positions and groove width and operating conditions which include rotational velocity and delivery pressure.

• Journal of the KSME
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• v.32 no.11
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• pp.947-954
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• 1992

이 글에서는 엔진 윤활 시스템해석 프로그램의 구성 요인 및 프로우차트를 열거했으며 이렇게 만들어진 프로그램을 이용하여 엔진의 개선 및 신엔진 개발 시에 매개변수를 변화시켜가며 오일 유로의 설계와 요구되는 오일량을 결정하여 최적의 윤활시스템을 설계할 수 있다고 본다. 참고로 밸브시스템의 정상적인 작동을 유지하는 상태에서 요구되는 토출 유압과 유량이 줄어들면 오일 펌프의 용량을 줄일 수 있고 그로 인해 오일 펌프 구동손실도 줄일 수 있다. 또한 최적 유량이 공급될 때 엔진 구동손실을 최소화할 수 있다. 더나아가 본 해석으로 얻은 최적화된 유량이 만족 된 이상적인 윤활 부위의 치수가 결정된 상태에서 운동부의 마찰을 최소화하는 엔진 마찰의 수치해석적 모델을 개발하는 것도 흥미있는 과제이다. 또한 간단한 테스트 리그 제작에 의한 각 윤활 부품에서의 압력-유량 관계 실험식의 정확도를 높이는 것도 앞으로의 과제이다.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.277-277
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• 2011

본 논문은 $CO_2$ 히트펌프용 모세관의 기초 설계자료를 제공하기 위해서 모세관 길이 예측에 대해서 이론 및 실험적으로 조사하였다. 본 연구에서 고려된 작동변수로는 증발온도, 가스냉각기 냉각압력, 냉매유량, 모세관의 관경 등이다. 몇몇연구자들의 자료를 바탕으로 $CO_2$ 모세관 길이를 예측할 수 있는 수학적 모델식을 작성하였다. 그리고 단열 모세관 팽창장치내 $CO_2$의 증발온도, 냉매유량, 냉각압력 등에 대해서 실험한 결과, Fig. 1에 나타낸 것처럼, 모세관 길이가 증가할수록 증발온도는 감소하는 것을 알 수 있다. 그리고 증발온도에 대한 실험값과 예측값의 비교 결과, 실험값이 예측값보다 약간 높게 나타났다. $CO_2$냉매가 모세관내를 통과할 때 플래쉬 가스(flash gas)의 발생으로 인해 액상의 양보다 기상의 양이 많아지고 액상의 압력강하보다 기상의 압력강하가 휠씬 더 크기 때문이다. 또한 증발온도에 대한 실험값과 예측값은 6.5~9.9% 이내에서 좋은 일치를 보였다. Fig. 2에 나타낸 것처럼, 모세관 길이가 증가할수록 냉매유량은 감소하는 것을 알 수 있다. 이는 전술한 바와 같이 모세관 길이가 증가할수록 냉매 압력강하가 더욱더 증가하기 때문이다. 그리고 냉매유량에 대한 실험값과 예측값의 비교 결과, 실험값이 예측값보다 약간 높게 나타났다. 이는 전술한 증발온도와 동일한 이유로 실제 $CO_2$냉매가 모세관내를 통과할 때 플래쉬 가스의 발생량이 많아지기 때문이다. 또한 냉매유량에 대한 실험값과 예측값은 0.64~10.9% 이내에서 좋은 일치를 보였다. Fig. 3에 나타낸 것처럼, 모세관 길이가 증가할수록 냉각압력은 증가하는 것을 알 수 있다. 이는 증발온도가 일정한 경우 모세관 길이가 증가할수록 냉매유량이 감소하여 압축기 토출측 온도(압력)가 상승하기 때문이다. 그리고 냉각압력에 대한 실험값과 예측값의 비교 결과, 실험값이 예측값보다 약간 낮게 나타났으며 실험값과 예측값은 1.04~3.7% 이내에서 좋은 일치를 보였다. 따라서 본 연구에서는 수송기계용 $CO_2$ 열펌프 단열 모세관에 대한 기초설계 자료로서, 냉각압력, 증발온도, 모세관 직경, 냉매유량 등의 조건으로부터 모세관 길이를 계산해낼 수 있는 예측 상관식을 제안하였다.

• Journal of the Korea Institute of Building Construction
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• v.15 no.4
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• pp.375-381
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• 2015

In this study, high performance concrete of C60 and C80 were applied to a super tall building and those had satisfactory properties of fresh and hardened concrete to the requirements even changes according to time. Especially the evaluation and analysis of the relation of the rheological properties and puMPability of high performance concrete, C60-14 which was applied to the height of from 500m to 575m in the building, was carried out bymeasuring pumping pressure and pumping speed, testing concrete properties at before and after pumping. As results, themax. pumping pressure showed increase of 5% at every 25m higher pumping and the average pumping speed showed the above $25m^3$ per hour whichmeans proper productivity. Additionally it was verified that the loss of slump flow after pumping was increased according to plastic viscosity values and the increment of temperature through concrete pumping.

• Journal of the Korean Institute of Gas
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• v.26 no.4
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• pp.1-8
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• 2022

DME, a clean fuel that is being studied as an alternative fuel for diesel engines, can reduce exhaust gas, which is the one of the crucial problems of diesel engines, and has a very high cetane number and high oxygen content. DME is a fuel has properties similar with LPG and can use the infrastructure of LPG. In this study, The target was to build a database of basic data on the mass flow rate discharged for the performance evaluation of the plunger-type high pressure pump. In this study, the mass flow rate of the DME plunger type high pressure pump was analyzed by changing the common rail pressure and the motor rotation speed. The experimental conditions were the common rail pressure was changed from 300 to 500 bar and the motor rotation speed was changed from 300 to 1000 rpm. In addition, basic mass flow data were constructed to high-pressure pumps for DME. As a result of the experiment, in both cases the mass flow rate was increased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.883-890
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• 2011

A numerical study was conducted to determine the optimal design for a vehicle vacuum pump. The degree of vacuum was examined for different design factors such as the angle of vanes, number of vanes, angle and position of the pump inlet-outlet pipe, and angular rotational speed of vanes. The results show that there is a little difference in the degree of vacuum when the angle of vanes are changed, but an angular change in the outlet pipe reduces the pump loss. As the rotational speed is increased, the mass flow rate increases, but a high rotational speed does not result in the maximum degree of vacuum. In addition, when the number of vanes is increased, the scattering range of mass flow rate decreases and pressure drop is abated.