Numerical Investigation of Secondary Flow and Loss Development in a Low-Pressure Turbine Cascade with Divergent Endwalls

Ciorciari, Roberto; Schubert, Tobias; Niehuis, Reinhard

doi:10.3390/ijtpp3010005

Cited by 9 publications

(7 citation statements)

References 17 publications

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“…Contrary to the axially varying effect of unsteady inflow conditions, decreasing the inlet endwall boundary layer height results in a nearly constant reduction of the endwall loss generation, beginning around the midpoint of the blade passage where the secondary flow is formed. Lastly, the effect of increased frontal blade loading leads to a rise in profile losses in the front part of the passage followed by increased secondary losses due to stronger transverse pressure gradients [49].…”

Section: Current Investigations and Resultsmentioning

confidence: 99%

Near-Wall Flow in Turbomachinery Cascades—Results of a German Collaborative Project

Engelmann

Sinkwitz

Mare

et al. 2021

IJTPP

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This article provides a summarizing account of the results obtained in the current collaborative work of four research institutes concerning near-wall flow in turbomachinery. Specific questions regarding the influences of boundary layer development on blades and endwalls as well as loss mechanisms due to secondary flow are investigated. These address skewness, periodical distortion, wake interaction and heat transfer, among others. Several test rigs with modifiable configurations are used for the experimental investigations including an axial low speed compressor, an axial high-speed wind tunnel, and an axial low-speed turbine. Approved stationary and time resolving measurements techniques are applied in combination with custom hot-film sensor-arrays. The experiments are complemented by URANS simulations, and one group focusses on turbulence-resolving simulations to elucidate the specific impact of rotation. Juxtaposing and interlacing their results the four groups provide a broad picture of the underlying phenomena, ranging from compressors to turbines, from isothermal to non-adiabatic, and from incompressible to compressible flows.

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Section: Current Investigations and Resultsmentioning

confidence: 99%

Near-Wall Flow in Turbomachinery Cascades—Results of a German Collaborative Project

Engelmann

Sinkwitz

Mare

et al. 2021

IJTPP

Self Cite

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“…Moreover, the pressure surface separation does not significantly alter the total number of losses but rather redistributes them throughout the blade passage. In addition, other researchers [1,[14][15][16][17][18] such as Lin et al [17] investigated the mechanism of local entropy generation to understand losses in compressible flow through a high-pressure single-entry turbine. They concluded that the entropy generation rate, which is a useful parameter for calculating local and overall losses, is influenced by two main parameters: viscous irreversibility and heat transfer irreversibility.…”

Section: Introductionmentioning

confidence: 99%

“…The use of double-entry turbines [20][21][22][23][24][25][26][27][28][29], especially with asymmetric volute in secondary flow research, is limited compared to single-entry turbines, which have received extensive attention [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. In addition, the influence of nozzle vanes on the secondary flow development and centrifugal pressure head did not achieve much attention in the public domain.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Secondary Flow Characteristics in Mixed-Flow Turbine between Nozzleless and Symmetric Nozzle Vane Angles under Steady-State Flow at Full Admission

Jama’a,

Gurunathan,

Botas

et al. 2023

Energies

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In industrial applications, radial or mixed-flow turbines are frequently used in energy recovery systems, small turbines for producing power, and turbochargers. The implementation of radial or mixed-flow turbines helps to maintain high efficiency at a large range of pressure ratios by reducing the overall turbine losses and secondary flow losses. Numerous findings on secondary flow development research adopting double-entry turbines can be obtained in the public domain, except asymmetric volute, which is less well-researched. The focus of the present work is to investigate the evolution of secondary flows and their losses in a mixed-flow turbine used in an asymmetric volute turbine, by employing an experimentally validated three-dimensional computational fluid dynamics (CFD). The flow topology is analyzed to explain the formation and evolution of flow separations at the pressure, suction, and hub surfaces. As the opening angle of the nozzle vane increases, the incidence angle falls into the positive range while the maximum pressure difference between the shroud and hub decreases by about 40%. The results also show that the development of secondary flow accounts for the majority of losses and induced the centrifugal pressure head influence. The presence of symmetric nozzle vanes in both large and small scrolls is also found to have a significant detrimental effect on the turbine efficiency, which is 4% lower than the nozzleless case. Furthermore, significant flow separation is observed in the symmetrical nozzle vane configuration as opposed to that of nozzleless. In addition, the centrifugal pressure head indicated by the maximum pressure difference between the hub and shroud influences the overall turbine efficiency, as the symmetrical nozzle vane arrangement is introduced with two different turbine rotational speeds of 30 K rpm and 48 K rpm.

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“…Flow visualization studies by Goldstein and Spores [15], Langston et al [16], Sieverding and Bosche [17], and Wang et al [18] have indicated that the pressure-side leg of the horseshoe vortex is a dominant constituent of the passage vortex system. Ciorciar et al investigated the effect of periodically incoming wakes on the axial loss development [19]. They found higher front-loading results in a lower intensity of the secondary flow downstream of the trailing edge.…”

Section: Introductionmentioning

confidence: 99%

Radial Gradient Pressure Effects on Flow Behavior in a Dual Volute Turbocharger Turbine

2018

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The pressure gradient in the dual volute radial turbocharger turbines is the primary source of the vortices’ formation in rotor passages. The effects of the upstream non-uniform flow conditions on the development of secondary flows are not well known. In this study, the effect of highly skewed and non-uniform mass flow on the secondary vortices in different admission cases in a dual entry turbine was investigated using CFD modeling. The results agree well with the experiment, and show that increasing the inequality of the pressure between the entries leads to a reduction in the turbine’s performance. Some useful energy dissipates due to mixing the flows of the entries. Isolating the rotor sectors in the tongues region was applied with the purpose of limiting the mixing. Also, the vortices’ behavior in the rotor passages with different surface pressure ratios for the passage sides were investigated for both equal and partial admission. The surface pressure of the airfoil pressure side was more effective on the tip and trailing edge vortex than the suction side, while the leading-edge root vortex did not change by any variation in the surface pressure ratio. The vortices’ center location shifted with the pressure variation, and consequently, by decreasing the pressure level, the center of the tip vorticity turned to the upstream sections, and the leading-edge root vortex center moved closer to the pressure side.

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Numerical Investigation of Secondary Flow and Loss Development in a Low-Pressure Turbine Cascade with Divergent Endwalls

Cited by 9 publications

References 17 publications

Near-Wall Flow in Turbomachinery Cascades—Results of a German Collaborative Project

Near-Wall Flow in Turbomachinery Cascades—Results of a German Collaborative Project

Comparison of Secondary Flow Characteristics in Mixed-Flow Turbine between Nozzleless and Symmetric Nozzle Vane Angles under Steady-State Flow at Full Admission

Radial Gradient Pressure Effects on Flow Behavior in a Dual Volute Turbocharger Turbine

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