Numerical Study on Flow and Windage Characteristics in Low Pressure Cylinder under Cylinder Cut-off Conditions
In order to study the operation capacity of the low-pressure cylinder cut-off condition,the three-dimensional numerical model of the single-channel flow field of the eight-stage cascade of the low-pressure cylinder was established by taking the low-pressure cylinder of the stream turbine in a domestic power plant as the research object,while the internal flow structure and aerodynamic performance of the low-pressure cylinder under different inlet flow rates and the windage heating characteristics of the final moving blade were analyzed.Results show that with the continuous decrease of the low-pressure cylinder inlet flow rate,the exhaust backflow and steam flow separation occur at the exhaust outlet and in the last stage cascade accompanied by the negative attack angle at the inlet of the rotor blade;when the inlet flow rate of low-pressure cylinder is reduced to 1.19％,the work done by the working medium cannot com-pensate for low-pressure cylinder rotor rotational work,and the whole machine of the low-pressure cylin-der cannot output power;when the inlet flow rate of low-pressure cylinder is reduced to 7.44％,a local high temperature region is appeared in the dynamic and static interface of the last stage channel near the top of the blade and in the last stage rotor blade channel near the top of the blade,which is manifested as the windage heating effect of the last stage rotor blade under the cylinder cut-off condition;meanwhile,the last stage stator blade windage heating temperature elevation is significantly higher than that of the ro-tor blade,compared with the rated condition,the maximum temperatures on the surfaces of the last stage stator and rotor blades under the cylinder cut-off condition are increased about 105.96％and 71.91％.
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