An Asymptotic Analysis of Mixing Loss

Fritsch, G.; Giles, Michael B.

doi:10.1115/93-gt-345

Cited by 12 publications

(10 citation statements)

References 5 publications

(5 reference statements)

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“…Although, at the large gap, both approaches give almost identical answers, 1 per cent drop in the efficiency was produced by the mixing-plane treatment at the small gap. The feature that the mixingplane treatment overpredicts stage losses in comparison with unsteady calculations was also observed by Fritsch and Giles [16]. The 1 per cent drop in stage efficiency is quite significant and therefore care must be taken when using the mixing-plane approach at small inter-row gaps.…”

Section: Effect Of Axial Gap On Turbine Stage Performancessupporting

confidence: 60%

Three-dimensional unsteady Navier—Stokes analysis of stator—rotor interaction in axial-flow turbines

2000

Proceedings of the Institution of Mechanical Engineers, Part A:

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A three-dimensional full Navier-Stokes method is developed and applied to calculations of unsteady flows through multiple blade rows in axial-flow turbomachinery. The solver adopts the cellcentred finite volume discretization and the four-stage Runge-Kutta time-marching scheme. Unsteady calculations are effectively accelerated by using a time-consistent multi-grid technique, resulting in a speed-up by a factor of 10–20 with adequate temporal accuracy. The computational efficiency and validity of the present multi-grid technique are illustrated by comparisons with the results of the conventional dual time-stepping scheme. Calculated unsteady pressures on blade surfaces for a turbine stage performances at different stator-rotor axial gaps reveals a marked three-dimensional behaviour of the interaction between incoming wakes and rotor passage-vortex structures. The time-averaged losses from unsteady calculations show a noticeable spanwise redistribution compared with the steady results. Two dimensional and three-dimensional calculations indicate opposite trends in stage efficiency variation when the stator—rotor gap is reduced.

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Section: Effect Of Axial Gap On Turbine Stage Performancessupporting

confidence: 60%

Three-dimensional unsteady Navier—Stokes analysis of stator—rotor interaction in axial-flow turbines

2000

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…As showed by Firtsch and Giles [9] entropy is the appropriate variable to measure any irreversibility occurring in a fluid process which, in fact, can present a complex variety of phenomena in case of turbomachinery flows. Indeed entropy can take into account the effect of heat transfer, the density variations associated with entropy waves, and the effect of pressure waves (i.e.…”

Section: Aerodynamic Losses and Entropy Generation By Viscous Flowsmentioning

confidence: 99%

Profile Loss Coefficient Definitions Revisited

Calzada

2011

International Journal of Turbo and Jet Engines

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A critical and integrated view on the profile loss coefficient definitions commonly used in turbomachinery is offered. By solving the compressible flow equations in boundary layers (characterized by their integral parameters) mixing at constant area the dependence of different loss coefficients (total pressure loss and kinetic energy loss coefficient, KSI) on the Mach number and boundary layer characteristics is investigated. KSI appears as the best parameter to measure the merit of the process since it is fundamentally independent of Mach number and only dependent on the boundary layer parameters. Results from expressions obtained by different formulations and levels of approximations are compared with the solution of the full set of compressible equations. KSI estimated by the expression 2Â=.t ı / C .ı =t/ 2 is identified as the best parameter of merit to be used as profile loss coefficient. Additionally a comparison between losses from boundary layers discharging into constant area and discharging into constant pressure is given and the relevance played by the shape parameter, H , in the latter case is remarked.

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“…However, Fritsch and Giles [3] have demonstrated that a large entropy rise is produced in the mixing plane because of the averaging process. Another approach, of using fully unsteady methods, has been pioneered by Rai [4].…”

Section: Introductionmentioning

confidence: 98%

“…One approach described by Dawes [1] and Denton [2] in 1992, uses the mixing plane to communicate flow information across blade rows. However, Fritsch and Giles [3] have demonstrated that a large entropy rise is produced in the mixing plane because of the averaging process. Another approach, of using fully unsteady methods, has been pioneered by Rai [4].…”

Section: Introductionmentioning

confidence: 99%

Reduced passage-averaged N-S equations of the threedimensional flowfield in a multi-stage environment

Gao¹,

Liu³

et al. 2007

Proceedings of the Institution of Mechanical Engineers, Part G:

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The passage-averaged flow model was proved to be a more rigorous and complicated model than the mixing plane model in the flow prediction of multi-stage turbomachinery using the steady-state method. In the present work, the novel time-and passage-averaging operators are applied and a reduced average-passage N-S equation system is derived, in which the bodyforce and the blockage factor are eliminated. In order to consider the time-averaged effect of the periodic unsteadiness, a semi-empirical model with the interface approach is employed to evaluate the deterministic stresses instead of overlapping domain approach. Finally, two computations for a tested centrifugal compressor are performed and compared with the corresponding experimental data to verify the reduced passage-averaged equation system and the corresponding numerical method: one is the solution of the reduced passage-averaged equations with a semiempirical model and; the other is that of the steady Navier-Stokes equations with the mixing plane.

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An Asymptotic Analysis of Mixing Loss

Cited by 12 publications

References 5 publications

Three-dimensional unsteady Navier—Stokes analysis of stator—rotor interaction in axial-flow turbines

Three-dimensional unsteady Navier—Stokes analysis of stator—rotor interaction in axial-flow turbines

Profile Loss Coefficient Definitions Revisited

Reduced passage-averaged N-S equations of the threedimensional flowfield in a multi-stage environment

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