Research Papers

Flow Patterns in High Pressure Steam Turbines During Low-Load Operation

[+] Author and Article Information
Matthias Binner

MTU Maintenance Hannover GmbH,
Muenchner Strasse 31,
Langenhagen 30855, Germany
e-mail: Matthias.Binner@mtu.de

Joerg R. Seume

Institute of Turbomachinery and Fluid Dynamics,
Leibniz University Hannover,
Appelstrasse 9,
Hannover 30167, Germany
e-mail: Seume@tfd.uni-hannover.de

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 20, 2012; final manuscript received June 30, 2013; published online November 21, 2013. Assoc. Editor: Dilip Prasad.

J. Turbomach 136(6), 061010 (Nov 21, 2013) (12 pages) Paper No: TURBO-12-1153; doi: 10.1115/1.4025162 History: Received July 20, 2012; Revised June 30, 2013

Due to the legislative efforts of promoting renewable energy sources, electricity from these sources is preferentially fed into the electrical grid. This requires more frequent part- and low-load operation of peak- and even of base-load power plants to compensate for the varying energy output of renewable energy sources. These requirements ultimately lead to an increased part- and low-load operation not only of low pressure (LP) steam turbines but also of high pressure (HP) steam turbines, putting them at risk of damage due to windage, i.e., strongly separated flow with associated heat generation. For the first time measurements of the steady-state flow field in a 7-stage model air turbine with a modern HP steam turbine blading are conducted in order to extend the understanding of the part- and low-load operation from LP to HP steam turbines. In comparison with LP steam turbines, similar flow fields develop during windage. However, differences exist especially concerning the vortex development in front of the turbine vane rows. The present, geometrically realistic 7-stage turbine, unlike other turbines investigated before, does not show these vortices, which is explained by the shape of the vane passages of this turbine blading. Furthermore, steady-state flow field measurements at different rotor speeds show that the flow coefficient can be used as a nondimensional parameter for maintaining flow field similarity even in part- or low-load operation. Additionally, unsteady circumferential pressure measurements show the existence of pressure perturbations moving circumferentially in front of the stage 7 blades. Seven pressure perturbations moving at 60% of the rotor speed are identified. Due to the shrouded design of the HP steam turbine blading used, the pressure perturbations are not due to tip leakage vortices. Hence, they are identified as features which are similar to “Rotating Stall” cells known from compressors.

Copyright © 2014 by ASME
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Fig. 1

Flow through a LP turbine during windage operation [3]

Grahic Jump Location
Fig. 2

Meridional stream traces through the 2-stage turbine during windage operation at design rotor speed and 9% of the design mass flow (φdesign=0.78) [8]

Grahic Jump Location
Fig. 3

Schematic of the windage flow field in a LP steam turbine [9]

Grahic Jump Location
Fig. 4

Predicted flow field development of the 7-stage model air turbine at design rotor speed and different mass flows [18]

Grahic Jump Location
Fig. 5

7-stage model air turbine with modern HP steam turbine blading

Grahic Jump Location
Fig. 6

Map of the 7-stage model air turbine

Grahic Jump Location
Fig. 7

Five-hole probe (all dimensions in mm)

Grahic Jump Location
Fig. 8

Flow field in the 7-stage turbine during design- and low-load operation

Grahic Jump Location
Fig. 9

Velocity triangles during design- and part-load operation of a turbine

Grahic Jump Location
Fig. 10

Change of angle of attack due to decreasing mass flow

Grahic Jump Location
Fig. 11

Stream traces in stages 5 and 6 of the 7-stage model air turbine during windage as predicted by Herzog [18]

Grahic Jump Location
Fig. 12

Turbine vane passage of the 2-stage turbine [8] (a) and the 7-stage turbine (b)

Grahic Jump Location
Fig. 13

Schematic of the growth of the pressure-side separation bubble on vanes and resulting influence on available flow area

Grahic Jump Location
Fig. 14

Schematic of windage flow fields with (a) and without (b) vortex in front of the vane row

Grahic Jump Location
Fig. 15

Part-load flow fields of the 7-stage turbine at different rotor speeds but equal flow coefficients

Grahic Jump Location
Fig. 16

Frequency spectrum of the static pressure in stage 7 during low-load operation

Grahic Jump Location
Fig. 17

Graphical scheme for determination of number and circumferential speed of pressure perturbations in stage 7 (CC X/Y = cross correlation of transducers X to Y, AC = autocorrelation)




Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In