• The KSFM Journal of Fluid Machinery
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• v.11 no.2
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• pp.55-63
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• 2008

An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30-50% of the shaft work input to the compressor stage, and for energy efficiency it is important to recover as much of this as possible. This is the function of the diffuser which follows the impeller. The purpose of this study is to investigate the sensitivity of how compressor performances changes as vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and its results were compared. First vaned diffuser type is based on NACA airfoil and second is channel diffuser and third is conformal transformation of NACA65(4A10)06 airfoil. Mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. And CFD analyses have been done for comparison and detailed interior flow pattern study. NACA65(4A10)06 airfoil showed the widest operating range and higher pressure characteristics than the others.

• Food Science and Preservation
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• v.6 no.4
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• pp.424-428
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• 1999

The performance of a 30K polysulfone membrane for clarification of depectinized peach juice was studied Ultrafiltration of peach juice could minimize to loss of flavor and many compounds and was expected to effectively remove precipitation and suspended solid. The results showed that permeate flux increased with the increase of operating pressure and temperature. The permeate flux declined continuously as the process time increased. The values of soluble solid and titratable acidity of permeate were decreased or were at the same level, the turbidity was largely decreased. Total resistance decreased with lower temperature and lower pressure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.12
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• pp.1031-1038
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• 2002

The effects of casing shape on the performance and interaction between the impeller and casing in a small-size turbo-compressor are investigated. Numerical analysis is conducted for the compressor with circular and single volute casings from inlet to discharge nozzle. In order to predict the flow pattern inside the entire impeller, vaneless diffuer and casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. For compressible turbulent flow fields, the continuity and three-dimensional time-averaged Wavier-Stokes equations are employed. To evaluate the performance of two types of casings, the static pressure and loss coefficients are obtained with 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. To prove the accuracy of numerical results, measurements of static pressure around casing and pressure difference between the inlet and outlet of the compressor are peformed for the circular casing. Comparisons of these results between the experimental and numerical analyses are conducted, and reasonable agreement is obtained.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.17-25
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• 2019

An intake of Aircraft becomes S-shaped geometry due to spatial limitation or procuring survivability. But curvature of the S-shaped geometry makes secondary flow or flow separation which is the cause of non-uniform pressure distribution. In this study, boundary layer suction is applied to RAE M 2129 S-Duct by attaching sub duct. Design variable is suction location and angle. A mass flow rate drawn out by suction at the sub duct outlet is constant over every model. A grid dependency test was conducted to verify validity of computation. The comparison among the CFD (Computation Fluid Dynamics), ARA experimental result, and ARA computation result of non-dimensional pressure distribution on the Port side and Starboard Side confirmed the validity of CFD. In this study, Distortion Coefficient was used for evaluating aerodynamic performance of S-Duct. The analysis, which was about flow separation, vortex, mass flow rate distribution, and pressure distribution were also investigated. Maximum 26.14% reduction in Distortion Coefficient was verified.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.8
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• pp.669-675
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• 2015

In this study, we investigate the performance variations of an automotive turbocharger compressor with respect to the height variation of the recirculating casing treatment (RCT). We use three RCT heights, namely 1.2 mm, 1.5 mm, and 1.8 mm. We vary the compressor speed from 90,000 to 150,000 rpm, and the flow rate from 0.015 kg/s to 0.08 kg/s. The calculation results of the total pressure ratio and isentropic efficiency showed good agreement with the performance data provided by the manufacturer within a 0.7 percent error. The results showed that the RCT heights of 1.2 mm, 1.8 mm, and 1.5 mm, in that order, exhibited a more uniform pressure distribution, higher pressure ratio, and wider operational range. As the number of revolutions per minute increased, we obtained typical characteristics of a compressor map having a narrower operational range in the region of higher pressure ratio.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.61-69
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• 2013

Numerical simulations have been performed for assessment of compressibility correction of two-equation turbulent models suitable for large scale separation flows perturbed by a pintle strokes. Two-equation turbulence models, the low Reynolds k-${\varepsilon}$ and the k-${\omega}$ SST models with or without compressibility correction proposed by Wilcox and Sarkar are evaluated. The detail flow structures are observed and static pressures along nozzle wall are compared with experimental results. Mach disk location and pressure recovery profiles in flow separation region are noticeably distinct between turbulent models of k-${\varepsilon}$ and k-${\omega}$ SST. The compressible effect corrections to those models improve resolving of separation flow behaviors. The compressibility corrections to k-${\varepsilon}$ model have provided very comparable results with test data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.4
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• pp.79-84
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• 2005

An experimental investigation for impingement of under-expanded, axisymmetric jets on a flat plate has been conducted, and the surface pressure, the adiabatic wall temperature distributions on the plate have been measured in detail. For the explanation on the wall temperature distributions, the total temperature distributions along a free jet have also been measured with total temperature probes. In this study, the under-expansion ratio and the nozzle-to-plate distance have been considered as experimental parameters. Depending on nozzle-to-plate distances, different distributions of adiabatic wall temperature are shown by the energy separation at a jet edge and a impinged surface. Also, the recovery factor on a stagnation point decreases significantly due to the isolation of fluid particles in a central region.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.393-396
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• 2006

This paper presents the characteristics of the performance parameters of dual mode(ramjet-scramjet combined) engine, inlet and combustor for wide range of flight Mach number, resulted from the analysis of its operating limitations. The transitional-critical flight Mach number from ramjet to scramjet and the performance of two types of combustors, such as constant pressure- and constant area- combustor, are conceptually evaluated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.141-146
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• 2005

This paper presents a theoretical analysis of a ramjet and scramjet engine according to flight Mach numbers. The main objective of this study is to give physical understanding on the performance parameters and to provide a more unified treatment of the fundamentals of ramjet and scramjet propulsion, mainly based on analytical methods. The effects of flight Mach number, inlet characteristics, and combustion on the performance of ramjet and scramjet are analysed. The cycle analysis are conducted on both combustors with constant pressure and with constant cross-section area, on which comparisons are made. Also the optimal Mach number at the entry of the combustor is studied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.11
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• pp.727-736
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• 2016

In this study, a high-pressure multistage pump used in the combined cycle power plants is analyzed. The pump performance characteristics (differential head and efficiency) are numerically analyzed for different shapes of the radial diffuser. The design variables selected for the radial diffuser are, number of vanes, diameter ratio ($D_4/D_3$), return channel outlet angle(${\alpha}_6$), and pressure recovery factor ($C_p$). The numerical analysis results showed that the differential head and efficiency are the highest when the diameter ratio is the highest. Further, it was observed that the differential head was lower when the return channel outlet angle was $60^{\circ}$ than when it was $90^{\circ}$, because of pre-swirl at the diffuser outlet.