Determination of Minimum Flow Rate of Low Pressure Cylinder of Steam Turbine under Deep Peak Load Regulation Conditions

doi:10.3901/JME.2020.16.098

Abstract

Abstract: The inlet flow rate of steam turbine obviously is reduced when the thermal power unit is involved in peak load operation, even under the small volume flow condition, which has the great influence on the safety of steam turbine. The fluid-structure coupling and modal analysis of the last stage blade is calculated by ANSYS-Workbench to determine the minimum flow rate within the stress limit of blade under deep peak regulation conditions. The results show that the position of blade maximum equivalent stress is different from that of blade maximum deformation. The maximum equivalent stress is located at the tip of the blade and the maximum deformation is at the middle of the blade. The maximum equivalent stress and maximum deformation decrease first and then increase with the decrease of flow rate. Under G₁/G₀=0.1 conditions,the maximum equivalent stress is 451.52 MPa, 18.94% higher than that at rated working condition. The maximum deformation is 0.725 74 mm, 7.8% lower than that at rated working condition. The maximum equivalent stress exceeds the stress limit and does not meet the stress requirements under G₁/G₀<0.1 condition. There is a big difference between the natural frequency and the exciting force frequency of blade, so the blade will not resonate. Therefore, the minimum flow rate of the low pressure cylinder should not be less than 10% of the rated flow rate when the influences of stress, strain, mode of vibration, frequency and other intensity factors are comprehensively considered.

Key words: steam turbine, minimum flow rate, fluid-structure coupling, modal analysis, stress analysis

CLC Number:

TK263

CAO Lihua, WANG Wenlong, LUO Huanhuan, HU Pengfei, WANG Yong, SUN Liang. Determination of Minimum Flow Rate of Low Pressure Cylinder of Steam Turbine under Deep Peak Load Regulation Conditions[J]. Journal of Mechanical Engineering, 2020, 56(16): 98-108.

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