• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.409-417
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• 2009

An investigation of surge inception in a centrifugal compressor was done with measurements of steady and unsteady static pressure. Vaneless diffuser and vaned diffuser were tested. Analyses of the static pressure and the pressure fluctuation showed that stall at the impeller leading edge occurred at first, and then it extended to downstream. In case of the vaneless diffuser, deterioration of the pressure rise in the impeller triggered instability. For the vande diffuser, instability that was generated in the impeller propagated into the vaned diffuser, however the pressure recovery by the vaned diffuser made the operation of the compressor stable at low flow rate.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.134-140
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• 1999

A three-dimensional CSCM upwind flux difference splitting Navier-stokes code with two-equation turbulence models was developed to predict the transonic flows in centrifugal compressor diffuser. The k-$\epsilon$ model of Abe et al. performed well in predicting the pressure distribution in the shock wave/turbulent boundary-layer interaction. Three turbulence models predicted the similar distribution of static pressure through the diffuser and showed a good agreement with the experimental results. The secondary flows in the corner were predicted well by these turbulence models. The pressure increase before the throat of the diffuser vane is important for the overall pressure recovery. As the mass flow rate increased the blockage decreased at the throat. The pressure coefficient distribution through the diffuser depended on the throat blockage not on the rotational speed of the impeller.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2603-2608
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• 2007

Flows in the centrifugal compressor volute with circular cross section are numerically investigated. The computational grid for the calculation utilized a multi-block arrangement to form a butterfly grid and flow calculations are performed using commercial CFD software, CFX-TASCflow. The centrifugal compressor of this study has axial diffuser after radial diffuser because of the shape of inlet duct and installation constraints. Due to this feature the swirling flow pattern is different from the other investigations. The flow inside volute is very complex and three dimensional with strong vortex and recirculation through volute tongue. The calculation results show circumferential variations of the swirl and through flow velocity and pressure distribution. The mechanism deciding flow structure is explained by considering the force balance in volute cross section. And static pressure recovery and total pressure loss are estimated from the calculated results and compared with Japikse model.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.69-75
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• 2001

A new method to calculate the aeroacoustic pressure of a centrifugal fan was developed The fan consists of an impeller, diffuser and circular casing. Due to the high rotating velocity and the small gap between the impeller and diffuser, the centrifugal fan makes very high noise level at BPF and its harmonic frequencies. The aeroacoustic pressure is calculated acoustic analogy In this paper, only dipole term is considered in the equation. The acoustics generated by moving impeller and stationary diffuser is calculated separately. The unsteady flow field data is calculated by the vortex method The predicted acoustic pressure agrees very well to the measured data. The difference of the two is smaller than 3dBA.

• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1728-1738
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• 2001

Measurements have been made in an automotive HVAC b1ower for two different centrifugal fans. This work is directed at improving the performance of a conventional forward-curved centrifugal fan for a given small blower casing. Mean velocities and pressure have been measured using a miniature five-hole probe and a pressure scanning unit connected to an online data acquisition system. First, we obtained the fan performance versus flow rates showing a significant attenuation of unstable nature achieved with the new fan rotor in the surging operation range. Second, aerodynamic characterizations were carried out by investigating the velocity and pressure fields in the casing flow passage for different fan operating conditions. The measurements stowed that performance coefficients are strongly influenced by flow characteristics at the throat region. The main flow features ware common in both fans, but improved performance is achieved with tole new fan rotor, particularly in lower flow rate legions. Based on the measured results, design improvements were carried out in an acceptable operation range, which gave considerable insight into what features of flow behavior ware most important.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1005-1009
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• 2002

The objective of this research is to suggest the noise prediction method of the centrifugal compressor. It is focused on the Blade Passing Frequency (BPF) component which is regarded as the main part of the rotating impeller noise. Euler solver is used to simulate the flow-field of the centrifugal compressor and time-dependent pressure data are calculated to perform the near-field noise prediction by Ffowcs Williams-Hawkings (FW-H) formulation. Indirect Boundary Element Method (IBEM) is applied to consider the noise propagation effect. Pressure fluctuations of the inlet and the outlet in the centrifugal compressor impeller are presented and Sound Pressure Level (SPL) prediction results are compared with the experimental data.

• International Journal of Advanced Culture Technology
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• v.3 no.2
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• pp.58-66
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• 2015

This paper aims to compare the use of Centrifugal Turbine and Tesla Turbine in an application of Organic Rankine Cycle (ORC) Machine using Isopentane as working fluid expanding. The working fluid has boiling point below boiling water and works in low-temperature sources between $80-120^{\circ}C$ which can be produced from waste heat, solar-thermal energy and geothermal energy etc. The experiment on ORC machine reveals that the suitability of high pressure pump for working fluid has result on the efficiency of work. In addition, Thermodynamics theory on P-h diagram also presented the effect of heat sources' temperature and flow rate on any work. Thus, the study and design on ORC machine has to concern mainly on pressure pump, flow rate and optimized temperature. Result experiment and calculate ORC Machine using centrifugal Turbine efficiency better than Tesla turbine 30% but Tesla Turbine is cheaper and easily structure. Further study on the machine can be developed throughout the county due to its low cost and efficiency.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.3
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• pp.132-139
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• 2003

The effects of casing shapes on the performance and the interaction between an impeller and a casing in a small-sized centrifugal compressor are investigated. Especially, numerical analyses are conducted for the centrifugal compressor with both a circular casing and a volute one. The optimum design for each element (i.e., impeller, diffuser and casing) is important to develop an efficient and compact compressor using alternative refrigerant as working fluids. Typical rotating speed of the compressor is in the range of 40,000∼45,000 rpm. The impeller has backswept blades due to tip clearance and a vane diffuser has wedge type. In order to predict the flow pattern inside an entire impeller, vaneless diffuser and casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. For computations of compressible turbulent flow fields, the continuity and time-averaged Navier-Stokes equations are employed. To evaluate the performance of two types of casings, the static pressure recovery and loss coefficients are obtained for various flow rates. Also, static pressure distributions around casings are studied for different casing shapes, which are very important to predict the distribution of radial load. The static pressure around the casing and pressure difference between the inlet and outlet of the compressor are measured for the circular casing.

• The KSFM Journal of Fluid Machinery
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• v.4 no.3 s.12
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• pp.39-45
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• 2001

It is reported recently that the pump head deterioration near the best efficiency point, from single-phase flow to the choke due to air entrainment became less in a screw-type centrifugal pump than in a general centrifugal pump. Moreover, at a narrow tip clearance, the pump head became partially higher in two-phase flow than that in single-phase flow. However, the internal pressure fluctuations on this pump due to air entrainment have not been studied yet. For that reason, we have examined the influences of void fraction, flow coefficient and impeller tip clearance on pressure fluctuations in the casing. The void fraction became larger, the influence of tip clearance on pressure distribution became less.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.5
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• pp.589-596
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• 2006

This study aims to propose a new model axial flow fan which attachs centrifugal blades, and to investigate the effect of centrifugal blades on the performance improvement of new model axial flow fan. A numerical simulation has been conducted using STAR-CD commercial code to solve the three dimensional incompressible Navier-Stokes equation for high Reynolds number $k-{\epsilon}$ turbulent model. Numerical simulation is carried out to investigate the detail phenomenon in the flow field and performance characteristics of new model and normal model fan. Calculation results are compared with normal model's results to investigate which centrifugal blades effect on velocity profile and pressure distribution at various flow field positions. and calculation results show that new model fan can improve the performance of total pressure.