NUMERICAL ANALYSIS OF ADAPTIVE CONTROL IN LP TURBINES

Abstract

A new design idea of adaptive control in LP steam turbines under conditions of (1) extraction of steam to the extraction point and (2) seasonal changes of pressure in the condenser is described in the paper. Nozzle blades of a stage located directly downstream of the extraction point or of the exit stage located upstream of the exit diffuser have adjustable trailing edges that can adapt the geometry of the blading system to changing flow conditions. The idea is validated numerically on a group of two exit stages of an extraction/condensation turbine of power 60MW. A series of flow calculations are made using a code FlowER for solving the flow of compressible viscous gas in a 3D turbomachinery environment. As a result of calculations, characteristics of the design, including the mass flow rate, flow angles in characteristic sections, enthalpy losses and turbine power are obtained in a range of given pressure drops and nozzle blade stagger angles. The adequate position of the nozzle blade is found based on these characteristics. Advantages of adaptive control in the form of increase of turbine efficiency and power are also estimated.