Search

Hydraulic Design of the Bleeding Chamber for the Steam Turbine Hydraulic loss coefficients in the turbine flow discharge section were calculated on the basis of experimental determination of pressure losses in the turbine section designed for the heating bleeding in the steam turbine. It has been established that these loss coefficients are affected by the number of outlet branches, the diameters of outlet branches, a value of throat cross-section (narrow), radial cone cross-section through which the steam enters the bleeding section, and a relative flow of effluent medium (up to 35 %). The investigation was carried out using the aerodynamic test bench. The bleeding chamber was designed with the axial symmetry and had a large volume peculiar for the turbines with large uncontrolled steam bleedings. Consideration was given to the operation of the options of bleeding channels that have radial cone elements and also the options that have no radial cone. The technique was given that allows us to calculate pressure losses in the region between the flow passage of real steam turbine and the bleeding branches. This technique was developed based on the experimental investigation of bleeding channel carried out using the stationary aerodynamic test bench. It has been established that the use of two outlet branches instead of one results in a more substantial decrease of losses in the diffuser bleeding channel in comparison with the approach when the area of one outlet branch is increased two times.

The leakage above the rotor wheel in the last turbine stage can positively influence the characteristics of the diffuser acting by analogy to the special inflation of the flow into the boundary layer in the external bypass of the diffuser. Contemporary structures of high pressure cylinders are equipped with axial-radial diffuser or diffuser installed in the exhaust pipe branch; therefore the problem of influence of the above-shroud leakage in the last stage on the aerodynamics of the exit diffuser of high pressure cylinders is rather vital. Computing investigations were carried out using CFD of the axisymmetric axial-radial diffuser peculiar for the exhaust pipe branches of high pressure cylinders of steam turbines in a wide range of pressure variations that define a value of the above-shroud leakage in the rotor wheel of the last stage. The flow behavior in the diffuser, the coefficients of losses and the pressure distribution on the diffuser cowling have been studied. It has been established that at the minimum values of leakage, which is peculiar for the seals of a cellular structure the flow in the diffuser is detachable and a coefficient of full losses has maximum values and at an increased above-shroud leakage that occurs in the traditional seals of a labyrinth type the point of flow separation from the cowling shifts towards the exit section lowering considerably the coefficient of full losses.