403 Turbulence Measurements of a Lateral Vortex Interacting with a Wall Boundary Layer

Premixed combustion of hydrogen-rich mixtures involves the risk of flame flashback through wall boundary layers. For laminar flow conditions, the flashback mechanism is well understood and is usually correlated by a critical velocity gradient at the wall. Turbulent transport inside the boundary layer considerably increases the flashback propensity. Only tube burner setups have been investigated in the past and thus turbulent flashback limits were only derived for a fully-developed Blasius wall friction profile. For turbulent flows, details of the flame propagation in proximity to the wall remain unclear. This paper presents results from a new experimental combustion rig, apt for detailed optical investigations of flame flashbacks in a turbulent wall boundary layer developing on a flat plate and being subject to an adjustable pressure gradient. Turbulent flashback limits are derived from the observed flame position inside the measurement section. The fuels investigated cover mixtures of methane, hydrogen and air at various mixing ratios. The associated wall friction distributions are determined by RANS computations of the flow inside the measurement section with fully resolved boundary layers. Consequently, the interaction between flame back pressure and incoming flow is not taken into account explicitly, in accordance with the evaluation procedure used for tube burner experiments. The results are compared to literature values and the critical gradient concept is reviewed in light of the new data.

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Wall Boundary Layers in Turbomachines

Journal of Mechanical Engineering Science ◽

10.1243/jmes_jour_1972_014_052_02 ◽

1972 ◽

Vol 14 (6) ◽

pp. 411-423 ◽

Cited By ~ 2

Author(s):

H. Marsh ◽

J. H. Horlock

Keyword(s):

Boundary Layer ◽

Integral Equations ◽

Cross Flow ◽

Inlet Guide Vanes ◽

Wall Boundary Layer ◽

Wall Boundary ◽

Alternative Approach ◽

Flow Through ◽

The Many ◽

Momentum Integral

Equations for the passage-averaged flow in a cascade are used to derive the momentum integral equations governing the development of the wall boundary layer in turbomachines. Several existing methods of analysis are discussed and an alternative approach is given which is based on the passage-averaged momentum integral equations. The analysis leads to an anomaly in the prediction of the cross flow and to avoid this it is suggested that for the many-bladed cascade there should be a variation of the blade force through the boundary layer. This variation of the blade force can be included in the analysis as a force deficit integral. The growth of the wall boundary layer has been calculated by four methods and the predictions are compared with two sets of published experimental results for flow through inlet guide vanes.

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An Axial Compressor End-Wall Boundary Layer Calculation Method

Journal of Engineering for Power ◽

10.1115/1.3446474 ◽

1979 ◽

Vol 101 (2) ◽

pp. 233-245 ◽

Cited By ~ 5

Author(s):

J. De Ruyck ◽

C. Hirsch ◽

P. Kool

Keyword(s):

Experimental Data ◽

Boundary Layer ◽

Velocity Profile ◽

Three Dimensional ◽

Axial Compressor ◽

Tip Clearance ◽

Wall Region ◽

Wall Boundary Layer ◽

Wall Boundary ◽

End Wall

An axial compressor end-wall boundary layer theory which requires the introduction of three-dimensional velocity profile models is described. The method is based on pitch-averaged boundary layer equations and contains blade force-defect terms for which a new expression in function of transverse momentum thickness is introduced. In presence of tip clearance a component of the defect force proportional to the clearance over blade height ratio is also introduced. In this way two constants enter the model. It is also shown that all three-dimensional velocity profile models present inherent limitations with regard to the range of boundary layer momentum thicknesses they are able to represent. Therefore a new heuristic velocity profile model is introduced, giving higher flexibility. The end-wall boundary layer calculation allows a correction of the efficiency due to end-wall losses as well as calculation of blockage. The two constants entering the model are calibrated and compared with experimental data allowing a good prediction of overall efficiency including clearance effects and aspect ratio. Besides, the method allows a prediction of radial distribution of velocities and flow angles including the end-wall region and examples are shown compared to experimental data.

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A model of the wall boundary layer for ducted propellers

10.2514/6.1987-2742 ◽

1987 ◽

Cited By ~ 1

Author(s):

WALTER EVERSMAN ◽

WILLI MOEHRING

Keyword(s):

Boundary Layer ◽

Wall Boundary Layer ◽

Wall Boundary ◽

Ducted Propellers

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LES and RANS Analysis of the End-Wall Flow in a Linear LPT Cascade: Part I — Flow and Secondary Vorticity Fields Under Varying Inlet Condition

Volume 2B: Turbomachinery ◽

10.1115/gt2018-76233 ◽

2018 ◽

Cited By ~ 6

Author(s):

R. Pichler ◽

Yaomin Zhao ◽

R. D. Sandberg ◽

V. Michelassi ◽

R. Pacciani ◽

...

Keyword(s):

Boundary Layer ◽

Secondary Flow ◽

Flow Characteristics ◽

Flow Region ◽

Secondary Flows ◽

Wall Boundary Layer ◽

Wall Boundary ◽

Wall Flow ◽

End Wall ◽

The Impact

In low-pressure-turbines (LPT) around 60–70% of losses are generated away from end-walls, while the remaining 30–40% is controlled by the interaction of the blade profile with the end-wall boundary layer. Experimental and numerical studies have shown how the strength and penetration of the secondary flow depends on the characteristics of the incoming end-wall boundary layer. Experimental techniques did shed light on the mechanism that controls the growth of the secondary vortices, and scale-resolving CFD allowed to dive deep into the details of the vorticity generation. Along these lines, this paper discusses the end-wall flow characteristics of the T106 LPT profile at Re = 120K and M = 0.59 by benchmarking with experiments and investigating the impact of the incoming boundary layer state. The simulations are carried out with proven Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulation (LES) solvers to determine if Reynolds Averaged models can capture the relevant flow details with enough accuracy to drive the design of this flow region. Part I of the paper focuses on the critical grid needs to ensure accurate LES, and on the analysis of the overall time averaged flow field and comparison between RANS, LES and measurements when available. In particular, the growth of secondary flow features, the trace and strength of the secondary vortex system, its impact on the blade load variation along the span and end-wall flow visualizations are analysed. The ability of LES and RANS to accurately predict the secondary flows is discussed together with the implications this has on design.

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