Numerical Study of Unsteady Flow Phenomena in a Partial Admission Axial Steam Turbine

• This paper presents a numerical investigation of unsteady flow phenomena in a two-stage partial admission axial steam turbine. Results from unsteady three-dimensional computations are analyzed and compared with the available experimental data. Partial admission in the present study is introduced into the model by blocking only one segmental arc of the inlet guide vanes. Blocking only one segment (which corresponds to the experimental setup) makes the model unsymmetrical; therefore it is necessary to model the whole annulus of the turbine. The first stage rotor blades experience large static pressure change on their surface while passing the blocked channel. The effect of blockage on the rotor blades' surface pressure can be seen few passages around the blocked channel. Strong changes of the blades' surface pressure impose large unsteady forces on the blades of first stage rotor row.The circumferential static pressure plots at different cross sections along the domain indicate how the non-uniformity propagates in the domain. A peak pressure drop is seen at the cross section downstream of the first stage stator row. At further downstream cross sections, the static pressure becomes more evenly distributed. Entropy generation is higher behind the blockage due to the strong mixing and other loss mechanisms involved with partial admission. Analysis of the entropy plots at different cross sections indicates that the peak entropy moves in a tangential direction while traveling to the downstream stages. Comparisons of the unsteady three-dimensional numerical results and the experimental measurement data show good agreement in tendency. However some differences are seen in the absolute values especially behind the blockage.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering (hsv//eng)

Nyckelord

Absolute values

Axial steam turbine

Cross section

Entropy generation

Experimental data

Experimental measurements

Experimental setup

Inlet guide vane

Loss mechanisms

Nonuniformity

Numerical investigations

Numerical results

Numerical studies

Peak pressure

Rotor blades

Static pressure

Strong-mixing

Surface pressures

Tangential directions

Three-dimensional computations

Two stage

Unsymmetrical

Aerodynamics

Engines

Entropy

Fluid dynamics

Marine engines

Pressure effects

Three dimensional

Turbomachine blades

Unsteady flow

Engineering mechanics

Teknisk mekanik

Publikations- och innehållstyp

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