• Applied Science and Convergence Technology
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• 제24권1호
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• pp.9-15
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• 2015

The practical pumping speed of a dry pump is considerably lower than the intrinsic speed because of back-streaming through finite gaps of the rotor assembly. The maximum compression ratio and the ultimate pressure of the pump are also directly influenced by the back-streaming rate. Therefore, information on the gap conductance, which determines the back-streaming characteristics of the rotor assembly, is the most important key for estimating the pumping performance of a dry pump. In this paper, the feasibility of calculating analytically the pumping performance of a multi-stage Roots pump, one of the most popular types of dry pumps, by quantifying the gap conductance in a rational way, is discussed.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.203-208
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• 2001

In this paper, the pumping performance of the three-stage disk-type drag pump which works in the outlet pressure range from 4 to 0.01 Torr is studied experimentally. The rotational speed of the pump is 24,000rpm, and nitrogen is used as a test gas, The pumping characteristics of various drag pumps are investigated. The inlet pressures are measured for various outlet pressures of the test pump. The maximum compression ratios for zero throughput are measured for three-stage, two-stage BSC type, helical-type, one-stage BSC type and one-stage OSC type, respectively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.347-352
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• 2001

In this paper, the pumping performance of the two-stage disk-type drag pump which works in the outlet pressure range from 3 to 0.001 Torr is studied experimentally. The rotational speed of the pump is 24,000rpm, and nitrogen is used as a test gas. The pumping characteristics of various drag pumps are performed. The inlet pressures are measured for various outlet pressures of the test pump. The maximum compression ratios for zero throughput are 1000(two-stage BSC type), 740(helical-type), 90(BSC type) and 85(OSC type), respectively. The ultimate pressure of the two-stage disk-type drag pump is $8.1\times10^6$ Torr.

• Journal of Magnetics
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• 제19권1호
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• pp.49-54
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• 2014

The influence regarding the dehydrogenation speed, at the desorption-recombination state during the hydrogenation-disproportionation-desorption-recombination (HDDR) process, on the microstructure and magnetic properties of Nd-Fe-B magnetic powders has been studied. Strip cast Nd-Fe-B-based alloys were subjected to the HDDR process after the homogenization heat treatment. During the desorption-recombination stage, both the pumping speed and time of hydrogen were systematically changed in order to control the speed of the desorption-recombination reaction. The magnetic properties of HDDR powders were improved as the pumping speed of hydrogen at the desorption-recombination stage was decreased. The lower pumping speed resulted in a smaller grain size and higher DoA. The coercivity and the remanence of the 200-300 ${\mu}m$ sized HDDR powder increased from 12.7 to 14.6 kOe and from 8.9 to 10.0 kG, respectively. In addition, the remanence was further increased to 11.8 kG by milling the powders down to about 25-90 ${\mu}m$, resulting in $(BH)_{max}$ of 28.8 MGOe.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권3호
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• pp.111-119
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• 2005

In the magnetic fluid linear pump, the pumping forces and pumping speed mainly depend on the current patterns. In this research, a new design to reduce the discontinuities of the pumping forces of the MFLP was studied. Continuous pumping of the newly designed MFLP by using AC current increases pumping efficiency and reduces the pumping force. Forming shapes of the magnetic fluid at the intermediate state were computed and compared to measurement. Since the back flow of the fluid is reduced remarkably, 4 yoke's AC driving is more efficient than 7 yoke's DC driving. The size, weight and pumping discontinuity are also reduced.

• 한국건축시공학회지
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• 제11권4호
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• pp.387-395
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• 2011

In the construction of tall-building, concrete pumping influences the success of the project. In order to establish pumping technology for high speed construction of tall building, study for quantitative evaluation of flow characteristics and pumpability should be conducted. So in this study, the characteristics including the inner pipe pressure, rheological properties of concrete and mortar through the continuous pumping test were evaluated. Then we analyzed the relations between rheological properties and pumpability. In the result of test, there are high correlations between the rheological characteristics which represented by yield stress and plastic viscosity and pressure loss with pipe length. Also, we estimated pressure loss according to conditions of concrete mix and pumping through the evaluation of inner pipe friction.

• Journal of Biosystems Engineering
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• 제14권1호
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• pp.33-40
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• 1989

The flow properties of water added com-cob-mix(CCM) were studied in order to provide basic information for designing its pumping system. For the study, a model system similar to actual situation was constructed. From the experiment, it can be concluded that the flow properties of the water added CCM has close relationship with its moisture content as follows; 1. The pressure drop caused by friction was very low when the moisture content of water added CCM was more than 70%. However, when the moisture content of the material is about 60%, the pressure drop increases up to 10 kPa/m at low pumping speed, and 20 kPa/m at high pumping speed, respectively. 2. The water added CCM having about 65% moisture content showed pseudo-plastic flow characteristics. 3. As the moisture content of the material decreases, the shear stress increases more rapidly than the shear rate does. Finally, below approximately 60% moisture, the shear stress becomes a linear relationship with the shear rate. 4. It was possible to pump the material having the moisture content down to 58% through a pipe having 80 mm diameter by a pump operating at 234 rpm. However, by either increasing the diameter of the pipe or decreasing the pumping speed, it can be possible to pump the material having lower moisture content than 55%.

• 한국진공학회지
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• 제22권2호
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• pp.45-54
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• 2013

맥동관형 크라이오펌프 개발 사업 2단계를 맞아 우성진공(유)을 중심으로 상용화 시제품 개발이 성공적으로 끝나가고 있다. 최종 크라이오펌프 개발품은 흡기구 직경(내경) 16.5 (14) 인치에 질소 배기속도 3,600 L/s 이상을 목표로 하고 있다. 개발품의 성능확인을 위해 우선 몬테카를로 계산을 통해 배기속도를 예측하고 구조설계를 최적화했으며 이를 바탕으로 가공 조립된 크라이오펌프 시제품의 성능을 표준화된 장치에서 표준화된 절차를 통해 평가하여 설계 목표값과 비교했다. 시제품의 질소 배기속도는 4,600 L/s로 측정되어 설계값과 잘 일치하였으며 개발목표를 훨씬 상회하였다.

• 한국정밀공학회지
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• 제12권7호
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• pp.148-157
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• 1995

This study deals with controlling the speed of Hydrostatic Transmission (HST) system throuth the control of pumping stroke of positive displacement pump using high-speed solenoid valve controlled by digital closed loop PWM method. The method which was done in this study is as follows: First, we modified original positive displacement pump and designed pumping stroke control system of HST by using the high-speed solenoid valve. Second, after experimenting static and dynamic characteristics on each signal flow, we identified system parameter of approximated model. Finally, to control the speed of HST, we controlled the angle of the swash plate of positive displacement pump by controlling the pressure in the control cylinder chamber. Test which was carried out in the laboratory shows that transient and steady state response could be improved by PID controller.

• 한국진공학회지
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• 제12권2호
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• pp.86-92
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• 2003

초고진공용으로 시판되고 있는 G-M 냉동기 부착형 크라이오 펌프의 여러 기체에 대한 배기특성을 조사했다. 수소 및 중수소, 헬륨, 알곤, 질소, 일산화탄소의 배기량에 따른 배기속도의 변화를 측정하고 질소의 배기용량을 측정하였으며 그 경향을 이론적으로 분석했다. 또 크라이오펌프로 배기할 때 시스템의 잔류기체 변화에 대해서도 조사했다.