A blackbox optimization of volumetric heating rate for reducing the wetness of the steam flow through turbine blades

This paper proposes to use a blackbox optimization to obtain the optimal volumetric heating required to reduce the wetness at the last stages of steam turbines. For this purpose, a global multiobjective optimization is utilized through the automatic linking of genetic algorithm and CFD code, where the blackbox function evaluations are performed by CFD runs. The logarithm of number of droplets per volume (LND), the droplet average radius (DAR), and the integral of local entropy (ILE) at the end of the cascade (after the condensation location) are minimized, while the volumetric heating rate is the optimization parameter. The Eulerian–Eulerian approach is implemented to model the two-phase wet steam turbulent flow and the numerical results are validated against well-established experiments. Since higher volumetric heating rates reduce DAR and LND, while increase ILE, according to optimization results, there is an optimum for the volumetric heating rate to reach the best performance of steam turbines. For case studies presented in this work, the optimal volumetric heating rates of 5.21x10^8 and 4.67x10^8 W/m^2 are obtained for two different cases of supersonic and subsonic outlets, respectively. Particularly, these rates improve DAR by 45.7% and 57.5%, and LND by 6.0% and 7.8% for respective cases

On the application of isogeometric finite volume method in numerical analysis of wet-steam flow through turbine cascades

The isogeometric finite volume analysis is utilized in this research to numerically simulate the two-dimensional viscous wet-steam flow between stationary cascades of a steam turbine for the first time. In this approach, the analysis-suitable computational mesh with ‘‘curved’’ boundaries is generated for the fluid flow by employing a non- uniform rational B-spline (NURBS) surface that describes the cascade geometry, and the governing equations are then discretized by the NURBS representation. Thanks to smooth and accurate geometry representation of the NURBS formulation, the employed isogeometric framework not only resolves issues concerning the conventional mesh generation techniques of the finite volume method in steam turbine problems, but also, as validated against well-established experiments, significantly improves the accuracy of the numerical solution. In addition, the shock location in the cascade is predicted and tracked with a sufficient accuracy

Numerical Investigation of Wet Inflow in Steam Turbine Cascades Using NURBS-based Mesh Generation Method

In this paper, the impact of existence of wetness in the inflow of stationary cascades of steam turbine blades has been numerically investigated. A new mesh generation method based on non-uniform rational B-splines (NURBS) has been adopted to reduce the numerical error of the wet inflow simulation. Moreover, two common meshing scenarios namely blade-to-blade (B-B) and periodic-to-periodic boundary (P-P) are studied and different angle of the grid at the trailing edge have been considered. The classical nucleation theory corrected by Courtney–Kantrowitz model and the Young's droplet growth model are employed to simulate the condensation phenomenon. By validating against experimental data, the results showed that implementing the proposed NURBS-based meshing technique decreased the prediction errors of static pressure distribution and droplet average radius by 35.64% and 78.44%, respectively, in comparison to typical grid generation methods. In addition, it was observed that existence of wetness at inlet significantly decreased the supercooling degree and postponed the nucleation process. Thus, the nucleation rate could be ameliorated in the case when we have a specific amount of wetness fraction in the inflow

Quantitative comparison of ammonia and 3-indoleacetic acid production in halophilic, alkalophilic and haloalkalophilic bacterial isolates in soil

In order to measure the concentration of ammonia production via corrected Nesslerization method and 3-indoleacetic acid as Salkowski method in halophilic, alkalophilic and haloalkalophilic bacterial isolates, soil samples were collected from six different areas of Khorasan Razavi and bacterial isolates isolated and purified using different growth medium accordingly. The alkalophiles isolates showed maximum ammonia production (0.055%) among the three groups of bacteria which this amount was 9.5 times of its average in haloalkalophiles isolates (0.0058%) and 13 times of ammonia production average in halophiles (0.004%). Mean comparison of the concentration3-indoleacetic acid production in three groups also showed that the most isolates of halophiles, alkalophiles and haloalkalophiles were IAA producer with 0.0003, 0.0001 and 0.0021percent respectively that the IAA amount in haloalkalophilic group was about 6 and 14.5 times of it in halophilic and alkalophilic isolates respectively. Equations to predict the concentration of ammonia and 3-indole acetic acid production was only significant in the haloalkalophilic isolates for ammonia production (P=0.046) and halophilic isolates for IAA production (P=0.015) under effect of electrical conductivity and pH in 0.05 probability level. Results represented that the multiple regression analysis for prediction of ammonia and IAA concentrations producing by isolates had not any significant performance in high and low concentrations under effect of electrical conductivity and pH. It seems that the uses of the two sensitive measuring methods (Nesslerization and Salkowski) after some modifications show promises and are recommend able in research due to their ease of implementation and relatively accurate results.Keywords: Alkalophiles; haloalkalophiles; halophiles; 3-indoleacetic acid; nesslerization method; salkowski method

Nitric oxide metabolite levels during the ectopic osteoinduction in rats

Abstract Nitric oxide (NO) is a cell-signaling molecule that has diverse biological functions. Recent evidence suggests that its production may regulate the metabolism of the osteoblasts and osteoclasts. The aim of this study was to evaluate levels of nitrite and nitrates (NO metabolites) during ectopic osteoinduction in rats. Eighteen male Sprague–Dawley rats (body weight 200–300 g) were used in this study. All animals were anesthetized and the right and left flank areas were shaved, and under aseptic conditions, a muscular pouch was created in each flank: the left was filled with 20 mg of demineralized bone matrix and the right remained empty (sham). Radiographs were taken at 2, 4, and 6 weeks after surgery to trace the ectopic bone formation and muscle mineralization. Blood samples were taken before (as baseline values) and at 2, 4, and 6 weeks after surgery. The mean values of NO metabolites after 6 weeks were significantly higher (p<0.05) than baseline data and at 2 weeks post-surgery. Results from this study indicate that the ectopic osteoinduction caused increased activity of the osteoblasts which subsequently caused increased serum levels of NO metabolites (nitrites and nitrates)

COVID-19 spread in a classroom equipped with partition – A CFD approach

In this study, the motion and distribution of droplets containing coronaviruses emitted by coughing of an infected person in front of a classroom (e.g., a teacher) were investigated using CFD. A 3D turbulence model was used to simulate the airflow in the classroom, and a Lagrangian particle trajectory analysis method was used to track the droplets. The numerical model was validated and was used to study the effects of ventilation airflow speeds of 3, 5, and 7 m/s on the dispersion of droplets of different sizes. In particular, the effect of installing transparent barriers in front of the seats on reducing the average droplet concentration was examined. The results showed that using the seat partitions for individuals can prevent the infection to a certain extent. An increase in the ventilation air velocity increased the droplets’ velocities in the airflow direction, simultaneously reducing the trapping time of the droplets by solid barriers. As expected, in the absence of partitions, the closest seats to the infected person had the highest average droplet concentration (3.80 × 10−8 kg/m3 for the case of 3 m/s)

Numerical investigation of roughness effect on wet steam ejector performance in the refrigeration cycle

Machining operation and presence of water droplets cause increase the surface roughness of wet steam ejector walls and change its performance in the refrigeration cycle. The purpose of this work is to investigate the influences of the primary nozzle surface roughness on wet steam ejectors in the refrigeration cycle with steam water as a working flow. The Eulerian-Eulerian model is validated by a comparison of numerical results with experimental data. Moreover, different surface roughness has been successfully applied to the primary nozzle, and its effect on the entire flow is shown. Six properties of wet steam are selected, including pressure, temperature, Mach number, average droplet radius, droplet growth rate, and liquid mass fraction. The result shows increasing roughness resulted in a shift of the shock chain to the primary nozzle, damping shock strength, and rising temperature in the diffuser. In addition, increment of the primary nozzle surface roughness decreases ER and COP of the refrigeration cycle by 3.67% and 3.8%, respectively. The designers and operators should be considered the roughness effects in the design and operation of wet steam ejectors due to the vital impact of the roughness on the liquid mass fraction, average droplet radius, droplet growth rate, ER, and COP. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature