STEAM TURBINE EXHAUST DUCT Russian patent published in 2006 - IPC F01D25/30 

FIELD: power engineering.

SUBSTANCE: invention can be used at designing and modification of low-pressure cylinders of steam turbines of thermal and nuclear power stations. Proposed exhaust duct of steam turbine contains manifold arranged after blades of last stage in root zone and connected to source of cooling steam and communicating with turbine blading through ring slot with guide assembly imparting tangential speed component to cooling steam in direction of rotation of working blades, optimum length of vanes of guide assembly being b=mL[5,2+20,81g(εP₀/P_B)]^-1 where b is length of vanes of guide assembly; m is relative extent of section of working blade trailing edges; L is length of working blades of last stage; ε is critical ratio of pressure of steam flowing out of guide assembly; P₀ is steam pressure in manifold; P_B is steam pressure in exhaust duct. Moreover, guide assembly is arranged at a distance not less than 0.22 mL from trailing edges of working blades of last stage in root section, angle of outlet α of guide assembly does not exceed 8°, step is made on convex surface of vanes from trailing edge to narrow section of vane channel with maximum depth in narrow section h=0,3tsinα where h is depth of step in narrow section; t is pitch of vanes of guide assembly; α is outlet angle of guide assembly.

EFFECT: improved reliability and increased economy of low pressure part at low consumption owing to effective cooling of last stage and exhaust duct, reliable erosion protection of trailing edges of working blades and reduced consumption of steam for cooling.