Influence of Trailing Edge Geometry on the Condensing Steam Flow in Low-Pressure Steam Turbine

2015 ◽  
Author(s):  
Giteshkumar Patel ◽  
Yogini Patel ◽  
Teemu Turunen-Saaresti
Keyword(s):  
Turbine Blades ◽  
Steam Flow ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Condensation Process ◽  
Trailing Edge ◽  
Ansys Fluent ◽  
Flow Angle ◽  
Flow Mixing ◽  
Model Flow

The paper describes the influence of trailing edge geometries on the non-equilibrium homogeneously condensing steam flow in the stationary cascade of turbine blades. The computational fluid dynamics (CFD) simulations were performed with the ANSYS Fluent CFD code using the Eulerian-Eulerian approach. The condensation phenomena were simulated on the basis of the classical nucleation theory, and the steam properties were calculated with the real gas model. Flow turbulence was solved by employing the modified version of the shear-stress transport (SST) k-ω turbulence model. For this study, three trailing edge profiles; that is, conic, semicircular and square were considered. The influence of the trailing edge shapes were discussed together with experimental data available in the literature. The presented results show that the trailing edge geometries influence on the nucleation process, the droplet size, wetness fraction, the shock waves structure generated at trailing edge and its angles, the flow angle, the entropy generation and flow mixing in the wake. The cascade loss coefficients were calculated for the low inlet superheat case and for the high inlet superheat case. The presented results demonstrated that the losses that occur due to the irreversible heat and mass transfer during the condensation process were also influenced due to the trailing edge shapes.

Numerical Investigation of Turbulence Modelling on Condensing Steam Flows in Turbine Cascade

2014 ◽  
Author(s):  
Yogini Patel ◽  
Teemu Turunen-Saaresti ◽  
Giteshkumar Patel ◽  
Aki Grönman
Keyword(s):  
Turbulence Modeling ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Turbulence Modelling ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Navier Stokes ◽  
Condensation Process ◽  
Turbine Cascade ◽  
Lp Turbine

Understanding the condensation process at the low-pressure (LP) turbine is important because condensation introduces extra losses, and erosion caused by the droplets wear turbine blades. The paper presents an investigation of the turbulence modelling on the non-equilibrium homogeneous condensing steam flow in a stationary turbine cascade employing 2D compressible Navier-Stokes (NS) equations. The classical nucleation theory is utilized to model the condensation phenomena. The performance of various turbulence models (i.e., the Spalart-Allmaras, the k-ω, the k-ε, the RNG k-ε, the Realizable k-ε, and the SST k-ω) in condensing steam flows is discussed. The SST k-ω model is modified and implemented into a commercial computational fluid dynamics (CFD) code. Substantial improvements in the prediction accuracy are observed when compared with the original SST k-ω model. Overall, the modified model is in excellent agreement with the measurements in all studied test cases of the turbine cascade. The qualitative and quantitative analysis illustrates the importance of turbulence modeling in wet-steam flows.

Numerical and Experimental Investigations of Steam Condensation in LP Part of a Large Power Turbine

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Włodzimierz Wróblewski ◽  
Sławomir Dykas ◽  
Andrzej Gardzilewicz ◽  
Michal Kolovratnik
Keyword(s):  
Stokes Equations ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Condensation Process ◽  
Governing Equations ◽  
Navier Stokes Equations ◽  
Flow Angle ◽  
Large Power

This paper presents the experimental investigations of steam flow with condensation in the blading system of the low-pressure (LP) part of a 360 MW turbine. To this end, special probes were used, which provided flow visualization opportunities including localization of the front of condensation, determining distributions of pressure, temperature, velocity, and flow angle in the inter-row gaps, measurements of water droplet concentration and sizes. The measurements have proved that the condensation process in the LP turbine might be of heterogeneous nature, depending on the concentration of chemical impurities in steam. The measurement results constituted the basis for computational fluid dynamics (CFD) flow calculations, which were performed using the time-dependent 3D Reynolds averaged Navier–Stokes equations coupled with two-equation turbulence model (k-ω SST) and additional conservation equations for the liquid phase. The set of governing equations has been closed by a “local” real gas equation of state. The condensation phenomena were modeled on the basis of the classical nucleation theory. The heterogeneous condensation model on the insoluble and soluble impurities was implemented into presented CFD code. The system of governing equations was solved by means of a finite volume method on a multiblock structured grid. The obtained numerical results and experimental data were compared and discussed.

The Feasibility of an Euler-Lagrange Approach for the Modelling of Wet Steam

2020 ◽  
Author(s):  
Tim Wittmann ◽  
Christoph Bode ◽  
Jens Friedrichs
Keyword(s):  
Optimal Parameter ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Droplet Growth ◽  
Wet Steam ◽  
Discrete Phase Model ◽  
Ansys Fluent ◽  
Validation Data ◽  
Numerical Validation ◽  
Lagrange Approach

Abstract This study investigates the applicability of an Euler-Lagrange approach for the calculation of nucleation and condensation of steam flows. Supersonic nozzles are used as generic validation cases, as their high expansion rates replicate the flow conditions in real turbines. Experimental and numerical validation data for these nozzles are provided by the International Wet Steam Modelling Project of Starzmann et al. (2018). In contrast to most participants of that project, an Euler-Lagrange approach is utilized for this study. Therefore, the classical nucleation theory with corrections and different droplet growth laws is incorporated into the Discrete Phase Model of ANSYS Fluent. Suggestions for an efficient implementation are presented. The Euler-Lagrange results show a good agreement with the experimental and numerical validation data. The sensitivities of the Euler-Lagrange approach to modelling parameters are analysed. Finally, an optimal parameter set for the calculation of nucleation and condensation is proposed.

An Experimental Investigation of the Flow in a 1½ Stage Axial Turbine With Regard to a High Level of Cooling-Air Injection

1999 ◽  
Author(s):  
U. Reinmöller ◽  
H. E. Gallus
Keyword(s):  
Film Cooling ◽  
Turbine Blades ◽  
Gas Injection ◽  
Leading Edge ◽  
Experimental Investigations ◽  
Flow Angle ◽  
Turbine Cooling ◽  
Flow Mixing ◽  
Reference Measurements ◽  
High Level

Experimental investigations of flow mixing due to film cooling of turbine blades have been performed. In a 1½-stage axial air turbine cooling gas (cool nitrogen down to −130 °C) was blown directly onto the leading edge of the first stator by special gas injector devices. In order to provide a database for the verification of numerical codes and to give an impression of the mixing process the gas has been injected at different radial positions. Furthermore the cooling massflow and cooling temperature were varied. The measuring data were obtained using pneumatic 5-hole probes with temperature sensors. The presented experimental data were simultaneous acquired in the planes behind both stators and the rotor. The results are compared and, discussed with reference measurements without cooling gas injection. It is shown that the effect of cooling gas injection is apparent in the wake of the first stator where it causes a small decrease in the pressure distribution as a result of increased flow mixing. Behind the first stator differences in the circumferentially averaged pitchwise flow angle due to the injected gas were not measured. Furthermore, temperature measurements clearly show the effect of the cooling gas injection in all planes. Even behind the second stator the different magnitudes of the temperature distribution are caused by the various injection of cooling gas.

A Preliminary 3D Steam Flow Analysis for CET Behavior During LSTF SBLOCA Experiment Using FLUENT Code

2013 ◽  
Author(s):  
Dwi Irwanto ◽  
Akira Satou ◽  
Takeshi Takeda ◽  
Hideo Nakamura
Keyword(s):  
Large Scale ◽  
Flow Analysis ◽  
Steam Flow ◽  
Test Facility ◽  
Ansys Fluent ◽  
Steady State Condition ◽  
The Core ◽  
Flow Mixing ◽  
Calculation Results ◽  
Core Height

A 3D steam flow within simulated fuel bundle of Large Scale Test Facility (LSTF), a PWR system simulator, has been investigated by Computational Fluid Dynamics (CFD) analysis with Ansys Fluent code to clarify influences of the steam flow on Core Exit Temperature (CET) response. A LSTF SBLOCA experiment with 1.5% hot leg break as the OECD/NEA ROSA-2 Project Test 3 was simulated by the CFD code to clarify relation between CET and fuel rod surface temperature. A portion of the LSTF core above the mixture level up to around CET sensors was modeled by taking into account high, medium and low heat-zone heater rod bundle, including internal structures such as end-box and upper core plate (UCP). Simulation of steady-state condition at a certain time when mixture level lowered to a certain position at around half of the core height (post-5) was carried out by considering relevant boundary conditions which were developed based on the LSTF Test 3 results. The calculation results revealed that inner structures of the core such as core spacer, end box and UCP indeed affect the CET due to heat transfer from hot steam to these cool structures. 3D flow mixing may also contribute to the final CET values and the delayed increase in the CET relative to the Peak Cladding Temperature (PCT) in the core.

Quantification of Stator Blade Shape Influence on Non-Equilibrium Condensation in Low-Pressure Steam Turbine

2017 ◽  
Author(s):  
Giteshkumar Patel ◽  
Yogini Patel ◽  
Teemu Turunen-Saaresti ◽  
Aki Grönman
Keyword(s):  
Steam Turbine ◽  
Stokes Equations ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Droplet Growth ◽  
Condensation Process ◽  
Trailing Edge ◽  
Ansys Fluent ◽  
Pressure Surface ◽  
Blade Shape

The expansion of steam flow and the condensation phenomena in an LP turbine depend on both the flow passage shape and the operating conditions. This paper presents the quantification of the influence of local geometrical details of the steam turbine blade including blade surface tapering, dimple inclusion and trailing edge shapes on flow expansion and condensation phenomena. For this purpose, the wet-steam model of ANSYS FLUENT, based on the Eulerian-Eulerian approach, was used. The mixture of vapor and liquid phases was solved by compressible Reynolds-averaged Navier-Stokes equations. The low inlet superheat case of White et al. [1] which is conducted with planar stator cascade was used as reference for this study. Various modifications including blade trailing edge shapes, blade shape modification via blade pressure and suction surfaces’ tapering, and addition of dimple feature to the blade pressure surface were applied to the blade profile. The presented results revealed that the applied blade shape modifications affected nucleation and droplet growth processes, shock wave structures and entropy generation rates. The influence of blade shape on loss generation was presented by calculating the Markov energy loss coefficients. The presented analysis exhibits that the blade shape alteration influences the overall loss generation that occur due to the irreversible heat and mass transfer during the condensation process.

Two-Phase Eulerian/Lagrangian Model for Nucleating Steam Flow

2002 ◽  
Vol 124 (2) ◽  
pp. 465-475 ◽  
Author(s):  
A. G. Gerber
Keyword(s):  
Three Dimensional ◽  
Low Pressure ◽  
Steam Flow ◽  
Nucleation Theory ◽  
Lagrangian Model ◽  
Classical Nucleation Theory ◽  
Navier Stokes ◽  
Steam Turbines ◽  
Complex Flow ◽  
Two Phase

This paper describes an Eulerian/Lagrangian two-phase model for nucleating steam based on classical nucleation theory. The model provides an approach for including spontaneous homogeneous nucleation within a full Navier-Stokes solution scheme where the interaction between the liquid and gas phases for a pure fluid is through appropriately modeled source terms. The method allows for the straightforward inclusion of droplet heat, mass, and momentum transfer models along with nucleation within complex flow systems as found, for example, in low pressure steam turbines. The present paper describes the solution method, emphasizing that the important features of nucleating steam flow are retained through comparison with well-established 1-D solutions for Laval nozzle flows. Results for a two-dimensional cascade blade and three-dimensional low pressure turbine stage are also described.

Unsteady Flow Simulation Through Stator-Rotor Blade Rows in Intermediate-Pressure Steam Turbines With Cutback Blades

2020 ◽  
Author(s):  
Hironori Miyazawa ◽  
Akihiro Uemura ◽  
Takashi Furusawa ◽  
Satoru Yamamoto ◽  
Koichi Yonezawa ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Flow Simulation ◽  
Negative Influence ◽  
Rotor Blades ◽  
Steam Flow ◽  
Metal Fatigue ◽  
Steam Turbines ◽  
Trailing Edge ◽  
Intermediate Pressure ◽  
Pressure Steam

Abstract Stator and rotor blades in intermediate-pressure steam turbines gradually deteriorate during operation because of solid particle erosion. In addition to that, turbine blades unexpectedly crack because of metal fatigue or thermal stress deformation. As eroded blades increase the aerodynamic losses and cracked blades may induce rupture of the blade, the periodic maintenance, repair, and overhaul of steam turbines is essential. Eroded or cracked blades should be replaced with new ones or repaired for further use. Cutback treatment is one of the repair methods wherein the deteriorated trailing edge on a turbine blade is removed to avoid further cracking and blade fracturing. The use of cutback blades can reduce the replacement cost; however, that may affect the steam flow and the turbine’s performance. In this study, we numerically investigated the effect of the blade deterioration on the performance of a three-stage intermediate-pressure steam turbine using a numerical method that was developed at Tohoku University. Further various cutback lengths were considered for the deteriorated first-stage stator-blade trailing edge. The obtained numerical results indicate that the cutback first-stage stator blades certainly affected the steam flow in the turbine, resulting in a negative influence on the torque obtained from the adjacent rotor blades, which depends on the cutback length. However, the torque decrement can be mitigated by arranging the cutback and non-cutback stator blades alternately in a row.

Vapor–liquid nucleation in two dimensions: On the intriguing sign switch of the errors of the classical nucleation theory

2012 ◽  
Vol 137 (19) ◽  
pp. 194304 ◽  
Author(s):  
Troy D. Loeffler ◽  
David E. Henderson ◽  
Bin Chen
Keyword(s):  
Two Dimensions ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Vapor Liquid
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