Low pressure turbine exhaust diffuser with turbulators

Abstract

A turbine exhaust diffuser for use adjacent a last stage row of buckets fixed to a turbine rotor includes an annular inner diffuser ring and an annular outer diffuser ring defining a flow path for steam exiting a last stage row of buckets in a first substantially axial direction at a diffuser inlet, and turning substantially ninety degrees to a diffuser outlet. The outer diffuser ring has a curved steam guide surface extending between the diffuser inlet and the diffuser outlet including a first portion extending away from the diffuser inlet and a second portion extending to said diffuser outlet, the second portion shaped to extend beyond vertical and back toward the diffuser inlet so as to establish a flow component in a second opposite axial direction. The second portion is also provided with a plurality of turbulators to minimize flow separation along the steam guide surface.

Description

BACKGROUND OF THE INVENTION[0001]This invention relates to steam turbine technology in general, and to an axial-to-radial flow, low pressure, steam turbine exhaust gas diffuser in particular.[0002]A steam turbine low pressure (LP) section typically includes an inlet domain, multiple turbine stages and an exhaust gas diffuser (sometimes referenced to as an exhaust hood). The exhaust gas diffuser is typically located at the last row of rotating blades or buckets, and is formed to include a steam flow guide between an axial flow inlet and a radial flow outlet. Flow diffusion takes place in the initial section of the diffuser, formed by the diffuser steam flow guide while the remainder of the diffuser features collect the gas flow in a chamber and guide it to the condenser.[0003]One of the main functions of the diffuser or exhaust hood is to recover static pressure as it guides the exhaust gas flow from the last stage row of buckets into the condenser. In fact, diffusers are typically d...

AI Technical Summary

Benefits of technology

The patent describes a method to increase the area of a turbine exhaust diffuser and reduce the separation of flows along its outer wall. This is achieved by shaping the outer wall and adding turbulators to create vortices that minimize flow separation. The technical effect is improved performance of the turbine exhaust diffuser.

Problems solved by technology

Generally, maximum pressure recovery comes at the end of the steam guide, but after that, pressure losses occur due to improper area scheduling.

A reduced shaft length results in reduced available Area Ratio at the end of the steam guide.

The consequence of such an aggressive design, however, is flow separation along the steam guide, i.e., along the outer steam guide wall portion closest to the last stage bucket tips, and particularly at the outlet end of the outer steam guide wall portion.

Images