• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.123-128
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• 1998

This study presents the measurement techniques on the periodic fluctuating flow such as the discharge flow of a centrifugal impeller in unstable operating region. During rotating stall, the flow at the exit of a centrifugal compressor impeller fluctuates periodically with lower frequency than that of the blade passing. To observe the blade-to-blade flow characteristics during rotating stall, the phases of all the sampled data sets should be adjusted to those of the reference signals with two processes, in these processes, DPLEAT (Double Phase-Locked Ensemble Averaging Technique) can be used. From these measurement and data processing techniques, the characteristics not only on the blade-to-blade flow with high frequency, but also on the periodic rotating stall flow with low frequency at the centrifugal impeller exit can be clearly observed.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.219-225
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• 2000

Primary function of a centrifugal compressor volute is to serve the flow from the impeller and diffuser to pipe system. But losses in volutes at off-design lead to poor stage efficiency and reduction of operating range. This is largely caused by the interaction between the impeller and volute flow fields. The magnitude of distortion is increased as the operating point is away from the design point and, as a result, the interaction between the impeller and volute is stronger. The objective of present study is to find the characteristics of tile flow in the diffuser and volute of the centrifugal compressor with rectangular cross-sectional volute. The measurements are carried out in two cases with the existence and nonexistence of the volute casing. The detailed pressure is presented by comparing the experimental results obtained at two cases with each others.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.585-588
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• 2002

Pump casing has blockage effects on Impeller flow in a centrifugal pump such that the flow field around volute tongue has quite large change when the impeller rotates. A double suction pump is widely used in industrial world because it has lower NPSH required than a single suction pump. Thus, in this study, the interaction between impeller and volute casing has been investigated by using CFD for a double-suction centrifugal pump. Quasi-steady method and full pump model has been employed for the numerical calculation.

• 한국소음진동공학회논문집
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• 제14권10호
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• pp.939-944
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• 2004

The numerical methods including the performance analysis and the noise prediction of the centrifugal compressor impeller are coupled with the optimization design skill, which consists of response surface method, statistical approach, and genetic algorithm. The flow-field Inside of a centrifugal compressor is obtained numerically by solving Wavier-Stokes equations. and then the propagating noise is estimated from the distributed surface pressure by using Ffowcs Williams-Hawkings formulation. The quadratic response surface model with D-optimal 3-level factorial experimental design points is constructed to optimize the impeller geometry for the advanced centrifugal compressor. The statistical analysis shows that the quadratic model exhibits a reasonable fitting quality resulting in the impeller blade design with high performance and low far-field noise level. The influences of selected design variables, objective functions, and constraints on the impeller performance and the impeller noise are also examined as a result of the optimization process.

• 한국유체기계학회 논문집
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• 제2권1호
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• pp.81-87
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• 1999

This study presents the measurement techniques on the periodic fluctuating flow such as the discharge flow of a centrifugal impeller in an unstable operating region. During rotating stall, the flow at the exit of a centrifugal compressor impeller fluctuates periodically with a lower frequency than that of the blade passing. To observe the blade-to-blade flow characteristics during the rotating stall, the phases of all the sampled data sets should be adjusted to those of the reference signals with two processes, in these processes, DPLEAT (Double Phase-Locked Ensemble Averaging Technique) can be used. From these measurements and data processing techniques, the characteristics illustrated a blade-to-blade flow with high frequency, but also a periodic rotating stall flow with a low frequency at the centrifugal impeller exit which was clearly observed.

• 대한기계학회논문집B
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• 제29권7호
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• pp.784-794
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• 2005

In the very low specific speed range ($n_s=0.24$ < 0.25, non-dimensional), the efficiency of centrifugal pump designed by a conventional method is very low in common. Therefore, positive-displacement pumps have long been used widely. Recently, since the centrifugal pumps are becoming higher in rotational speed and smaller in size, there expects to develop a new centrifugal pump with a high performance to replace the positive-displacement pumps. The purpose of this study is to investigate the internal flow characteristics of a very low specific speed centrifugal pump and to examine the effect of internal flow pattern on pump performance. The results show that the theoretical head definition of semi-open impeller should be revised by the consideration of high slip factor in the semi-open impeller, and the leakage flow through the tip clearance results in a large effect on the impeller internal flow. Strong reverse flow at the outlet of semi-open impeller reduces the absolute tangential velocity considerably, and the decreased absolute tangential velocity increasese the slip factor with the reduction of theoretical head.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.801-806
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• 2001

The objective of present study is to find the interaction between volute and impeller of the centrifugal turbomachinery with rectangular cross-sectional volute. Flow measurement were taken in shrouded impeller with 12 backward type blades by using a five-hole pressure probe. The measurements are carried out in 7 flow rate, respectively. Primary function of a centrifugal turbo machinery volute is to serve the flow from the impeller and diffuser to pipe system. For the off-design conditions, Influence of pressure distortion was shown by these measurements. As a result, It has caused the decrease of total efficiency of centrifugal turbomachinery. We have also taken data to design volute by these measurements.

• Journal of Advanced Marine Engineering and Technology
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• 제28권2호
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• pp.376-381
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• 2004

A rig was constructed to test the performance characteristics and compare the hydraulic forces exerted on a centrifugal type artificial heart impeller. A conventional shaft. seal and bearing system. while driven by a small electric motor. supported the impeller which was separated from the pump casing by a six degree of freedom force transducer (JR3 Ine). Radial (x. y) and axial (z) hydraulic forces were recorded and compared. At physiological operating conditions. the results indicate that the double entry/exit centrifugal pump encounters a smaller radial force and significantly reduced axial thrust. These experimental results are valuable in the design of a magnetic bearing system to suspend the impeller of a centrifugal artificial heart pump. This experimental technique may also be applied to evaluate the required capacity and predict the lifetime of contact bearings in marine pumps.

• 대한기계학회논문집
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• 제19권9호
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• pp.2261-2270
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• 1995

Flow patterns were measured in an unshrouded centrifugal impeller. The flow rate in measurements was fixed at the value corresponding to a nearly zero incidence at the blade inlet. By using a single slanted hot-wire probe and a Kiel probe mounted on the impeller hub disk, the 3-D relative velocities and the rotary stagnation pressures were measured in seven circumferential planes from the inlet to the outlet of the impeller rotating at 700rpm, which diameter is 0.39 meter, and the static pressures and the slip factor at the impeller outlet were calculated from the measured values. From the measured data, the primary/secondary flows, the leakage flows, the wake-jet flows, static pressure distribution on blade surfaces and the wake production mechanism in the impeller passage were investigated.

• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1147-1155
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• 2002

Discharge flows from a centrifugal pump impeller with a specific speed of 150 [rpm, m$^3$/min, m] were experimentally investigated. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow, i.e. without interaction of the impeller and the volute. The unsteady flow was measured at the impeller exit and vaneless diffuser using a hot film probe and a pressure transducer. The flow at impeller exit showed pronounced jet-wake flow patterns. The wake, which was on the suction/hub side at high flow rate, became enlarged pitchwisely on both the hub and the shroud side as the flow rate decreases. The pitchwise non-uniformity of the flow rapidly decreased along the downstream and the non-uniformity almost disappeared at radius ratio of 1.18 for medium flow rate. The mean vaneless diffuser flow was reasonably predicted using a one dimensional analysis when an empirical constant was used to specify the skin friction coefficient. The data can be used for a centrifugal pump impeller design and validation of CFD codes and flow modeling.