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Research Papers: Gas Turbines: Turbomachinery

An Experimentally Derived Model to Predict the Water Film in a Compressor Cascade With Droplet Laden Flow

[+] Author and Article Information
Niklas Neupert

Laboratory for Tubomachinery,
Department of Power Engineering,
Helmut Schmidt University,
Hamburg D-22043, Germany
e-mail: Niklas.Neupert@gmx.de

Janneck Christoph Harbeck

Laboratory for Turbomachinery,
Department of Power Engineering,
Helmut Schmidt University,
Hamburg D-22043, Germany
e-mail: Harbeck@hsu-hh.de

Franz Joos

Laboratory for Tubomachinery,
Department of Power Engineering,
Helmut Schmidt University,
Hamburg D-22043, Germany
e-mail: Joos@hsu-hh.de

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received September 14, 2017; final manuscript received October 9, 2017; published online June 5, 2019. Assoc. Editor: David Wisler.

J. Eng. Gas Turbines Power 141(9), 092601 (Jun 05, 2019) (10 pages) Paper No: GTP-17-1512; doi: 10.1115/1.4043690 History: Received September 14, 2017; Revised October 09, 2017

In recent years, overspray fogging has become a powerful means for power augmentation of industrial gas turbines. Despite the positive thermodynamic effect on the cycle, droplets entering the compressor increase the risk of water droplet erosion and deposition of water on the blades leading to an increase of required torque and profile loss. Due to this, detailed information about the structure and the amount of water on the surface is key for compressor performance. Experiments were conducted with a droplet laden flow in a transonic compressor cascade focusing on the film formed by the deposited water. Two approaches were taken. In the first approach, the film thickness on the blade was directly measured using white light interferometry. Due to significant distortion of the flow caused by the measurement system, a transfer of the measured film thickness to the undisturbed case is not possible. Therefore, a film model is adapted to describe the film flow in terms of height averaged film parameters. In the second approach, experiments were conducted in an undisturbed cascade setup and the water film pattern was measured using a nonintrusive quantitative image processing tool. Utilizing the measured flow pattern in combination with findings from the literature, the rivulet flow structure is resolved. From continuity of the water flow, a film thickness is derived showing good agreement with the previously calculated results. Using both approaches, a three-dimensional (3D) reconstruction of the water film pattern is created giving first experimental results of the film forming on stationary compressor blades under overspray fogging conditions.

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References

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Figures

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Fig. 1

OCS profile under droplet laden flow at design inflow Mach number and incidence angle α = 4 deg

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Fig. 2

Definition of the impact region

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Fig. 3

Forces acting on a shear driven rivulet [17]

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Fig. 4

Assumed shape of rivulets for different rivulet widths

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Fig. 5

Velocity profiles for varying θ: linear velocity profile (dotted), analytical velocity profile (dashed), and numerically calculated velocity profile (solid)

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Fig. 6

Sketch of the test rig

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Fig. 7

Film thickness measurement setup

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Fig. 8

Local film thickness at α = −3 deg (OCS, circle) and α = −4 deg (MCS, triangle) at v1 = 80–160 m/s and spray A

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Fig. 9

Influences on the film movement on the suction side in measurement setup (gray) and in clean condition (black). For the measurement setup, the boundary conditions were set to the maximum possible inlet velocity v1 = 160 m/s and α = 0 deg, and for the clean condition, the design case of the cascade v1 = 290 m/s and α = 0 deg.

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Fig. 10

Nondimensionalized film height H+ for v1 = 80–160 m/s, α = −4 deg (MCS, triangle) and α = −3 deg (OCS, circles) on the suction side for spray A (open symbols) and spray B (filled symbols). The lines represent the calculated results for ηcoll = 1.

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Fig. 11

Comparison of different functions for ηimp for the OCS profile at v1 = 100 m/s, spray A and α = −3 deg

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Fig. 12

Comparison of different functions for ηdep for the OCS profile at v1 = 100 m/s, spray A and α = −3 deg

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Fig. 13

Calculated film thickness for the clean cascade flow for the OCS (black) and MCS (gray) profile at design Mach number, spray A and α = 0 deg (solid) and α = 4 deg (dashed)

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Fig. 14

Detached flow on suction side of MCS under design Mach number, spray A and α = 4 deg

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Fig. 15

Processed images for α = −4 deg, 0 deg, and 4 deg (upper left), the histogram curves for the relative film breakup position x/c (upper right), the rivulet width b (lower left), and the fraction of wetted surface in the rivulet region F (lower right)

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Fig. 16

Results of the nondimensionalized film thickness at film breakup for the MCS (gray) and OCS (black) profile

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Fig. 17

Derived 3D wall film pattern for MCS at design Mach number with spray A and α = 4 deg

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