Особенности теплообмена в зазоре между ободом диафрагмы и корпусом турбины

Abstract

В работе приведена методика определения граничных условий на поверхностях зазоров между внутренним корпусом и ободом диафрагмы, апробированая при расчете температуры и коэффициентов теплоотдачи для указанных элементов в четвертой ступени ЦВД паровой турбины К-325-23,5 ОАО «Турбоатом» на режиме номинальной мощности. Выбор областей определения граничных условий в зазорах проведен с учетом термических сопротивлений пограничных слоев.This paper describes the methodological approach to the determination of boundary conditions on the surfaces of the diaphragm rim and internal cylinder casing of the steam turbine. The thermal flow running from the flow pass section to the intercasing space through the diaphragm rim and the internal casing is divided into three regions according to specified boundary conditions on the surfaces of narrow slots between the diaphragm rim and the casing boring, on the contact diaphragm bearing surface and on the surface of the clearance formed by the flange of the tip-clearance leakage seal. The regions were selected taking into consideration the thermal resistance of boundary layers in the vane set of the flow pass section, on the surfaces of the internal cavity between the outer and the inner casings and the metal used for the diaphragm rim and the internal casing. The steam medium in the clearances was considered without taking into consideration the radiant heat exchange between the casing surface and the rim surface, and the thermal resistance of bearing surfaces was determined taking into consideration their roughness. Boundary conditions on the surfaces of the clearances and the contact bearing surface of the diaphragm and the casing computed using the considered technique for the nominal operation mode of the turbine can be used as the initial data for the computation of the thermally stressed states of flow section elements.