The Feasibility of an Euler–Lagrange Approach for the Modeling of Wet Steam

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Tim Wittmann ◽  
Christoph Bode ◽  
Jens Friedrichs
Keyword(s):  
Optimal Parameter ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Droplet Growth ◽  
Wet Steam ◽  
Discrete Phase Model ◽  
Validation Data ◽  
Numerical Validation ◽  
Discrete Phase ◽  
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 Modeling Project of Starzmann et al. (2018, “Results of the International Wet Steam Modeling Project,” Proc. Inst. Mech. Eng. A, 232(5), pp. 550–570). 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 ansysfluent. 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 modeling parameters are analyzed. Finally, an optimal parameter set for the calculation of nucleation and condensation is proposed.

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.

Two-Phase Flow Modeling and Measurements in Low-Pressure Turbines: Part 2 — Turbine Wetness Measurement and Comparison to CFD-Predictions

2014 ◽  
Author(s):  
M. Schatz ◽  
T. Eberle ◽  
M. Grübel ◽  
J. Starzmann ◽  
D. M. Vogt ◽  
...  
Keyword(s):  
Experimental Data ◽  
Steam Turbine ◽  
Physical Models ◽  
Droplet Growth ◽  
Steam Turbines ◽  
Wet Steam ◽  
Validity And Reliability ◽  
Two Phase ◽  
Validation Data ◽  
Subsequent Formation

The correct computation of steam subcooling, subsequent formation of nuclei and finally droplet growth is the basic prerequisite for a quantitative assessment of the wetness losses incurred in steam turbines due to thermal and inertial relaxation. The same basically applies for the prediction of droplet deposition and the resulting threat of erosion. Despite the fact that there are many CFD-packages that can deal with real-gas effects in steam flows, the accurate and reliable prediction of subcooling, condensation and wet steam flow in steam turbines using CFD is still a demanding task. One reason for this is the lack of validation data for turbines that can be used to assess the physical models applied. Experimental data from nozzle and cascade tests can be found in the open literature; however, this data is only partly useful for validation purposes for a number of reasons. With regard to steam turbine test data, there are some publications, yet always without any information about the turbine stage geometries. This publication is part of a two-part paper; whereas part 1 focuses on the numerical validation of wet steam models by means of condensing nozzle and cascade flows, the focus in this part lies on the comparison of CFD results of the turbine flow to experimental data at various load conditions. In order to assess the validity and reliability of the experimental data, the method of measurement is presented in detail and discussed. The comparison of experimental and numerical results is used for a discussion about the challenges in both modeling and measuring steam turbine flows, presenting the current experience and knowledge at ITSM.

scholarly journals Numerical simulation of multiphase flow in ventilation mill and channel with louvers and centrifugal separator

2011 ◽  
Vol 15 (3) ◽  
pp. 677-689 ◽  
Author(s):  
Mirko Kozic ◽  
Slavica Ristic ◽  
Mirjana Puharic ◽  
Boris Katavic
Keyword(s):  
Multiphase Flow ◽  
Numerical Simulations ◽  
Volume Fraction ◽  
Complex Geometry ◽  
Mixture Distribution ◽  
Flow Simulation ◽  
Centrifugal Separator ◽  
Discrete Phase Model ◽  
Discrete Phase ◽  
Lagrange Approach

This paper presents the results of numerical flow simulation in ventilation mill of Kostolac B power plant, where louvers and centrifugal separator with adjustable blade angle are used. Numerical simulations of multiphase flow were performed using the Euler-Euler and Euler-Lagrange approach of ANSYS FLUENT software package. The results of numerical simulations are compared with measurements in the mill for both types of separators. Due to very complex geometry and large number of the grid cells, convergent solution with the Eulerian model could not be obtained. For this reason the mixture model was employed resulting in very good agreement with measurements, concerning the gas mixture distribution and velocity at the main and secondary burners. There was large difference between the numerical results and measurements for the pulverized coal distribution at the burners. Taking into consideration that we analyzed dilute mixture with very low volume fraction of the coal, the only choice was the Euler-Lagrange approach, i.e. discrete phase model limited to volume fraction of the discrete phase less than 10-12%. Obtained distributions of the coal at the burners agree well for both types of separators.

Asymptotic solution of shock tube flows with homogeneous condensation

1995 ◽  
Vol 287 ◽  
pp. 93-118 ◽  
Author(s):  
Can F. Delale ◽  
Günter H. Schnerr ◽  
Jürgen Zierep
Keyword(s):  
Shock Wave ◽  
Asymptotic Solution ◽  
Shock Tube ◽  
Complete Solution ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Droplet Growth ◽  
Homogeneous Condensation ◽  
Shock Fitting ◽  
Supercritical Flows

The asymptotic solution of shock tube flows with homogeneous condensation is presented for both smooth, or subcritical, flows and flows with an embedded shock wave, or supercritical flows. For subcritical flows an analytical expression, independent of the particular theory of homogeneous condensation to be employed, that determines the condensation wave front in the rarefaction wave is obtained by the asymptotic analysis of the rate equation along pathlines. The complete solution is computed by an algorithm which utilizes the classical nucleation theory and the Hertz–Knudsen droplet growth law. For supercritical flows four distinct flow regimes are distinguished along pathlines intersecting the embedded shock wave analogous to supercritical nozzle flows. The complete global solution for supercritical flows is discussed only qualitatively owing to the lack of a shock fitting technique for embedded shock waves. The results of the computations obtained by the subcritical algorithm show that most of the experimental data available exhibit supercritical flow behaviour and thereby the predicted onset conditions in general show deviations from the measured values. The causes of these deviations are reasoned by utilizing the qualitative global asymptotic solution of supercritical flows.

Modelling of condensing steam flows in Laval nozzles with ANSYS CFX

2017 ◽  
Vol 232 (5) ◽  
pp. 571-575 ◽  
Author(s):  
Marius Grübel ◽  
Jörg Starzmann ◽  
Markus Schatz ◽  
Damian M Vogt
Keyword(s):  
Measurement Data ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Test Cases ◽  
Wet Steam ◽  
Flow Solver ◽  
Spontaneous Condensation ◽  
Ansys Cfx ◽  
Fluid Properties ◽  
Laval Nozzles

The results of the International Wet Steam Modelling Project presented at the Wet Steam Conference in Prague in 2016 again gave rise to a discussion about the suitability of the flow solver ANSYS CFX for the prediction of spontaneous condensation. In this article, the main reason for the discrepancy between results obtained with CFX and measurement data is identified. It could be found that in CFX the temperature of already existing droplets is used for evaluating the fluid properties involved in the nucleation process. This is not in agreement with the isothermal classical nucleation theory, which is based on the assumption that clusters of critical radius are formed at vapour temperature. The most dominant parameter affected by this is the surface tension, the evaluation of which can be altered easily by the user. The influence of the correction is illustrated by means of standard Laval nozzle test cases, and a significant improvement of the results compared to measurement data can be observed.

scholarly journals Numerical investigation of condensing flow of low pressure steam turbine at different flow rate conditions

2017 ◽  
Vol 21 (suppl. 1) ◽  
pp. 161-167 ◽  
Author(s):  
Kezhen Huang ◽  
Lin Cai ◽  
Jianshu Gao ◽  
Zhuo Liu ◽  
Xinggang Yu
Keyword(s):  
Steam Turbine ◽  
Numerical Investigation ◽  
Low Pressure ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Wet Steam ◽  
Pressure Steam ◽  
Static Performance ◽  
Wet Steam Flow ◽  
Two Stages

The numerical investigation on the wet steam flow in the last two stages of a 1000 MW fossil-fired low pressure steam turbine is presented in this paper. The non-equilibrium model via the classical nucleation theory is employed to simulate the condensing flow of the wet steam. The characteristics of the flow filed from design condition to low volume flow condition are calculated and the static performance of last stage moving blade is also obtained. The development of the backflow phenomenon is clearly captured through the analysis of the velocity triangle.

Instabilities and bifurcation of non-equilibrium two-phase flows

1997 ◽  
Vol 348 ◽  
pp. 1-28 ◽  
Author(s):  
STEPHAN ADAM ◽  
GÜNTER H. SCHNERR
Keyword(s):  
Equilibrium Phase ◽  
Practical Interest ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Droplet Growth ◽  
Sudden Increase ◽  
Pressure Amplitude ◽  
Two Phase ◽  
Supersonic Wind Tunnel ◽  
Non Equilibrium

New instabilites of unsteady transonic flows with non-equilibrium phase transition are presented including unsymmetric flow patterns with moving oblique shock systems in supersonic nozzles with perfectly symmetric shapes. The phenomena were first detected when performing experiments in our supersonic wind tunnel with atmospheric supply and could be perfectly reproduced by numerical simulations based on the Euler equations, i.e. neglecting the viscosity of the fluid. The formation of the liquid phase is modelled using the classical nucleation theory for the steady state together with the Hertz–Knudsen droplet growth law and yields qualitatively and quantitatively excellent agreement with experiments in the unsteady flow regime with high-frequency oscillations including the unstable transient change of the structure from symmetric to unsymmetric flow.For engineering applications the sudden increase or decrease of the frequency by a factor 2 or more and of the pressure amplitude at the bifurcation limits is of immediate practical interest, e.g. for flutter excitation of turbomachinery blading.

Numerical Sensitivity Study and Calibration of Non-Equilibrium Wet Steam Model

2013 ◽  
Author(s):  
F. J. Moraga ◽  
L. Wang ◽  
W.-M. Ren
Keyword(s):  
Droplet Diameter ◽  
Sensitivity Study ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Transfer Model ◽  
Wet Steam ◽  
Cfd Simulations ◽  
Pressure Profiles ◽  
Non Equilibrium

Comparisons between one- and two-dimensional experiments and non-equilibrium wet steam CFD simulations are conducted paying attention not only to pressure profiles and wetness but also to the more difficult to match droplet diameter. To achieve the objective of optimizing the match of data the heat transfer model between the droplet and its surrounding vapor proposed by Young and the corrections to classical nucleation theory proposed by Moore and popularized by Gerber are adopted. It is found that the proposed models produce a better agreement with droplet diameter, without affecting the overall quality of the predictions for other quantities.

Classical Nucleation Theory and Its Application to Condensing Steam Flow Calculations

2005 ◽  
Vol 219 (12) ◽  
pp. 1315-1333 ◽  
Author(s):  
F Bakhtar ◽  
J B Young ◽  
A J White ◽  
D A Simpson
Keyword(s):  
Predictive Accuracy ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Droplet Radius ◽  
Droplet Growth ◽  
Wide Range ◽  
Recent Developments ◽  
Judicious Choice ◽  
The Many ◽  
Low Pressures

The paper discusses the classical theory of the homogeneous nucleation of water droplets from supersaturated vapour and its application in predicting condensation in steam nozzles. The first part consists of a review of classical nucleation theory, focusing on the many modifications made to the original Becker-Döring theory and providing some new insights into recent developments. It is concluded that the predictive accuracy required for engineering calculations is not yet attainable with a theory derived from first principles. The areas that require most attention relate to the properties of small molecular clusters and the energy transfer processes in the non-isothermal theory. Experiments in converging-diverging nozzles provide the best means for validation at the very high nucleation rates of interest, but measurements of pressure distribution and the Sauter mean droplet radius are insufficient to provide independent checks on the separate theories of nucleation and droplet growth. Nevertheless, a judicious choice for the nucleation rate equation, in combination with a standard droplet growth model and a suitable equation of state for steam, can provide accurate predictions over a wide range of conditions. The exception is at very low pressures where there is evidence that the droplet growth rate in the nucleation zone is underestimated.

Two-Phase Flow Modeling and Measurements in Low-Pressure Turbines—Part II: Turbine Wetness Measurement and Comparison to Computational Fluid Dynamics-Predictions

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
M. Schatz ◽  
T. Eberle ◽  
M. Grübel ◽  
J. Starzmann ◽  
D. M. Vogt ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Steam Turbine ◽  
Physical Models ◽  
Droplet Growth ◽  
Steam Turbines ◽  
Wet Steam ◽  
Validation Data ◽  
Subsequent Formation

The correct computation of steam subcooling, subsequent formation of nuclei and finally droplet growth is the basic prerequisite for a quantitative assessment of the wetness losses incurred in steam turbines due to thermal and inertial relaxation. The same basically applies for the prediction of droplet deposition and the resulting threat of erosion. Despite the fact that there are many computational fluid dynamics (CFD)-packages that can deal with real-gas effects in steam flows, the accurate and reliable prediction of subcooling, condensation, and wet steam flow in steam turbines using CFD is still a demanding task. One reason for this is the lack of validation data for turbines that can be used to assess the physical models applied. Experimental data from nozzle and cascade tests can be found in the open literature; however, these measurement results are only partly useful for validation purposes for a number of reasons. With regard to steam turbine test data, there are some publications, yet always without any information about the turbine stage geometries. This publication is part of a two-part paper; whereas Part I focuses on the numerical validation of wet steam models by means of condensing nozzle and cascade flows, the focus in this part lies on the comparison of CFD results of the turbine flow to experimental data at various load conditions. In order to assess the validity and reliability of the experimental data, the method of measurement is presented in detail and discussed. The comparison of experimental and numerical results is used for a discussion about the challenges in both modeling and measuring steam turbine flows, presenting the current experience and knowledge at Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM).

Sign in / Sign up

Export Citation Format

Share Document