scholarly journals Numerical and experimental study of droplet-film-interaction for low pressure steam turbine erosion protection applications

2021 ◽  
Vol 5 ◽  
pp. 90-103
Author(s):  
Dieter Bohn ◽  
Tatsuya Uno ◽  
Takeshi Yoshida ◽  
Christian Betcher ◽  
Jan Frohnheiser ◽  
...  
Keyword(s):  
Water Film ◽  
Low Pressure ◽  
Numerical Approach ◽  
Fluid Film ◽  
Steam Turbines ◽  
Airfoil Surface ◽  
Collection Rate ◽  
Lagrangian Simulation ◽  
Pressure Steam ◽  
Surrounding Fluid

One common approach for anti-erosion measures in low pressure steam turbines is to equip a hollow stator vane with slots on the airfoil surface in order to remove the water film by suction and consequently reduce the amount of secondary droplets. The purpose of this paper is to build an understanding of the predominant effects in fluid-film interaction and to examine the suitability of modern numerical methods for the design process of such slots. The performance of a suction slot in terms of collection rate and air leakage is investigated numerically in a flatplate setup with upstream injection of water. In order to model the relevant phenomena (film transport, edge stripping of droplets, transport of droplets in the surrounding fluid, wall impingement of droplets) an unsteady Eulerian-Lagrangian simulation setup is applied. The accuracy of the numerical approach is assessed by comparison with experimental measurements. The comparison of four cases with the measured data demonstrates that the chosen simulation approach is able to predict the main features of film flow and interaction with the surrounding fluid. The collection rate as well as fluid film properties show the same qualitative dependency from water mass flow rate and air velocity.

Sequential vs Multidisciplinary Coupled Optimization and Efficient Surrogate Modelling of a Last Stage and the Successive Axial Radial Diffuser in a Low Pressure Steam Turbine

2014 ◽  
Author(s):  
Kevin Cremanns ◽  
Dirk Roos ◽  
Arne Graßmann
Keyword(s):  
Steam Turbine ◽  
Design Process ◽  
Energy Demand ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Low Pressure ◽  
Steam Turbines ◽  
Low Pressure Turbine ◽  
Pressure Steam ◽  
Last Stage

In order to meet the requirements of rising energy demand, one goal in the design process of modern steam turbines is to achieve high efficiencies. A major gain in efficiency is expected from the optimization of the last stage and the subsequent diffuser of a low pressure turbine (LP). The aim of such optimization is to minimize the losses due to separations or inefficient blade or diffuser design. In the usual design process, as is state of the art in the industry, the last stage of the LP and the diffuser is designed and optimized sequentially. The potential physical coupling effects are not considered. Therefore the aim of this paper is to perform both a sequential and coupled optimization of a low pressure steam turbine followed by an axial radial diffuser and subsequently to compare results. In addition to the flow simulation, mechanical and modal analysis is also carried out in order to satisfy the constraints regarding the natural frequencies and stresses. This permits the use of a meta-model, which allows very time efficient three dimensional (3D) calculations to account for all flow field effects.

Advanced Water Droplet Erosion Protection for Modern Low Pressure Steam Turbine Steel Blades

2015 ◽  
Author(s):  
Joerg Schuerhoff ◽  
Andrei Ghicov ◽  
Karsten Sattler
Keyword(s):  
Steam Turbine ◽  
Water Droplet ◽  
Precipitation Hardening ◽  
Turbine Blades ◽  
Low Pressure ◽  
Steam Turbines ◽  
Treatment Facility ◽  
Material Loss ◽  
Pressure Steam ◽  
Steam Turbine Blades

Blades for low pressure steam turbines operate in flows of saturated steam containing water droplets. The water droplets can impact rotating last stage blades mainly on the leading edge suction sides with relative velocities up to several hundred meters per second. Especially on large blades the high impact energy of the droplets can lead to a material loss particularly at the inlet edges close to the blade tips. This effect is well known as “water droplet erosion”. The steam turbine manufacturer use several techniques, like welding or brazing of inlays made of erosion resistant materials to reduce the material loss. Selective, local hardening of the blade leading edges is the preferred solution for new apparatus Siemens steam turbines. A high protection effect combined with high process stability can be ensured with this Siemens hardening technique. Furthermore the heat input and therewith the geometrical change potential is relatively low. The process is flexible and can be adapted to different blade sizes and the required size of the hardened zones. Siemens collected many years of positive operational experience with this protection measure. State of the art turbine blades often have to be developed with precipitation hardening steels and/or a shroud design to fulfill the high operational requirements. A controlled hardening of the inlet edges of such steam turbine blades is difficult if not impossible with conventional methods like flame hardening. The Siemens steam turbine factory in Muelheim, Germany installed a fully automated laser treatment facility equipped with two co-operating robots and two 6 kW high power diode laser to enable the in-house hardening of such blades. Several blade designs from power generation and industrial turbines were successfully laser treated within the first year in operation. This paper describes generally the setup of the laser treatment facility and the application for low pressure steam turbine blades made of precipitation hardening steels and blades with shroud design, including the post laser heat treatments.

A Methodology for a Detailed Loss Prediction in Low Pressure Steam Turbines

2017 ◽  
Author(s):  
Marius Grübel ◽  
Robin M. Dovik ◽  
Markus Schatz ◽  
Damian M. Vogt
Keyword(s):  
Boundary Layer ◽  
Evaluation Method ◽  
Three Dimensional ◽  
Low Pressure ◽  
Steam Turbines ◽  
Cfd Simulations ◽  
Depth Analysis ◽  
Pressure Steam ◽  
The Impact ◽  
Loss Mechanisms

An evaluation method for CFD simulations is presented, which allows an in-depth analysis of different loss mechanisms applying the approach of entropy creation proposed by Denton. The entropy creation within each single mesh element is determined based on the entropy flux through the cell faces and therefore the locations, where losses occur, can be identified clearly. By using unique features of the different loss mechanisms present in low pressure steam turbines, the losses are categorized into boundary layer, wake mixing and shock losses as well as thermodynamic wetness losses. The suitability of the evaluation method is demonstrated by means of steady state CFD simulations of the flow through a generic last stage of a low pressure steam turbine. The simulations have been performed on streamtubes extracted from three-dimensional simulations representing the flow at 10 % span. The impact of non-equilibrium steam effects on the overall loss composition of the stator passage is investigated by comparing the results to an equilibrium steam simulation. It is shown, that the boundary layer losses for the investigated case are of similar magnitude, but the shock and wake losses exhibit significant differences.

Coarse water in low-pressure steam turbines

2014 ◽  
Vol 228 (2) ◽  
pp. 153-167 ◽  
Author(s):  
Xiaoshu Cai ◽  
Deliang Ning ◽  
Jiangfeng Yu ◽  
Junfeng Li ◽  
Li Ma ◽  
...  
Keyword(s):  
Low Pressure ◽  
Steam Turbines ◽  
Pressure Steam

A generic low-pressure steam turbine test case for aeromechanics and condensation

2019 ◽  
Vol 233 (7) ◽  
pp. 953-958
Author(s):  
Christopher Fuhrer ◽  
Marius Grübel ◽  
Damian M Vogt
Keyword(s):  
Steam Turbine ◽  
Numerical Test ◽  
Low Pressure ◽  
Test Case ◽  
Test Cases ◽  
Steam Turbines ◽  
Aerodynamic Damping ◽  
Spontaneous Condensation ◽  
Pressure Steam ◽  
Turbine Design

At the Institute of Thermal Turbomachinery and Machniery Laboratory (ITSM) a generic test case was designed to investigate aeromechanical phenomena and condensation in low-pressure steam turbines. This test case, referred to as Steam turbine Test case for Aeromechanics and Condensation (STAC) consists of the two last stages of a low-pressure steam turbine and is representative for a modern steam turbine design. STAC is intended to serve as a numerical test case to allow studying the fields of aerodynamic damping and spontaneous condensation in low-pressure steam turbine last stages. The geometry of the turbine is made available online at www.itsm.uni-stuttgart.de/research/test-cases/ .

The Influence of Lean and Sweep in a Low Pressure Steam Turbine: Throughflow Modelling and Experimental Measurements

2008 ◽  
Author(s):  
Lutz Vo¨lker ◽  
Michael Casey ◽  
John Dunham ◽  
Heinrich Stu¨er
Keyword(s):  
Steam Turbine ◽  
Field Measurements ◽  
Low Pressure ◽  
Companion Paper ◽  
Test Results ◽  
Steam Turbines ◽  
Performance Measurements ◽  
Cfd Simulations ◽  
Pressure Steam ◽  
Throughflow Model

This paper describes experimental and throughflow investigations on two configurations of a model three-stage low pressure steam turbine. A companion paper describes 3D CFD simulations of the same turbine test data. Global performance measurements and detailed flow field measurements with pneumatic flow probes were carried out to quantify the changes in the design due to the introduction of sweep in the last stator nozzle vanes. An existing 2D throughflow code was improved to enable the present calculations to be completed. The test results have been used in this paper to calibrate the 2D throughflow model, by adjustment of empirical correlation data to match the experimental data on one of the configurations. This throughflow model was then used to examine the influence of lean and sweep on the design. The results identify that throughflow calculations can model the global effects of lean and sweep in the last stages of steam turbines. Some insight is gained on the losses across the span for the different configurations and on the benefits of lean and sweep in reducing the hub reaction in such stages.

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