Weizhe Wang
Shanghai Jiao Tong University
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Journal of Engineering for Gas Turbines and Power-transactions of The Asme | 2014
Jianfeng Mao; Weizhe Wang; Y. Z. Liu; Junhui Zhang
Future coal-fired steam turbines promise increased efficiency and low emissions. However, this comes at the expense of increased thermal load from higher inlet steam temperatures and pressures leading to severe creep that significantly influences the sealing behavior and high temperature strength of bolted flange-seal couplings. Flanges with different thicknesses were employed for a comparative study. The important stress/creep values in the flanges and U-type seals had been obtained for variations in flange thickness and bolt relaxation while maintaining other leading parameters constant. The variation of contact stresses due to creep deformation plays an important role in achieving a leak proof sealing. In this paper, a two-dimensional finite element analysis of bolted flange-seal couplings has been carried out by taking the relaxation of bolt stress under full-loading turbine service. The creep strength of flanges and U-type seals are investigated by Cocks–Ashby (C–A) equivalent strain method. The multiaxial state of stresses is considered in this method by using C–A multiaxial coefficient. According to ASME allowable creep limit, the C–A equivalent strains of three flange-seal couplings are evaluated and compared. Furthermore, based on the results of contact stresses, the creep behavior of U-type seals is analyzed varying flange thickness. Finally, analysis shows that the thinner flange-seal coupling has larger long-term contact stress, while the U-type seal with the thicker flange has the least creep strength.
Journal of Engineering for Gas Turbines and Power-transactions of The Asme | 2014
Weizhe Wang
A multi-axial continuum damage mechanics (CDM) model was proposed to calculate the multi-axial creep–fatigue damage of a high temperature component. A specific outer cylinder of a 1000 MW supercritical steam turbine was used in this study, and the interaction of the creep and fatigue behavior of the outer cylinder was numerically investigated under a startup–running–shutdown process. To this end, the multi-axial stress–strain behavior of the outer cylinder was numerically studied using Abaqus. The in-site measured temperatures were provided to validate the heat transfer coefficients, which were used to calculate the temperature field of the outer cylinder. The multi-axial mechanics behavior of the outer cylinder was investigated in detail, with regard to the temperature, Mises stress, hydrostatic stress, multi-axial toughness factor, multi-axial creep strain, and damage. The results demonstrated that multi-axial mechanics behavior reduced the total damage.
Journal of Engineering for Gas Turbines and Power-transactions of The Asme | 2014
Weizhe Wang
The fatigue behavior of a specific inner casing of a 1000 MW supercritical steam turbine was investigated during a complete startup phase. The Ramberg–Osgood model and Manson–Coffin strain-life law were used to describe the stress–strain behavior and calculate the damage. The temperature variation during the startup phase revealed that the startup phase could be divided into a warming-up phase, transition phase, and elevated temperature phase. The thermal stress that dominated in the inner casing could also be divided into the same three phases. The damage caused by the alternating stress during the warming-up phase was around 70% of the total damage. The remaining 30% of the damage was contributed by the transition and elevated temperature phases. The fatigue life was improved by shortening the warming-up phase and extending the elevated temperature phase. The damage was reduced by approximately 20%.
ASME Turbo Expo 2014: Turbine Technical Conference and Exposition | 2014
Weizhe Wang; J. H. Zhang; Huaxu Liu; Y. Z. Liu
Linear damage method is widely used to calculate low-cycle fatigue damage of turbine rotor in the long-term operation without fully considering the interaction between creep and low cycle fatigue. However, with the increase of steam turbine pressure and temperature, the influence of high-temperature creep on the strain distribution of turbine rotor becomes significant. Accordingly, the strain for each start-up or shut-down process is different. In the present study, the stress and strain during 21 iterations of continuous start-up, running and shut-down processes was numerically investigated by using the finite element analysis. The influence of high-temperature creep on low cycle fatigue was analyzed in terms of equivalent strain, Mises stress and low cycle fatigue damage. The results demonstrated that the life consumption of turbine rotor due to low cycle fatigue in the long-term operation of startup, running and shutdown should be determined from the full-time coverage of the load of turbine rotor.Copyright
Volume 5: Manufacturing Materials and Metallurgy; Marine; Microturbines and Small Turbomachinery; Supercritical CO2 Power Cycles | 2012
P. N. Jiang; Weizhe Wang; G. C. Jiao
A model of the nut connection components of a 600MW supercritical steam turbine was established by finite element analysis to investigate the influence of creep on the nut connection components. Due to the complex structure and the multi-axial loadings, Cocks-Ashby coefficients were used to depict the multi-axial creep behavior. Multi-axial creep deformation criteria (MCDC) and multi-axial creep rupture criteria (MCRC) were used to assess the structure reliability. In addition, sealing performance of the nut connection components in the creep time of 2×105 hours was numerically investigated in terms of the contact pressure and the radial contact length. The results demonstrated that the creep strength of the nut connection components after 2×105 hours could maintain the safety operation of the nut connection components. The contact pressure distribution and the radial contact length in circumferential could prevent the leakage steam flow from the high pressure zone to the low pressure zone.© 2012 ASME
Journal of Fluids and Structures | 2009
Weizhe Wang; Y. Z. Liu; Guang Meng; P.N. Jiang
Journal of Mechanical Science and Technology | 2015
Jianfeng Mao; Weizhe Wang; Junhui Zhang; Y. Z. Liu
Journal of Mechanical Science and Technology | 2009
Weizhe Wang; Y. Z. Liu; Guang Meng; P. N. Jiang
Archive of Applied Mechanics | 2012
P. N. Jiang; Weizhe Wang; Y. Z. Liu; G. Meng
Journal of Mechanical Science and Technology | 2012
Jianfeng Mao; Weizhe Wang; Y. Z. Liu