On Kinematic Relaxation and Deposition of Water Droplets in the Last Stages of Low Pressure Steam Turbines

2013 ◽  
Vol 136 (7) ◽  
Author(s):  
J. Starzmann ◽  
P. Kaluza ◽  
M. V. Casey ◽  
F. Sieverding
Keyword(s):  
Turbulent Diffusion ◽  
Guide Vane ◽  
Operating Conditions ◽  
Three Dimensions ◽  
Steam Turbines ◽  
Droplet Deposition ◽  
Simple Method ◽  
Advantages And Disadvantages ◽  
Droplet Sizes ◽  
Last Stage

In the first part of the paper steady two-phase flow predictions have been performed for the last stage of a model steam turbine to examine the influence of drag between condensed fog droplets and the continuous vapor phase. In general, droplets due to homogeneous condensation are small and thus kinematic relaxation provides only a minor contribution to the wetness losses. Different droplet size distributions have been investigated to estimate at which size interphase friction becomes more important. The second part of the paper deals with the deposition of fog droplets on stator blades. Results from several references are repeated to introduce the two main deposition mechanisms which are inertia and turbulent diffusion. Extensive postprocessing routines have been programmed to calculate droplet deposition due to these effects for a last stage stator blade in three-dimensions. In principle the method to determine droplet deposition by turbulent diffusion equates to an approach for turbulent pipe flows and the advantages and disadvantages of this relatively simple method are discussed. The investigation includes the influence of different droplet sizes on droplet deposition rates and shows that for small fog droplets turbulent diffusion is the main deposition mechanism. If the droplets size is increased inertial effects become more and more important and for droplets around 1 μm inertial deposition dominates. Assuming realistic droplet sizes the overall deposition equates to about 1% to 3% of the incoming wetness for the investigated guide vane at normal operating conditions.

On Kinematic Relaxation and Deposition of Water Droplets in the Last Stages of Low Pressure Steam Turbines

2013 ◽  
Author(s):  
J. Starzmann ◽  
P. Kaluza ◽  
M. V. Casey ◽  
Frank Sieverding
Keyword(s):  
Turbulent Diffusion ◽  
Guide Vane ◽  
Operating Conditions ◽  
Three Dimensions ◽  
Steam Turbines ◽  
Droplet Deposition ◽  
Simple Method ◽  
Advantages And Disadvantages ◽  
Droplet Sizes ◽  
Last Stage

In the first part of the paper steady two-phase flow predictions have been performed for the last stage of a model steam turbine to examine the influence of drag between condensed fog droplets and the continuous vapour phase. In general, droplets due to homogeneous condensation are small and thus kinematic relaxation provides only a minor contribution to the wetness losses. Different droplet size distributions have been investigated to estimate at which size inter-phase friction becomes more important. The second part of the paper deals with the deposition of fog droplets on stator blades. Results from several references are repeated to introduce the two main deposition mechanisms which are inertia and turbulent diffusion. Extensive post-processing routines have been programmed to calculate droplet deposition due to these effects for a last stage stator blade in three-dimensions. In principle the method to determine droplet deposition by turbulent diffusion equates to that of Yau and Young [1] and the advantages and disadvantages of this relatively simple method are discussed. The investigation includes the influence of different droplet sizes on droplet deposition rates and shows that for small fog droplets turbulent diffusion is the main deposition mechanism. If the droplets size is increased inertial effects become more and more important and for droplets around 1 μm inertial deposition dominates. Assuming realistic droplet sizes the overall deposition equates to about 1% to 3% of the incoming wetness for the investigated guide vane at normal operating conditions.

Fog Droplet Deposition and Coarse Water Formation in Low-Pressure Steam Turbines: A Combined Experimental and Theoretical Analysis

1988 ◽  
Vol 110 (2) ◽  
pp. 163-172 ◽  
Author(s):  
J. B. Young ◽  
K. K. Yau ◽  
P. T. Walters
Keyword(s):  
Size Spectrum ◽  
Steam Turbines ◽  
Droplet Deposition ◽  
Deposition Rates ◽  
Water Formation ◽  
Pressure Steam ◽  
Order Of Magnitude ◽  
Droplet Sizes ◽  
Inversion Procedure ◽  
Last Stage

The paper describes a theoretical and experimental study of fog droplet deposition and coarse water formation in the LP cylinders of two 500 MW steam turbines. Measurements of coarse water flow rates entering and leaving the final stage of each turbine were performed using a new design of water absorbent probe. From these measurements it was possible to deduce the rate of deposition of fog droplets onto the last stage blading of each machine. Aerodynamic and optical traverses provided experimental data on the fog droplet mean diameter and wetness faction, and the application of an inversion procedure generated an approximation to the droplet size spectrum itself. Using these data and theoretical methods for predicting inertial and diffusional deposition rates, a second estimate was obtained for the stage deposition rates. The two different approaches show excellent agreement, in contrast with previously published work, which was unable to reconcile (to within one order of magnitude) deposition theory with measured fog droplet sizes and coarse water quantities.

Unsteady Flow Field and Coarse Droplet Measurements in the Last Stage of a Low Pressure Steam Turbine With Supersonic Airfoils Near the Blade Tip

2016 ◽  
Author(s):  
Ilias Bosdas ◽  
Michel Mansour ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Shigeki Senoo
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Leading Edge ◽  
Suction Side ◽  
Fast Response ◽  
Operating Conditions ◽  
Electricity Production ◽  
Test Facility ◽  
Steam Turbines ◽  
Last Stage

The largest share of electricity production worldwide belongs to steam turbines. However, the increase of renewable energy production has led steam turbines to operate under part load conditions and increase in size. As a consequence long rotor blades will generate a relative supersonic flow field at the inlet of the last rotor. This paper presents a unique experiment work that focuses at the top 30% of stator exit in the last stage of an LP steam turbine test facility with coarse droplets and high wetness mass fraction under different operating conditions. The measurements were performed with two novel fast response probes. A fast response probe for three dimensional flow field wet steam measurements and an optical backscatter probe for coarse water droplet measurements ranging from 30 up to 110μm in diameter. This study has shown that the attached bow shock at the rotor leading edge is the main source of inter blade row interactions between the stator and rotor of the last stage. In addition, the measurements showed that coarse droplets are present in the entire stator pitch with larger droplets located at the vicinity of the stator’s suction side. Unsteady droplet measurements showed that the coarse water droplets are modulated with the downstream rotor blade-passing period. This set of time-resolved data will be used for in-house CFD code development and validation.

Analysis of influence of guide vane wrap angle and blade number on propulsive performance of a water jet propulsor

2021 ◽  
Author(s):  
Wei Han ◽  
Wenjuan Xie ◽  
Rennian Li ◽  
Haojie Wang ◽  
Yanzhi Pan ◽  
...  
Keyword(s):  
Numerical Calculation ◽  
Guide Vane ◽  
Operating Conditions ◽  
Guide Vanes ◽  
Propulsion Efficiency ◽  
Main Research ◽  
Advantages And Disadvantages ◽  
Propulsion Performance ◽  
Calculation Results ◽  
Wrap Angle

In this paper, the propulsion performance of a screw mixed-flow jet propulsion pump is studied systematically. The optimum thrust performance is achieved by changing the geometrical dimensions of the guide vanes. Under the condition of keeping other parameters unchanged, the operating conditions of the pump can be effectively adjusted by changing the number of guide vanes and wrap angle. The focus of this paper is on the presentation and demonstration of a strategy that takes the number of guide vanes and wraps angle as the main research object and its propulsion efficiency as the main reference index to analyze the advantages and disadvantages of each working condition in detail. The CFD numerical simulation technology has been used for numerical calculation. The simulation results are compared with the experimental results, and the numerical calculation results are in good agreement with the experimental values. The results show that the kinetic energy of the propulsion pump increases with the number of guide vane blades and the angle of wrap angle. The increase of guide angle and the number of blades will reduce the overall propulsion efficiency of the propeller. Finally, a mathematical model of propeller efficiency with the number of guide vane blades and the angle coefficient of guide vanes is established.

Three-Dimensional Blade Stacking Strategies and Understanding of Flow Physics in Low-Pressure Steam Turbines—Part II: Stacking Equivalence and Differentiators

2015 ◽  
Vol 138 (6) ◽  
Author(s):  
Said Havakechian ◽  
John Denton
Keyword(s):  
Guide Vane ◽  
Three Dimensional ◽  
Low Pressure ◽  
Cfd Modeling ◽  
Steam Turbines ◽  
Flow Parameters ◽  
Pressure Steam ◽  
Computational Fluid Dynamics Cfd ◽  
Last Stage ◽  
Two Stages

Optimization of blade stacking in low-pressure (LP) steam turbine development constitutes one of the most delicate and time-consuming parts of the design process. This is the second part of two papers focusing on stacking strategies applied to the last stage guide vane and represents an attempt to discern the aerodynamic targets that can be achieved by each of the well-known and most often used basic stacking schemes. The effects of lean and twist have been investigated through an iterative process, involving comprehensive 3D computational fluid dynamics (CFD) modeling of the last two stages of a standard LP, where the basic lean and twist stacking schemes were applied on the last stage guide vanes while keeping the throat area (TA) unchanged. It has been found that it is possible to achieve the same target value and pattern of stage reaction by applying either tangential lean or an equivalent value of twist. Moreover, the significance of axial sweep on hub reaction has been found to become pronounced when the blade sweep is carried out at constant TA. The importance of hub-profiling has also been demonstrated and assessed. Detailed analysis of the flow fields has provided an overall picture, revealing the differences in the main flow parameters as produced by each of the alternative basic stacking schemes.

Three-Dimensional Blade-Stacking Strategies and Understanding of Flow Physics in Low-Pressure Steam Turbines—Part I: Three-Dimensional Stacking Mechanisms

2015 ◽  
Vol 138 (5) ◽  
Author(s):  
Said Havakechian ◽  
John Denton
Keyword(s):  
Guide Vane ◽  
Three Dimensional ◽  
Low Pressure ◽  
Stagnation Pressure ◽  
Steam Turbines ◽  
Wet Steam ◽  
Pressure Steam ◽  
Computational Fluid Dynamics Cfd ◽  
Last Stage ◽  
3D Stacking

Optimization of blade stacking in the last stage of low-pressure (LP) steam turbines constitutes one of the most delicate and time-consuming parts of the design process. This is the first of two papers focusing on the stacking strategies applied to the last stage guide vane (G0). Following a comprehensive review of the main features that characterize the LP last stage aerodynamics, the three-dimensional (3D) computational fluid dynamics (CFD) code used for the investigation and options related to the modeling of wet steam are described. Aerodynamic problems related to the LP last stage and the principles of 3D stacking are reviewed in detail. In this first paper, the results of a systematic study on an isolated LP stator row are used to elucidate the effects of stacking schemes, such as lean, twist, sweep, and hub profiling. These results show that stator twist not only has the most powerful influence on the reaction variation but it also produces undesirable spanwise variations in angular momentum at stator exit. These may be compensated by introducing a positive stagnation pressure gradient at entry to the last stage.

3D Blade Stacking Strategies and Understanding of Flow Physics in Low Pressure Steam Turbines: Part II — Stacking Equivalence and Differentiators

2015 ◽  
Author(s):  
Said Havakechian ◽  
John Denton
Keyword(s):  
Iterative Process ◽  
Guide Vane ◽  
Low Pressure ◽  
Main Flow ◽  
Steam Turbines ◽  
Cfd Modelling ◽  
Flow Parameters ◽  
Pressure Steam ◽  
Last Stage ◽  
Two Stages

Optimization of blade stacking in Low Pressure (LP) steam turbine development constitutes one of the most delicate and time consuming parts of the design process. This is the second part of two papers focusing on stacking strategies applied to the last stage guide vane and represents an attempt to discern the aerodynamic targets that can be achieved by each of the well-known and most often used basic stacking schemes. The effects of lean and twist have been investigated through an iterative process, involving comprehensive 3D CFD modelling of the last two stages of a standard LP, where the basic lean and twist stacking schemes were applied on the last stage guide vanes whilst keeping the throat area unchanged. It has been found that it is possible to achieve the same target value and pattern of stage reaction by applying either tangential lean or an equivalent value of twist. Moreover, the significance of axial sweep on hub reaction has been found to become pronounced when the blade sweep is carried out at constant throat area. The importance of hub-profiling has also been demonstrated and assessed. Detailed analysis of the flow fields has provided an overall picture, revealing the differences in the main flow parameters as produced by each of the alternative basic stacking schemes.

Design, Manufacturing and Testing of a New Family of Steam Turbine Low Pressure Stages

2007 ◽  
Author(s):  
Lorenzo Cosi ◽  
Jonathon Slepski ◽  
Steven DeLessio ◽  
Michele Taviani ◽  
Amir Mujezinovic´
Keyword(s):  
Power Generation ◽  
Steam Turbine ◽  
Low Pressure ◽  
Full Scale ◽  
Operating Conditions ◽  
Test Facility ◽  
Steam Turbines ◽  
Wide Range ◽  
The Family ◽  
Last Stage

New low pressure (LP), stages for variable speed, mechanical drive and geared power generation steam turbines have been developed. The new blade and nozzle designs can be applied to a wide range of turbine rotational speeds and last stage blade annulus areas, thus forming a family of low pressure stages—High Speed (HS) blades and nozzles. Different family members are exact scales of each other and the tip speeds of the corresponding blades within the family are identical. Thus the aeromechanical and aerodynamic characteristics of the individual stages within the family are identical as well. Last stage blades and nozzles have been developed concurrently with the three upstream stages, creating optimised, reusable low pressure turbine sections. These blades represent a step forward in improving speed, mass flow capability, reliability and aerodynamic efficiency of the low pressure stages for the industrial steam turbines. These four stages are designed as a system using the most modern design tools applied on Power Generation and Aircraft Engines turbo-machineries. The aerodynamic performance of the last three stage of the newly designed group will be verified in a full-scale test facility. The last stage blade construction incorporates a three hooks, axial entry dovetail with improved load carrying capability over other blade attachment methods. The next to the last stage blade also uses a three hooks axial entry dovetail, while the two front stage blades employ internal tangential entry dovetails. The last and next to the last stage blades utilize continuous tip coupling via implementation of integral snubber cover while a Z-lock integral cover is employed for the two upstream stages. Low dynamic strains at all operating conditions (off and on resonance speeds) will be validated via steam turbine testing at realistic steam conditions (steam flows, temperatures and pressures). Low load, high condenser pressure operation will also be verified using a three stage test turbine operated in the actual steam conditions as well. In addition, resonance speed margins of the four stages have been verified through full-scale wheel box tests in the vacuum spin cell, thus allowing the application of these stages to Power Generation applications. Stator blades are produced with a manufacturing technology, which combines full milling and electro-discharge machining. This process allows machining of the blades from an integral disc, and thus improving uniformity of the throat distribution. Accuracy of the throat distribution is also improved when compared to the assembled or welded stator blade technology. This paper will discuss the aerodynamic and aeromechanical design, development and testing program completed for this new low pressure stages family.

Unsteady Flow Field and Coarse Droplet Measurements in the Last Stage of a Low-Pressure Steam Turbine With Supersonic Airfoils Near the Blade Tip

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Ilias Bosdas ◽  
Michel Mansour ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Shigeki Senoo
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Leading Edge ◽  
Low Pressure ◽  
Fast Response ◽  
Operating Conditions ◽  
Electricity Production ◽  
Test Facility ◽  
Steam Turbines ◽  
Last Stage

The largest share of electricity production worldwide belongs to steam turbines. However, the increase of renewable energy production has led steam turbines to operate under part load conditions and increase in size. As a consequence, long rotor blades will generate a relative supersonic flow field at the inlet of the last rotor. This paper presents a unique experiment work that focuses at the top 30% of stator exit in the last stage of an low pressure (LP) steam turbine test facility with coarse droplets and high wetness mass fraction under different operating conditions. The measurements were performed with two novel fast response probes: a fast response probe for three-dimensional flow field wet steam measurements and an optical backscatter probe for coarse water droplet measurements ranging from 30 μm up to 110 μm in diameter. This study has shown that the attached bow shock at the rotor leading edge is the main source of interblade row interactions between the stator and rotor of the last stage. In addition, the measurements showed that coarse droplets are present in the entire stator pitch with larger droplets located at the vicinity of the stator's suction side. Unsteady droplet measurements showed that the coarse water droplets are modulated with the downstream rotor blade-passing period. This set of time-resolved data will be used for in-house computational fluid dynamics (CFD) code development and validation.

Development of Highly Efficient and Robust Ultra-Long Last Stage Blade for High Backpressure

2019 ◽  
Author(s):  
Ondrej Novak ◽  
Marek Bobcik ◽  
Vaclav Slama ◽  
Bartolomej Rudas ◽  
Josef Kellner ◽  
...  
Keyword(s):  
Natural Frequencies ◽  
Operating Conditions ◽  
Thermodynamic Efficiency ◽  
Steam Turbines ◽  
Supersonic Wind Tunnel ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Blade Shape ◽  
Last Stage ◽  
Very High

Abstract For modern steam turbines with large operating range and enhanced efficiency an ultra-long last stage rotor blade in a low pressure turbine part for high backpressure and 50 Hz fixed speed operation have been developed. An advanced design approach was used to create the blade shape with a high thermodynamic efficiency, high natural frequencies and a very high safety factor of average radial static stress in the blade span. Furthermore, the tip section of the bucket was improved to decrease a static tension and the hub section was refined to simplify the assembly. Tip and hub airfoils were experimentally validated in a supersonic wind tunnel. An advanced in-house procedure using numerical analysis to predict a potential danger of unstalled flutter was carried out for wide range of operating conditions.

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