Abstract
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.
Highlights
Efficiency enhancement of steam turbines, which are important components of the power generation industry, has been always considered by designers
To obtain the optimum convergence parameter z, first, the novel hybrid method (Jameson) + Convective Upstream Pressure Splitting (CUSP)) is used alongside the inverse method for different geometrical cases with steam (scalar (Jameson) + CUSP) is used alongside the inverse method for different geometrical cases with two-phase nucleating condition which are similar to the main cases investigated in this study, where steam two-phase nucleating condition which are similar to the main cases investigated in this study, the results of each case is explained
CUSP, and indicates a new achievement in better satisfying the conservation laws and verification of the results. The aim of this present research was to improve the numerical modeling of steady state steam two-phase vapor-liquid flows in the convergent-divergent channels and in cascaded blades of transonic steam turbines, the motivation being the fact that iterative numerical methods tend to give high errors in such complex flows, in the relatively complicated geometries of the tip-section of turbine blades, so it is of paramount importance to reduce the numerical errors to improve the results
Summary
Efficiency enhancement of steam turbines, which are important components of the power generation industry, has been always considered by designers. Energies 2017, 10, 1285 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, minimal numerical errors as one of the important challenges faced by computational fluid dynamics (CFD) [4,5,6,7].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
