• 한국유체기계학회 논문집
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• 제18권3호
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• pp.12-19
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• 2015

As a means of improving cycle performance of a R410A air-conditioning system, a combined structure of compressor and expander was introduced. A vane rotary type expander was designed to share a common shaft with twin type rolling piston rotary compressor in a housing. Numerical simulation on the performance of the combined compressor and expander was carried out. At ARI condition, the volumetric and total efficiencies of the designed vane expander were 69.37% and 30.23%, respectively. With the application of this expander, the compressor input was reduced by 3.91%, and the cooling capacity was increased by 3.98%. As a result, COP of the air-conditioning system was improved by 8.2%. As the pressure difference between the condenser and the evaporator becomes large, COP improvement increases unless the mass flow rate in the expander exceeds that in the compressor.

• 대한의용생체공학회:의공학회지
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• 제19권1호
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• pp.33-38
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• 1998

심장내 이식형 축류 혈액 펌프의 개발을 시도하였다. 이 펌프는 해부학적인 적합성이 좋고, 혈액과 접촉하는 면적이 적으며, 심장판막의 위치에 이식할 수 있어 이식술이 용이한 등의 이점이 있다. 축류혈액펌프는 입펠러와 소형 모터에 의해 구성되었으며, 모터축과 펌프의 본체의 밀봉은 자성유체 축봉이 이용되었다. 본 연구에서 개발한 혈액펌프의 펌프 특성은 4매 임펠러의 경우 회전수 7091[rmp], 6매 임펠러의 경우 회전수 6402[rpm]에서 유량 5[l/min], 차압 100[mmHm]을 얻을 수 있었으며, 자성유체 축봉의 내압 특성은 회전수 7000[rpm], 압력ㄹ 150[mmHg]에서 24시간 이상의 내구성을 얻을 수 있었다. 그리고, 용혈에 대하여 검토한 결과 4매 임펠러의 1H 는 0.0561[g/100L]이고, 6매 임펠러의 경우는 1H=0.214[g/100L]을 얻을 수 있었다. 이상의 실험결과는 심장내 이식 축류형 혈액펌프의 실현 가능성을 보여 주는 것으로 앞으로 큰 기대를 걸수 있다고 생각된다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1027-1033
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• 2000

This paper describes the characteristics of vibration of a hydraulic turbine mainly due to cavitation occurrence. The analysis of vibration spectra of the turbine shaft shows that hub vortex cavitation occurs in the downstream of the turbine runner, which is verified from coherence analysis between shaft vibration displacement and dynamic pressure at the draft tube. Even though acceleration level measured at the guide vane lever, which is usually used for evaluation of cavitations performance, is decreased during forced aeration, it is found from the analysis of dynamic pressure spectra that cavitation around runner blades still remains unchanged. It is also found that lateral vibration of the turbine shaft is mainly due to the hub vortex cavitation of the turbine runner.

• 신재생에너지
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• 제10권4호
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• pp.9-15
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• 2014

In this study pressure and shaft torque pulsation were measured with variation of head and flow during the model test for a 15 MW Francis Turbine. Pressure pulsations were measured at the inlet of the spiral casing and 4 points in the cone of the diffuser and shaft torque pulsation at the upper position of the turbine. The maximum amplitude of pressure pulsation appeared 2.03% of the maximum rated head with the frequency of 25% of the rated revolution and at the guide vane opening of $10^{\circ}$. Shaft torque pulsation appeared 0.01% of the rated shaft torque, fairly low value. Air was admitted through the cone and pressure pulsation gradually decreased with increase of air flow and kept nearly constant after 5% of the rated flow. A new Francis turbine of which specific speed is 115 m-kW had been designed to rehabilitate the old one and the model test was performed at EPFL. The commercial code, STAR-$CCM^+$ was used for numerical simulation of flow.

• 대한조선학회논문집
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• 제43권3호
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• pp.294-303
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• 2006

A surface piercing propeller (SPP) in tunnel has been proposed recently as a new propulsion system for a high speed air cavity ship. The purpose of the present study is to investigate the characteristics of the SPP in tunnel through a series of model tests. A model propulsion system is placed on a dummy body made of Acrylics. The tunnel is divided into two regions by a guide vane extending from the inlet to the center of the propeller shaft. Air has been supplied from an air nozzle placed at the bottom of the dummy body and the changes in propeller performances caused by the air flow are investigated. The measurements are done for open water and in-tunnel conditions, both for fully and partially submerged propeller. The influence of the guide vane configurations on the propeller performance is also studied. The experiments are performed at the variable pressure circulation water channel of Inha University

• 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.

• Journal of Advanced Marine Engineering and Technology
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• 제39권2호
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• pp.143-151
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• 2015

Recently, tidal current energy conversion is a promising way to harness the power of tides in order to meet the growing demands of energy utilization. A new concept of tidal current energy conversion device, named Vane Tidal Turbine (VTT), is introduced in this study. VTT has several special features that are potentially more advantageous than the conventional tidal turbines, such as propeller type tidal turbines. The purpose of this study on VTT is to analyze the possibility of extracting the hydrokinetic energy of tidal current and converting it into electricity, and evaluate the performance of turbines for various numbers of blades (six, eight and twelve) using Computational Fluid Dynamics (CFD). At various tip-speed ratios (TSR), the six-bladed turbine obtains the highest power and torque coefficients, power efficiency is up to 28% at TSR = 1.89. Otherwise, the twelve blade design captures the smallest portion of available tidal current energy at all TSRs. However, by adding more blades, torque extracted from the rotor shaft of twelve-bladed turbine is more uniform due to the less interrupted generation of force for a period of time (one revolution).

• 대한조선학회 특별논문집
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• 대한조선학회 2007년도 특별논문집
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• pp.107-117
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• 2007

A surface piercing propeller (SPP) in tunnel has been proposed recently as a new propulsion system for a high speed air cavity ship. The purpose of the present study is to investigate the characteristics of the SPP in tunnel through a series of model tests. A model propulsion system is placed on a dummy body made of Acrylics. The tunnel is divided into two regions by a guide vane extending from the inlet to the center of the propeller shaft. Air has been supplied from an air nozzle placed at the bottom of the dummy body and the changes in propeller performances caused by the air flow are investigated. The measurements are done for open water and in-tunnel conditions, both for fully and partially submerged propeller. The influence of the guide vane configurations on the propeller performance is also studied. The experiments are performed at the variable pressure circulation water channel of Inha University.

• 설비공학논문집
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• 제30권3호
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• pp.107-115
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• 2018

A design combining the use of a compressor and expander was introduced in order to improve the cycle performance of a $CO_2$ automotive air conditioning system. Both the compressor and expander used were of rotary vane type and were designed to share a common shaft in a housing. Numerical simulation was carried out to evaluate the merit of the combined unit. In a typical automotive air conditioning operating conditions, the COP of the system was improved by 8.7% by the application of the combined unit. The compressor input was reduced by 5.2% through use of the expander output. In addition, about 3.06% increase in the cooling capacity was obtained through isentropic expansion in the expander. Our study noted that, as the pressure difference between the gas cooler and the evaporator becomes larger, the COP of the system improved increases unless the mass flow rate in the expander exceeds that in the compressor.

• 한국정밀공학회지
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• 제27권12호
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• pp.107-112
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• 2010

A gas turbine consists of an upstream compressor and a downstream turbine with a combustion chamber, and also the compressor and the turbine are generally coupled using a single shaft. Large scale gas turbine compressor is designed as multi-stage axial flow and the blade is fan-type which is thick and wide. Recently radial cracking happens occasionally at the compressor blade tip of large scale gas turbine. So, FEM was performed on the compressor blade and vibration modes and dynamic stresses were analyzed. According to the analysis, 9th natural frequency mode of the blade, which is 2 strip mode, is near the vane passing frequency by the vane located at the upstream of the blade.