Multi-tier steam turbines. Prospects and particularities. Part 1: Overview of two-tier low-pressure turbines

Abstract

This article considers whether the unit power of steam-turbine plants can be increased through increasing the capacity of the low-pressure cylinders (LPC) of 1022 Arkadiy Zaryankin et al. steam turbines. At the current stage of development of science and technology, the common level of unit power of a fossil-fuel power unit with 50 Hz steam turbines is a 1200 MW plant. One of the main factors determining the marginal unit power of steam-turbine units is the capacity of low-pressure cylinders. A promising way to increase the steam passage through the LPC is switching to two-tier wheel spaces. This approach allows increasing the capacity of one exhaust by more than 40%. With the same height of the last-stage blade of 1200 mm, application of the two-tier wheel space helps to increase the exhaust area from 11.3 m 2 to 16.3 m 2. The studies show that the two-tier cylinder has high levels of performance, its internal relative efficiency is 87.1%, which in some cases exceeds the similar characteristics of low-pressure cylinders with a conventional construction. If the solutions under consideration are used, the highest capacity of the high-speed turbine unit may be as high as 2000 MW.

Aerodynamics and strength of a two-tier stage based on a fork-shape blade

“…The pressure side steam pressure in upper and lower tiers is assumed from the power Nu re-calculation in each tier mean diameter and each airfoil pressure side area. Each tier power production is taken from the two-tier LPT flowpath thermal calculation Zaryankin, et. al, 2017;.…”

“…An alternative solution of this problem is a transition to the two-tier LPT. It allows application of successful 1200 mm long blade combined with the maximal power increase similar to application of longer 1500 mm blades Zaryankin, et. al, 2017;Zaryankin, et.…”

“…The problems of two-tier stages efficiency and reasonable design are sufficiently described in published papers Zaryankin, et. al, 2016;Zaryankin, et.…”

“…The problems of two-tier stages efficiency and reasonable design are sufficiently described in published papers Zaryankin, et. al, 2016;Zaryankin, et. al, 2017) but the practical introduction and the strength and vibration reliability are presented for wide discussions for the first time.…”