Numerical Investigation of the Influence of the Tip Clearance on Wake Formation Inside a Radial Impeller

Weiß, Carsten; Grates, Daniel; Thermann, Hans; Niehuis, Reinhard

doi:10.1115/gt2003-38279

Cited by 15 publications

(12 citation statements)

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“…As for "Radiver", the distance between wedge diffuser inlet and impeller outlet is adjustable, here we chose the results of case "rle / rte = 1.04" for validation as this ratio almost equals to the ratio of the investigated pipe diffuser in this paper (rte and rle stands for the radius of impeller trailing edge and diffuser leading edge, respectively). Detailed introduction about the compressor "Radiver" and related experimental information could be found easily in published literatures (Ziegler et al 2002, Weiß et al 2003.…”

Section: Fig 6 Distribution Of Y+ On All Solid Wallsmentioning

confidence: 99%

Flow Characteristics of a Pipe Diffuser for Centrifugal Compressors

Sun¹,

Zheng²,

Linghu³

2017

JAFM

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The pipe diffuser, an efficient kind of radial bladed diffuser, is widely used in centrifugal compressors for gas turbine engines. This paper investigates flow characteristics of a pipe diffuser for centrifugal compressors by solving three-dimensional Reynolds-averaged Navier-Stokes equations. The results show that the pipe diffuser is adaptable to high Mach number incoming flows, and its unique leading edge could uniform the flow distortion. Numerical analysis indicates that the choke in pipe diffuser occurs suddenly, which leads to the dramatically steep performance curves near choke condition. Besides, it is found that the first half flow passage is particularly important to the pipe diffuser performance as it influences the choking behavior, the static pressure distribution, and the matching, so more attention should be paid to this region when designing or optimizing a pipe diffuser. Two counter-rotating vortices generated in the diffuser inlet region are captured by numerical simulation, and they can exist in the downstream of the diffuser passage. More detailed analysis show that these two vortices dominate the flow structure in the whole diffuser passage by shifting flow to certain positions and forming high-momentum flow cells and wake flow cells. The leading edge formed by the intersection of adjacent diffuser passages significantly affects this pair of vortices. In addition, these two vortices also affect the flow separation in pipe diffuser flow passages, they suppress separation near the front wall and back wall while facilitate separation at center locations. Therefore, it is recommended to design the leading edge of the pipe diffuser carefully to control the vortices and obtain a better flow field.

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Section: Fig 6 Distribution Of Y+ On All Solid Wallsmentioning

confidence: 99%

Flow Characteristics of a Pipe Diffuser for Centrifugal Compressors

Sun¹,

Zheng²,

Linghu³

2017

JAFM

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“…To the authors' knowledge, only two published numerical studies have considered the Radiver test case: Weiß et al [18] computed the vaneless configuration; and Boncinelli et al [19] analyzed the impeller-diffuser interaction.…”

Section: Verification and Validation For The Radiver Test Casementioning

confidence: 99%

“…, the following experimental uncertainties must be considered: (i) pressure measurements are accurate to 0.2 %; (ii) temperature measurements are accurate to 0.3 %, combining this with the accuracy of pressure measurement, uncertainty analysis yields an accuracy of 0.8 efficiency points for the isentropic efficiency; (iii) L2F measurements are accurate to about 2 % for velocities and 3 • for flow angles.For the geometry modeling, the bulb upstream of the rotor was partially included: Weiß et al[18] report a negligible influence of the inlet duct, and available experimental results suggest that the corresponding pressure loss is less than measurement accuracy. Although results are only extracted just aft of the rotor, the vaneless diffuser was modeled up to a…”

mentioning

confidence: 99%

Assessing Rotation/Curvature Corrections to Eddy-Viscosity Models in the Calculations of Centrifugal-Compressor Flows

Dufour

Cazalbou

Carbonneau

et al. 2008

Journal of Fluids Engineering

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Rotation and curvature (RC) effects on turbulence are expected to impact losses and flow structure in turbomachines. This paper examines two recent eddy-viscosity-model corrections devised to account for these effects: the Spalart and Shur (1997, “On the Sensitization of Turbulence Models to Rotation and Curvature,” Aerosp. Sci. Technol., 1(5), pp. 297–302) correction to the model of Spalart and Allmaras (1994, “A One-Equation Turbulence Model for Aerodynamic Flows,” Rech. Aerosp., 1, pp. 5–21) and the correction of Cazalbou et al. (2005, “Two-Equation Modeling of Turbulent Rotating Flows,” Phys. Fluids., 17, p. 055110) to the (k,ϵ) model. The method of verification and validation is applied to assess the impact of these corrections on the computation of a centrifugal-compressor test case. First, a review of RC effects on turbulence as they apply to centrifugal compressors is made. The two corrected models are then presented. Second, the Radiver open test case (Ziegler K. U., Gallus, H. E., and Niehuis R., 2003, “A Study on Impeller Diffuser Interaction Part 1: Influence on the Performance,” ASME J. Turbomach, 125, pp. 173–182) is used as a basis for the assessment of the two corrections. After a physical-consistency analysis, the Richardson extrapolation is applied to quantify the numerical errors involved in all the calculations. Finally, experimental data are used to perform validation for both global and local predictions. The consistency analysis shows that both corrections lead to significant changes in the turbulent field, in perfect agreement with the underlying theoretical considerations. The uncertainty analysis shows that the predictions of the global performances are more sensitive to grid refinement than they are to RC turbulence modeling. However, the opposite conclusion is drawn with regard to the prediction of some local flow properties: Improvements are obtained with the RC corrections, the best results being observed for the RC-corrected (k,ϵ) model.

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“…The extension of the low meridional velocity region along the axial direction away from the shroud was overpredicted by CFD due to a higherintensity tip clearance flow, which was caused by a uniform tip clearance. Improved results may be obtained by applying a nonuniform tip clearance height (0.7-0.48 mm) [13].…”

Section: Validation For Uniform Tip Clearancementioning

confidence: 99%

“…The influence of the tip clearance flow on the performance and flow structure in centrifugal compressors has been studied by many researchers [4][5][6][7][8][9][10][11][12][13][14]. In previous studies, it was found that the swirling flows and vortex motions within unshrouded impellers are sensitive to the tip clearance flow.…”

Section: Introductionmentioning

confidence: 99%

Effects of a Nonuniform Tip Clearance Profile on the Performance and Flow Field in a Centrifugal Compressor

Jung

Choi

et al. 2012

International Journal of Rotating Machinery

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This paper presents a numerical investigation of the effects of a nonuniform tip clearance profile on the performance and flow field in a centrifugal compressor with a vaneless diffuser. This study focuses in particular on the magnitude and location of the wake. Six impellers with different tip clearance profiles were tested in the flow simulations. The accuracy of the numerical simulations was assessed by comparing the experimental data with the computational results for a system characterized by the original tip clearance. Although the performance improved for low tip clearances, a low tip clearance at the trailing edge improved the compressor performance more significantly than a low tip clearance at the leading edge. The flow field calculated for a system characterized by a low tip clearance at the trailing edge produced a more uniform velocity distribution both in the circumferential and in the axial directions at the impeller exit because the wake magnitude was reduced. As a consequence, this impeller provided a better potential for diffusion processes inside a vaneless diffuser.

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Numerical Investigation of the Influence of the Tip Clearance on Wake Formation Inside a Radial Impeller

Cited by 15 publications

References 0 publications

Flow Characteristics of a Pipe Diffuser for Centrifugal Compressors

Flow Characteristics of a Pipe Diffuser for Centrifugal Compressors

Assessing Rotation/Curvature Corrections to Eddy-Viscosity Models in the Calculations of Centrifugal-Compressor Flows

Effects of a Nonuniform Tip Clearance Profile on the Performance and Flow Field in a Centrifugal Compressor

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