Numerical Analysis of Aerodynamic Characteristics of Exhaust Passage with Consideration of Wet Steam Effect in a Supercritical Steam Turbine

Qing Xu,Chen Liu,Yu Duan,Naseem Ahmad,Aqiang Lin,Yuhang Cai

doi:10.3390/en13071560

Qing Xu, Chen Liu + Show 4 more

Open Access

https://doi.org/10.3390/en13071560

Copy DOI

Abstract

To investigate the aerodynamic performance of exhaust passage under multi-phase flow, an actual case is conducted in the low-pressure double exhaust passages of 600 MW steam turbine. Then, the flow field is compared and analyzed with and without the built-in extraction pipelines based on the Eulerian–Eulerian homogenous medium multiphase method. Results show that the upstream swirling flow and downstream mixed swirling flow are the main causes to induce the entropy-increase in the exhaust passage. Moreover, the flow loss and static-pressure recovery ability in the exhaust hood are greater than those in the condenser neck. Compared with the flow field without the steam extraction pipelines, the entropy-increase increases, the static pressure recovery coefficient decreases, and the spontaneous condensation rates of wet steam decrease in the downstream area of the pipelines. With the increase of steam turbine loads, an increment in entropy-increase in the exhaust passage is 0.98 J/(kg·K) lower than that without steam extraction pipelines. Moreover, the incrementing range of uniformity coefficient is increased from 14.5% to 40.9% at the condenser neck outlet. It can be concluded that the built-in exhaustion pipeline can improve the aerodynamic performance of exhaust passage and better reflect the real state of the flow field. These research results can serve as a reference for turbine passage design.

Highlights

Energy consumption [1,2], energy conversion [3], energy saving [4], and their problem-solving method is getting more and more attention for rotating machinery [5,6,7]
As a key component of power plant, low-pressure (LP) exhaust passage consists of a condenser neck and exhaust hood, where its performance strongly affects the efficiency of LP steam turbine [8,9]
It is notable that three different mixing flows occur along the Cartesian coordinates y and z directions, as well as near the steam exhaust inlet of boiler feed pump turbine (BFPT)

Summary

Introduction

Energy consumption [1,2], energy conversion [3], energy saving [4], and their problem-solving method is getting more and more attention for rotating machinery [5,6,7]. As a key component of power plant, low-pressure (LP) exhaust passage consists of a condenser neck and exhaust hood, where its performance strongly affects the efficiency of LP steam turbine [8,9]. The exhaust passage can decelerate and guide the exhaust steam leaving the last stage blades (LSBs) into the condenser, converting the leaving kinetic energy to pressure energy [10]. The energy of exhaust steam is approximately equivalent to 1%–2% of the total available isentropic energy, accounting for about 10%–15% of the total loss of steam turbines [11]. The efficiency can increase by 0.15% for every 10% decrease in total pressure loss in the exhaust passage [12]. The research on the performance of LP exhaust passage has great potential to improve the efficiency of steam turbines

Methods

Results

Conclusion