Non-equilibrium spontaneous condensation in transonic steam flow

Yousif, Assim H.; Al-Dabagh, Amer M.; Al-Zuhairy, Reyadh Ch.

doi:10.1016/j.ijthermalsci.2013.01.002

Cited by 45 publications

(14 citation statements)

References 12 publications

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“…The droplet growth rate is calculated based on the heat transfer process and mass transfer between the droplets and vapor in different flow regimes in the passage and it should be noted that the mentioned heat transfer depends on the unknown temperature of the droplet, (T L ). In this research, the droplets temperature is obtained using Gyarmathy's approximation [1,7,19,33] and also, to further reduce of the volume of calculations for Equation (9a) only in the wet region (or relative equilibrium condition), a direct approximation is used, as introduced by Equation (9b) [1,9,12,19]:…”

Section: Relations Of Droplet Growthmentioning

confidence: 99%

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

Rad

Mahpeykar

2017

Energies

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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...

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Section: Relations Of Droplet Growthmentioning

confidence: 99%

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

Rad

Mahpeykar

2017

Energies

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“…The steam condensing flow was modeled through the Laval nozzles at low and high inlet pressures by means of the single-fluid model [22]. The Eulerian-Eulerian approach was adopted for modeling the condensing steam flow, and the simulation was conducted on the commercial ANSYS FLUENT 12.1 platform [23].…”

Section: Introductionmentioning

confidence: 99%

CFD modeling of condensation process of water vapor in supersonic flows

Yang

Walther

Yan

2017

Applied Thermal Engineering

109

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“…The effect of back pressure on the non-equilibrium condensation through a turbine cascade was studied numerically and experimentally by Yousif et al [11]. It was reported that low back pressure causes a high level of liquid mass fraction for a wide range of inlet conditions.…”

Section: Introductionmentioning

confidence: 99%

CFD-based shape optimization of steam turbine blade cascade in transonic two phase flows

Abadi

Ahmadpour

Abadi

et al. 2017

Applied Thermal Engineering

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Highlights• CFD-based shape optimization of a nozzle and a turbine blade regarding nucleating steam flow is performed.• Nucleation rate and droplet radius are the best suited objective functions for the optimization p rocess.• Maximum 34% reduction in entropy generation rate is reported for turbine cascade.• A maximum 10% reduction in Baumann factor and a maximum 2.1% increase in efficiency is achieved for a turbine cascade. Abstract:In this study CFD-based shape optimization of a 3D nozzle and a 2D turbine blade cascade is undertaken in the presence of non-equilibrium condensation within the considered flow channels.A two-fluid formulation is used for the simulation of unsteady, turbulent, supersonic and compressible flow of wet steam accounting for relevant phase interaction between nucleated liquid droplets and continuous vapor phase. An in-house CFD code is developed to solve the governing equations of the two phase flow and was validated against available experimental

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Non-equilibrium spontaneous condensation in transonic steam flow

Cited by 45 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

CFD modeling of condensation process of water vapor in supersonic flows

CFD-based shape optimization of steam turbine blade cascade in transonic two phase flows

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