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CPOTE2020 logo
CPOTE2020
6th International Conference on
Contemporary Problems of Thermal Engineering
Online | 21-24 September 2020

Abstract CPOTE2020-1212-A

Book of abstracts draft
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On design and analysis of flow characteristics of the last stage of gas-steam turbine

Stanisław GŁUCH, Gdańsk University of Technology, Poland
Paweł ZIÓŁKOWSKI, Gdańsk University of Technology, Poland
Łukasz WITANOWSKI, Institute of Fluid-Flow Machinery Polish Academy of Sciences, Poland
Michał STAJNKE, Institute of Fluid-Flow Machinery Polish Academy of Sciences, Poland
Piotr ZIÓŁKOWSKI, Institute of Fluid-Flow Machinery Polish Academy of Sciences, Poland
Janusz BADUR, Institute of Fluid-Flow Machinery Polish Academy of Sciences, Poland

Research regarding blade design and analysis of flow have been conducted for over a century. Meanwhile new concepts and design approaches were created and improved. Advancements in information technologies allowed to introduce computational fluid dynamics (CFD) and computational flow mechanics (CFM). Currently a combination of mentioned methods is used for design of turbine blades. These methods enabled us to improve flow efficiency and strength of turbine blades. This paper relates to a new type turbine which is in the phase of theoretical analysis, because the working fluid is a mixture of steam and gas generated in wet combustion chamber. Conception of this cycle and thermodynamic calculations are presented in previous papers, therefore the main aim of this article is design and analysis of flow characteristics of the last stage of gas-steam turbine. This gas-steam turbine consists of high-pressure and low-pressure part. The number of stages of the high and low-pressure part of the turbine was determined, together with the kinematics and velocity vectors for subsequent stages of the axial turbine. The low-pressure part has two outlets. The length of the rotor blade of the last stage is 1587 mm. The design process takes into account the law of variation of the velocity peripheral component of the working medium along the radius of the turbine blade and it is conducted in a discrete way so that a 3D drawing of the resulting geometry can be performed. The circumferential velocity varies from 262 m/s near the blade root platform to 771 m/s near the blade tip. When creating the spatial model, the atlas of profiles of reaction turbine steps was used. In this paper results of CFD calculations of twisting of the last stage are presented. Blades geometry and the computational mesh are also presented. Triangles of velocity for selected dividing sections are presented. It is worth noting that the velocity along the pitch diameter varies greatly. Near the root it shows an action triangle, on the other hand, near the tip it presents a reaction type of triangle. Velocity fields and pressure fields show the flow characteristics of the last stage of gas-steam turbine. The net efficiency of the cycle is estimated as 54.35% regarding to enthalpy drop, however, the net efficiency taking into account the mechanical power determined from the stage theory is equal 52.61%.

Keywords: Axial turbine, Computational fluid dynamics (CFD), Last stage of low-pressure, Twisted blade, Blade design