Influence of Wet Steam on the Five-Stage Steam Turbine Efficiency

2018 ◽  
Author(s):  
Michal Hoznedl ◽  
Michal Kolovratník ◽  
Ladislav Tajč ◽  
Andreas P. Weiß ◽  
Lukáš Mrózek
Keyword(s):  
Steam Turbine ◽  
Optical Probe ◽  
Wet Steam ◽  
Turbine Efficiency ◽  
Last Stage ◽  
Path Efficiency ◽  
Steam Parameters ◽  
The Individual ◽  
The Impact ◽  
Stage Efficiency

In the paper the behaviour of the five-stage experimental steam turbine 10 MW is described during the expansion transition from superheated steam to wet steam as well as the influence of wet steam on the flow path efficiency. The influence of wet steam occurrence on one to four last stages is given by setting the inlet steam parameters. The wetness of steam behind the last stage is calculated using two methods, first by enthalpy drop with the output measured by water brake and second by an optical probe. The results of both methods are compared. The impact of steam wetness increasing on a decrease in turbine efficiency is observed. In the paper the influence of steam wetness on the individual stage efficiency is also described and wetness loss coefficient is determined. Using the optical probe, assessment of poly-disperse structure of fine droplets is carried out, which is presented here by Sauter mean diameter. A pneumatic probe is used to define the distribution of velocities and pressures along the blade length after the last stage.

Some Experiments on Wet Steam Flow Visualization in Large Steam Turbine Blading

1976 ◽  
Vol 98 (3) ◽  
pp. 573-577 ◽  
Author(s):  
J. Krzyz˙anowski ◽  
B. Weigle
Keyword(s):  
Steam Turbine ◽  
Steam Flow ◽  
Light Sources ◽  
Phase Flow ◽  
Wet Steam ◽  
Experimental Conditions ◽  
Advantages And Disadvantages ◽  
Primary Droplet ◽  
Last Stage ◽  
Wet Steam Flow

In a series of experiments aimed at the visualization of the wet steam flow in the exhaust part of a 200 MW condensing steam turbine a set of periscopes and light sources was used. The aim of the experiment was: 1 – The investigation of the liquid-phase flow over the last stage stator blading of the turbine mentioned. 2 – The investigation of the gaseous-phase flow through the last stage blading at full and part load. The first part of the program partially failed due to the opaqueness of the wet steam atmosphere for the turbine load higher than 10–20 MW. The detailed experimental conditions will be described. An assessment of the primary droplet size will also be given. The preliminary results of the second part of the program will be outlined. The advantages and disadvantages of the equipment used will be discussed.

Unsteady Wet Steam Flow Field Measurements in the Last Stage of Low Pressure Steam Turbine

2015 ◽  
Author(s):  
Ilias Bosdas ◽  
Michel Mansour ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari ◽  
Shigeki Senoo
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Total Pressure ◽  
Low Pressure ◽  
Operating Conditions ◽  
Test Facility ◽  
Flow Structures ◽  
Wet Steam ◽  
Operating Condition ◽  
Last Stage

Modern steam turbines need to operate efficiently and safely over a wide range of operating conditions. This paper presents a unique unprecedented set of time-resolved steam flowfield measurements from the exit of the last two stages of a low pressure (LP) steam turbine under various volumetric massflow conditions. The measurements were performed in the steam turbine test facility in Hitachi city in Japan. A newly developed fast response probe equipped with a heated tip to operate in wet steam flows was used. The probe tip is heated through an active control system using a miniature high-power cartridge heater developed in-house. Three different operating points, including two reduced massflow conditions, are compared and a detailed analysis of the unsteady flow structures under various blade loads and wetness mass fractions is presented. The measurements show that at the exit of the second to last stage the flow field is highly three dimensional. The measurements also show that the secondary flow structures at the tip region (shroud leakage and tip passage vortices) are the predominant sources of unsteadiness at 85% span. The high massflow operating condition exhibits the highest level of periodical total pressure fluctuation compared to the reduced massflow conditions at the inlet of the last stage. In contrast at the exit of the last stage, the reduced massflow operating condition exhibits the largest aerodynamic losses near the tip. This is due to the onset of the ventilation process at the exit of the LP steam turbine. This phenomenon results in 3 times larger levels of relative total pressure unsteadiness at 93% span, compared to the high massflow condition. This implies that at low volumetric flow conditions the blades will be subjected to higher dynamic load fluctuations at the tip region.

Numerical Investigation of the Impact of Part-Span Connectors on Aero-Thermodynamics in a Low Pressure Industrial Steam Turbine

2014 ◽  
Author(s):  
M. Häfele ◽  
J. Starzmann ◽  
M. Grübel ◽  
M. Schatz ◽  
D. M. Vogt ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Numerical Study ◽  
Three Dimensional ◽  
Measurement Data ◽  
Cross Flow ◽  
Low Pressure ◽  
Wet Steam ◽  
Flow Vortex ◽  
The Impact ◽  
Non Equilibrium

A numerical study on the flow in a three stage low pressure industrial steam turbine with conical friction bolts in the last stage and lacing wires in the penultimate stage is presented and analyzed. Structured high-resolution hexahedral meshes are used for all three stages and the meshing methodology is shown for the rotor with friction bolts and blade reinforcements. Modern three-dimensional CFD with a non-equilibrium wet steam model is used to examine the aero-thermodynamic effects of the part-span connectors. A performance assessment of the coupled blades at part load, design and overload condition is presented and compared with measurement data from an industrial steam turbine test rig. Detailed flow field analyses and a comparison of blade loading between configurations with and without part-span connectors are presented in this paper. The results show significant interaction of the cross flow vortex along the part-span connector with the blade passage flow causing aerodynamic losses. This is the first time that part-span connectors are being analyzed using a non-equilibrium wet steam model. It is shown that additional wetness losses are induced by these elements.

The Influence of Non-Equilibrium Wet Steam Effects on the Aeroelastic Properties of a Turbine Blade Row

2016 ◽  
Author(s):  
Christopher Fuhrer ◽  
Marius Grübel ◽  
Damian M. Vogt ◽  
Paul Petrie-Repar
Keyword(s):  
Steam Turbine ◽  
Turbine Blade ◽  
Ideal Gas ◽  
Test Case ◽  
Steam Turbines ◽  
Wet Steam ◽  
Flow Conditions ◽  
Flutter Analysis ◽  
Last Stage ◽  
Non Equilibrium

Turbine blade flutter is a concern for the manufacturers of steam turbines. Typically, the length of last stage blades of large steam turbines is over one meter. These long blades are susceptible to flutter because of their low structural frequency and supersonic tip speeds with oblique shocks and their reflections. Although steam condensation has usually occurred by the last stage, ideal gas is mostly assumed when performing flutter analysis for steam turbines. The results of a flutter analysis of a 2D steam turbine test case which examine the influence of non-equilibrium wet steam are presented. The geometry and flow conditions of the test case are supposed to be similar to the flow near the tip in a steam turbine as this is where most of the unsteady aerodynamic work contributing to flutter is done. The unsteady flow simulations required for the flutter analysis are performed by ANSYS CFX. Three fluid models are examined: ideal gas, equilibrium wet steam (EQS) and non-equilibrium wet steam (NES), of which NES reflects the reality most. Previous studies have shown that a good agreement between ideal gas and EQS simulations can be achieved if the prescribed ratio of specific heats is equal to the equilibrium polytropic index of the wet steam flow through the turbine. In this paper the results of a flutter analysis are presented for the 2D test case at flow conditions with wet steam at the inlet. The investigated plunge mode normal to chord is similar to a bending mode around the turbine axis for a freestanding blade in 3D. The influence of the overall wetness fraction and the size of the water droplets at the inlet are examined. The results show an increase of aerodynamic damping for all investigated interblade phase angles with a reduction of droplet size. The influence of the wetness fraction is in comparison of less importance.

Effect of Snubbers and Lacing Wire on Aerodynamic Performance of Last Stage Steam Turbine

2019 ◽  
Author(s):  
P. Sreekumar ◽  
Mahesh K. Varpe
Keyword(s):  
Aspect Ratio ◽  
Steam Turbine ◽  
Aerodynamic Performance ◽  
Base Line ◽  
Performance Loss ◽  
Performance Requirements ◽  
Last Stage ◽  
Lp Turbine ◽  
The Impact ◽  
Sensitive Behavior

Abstract The aerodynamics design of a steam turbine stage is an agreement between the performance requirements and the mechanical limitations. The design of last stage of the low-pressure steam (LP) turbine is the most complicated because of the blade twist and a tapered blade along with high aspect ratio due to the sharp increase in the specific volume of the steam during its expansion. The choice of higher aspect ratio for increased power generation makes the turbine blade experience the vibration due to lower modal frequencies which depend on the running speed of a turbine. Therefore, the sensitive behavior of these blades is reduced by damping the blade vibrations which comes with the penalty of aerodynamic performance. The investigation reported here discusses the impact of lacing wire and snubber mounted at 70% blade span. Both, the lacing wire and snubber aligned parallel to the rotor axis deteriorates the efficiency by 0.75% and 1.7% respectively. However, the aerodynamically shaped snubber aligned with the streamline direction recovers the efficiency to that of base line. The mechanism of streamwise aligned snubber in containing aerodynamic performance loss is quite interesting and is being discussed.

Numerical simulation of wet steam transonic condensation flow in the last stage of a steam turbine

2018 ◽  
Vol 28 (10) ◽  
pp. 2378-2403 ◽  
Author(s):  
Xu Han ◽  
Zhonghe Han ◽  
Wei Zeng ◽  
Peng Li ◽  
Jiangbo Qian
Keyword(s):  
Steam Turbine ◽  
Optimization Design ◽  
Great Influence ◽  
Parameter Distribution ◽  
Wet Steam ◽  
Saturation State ◽  
Content Type ◽  
Calculation Results ◽  
Last Stage ◽  
Condensation Flow

Purpose The purpose of this paper is to study the condensation flow of wet steam in the last stage of a steam turbine and to obtain the distribution of condensation parameters such as nucleation rate, Mach number and wetness. Design/methodology/approach Because of the sensitivity of the condensation parameter distribution, a double fluid numerical model and a realizable k-ε-kd turbulence model were applied in this study, and the numerical solution for the non-equilibrium condensation flow is provided. Findings The simulation results are consistent with the experimental results of the Bakhtar test. The calculation results indicate that the degree of departure from saturation has a significant impact on the wet steam transonic condensation flow. When the inlet steam deviates from the saturation state, shock wave interference and vortex mixing also have a great influence on the distribution of water droplets. Originality/value The research results can provide reference for steam turbine wetness losses evaluation and flow passage structure optimization design.

Aerodynamic Interaction Effects From Upstream and Downstream on the Down-Flow Type Exhaust Diffuser Performance in a Low Pressure Steam Turbine

2013 ◽  
Author(s):  
Tadashi Tanuma ◽  
Yasuhiro Sasao ◽  
Satoru Yamamoto ◽  
Yoshiki Niizeki ◽  
Naoki Shibukawa ◽  
...  
Keyword(s):  
Steam Turbine ◽  
Low Pressure ◽  
Interaction Effects ◽  
Wet Steam ◽  
Inlet Flow ◽  
Flow Type ◽  
Diffuser Flow ◽  
Aerodynamic Interaction ◽  
Pressure Steam ◽  
Last Stage

The purpose of this paper is to explain aerodynamic interaction effects from upstream and downstream on the down-flow type exhaust diffuser performance in a low pressure steam turbine. To increase exhaust diffuser performance, design data related to the aerodynamic interaction effects from upstream turbine stages and downstream exhaust hood geometry on the exhaust diffuser performance would be very useful. This paper presents numerical investigation of three dimensional wet steam flows in a down-flow type exhaust diffuser with non-uniform inlet flow from a typical last stage with long transonic blades designed with recent aerodynamic and mechanical design technology. Previous studies show that small scale model tests and CFD analyses of exhaust diffusers with uniform inlet flow conditions are not enough to investigate diffuser efficiency and detail diffuser flow mechanism because inlet flow structures including tip leakage flows and blade wakes superimposed from a last stage and several other upstream turbine stages in low pressure turbines affect flow separations that reduce the exhaust diffuser performance. Recent studies by the authors show that the introduction of radial distributions of velocities and flow angles at the inlet section of exhaust diffuser measured in a full scale development steam turbine increased the accuracy of numerical analysis of diffuser flow. In the present study, the computational domain was enhanced and the method of boundary condition definition was improved to increase the accuracy of boundary layer separation and separation vortex generation in wet steam flows. Using the improved method, the calculation results explained the aerodynamic interaction effects from upstream and downstream on the down-flow type exhaust diffuser performance.

scholarly journals The Possibility of Extending the Life of Cast Steel Hulls of the Steam Turbine

2019 ◽  
Vol 49 (3) ◽  
pp. 17-32
Author(s):  
Adam Charchalis ◽  
Tomasz Dyl ◽  
Agata Wieczorska
Keyword(s):  
Mechanical Properties ◽  
Steam Turbine ◽  
Cast Steel ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Cold Zone ◽  
Last Stage ◽  
The Impact ◽  
Non Destructive ◽  
Material Tests

Abstract The paper presents the analyze the lifetime of the HP steam turbine hull for the EC Gdynia TG1 combined heat and power plant as part of the renovation. The impact of exploitation on changes in mechanical properties of the steam turbine hulls was determined. At the preliminary material tests were carried out, qualifying the hull of the steam turbine to undertake the revitalization process. Then, after non-destructive testing, trepanation samples were taken from the cold zone and the hot hull, which were subjected to mechanical properties tests. The next stage of work was the revitalization process including hardening and tempering. The mechanical properties and metallographic were carried out testing. In the next stage of work, non-destructive testing was performed to detect cracks and a decision was made to repair these areas by welding. The last stage of the work includes an analysis of the vitality of the steam turbine hull after revitalization.

Paper 31: An Experiment on Erosion Control, Using a 60-Mw Steam Turbine

1967 ◽  
Vol 182 (8) ◽  
pp. 297-308 ◽  
Author(s):  
K. W. Todd ◽  
B. Gregory
Keyword(s):  
Field Study ◽  
Steam Turbine ◽  
Erosion Control ◽  
Water Extraction ◽  
Wet Steam ◽  
Flow Conditions ◽  
Erosion Rates ◽  
Laboratory Conditions ◽  
Trailing Edges ◽  
Last Stage

A twin-exhaust steam turbine of 60-MW output was used for a field study of a method of wet steam erosion control which had been examined previously under laboratory conditions. The last stage of one exhaust was modified so that measured quantities of steam and water could be extracted, or steam injected through slots in the trailing edges of the diaphragm blades. Variations in erosion rates of the last-stage moving blades in both exhausts were compared by recording continuously the changes in emissivity of radio-active labels attached to sample blades. An introscope was used to study flow conditions during the experiment, and after some five months' operation the set was opened up for inspection, which confirmed the estimates that water extraction reduced erosion by a factor of 5.

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