Influence of a Cylindrical Exhaust Hood Installation on the Last Stage Rotor Blades of a Low Pressure Model Steam Turbine

2017 ◽  
Author(s):  
Fabian F. Müller ◽  
Markus Schatz ◽  
Damian M. Vogt ◽  
Jens Aschenbruck
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Pressure Measurements ◽  
Exhaust Hood ◽  
Blade Vibration ◽  
Time Resolved ◽  
Vibration Behavior ◽  
Last Stage

The influence of a cylindrical strut shortly downstream of the bladerow on the vibration behavior of the last stage rotor blades of a single stage LP model steam turbine was investigated in the present study. Steam turbine retrofits often result in an increase of turbine size, aiming for more power and higher efficiency. As the existing LP steam turbine exhaust hoods are generally not modified, the last stage rotor blades frequently move closer to installations within the exhaust hood. To capture the influence of such an installation on the flow field characteristics, extensive flow field measurements using pneumatic probes were conducted at the turbine outlet plane. In addition, time-resolved pressure measurements along the casing contour of the diffuser and on the surface of the cylinder were made, aiming for the identification of pressure fluctuations induced by the flow around the installation. Blade vibration behavior was measured at three different operating conditions by means of a tip timing system. Despite the considerable changes in the flow field and its frequency content, no significant impact on blade vibration amplitudes were observed for the investigated case and considered operating conditions. Nevertheless, time-resolved pressure measurements suggest that notable pressure oscillations induced by the vortex shedding can reach the upstream bladerow.

Experimental Investigation of a Low Pressure Model Steam Turbine With Supporting Rib in Close Vicinity to the Last Stage Rotor Blades at Varying Operating Conditions

2016 ◽  
Author(s):  
Fabian F. Müller ◽  
Markus Schatz ◽  
Damian M. Vogt ◽  
Andreas Rehnsch
Keyword(s):  
Steam Turbine ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Reference Case ◽  
Blade Vibration ◽  
Close Vicinity ◽  
Last Stage ◽  
The University ◽  
Remarkable Reduction ◽  
Turbine Exhaust

Steam turbine retrofits often result in an increase of turbine size, aiming for more power and higher efficiency. As the existing LP steam turbine exhaust hoods are generally not modified, the last stage rotor blades frequently move closer to installations within the exhaust hood, such as baffles or ribs. To assess the influence of supporting ribs on the vibration behavior of the last stage rotor blades, tests with two rib configurations were performed in a single stage LP model steam turbine at the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) at the University of Stuttgart, Germany. At design load and overload operating conditions no significant change in blade vibration amplitudes is observed in case of a supporting rib in close vicinity to the rotor blades compared to the reference case without installations. However, at part load operating conditions a remarkable reduction in blade amplitudes is found rather unexpectedly. The present work shows that changes in the pattern and the frequency content of the flow within the diffuser, caused by the interaction between supporting rib and steam flow is evidently responsible for this.

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 Analysis of the Blade Forces Caused by Wake/Blade Interaction in the Last Stage of a Steam Turbine

2007 ◽  
Author(s):  
J. C. Garci´a ◽  
J. Kubiak ◽  
F. Sierra ◽  
G. Urquiza ◽  
J. A. Rodri´guez
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Pressure Field ◽  
Stokes Equations ◽  
Life Time ◽  
Rotor Blades ◽  
Three Dimensions ◽  
Useful Life ◽  
Last Stage ◽  
Axial Clearance

In a steam turbine stage there is an interaction between blades and the flow field. The blades are subjected to the forces caused by the flow field, but also the flow field is affected by the blades and its movement. The nozzle wakes cause uneven pressure field downstream and produce alternating forces on blades which lead to blade vibrations. Some of the vibrations originated in this way may damage the blades and affect the turbine performance. The results of numerical computations about the forces acting on the blades as a result of the variations in the flow field in the axial clearance rotor-stator in the last stage of a 110 MW steam turbine are presented. The analysis is focused on discussing the pressure field because it is necessary for further computation of the useful life time. The flow field was resolved using computational fluids dynamics and the computed pressure field was integrated around the blades to get the forces acting on blades. These computed dynamical forces will be used in the blade useful life estimation and in the investigation to the failure causes of these blades. The Navier-Stokes equations are resolved in two and three dimensions using a commercial program based on finite-volume method. 2-D and 3-D geometry models were built to represent the dimensional aspects of the last stage of the turbine. Periodic boundary conditions were applied to both sides of a periodic segment of the 2-D and 3-D models with the purpose of reducing computational efforts. The computations were conducted in steady state and transient conditions. The results show that the force magnitude acting on blades has an harmonic pattern. Finally a Fourier analysis was used to determine the coefficients and frequency of a Fourier equation which can be used to calculate the alternating stresses on the blade in order to predict the useful life of the blades. Also, the pressure and velocity fields are shown between the diaphragm and rotor blades along the axial clearance.

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.

Aeroelastic Analysis of Last Stage LP Steam Turbine Rotor Blades With Exhaust Hood for Various Non-Nominal Regimes

2018 ◽  
Author(s):  
Romuald Rzadkowski ◽  
Vitaly Gnesin ◽  
Lubov Kolodyazhnaya ◽  
Ryszard Szczepanik
Keyword(s):  
Pressure Distribution ◽  
Steam Turbine ◽  
Gas Flow ◽  
Element Model ◽  
Turbine Rotor ◽  
Ideal Gas ◽  
Rotor Blades ◽  
Exhaust Hood ◽  
Flow Through ◽  
Last Stage

Presented here are the numerical calculations of the 3D transonic flow of an ideal gas through an LP steam turbine last stage with exhaust hood, taking into account blade oscillations. The approach is based on a solution to the coupled aerodynamic-structure problem for 3D flow through a turbine stage using the partially integrated method. The blade oscillations and loads acting on the blades are a part of the solution. An ideal gas flow through the stator and moving rotor blades with periodicity on the whole annulus is described by unsteady Euler conservation equations, integrated with the Godunov-Kolgan explicit monotonous finite-volume difference scheme and a moving hybrid H-H rotor blade grid. The structural analysis uses the modal approach and a 3D finite element model of a blade. The proposed algorithm allows for the calculation of turbine stages with an arbitrary pitch ratio of stator and rotor blades, taking into account unsteady-load induced blade oscillations. The pressure distribution behind the rotor blades was non-uniform on account of the exhaust hood. As a result of the fluid-structure interaction and exhaust hood induced nonsymmetrical pressure distribution behind the rotor blades, the first blade mode was no longer bending but bending-torsion.

Study of Coupling Numerical Flow Field Simulation of Low-Pressure Last Stage Exhaust Passage in Steam Turbine

2014 ◽  
Vol 672-674 ◽  
pp. 1626-1632
Author(s):  
Zhen Song ◽  
Jian Qun Xu ◽  
Li Peng Sun ◽  
Ming Tao Liu
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Turbulence Model ◽  
Pressure Loss ◽  
Total Pressure ◽  
Exhaust Hood ◽  
Coupled Models ◽  
Field Simulation ◽  
Inlet Swirl ◽  
Last Stage

The model of coupled exhaust hood with condenser throat and the model of coupled exhaust hood, condenser throat with last stage were simulated based on the turbulence model Realizable k-ε. Calculated results show that due to the ignoring of the inlet swirl in the model coupled exhaust hood with condenser throat, the flow field is symmetrical and the pressure loss is small. Due to the influence of last stage, in the model of coupled exhaust hood, condenser throat with last stage, the flow field of the inlet of the exhaust hood is uneven, and the vortexes changed more complex, resulting in the increase of the pressure loss of each part and a greater influence in the diffuser pipe. The proportion of pressure loss of diffuser pipe in total pressure loss increases from 0.086 to 0.358, and there is a 70% decline of proportion of pressure loss in volute and condenser throat. In addition, the proportion of the pressure loss in volute is the largest one in these two coupled models. So more attention should be paid in the influence of the last stage, and weaken the vortexes in the volute when designing or optimizing the exhaust passage of steam turbine.

Numerical Model of Liquid Film Formation and Breakup in Last Stage of a Low-Pressure Steam Turbine

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Pietro Rossi ◽  
Asad Raheem ◽  
Reza S. Abhari
Keyword(s):  
Steam Turbine ◽  
Stokes Equations ◽  
Low Pressure ◽  
Liquid Films ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Last Stage ◽  
The Impact

Formation of thin liquid films on steam turbine airfoils, particularly in last stages of low-pressure (LP) steam turbines, and their breakup into coarse droplets is of paramount importance to assess erosion of last stage rotor blades given by the impact of those droplets. An approach for this problem is presented in this paper: this includes deposition of liquid water mass and momentum, film mass and momentum conservation, trailing edge breakup and droplets Lagrangian tracking accounting for inertia and drag. The use of thickness-averaged two-dimensional (2D) equations in local body-fitted coordinates, derived from Navier–Stokes equations, makes the approach suitable for arbitrary curved blades and integration with three-dimensional (3D) computational fluid dynamics (CFD) simulations. The model is implemented in the in-house solver MULTI3, which uses Reynolds-averaged Navier–Stokes equations κ – ω model and steam tables for the steam phase and was previously modified to run on multi-GPU architecture. The method is applied to the last stage of a steam turbine in full and part load operating conditions to validate the model by comparison with time-averaged data from experiments conducted in the same conditions. Droplets impact pattern on rotor blades is also predicted and shown.

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.

Experimental and Numerical Investigations of Steam Turbine Exhaust Hood Flow Field With Two Types of Diffusers

2019 ◽  
Author(s):  
Soichiro Tabata ◽  
Hisataka Fukushima ◽  
Kiyoshi Segawa ◽  
Koji Ishibashi ◽  
Yoshihiro Kuwamura ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Pattern ◽  
Steam Turbine ◽  
Three Dimensional ◽  
Internal Flow ◽  
Exhaust Hood ◽  
Scaled Model ◽  
Last Stage ◽  
Verification Test ◽  
Lp Turbine

Abstract The exhaust hood performance of LP turbine plays an important role in the efficiency of steam turbine. By improving the exhaust performance, the kinetic energy of the last stage rotating blades can be converted to the potential energy and it becomes possible to improve the turbine efficiency. However, the flow field in the diffuser is closely related to the flow pattern of the last stage rotating blade, and the flow field inside the exhaust chamber afterward has a complicated three dimensional flow field. Therefore, in this study, it conducted a scaled model steam turbine test using two types of diffusers and CFD, and evaluated exhaust performance and flow pattern. The verification test was carried out using a test turbine (4 stages) of × 0.33 scale, the velocity field and the pressure field were evaluated by traverse and the wall pressure measurements. The corresponding CFD was calculated by ANSYS CFX. All four stages of blades and seals, exhaust chambers were accurately modeled. Due to the detailed CFD, the internal flow of the exhaust chamber exhibiting complicated three-dimensionality was visualized and the flow pattern was evaluated. The verification test results and the corresponding CFD results were compared and evaluated, and it has been found that the overall performance predicted by CFD is well showing the verification test result. Therefore, it has been found that CFD can help to understand the internal flow of the exhaust chamber exhibiting complex three-dimensional characteristics.

Experimental research on the flow at the last stage of a 1090 MW steam turbine

2018 ◽  
Vol 232 (5) ◽  
pp. 515-524 ◽  
Author(s):  
Michal Hoznedl ◽  
Michal Kolovratník ◽  
Ondřej Bartoš ◽  
Kamil Sedlák ◽  
Robert Kalista ◽  
...  
Keyword(s):  
Service Life ◽  
Flow Field ◽  
Steam Turbine ◽  
Experimental Research ◽  
Rotor Blades ◽  
Saturated Steam ◽  
Vacuum Level ◽  
Left And Right ◽  
Last Stage ◽  
The Difference

This paper presents the experimental research for the flow of the last stage of a turbine for saturated steam with the nominal output 1090 MW. In addition, the flows in 600, 800, and 1070 MW output turbines were also measured. Pneumatic probes were used to determine the distribution of static pressures and absolute angles at the outlets from the penultimate and the last stages of the turbine. Optical probes were used to measure wetness distribution and were placed in positions similar to the pneumatic probes. The courses of static pressures, angles, and wetness for all outputs respectively were compared and discussed. The difference between wetness courses on the left and right side of the turbine as well as before and behind last stage was minimal. Absolute angles of steam behind the last stage are strongly influenced by the vacuum level in the condenser. Big difference between the outlet angles from last stage on the left and right side of the turbine is confirmed. The influence of the tie-boss was evident in both pneumatic and wetness measurements. Differences of the flow field on the left and right sides of the turbine behind the penultimate stage are noted and discussed. These differences lead to a dynamic loading of the penultimate rotor blades and could reduce the service life.

Sign in / Sign up

Export Citation Format

Share Document