Fig. 11 Thermal state of rotor and diaphragms of large steam turbine

Shaft temperature is practically uniform in zones of terminal labyrinth seals but it slightly (3-5K) higher the steam temperature due to windage heating.

Fig. 12 Fragment of temperature distribution of rotor and diaphragms

Lower pressure end of the shaft is heated over 60-70 K comparing with steam exit temperature due to more preheated steam leakage from previous stages.

The temperature distribution across the system is determined by the steam secondary flows through the seals and balance holes. As a result, the shaft temperature turns out to be slightly above the temperature on the periphery of disks and diaphragms.

Maximum of rotor’s axial elongation, taking into account its’ thermal state, makes up to near 17.5 mm at exit end of the shaft. Value of elongation obtained under assumption that shaft and steam have the same temperature is near 15.5 mm (Fig. 13).

Fig. 13 Rotor’s elongation from fix point, m. Simple – calculation based on assumption that temperature of the rotor equals to main steam temperature; CFDI – calculation based on rotor thermal state including heat exchange between main and secondary steam

Conclusions

Novel method that is based on the complete CFD analysis has been developed for solving coupled flow -thermal problem. It is found to be effective and highly informative when it was applied to the analysis of large thermodynamic systems.

The results of the study demonstrate successful analyses of secondary steam flow and thermal state of rotor and adjoined diaphragms in a large steam turbine. A full set of parameters for turbine’s reliable operation has been obtained.

During the study the following additional analyses have been performed yielding:

• Rotor thermal elongation;
  
• Axial forces upon a thrust bearing at the account of pressure drops on both sides of disks;
  
• Frictional energy losses caused by disks and shaft rotation in labyrinth seals.

  REFERENCES

  Wilson, M., Pilbrow, R., Owen, J.M., 1997, “Flow and heat transfer in a preswirl rotor-stator system,” ASME Journal of Turbomachinery, Vol. 119, pp.364-373

  Pilbrow, R., Karabay, H., Wilson, M., Owen, J.M., 1999, “Heat transfer in a “cover-plate” preswirl rotating-disk system,” ASME Journal of Turbomachinery, Vol. 121, pp.249-256

  Shvetz, I.T., Dyban, E.P., 1974, “Air cooling of gas turbine parts”, Kiev, 488 p. (in Russian)

  Boyko, A.V., Govorushchenko, Yu.N., Yershov, S.V., Rusanov, A.V., Severin, S.D., 2002, “Aerodynamic computation and optimal projection of turbomachinery flow paths”, Kharkov, NTU “KhPI”, 356 p. (in Russian)

  Phadke, U.P., Owen, J.M., 1988, “Aerodynamic aspect of the sealing of gas turbine rotor-stator system”, Int. Journal of Heat and Fluid Flow, Vol. 9, 11, pp. 98-112

  Matveev, Yu. Ya., Pustovalov, V.N., 1982, “Laminar viscous flow calculation between rotated disks”, Fluid and Gas Mechanics, Proceeding of the Academic Science of USSR, 1, pp. 76-81 (in Russian)

  Kapinos, V. M., 1966, “Convective heat transfer of turbulent flow between rotated disks in closed cavity”, Proceeding of Higher School “Aviation technique”, 1, pp. 132-129 (in Russian)

  V. M., Matveev, Yu. Ya., Pustovalov, V.N., 1983, “Natural convection of unventilated cavities of steam turbines rotors”, Thermal Engineering /Teploenergetika/, 8, pp. 36-39 (in Russian)