0

Full Content is available to subscribers

Subscribe/Learn More  >

Thermodynamic Aspects of Designing the New Siemens High Pressure Steam Turbine With Overload Valve for Supercritical Applications

[+] Author Affiliations
Frank Deidewig, Michael Wechsung

Siemens AG, Muelheim/Ruhr, Germany

Paper No. POWER2006-88020, pp. 253-260; 8 pages
doi:10.1115/POWER2006-88020
From:
  • ASME 2006 Power Conference
  • ASME 2006 Power Conference
  • Atlanta, Georgia, USA, May 2–4, 2006
  • Conference Sponsors: Power Division
  • ISBN: 0-7918-4205-3 | eISBN: 0-7918-3776-9
  • Copyright © 2006 by ASME

abstract

Huge coal fueled power plants in the 1000MWel class are requiring high efficient steam turbines which can handle supercritical steam conditions up to 300bar and 600°C. Besides these boundary conditions, the capability for stabilising the grid fluctuations is also one key requirement. Siemens is focussing on this topic by using the so-called overload valve(s), which enhance the maximum amount of main steam mass flow entering the high-pressure turbine by use of additional valve(s). Using this technique, a power increase in the range of up to 20% is theoretically achievable. Siemens PG has collected a lot of positive service experiences throughout the past decades with this technique, and therefore this principle is being well established in the field. The connection between the additional steam mass flow passing through the overload valve and the standard blading path is somewhat downstream from the first stage. These connecting points can be varied (for this current turbine design) — if necessary — between the third and fifth stage after the turbine inlet. From an economic point of view, the approach of extending the power range via overload valves is even better than throttling the whole machine during standard operating condition and opening the valves fully at certain peak load requirements. Historically based, Siemens designs and manufactures reaction stages, ‘reaction turbines’, which must be thrust compensated via a separate piston to equalize and reduce the overall axial thrust down to a small number. Increasing the main steam temperatures up to the previously mentioned levels makes the internal cooling device of this thrust equilibrium piston a major key point for the whole turbine. No external cooling pipe-work or special materials are required. In Figure 1 , a longitudinal cross-section 3D-view of the newly designed high-pressure turbine is drawn. The outer casing — at the steam inlet regime — is cast steel of 10% chromium content with significantly reduced wall thickness, whereas the outer casing at the hp-exhaust is a 1% chromium steel. The thrust-balancing piston on the shaft can be identified on the right hand side near the steam inlet channel. As noted further on, the steam outlet channels are both connected to the lower part of the turbine, whereas the inlet chambers are located at 3 o’clock and 9 o’clock, respectively. The outer casing has no horizontal splitting line; the turbine is being built as a barrel-design. This paper deals with the described turbine regarding the major design criteria from the thermodynamic point of view. Based on several calculations, the following design topics were covered: • Developing a turbine-internal cooling system for the thrust equilibrium/balancing piston as well as for the inner and outer casing. • Evaluation of staged piston with new internal cooling system adjusted for the impact on heat rate. • Quantification of all related mass flows, temperatures and pressures. • Axial thrust calculation to determine the required diameters of the staged piston. • General remarks concerning efficiency behaviour of hp-turbines with different geometrical designs.

Copyright © 2006 by ASME

Figures

Tables

Interactive Graphics

Video

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature

Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

NOTE:
Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

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 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