Abstract
Background
Cracks were found in the roots of the last stage rotor blades. Tip-timing measurements showed high vibration amplitudes in certain working conditions. The aim of this paper is to analyse unsteady forces acting in such working conditions on the last stage of rotor blades, taking into account unsteady flow in the exhaust hood.
Method
Using ANSYS CFX, this paper examines unsteady forces in a low pressure steam turbine last stage with an exhaust hood. A sliding mesh model was used for interaction between the stator-rotor blades and the rotor blade- exhaust hood. The study included a 3D transonic viscous flow. The CFD mesh included all the last stage stator, rotor blades. The rotor blades vibrated but do not rotate.
Results
Numerical static pressure and temperature values in selected exhaust hood crosssections were compared with experimental ones. Unsteady rotor blade forces and moments were analysed along the lengths of the blades.
Conclusions
This study has shown that interaction with the exhaust hood causes the non-symmetrical pressure and temperature along and behind the rotor blades. The low frequency unsteady harmonic is higher towards the tip of the blade. The greatest low component of unsteady forces was 50 Hz, which is far below the natural frequency and therefore irrelevant to rotor blade vibration. The second harmonic, 100 Hz, is much more dangerous, because is relatively close the natural frequency of the blade.
Similar content being viewed by others
Abbreviations
- p :
-
Pressure
- F :
-
Unsteady aerodynamic forces
- T :
-
Temperature
- \( \nu \) :
-
Natural mode frequency
- \( \bar{L} \) :
-
Dimensionless blade length
References
Zhou B, Mujezinovic A, Coleman A, Ning W, Ansari A (2011) Forced response prediction for steam turbine last stage blade subject to low engine order excitation, ASME Turbo Expo 2011. Turbine Technical Conference and Exposition, Vol 7. Turbomachinery, Parts A, B, and C, Vancouver, British Columbia, Canada, Paper No. GT2011–46856, pp 2447–2453
Shibukawa N, Tejima T, Iwasaki Y, Murakami I, Saito I (2011) A correlation between vibration stresses and flow feature of steam turbine long blades in low load conditions, ASME Turbo Expo 2011. Turbine Technical Conference and Exposition, Vol 7. Turbomachinery, Parts A, B, and C, Vancouver, British Columbia, Canada, Paper No. GT2011–46368, pp 2437–2446
Megerle B, McBean I, Rice T, Ott P (2013) Unsteady aerodynamics of low-pressure steam turbines operating under low volume flow, ASME Turbo Expo 2013. Turbine Technical Conference and Exposition, Vol 5B. Oil and Gas Applications, Steam Turbines, San Antonio, Texas, USA, Paper No. GT2013–95409
Miyake S, Koda I, Yamamoto S, Sasao Y, Momma K, Kiyawaki T, Ooyama H (2016) Unsteady wake and vortex interactions in 3-D steam turbine low pressure final three stages. ASME Turbo Expo 2016. Turbomachinery Technical Conference and Exposition, Vol 7B. Structures and Dynamics, Seoul, South Korea, Paper No. GT2016–57610
Finzel C, Schatz M, Casey MV, Gloss D (2011) Experimental investigation of geometrical parameters on the pressure recovery of low pressure steam turbine exhaust hoods, ASME 2011 Turbo Expo. Turbine Technical Conference and Exposition, Vol 7. Turbomachinery, Parts A, B, and C, Vancouver, British Columbia, Canada, Paper No. GT2011–45302, pp 2255–2263
Verstraete T, Prinsier J, Cosi L (2014) Design and off- design optimization of a low pressure steam turbine radial diffuser using an evolutionary algorithm and 3D CFD, ASME Turbo Expo 2014. Turbine Technical Conference and Exposition, Vol 1B. Marine; Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, Düsseldorf, Germany, Paper No. GT2014–26850
Fu JL, Liu JJ, Zhou SJ (2011) Unsteady interactions between axial turbine and non-axisymmetric exhaust hood under different operational conditions. ASME J Turbomachinery 134(4):041002
Burton Z, Ingram GL, Hogg S (2013) A novel method of coupling the steam turbine exhaust hood and the last stage blades using the non-linear harmonic method, ASME Turbo Expo 2013. Turbine Technical Conference and Exposition, Vol 5B. Oil and Gas Applications, Steam Turbines, San Antonio, Texas, USA, Paper No. GT2013–94184
Zhou DW, Liu B, Zhu XC, Du ZH (2014) Aerodynamics prediction and design of a steam turbine exhaust hood. J Eng Gas Turbine Power 136(4):0426021–426029
Li J, Li ZG, Feng ZP (2014) Effects of the last stage rotor tip leakage flow on the aerodynamic performance of the exhaust hood for steam turbines, ASME Turbo Expo 2014. Turbine Technical Conference and Exposition, Vol 1B. Marine; Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, Düsseldorf, Germany, Paper No. GT2014–25806
Burton ZG, Ingram L, Hogg S (2013) A literature review of low pressure steam turbine exhaust hood and diffuser studies. J Eng Gas Turbines Power 135(6):062001
Tanuma T, Sasao Y, Yamamoto S, Niizeki Y, Shibukawa N, Saeki H (2014) Numerical investigation of steam turbine exhaust diffuser flows and their three dimensional interaction effects on last stage efficiencies, ASME Turbo Expo 2014. Turbine Technical Conference and Exposition, Vol 1B. Marine; Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, Düsseldorf, Germany, Paper No. GT2014–26665
Tanuma T, Okuda H, Hashimoto G, Yamamoto S, Shibukawa N, Okuno K, Saeki H, Tsukuda T (2014) Aerodynamic and structural numerical investigation of unsteady flow effects on last stage blades, ASME Turbo Expo 2015. Turbine Technical Conference and Exposition, Vol 8. Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, Montreal, Quebec, Canada, Paper No. GT2015–43848
Liu B, Yang J, Zhou D, Zhu X, Du Z (2015) Numerical investigations of flow features in a low pressure steam turbine last stage under different mass flow rates, ASME Turbo Expo 2015. Turbine Technical Conference and Exposition, Vol 8. Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, Montreal, Quebec, Canada, Paper No. GT2015–42916
Gardzielewicz A, Swirydczuk J, Badur J, Karcz M, Werner R, Szyrejko C (2003) Methodology of CFD computations applied for analysing flows through steam turbine exhaust hoods. Trans Inst Fluid-Flow Machinery 113:157–168
Gardzielewicz A, Uzięblo W, Marcinkowski S (2013) Experimental dates for flutter calculation of last stage of steam turbine. Rep Diagnostyka Maszyn, 20/2013, Gdansk (in Polish)
Rzadkowski R, Gnesin V, Kolodyazhnaya L (2016) Unsteady forces in LP steam turbine last stage with non-uniform pressure distribution behind vibrating rotor blades. In: 16th international symposium on transport phenomena and dynamics of rotating machinery, ISROMAC, 10–15
Rzadkowski R, Maurin A, Kubitz L, Szczepanik R (2016) Forced vibration of last stage LP steam turbine mistuned bladed discs, ASME Turbo Expo 2016. Turbomachinery Technical Conference and Exposition, Vol 7A. Structures and Dynamics, Seoul, South Korea, Paper No. GT2016–57427
Acknowledgements
The authors wish to acknowledge NCBiR for the financial support of this work (POIR.04.01.04-00-0116/17).
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Rzadkowski, R., Surwiło, J., Kubitz, L. et al. Unsteady Forces in LP Last Stage 380 MW Steam Turbine Rotating and Non-vibrating Rotor Blades with Exhaust Hood. J. Vib. Eng. Technol. 6, 357–368 (2018). https://doi.org/10.1007/s42417-018-0055-y
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s42417-018-0055-y