Generalization of an Analytical Two-Phase Steam Flow Calculator to High-Pressure Cases

Kermani, M.J.; Zayemouri, M.; Saffar‐Avval, Majid

doi:10.1139/tcsme-2006-0036

Cited by 2 publications

(3 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Energies 2017, 10, 1285 11 of 36 degree is high, is rapid with a steep slope, but after the nucleation region has a slow growth and the flow relatively reaches equilibrium state. It should be noted that the difference between the radius calculated from theory is also reported in the results of other studies [2,41]. As mentioned, at this stage the aim of using inverse modeling is to obtain an optimum value for the parameter which will be calculated in the next section.…”

Section: Moore Nozzle Type Amentioning

confidence: 75%

A Novel Hybrid Approach for Numerical Modeling of the Nucleating Flow in Laval Nozzle and Transonic Steam Turbine Blades

Rad

Mahpeykar

2017

Energies

View full text Add to dashboard Cite

In the present research, considering the importance of desirable steam turbine design, improvement of numerical modeling of steam two-phase flows in convergent and divergent channels and the blades of transonic steam turbines has been targeted. The first novelty of this research is the innovative use of combined Convective Upstream Pressure Splitting (CUSP) and scalar methods to update the flow properties at each calculation point. In other words, each property (density, temperature, pressure and velocity) at each calculation point can be computed from either the CUSP or scalar method, depending on the least deviation criterion. For this reason this innovative method is named "hybrid method". The next novelty of this research is the use of an inverse method alongside the proposed hybrid method to find the amount of the important parameter z in the CUSP method, which is herein referred to as "CUSP's convergence parameter". Using a relatively simple computational grid, firstly, five cases with similar conditions to those of the main cases under study in this research with available experimental data were used to obtain the value of z by the Levenberg-Marquardt inverse method. With this innovation, first, an optimum value of z = 2.667 was obtained using the inverse method and then directly used for the main cases considered in the research. Given that the aim is to investigate the two-dimensional, steady state, inviscid and adiabatic modeling of steam nucleating flows in three different nozzle and turbine blade geometries, flow simulation was performed using a relatively simple mesh and the innovative proposed hybrid method (scalar + CUSP, with the desired value of z = 2.667). A comparison between the results of the hybrid modeling of the three main cases with experimental data showed a very good agreement, even within shock zones, including the condensation shock region, revealing the efficiency of this numerical modeling method innovation. The main factor in improving the aforementioned results was found to be a reduction of the numerical errors by up to 70% in comparison to conventional methods (scalar, Jameson original), so that the mass flow rate is well conserved, thereby proving better satisfaction of the conservation laws. It should be noted that by using this innovative hybrid method, one can take advantages of both central difference scheme and upstream scheme (scalar and CUSP, respectively) at the same time in simulating complex flows in any other finite volume scheme.presence of blades of tip-section geometry, given the relatively high complexities, there is still a need for improved numerical methods with reduced numerical errors, for accurate modeling of the flow. For this purpose, one may see the derivation of a more accurate numerical method to capture condensation shock and aerodynamic shocks (flow discontinuities) with minimum fluctuations and, particularly, minimal numerical errors as one of the important challenges faced by computational fluid dynamics (CFD) [4][5][6][7].Vapor flow through the no...

show abstract

Section: Moore Nozzle Type Amentioning

confidence: 75%

A Novel Hybrid Approach for Numerical Modeling of the Nucleating Flow in Laval Nozzle and Transonic Steam Turbine Blades

Rad

Mahpeykar

2017

Energies

View full text Add to dashboard Cite

show abstract

“…The temperature of the droplets can be determined by capillarity effect, and since the droplets have very small size, their temperatures are assumed uniform through the droplets. With the definition of T s as the saturation temperature at the local pressure, P, the temperature equation for water droplet can be shown as (9) where r * is the critical droplet radius that will be described subsequently.…”

Section: Energy Equationsmentioning

confidence: 99%

“…(12)). Where γ is the specific heat ratio (average value for γ of superheated steam equal to 1.32 has been used throughout this study [9]) and is the equilibrium latent heat. The gas constant and temperature of gas are R, and T g respectively.…”

Section: Nucleationmentioning

confidence: 99%

A numerical study of two-phase transonic steam flow through convergence-divergence nozzles with different rates of expansion

Nikkhahi

Shams

Ziabasharhagh

2010

Korean J. Chem. Eng.

View full text Add to dashboard Cite

During transonic flow of steam in divergence nozzles, flow first supercools and then nucleates to become two-phase droplet flow. This phenomenon especially occurs in the last stages of steam turbines and affects performance. In this research, a numerical scheme for two-phase flow in nozzle passages is developed. An Eulerian-Eulerian reference frame is used for both phases. The shear stress transport turbulence model is used to model the Reynolds stresses appearing in the averaged Navier-Stokes equations. The homogeneous nucleation model is applied for the mass transfer in the transonic conditions. In this paper three nozzles with different rate of expansion are employed to be under study. Overall pressure ratio (static to total pressure) and droplet size are compared with the experimental data and good agreements are observed.

show abstract

Generalization of an Analytical Two-Phase Steam Flow Calculator to High-Pressure Cases

Cited by 2 publications

References 12 publications

A Novel Hybrid Approach for Numerical Modeling of the Nucleating Flow in Laval Nozzle and Transonic Steam Turbine Blades

A Novel Hybrid Approach for Numerical Modeling of the Nucleating Flow in Laval Nozzle and Transonic Steam Turbine Blades

A numerical study of two-phase transonic steam flow through convergence-divergence nozzles with different rates of expansion

Contact Info

Product

Resources

About