The Transition Mechanism of Highly-Loaded LP Turbine Blades

Stieger, R. D.; Hodson, H. P.

doi:10.1115/gt2003-38304

Cited by 55 publications

(28 citation statements)

References 19 publications

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“…7, at t/T 0 = 1 and t/T 0 = 1.125, the boundary layer clearly features short near-wall separation zones at two distinct positions (identified by arrows), already highlighted by reference to the shape-factor and skin-friction plots. As noted earlier, a similar behavior has been observed by Opoka et al 28 and also by Stieger and Hodson,19,20 the latter in experiments for the same blade profile, but at a freestream-turbulence intensity of 0.5%. These features just precede the transition process, which, in the computations, is probably induced by the wake turbulence alone, and this results in the elimination of the separation zone.…”

Section: A Blade T106asupporting

confidence: 73%

“…Lardeau and Leschziner 18 have also used the baseline model, without transition modifications, to compute unsteady wake-blade interaction in a linear cascade of low-pressure turbine blades (denoted T106), investigated experimentally by Stieger and Hodson. 19,20 In this configuration, the inlet freestream-turbulence intensity was only 1%. However, the transition modifications introduced to the baseline model apply only to elevated freestream turbulence at which bypass transition may be assumed to be the primary effective mechanism.…”

Section: Introductionmentioning

confidence: 97%

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Modeling of Wake-Induced Transition in Linear Low-Pressure Turbine Cascades

Lardeau

Leschziner

2006

AIAA Journal

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An unsteady Reynolds-averaged Navier-Stokes (URANS) strategy is applied to the problem of wake-induced transition at high freestream turbulence on the suction side of two blades representative of those used in lowpressure turbines. Experimentally, the blades are arranged in high-aspect-ratio linear cascades, with upstream circular bars generating passing wakes, and two-dimensional flow conditions are, thus, assumed. The strategy combines an explicit algebraic Reynolds-stress turbulence model with transition-specific modifications targeted at capturing the effects of high freestream turbulence and of pretransitional laminar fluctuations. Close attention is paid to numerical accuracy, and grids of up to 140,000 cells are used in combination with 800 time steps per pitchwise traverse to resolve small-scale features in the blade boundary layers that are associated with the unsteady interaction. The computational results demonstrate that the combined model returns a good representation of the response of the suction-side boundary layer to the passing wakes in both blades. Specifically, in the boundary layer of one of the two blades, the wakes are observed to cause a periodic upstream shift in the transition onset and, thus, correspondingly periodic attachment and calming. In the other, no separation occurs, and the wakes are shown to produce a significant periodic reduction in shape factor and increase in skin friction in the blade boundary layer, again as a consequence of the upstream shift in the transition location. Nomenclature a i j = anisotropy tensor C = blade-chord length D = diameter of the bar f ω = wall-damping function H = shape factor, δ 1 /δ 2 k = turbulence energy n * = nondimensional wall distance, u ε n/ν Re t = turbulent Reynolds number, k 2 /νε S i j = strain tensor s = coordinate along the suction side of the blade T = period for one passage of the bar T u = turbulence intensity U b = streamwise velocity of the incoming flow u i u j = stress tensor u ε = Kolmogorov velocity scale, (νε) 1/4 V x = vertical velocity of the moving bar δ 1 = displacement thickness δ 2 = momentum thickness ε = dissipation rate of turbulence energy ν = viscosity ν t = turbulent viscosity i j = vorticity tensor ω = specific dissipation rate, ε/k

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Section: A Blade T106asupporting

confidence: 73%

Section: Introductionmentioning

confidence: 97%

Modeling of Wake-Induced Transition in Linear Low-Pressure Turbine Cascades

Lardeau

Leschziner

2006

AIAA Journal

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“…These features imply that the flow structure observed in Figure 23 could be a turbulent spot or turbulent patch, although it is not clear that the LES and the grid used in this study were capable of capturing any turbulent spot. It is unlikely that vortices shed from the disturbed separation bubble reported by Stiger, Hodson [8] or Sarkar and Voke [11] could be an alternative to account for the emergence of those structures, although much remains unknown. Figure 24 shows the mass-averaged loss coefficients for the steady-state conditions to understand the quantitative impact of the solidity reduction as well as the exit Reynolds number upon the loss coefficients.…”

Section: Loss Distributionsmentioning

confidence: 99%

“…Recently incoming wakes from the preceding blades and vanes are now being regarded as one of the promising remedies to avoid the loss increase induced by the separation or separation bubble. Accordingly, a lot of studies have been made to investigate the interaction of the incoming wakes with the separation bubble on the suction surface of LPT blades and some efforts among them successfully developed blade profiles and bladings for achieving ultra high lift (for example, Hodson et al [1], Halstead et al [2], Shulte and Hodson [3], Howell et al [4], Cardamone et al [5], Haselbach et al [6], Kalitzin et al [7], Stieger and Hodson [8] and Brear and Hodson [9]). Furthermore, a number of numerical works dealing with wake /blade interaction have been also published to date, using RANS [10], LES [11,12] or DNS [7,13].…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Investigations of Wake Passing Effects Upon Aerodynamic Performance of a LP Turbine Linear Cascade With Variable Solidity

Funazaki

Yamada

Ono

et al. 2006

Volume 6: Turbomachinery, Parts a and B

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This paper deals with experimental and numerical studies on the flow field around a low-pressure linear turbine cascade whose solidity is changeable. The purpose of them is to clarify the effect of incoming wakes upon the aerodynamic loss of the cascade that is accompanied with separation on the airfoil suction surface, in particular for low Reynolds number conditions and/or low solidity conditions. Cylindrical bars on the timing belts work as wake generator to emulate wakes that impact the cascade. Pneumatic probe measurement is made to obtain total pressure loss distributions downstream of the cascade. Hot-wire probe measurement is also conducted over the airfoil suction surface. Besides, LES-based numerical simulation is executed to deepen the understanding of the interaction of the incoming wakes with the boundary layer containing separation bubble.

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“…Kalitzin et al (2003) studied the transition mechanism on the blade suction side of a low-pressure turbine (LPT) blade passage subjected to a periodic wake inlet boundary condition using DNS. Stieger and Hodson (2003) also investigated transition on the blade suction side by means of LDA measurements using cylinders as the wake generators. Wissink (2003) has presented DNS results of a highly loaded linear turbine bladerow passage.…”

Section: Introductionmentioning

confidence: 99%