Development of a Design Approach for the Optimization of Steam Turbine Exhaust System Performance Through CFD Modelling

2021 ◽  
Author(s):  
Tommaso Diurno ◽  
Stella Grazia Tomasello ◽  
Tommaso Fondelli ◽  
Antonio Andreini ◽  
Bruno Facchini ◽  
...  
Keyword(s):  
Power Plants ◽  
Fluid Dynamic ◽  
Renewable Energy Sources ◽  
Computational Cost ◽  
Great Influence ◽  
Computational Effort ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Geometrical Parameters ◽  
Exhaust Hood

Abstract Nowadays, the ever-increasing world electricity generation by renewable energy sources has brought about changes in conventional power plants, especially in those ones where large steam turbines work, which were widely used to meet the world’s energy needs by operating mostly at fixed conditions. Now, instead, they have to be capable to operate with greater flexibility, including rapid load changes and quick starts as well, in order to make the most of the renewable resources while guaranteeing the coverage of any shortcomings of the latter with traditional fossil fuel systems. Such service conditions are particularly challenging for the exhaust hoods, which have a great influence on the overall turbine performance, especially at off-design conditions. In fact, the complex and high rotational 3D flow generated within the diffuser and the exhaust hood outer casing can cause an increase in aerodynamic losses along with the detriment of the hood recovery performance. For these reasons, an optimized design and adequate prediction of the exhaust hood performance under all the machine operating conditions is mandatory. Since it has been widely proven that the exhaust hood flow strongly interacts with the turbine rear stage, the necessity to model this as well into a CFD modeling becomes crucial, requiring a remarkable computational effort, especially for full transient simulations. Even if adopting simplified approaches to model the last stage and exhaust hood interfaces, such as the so-called Frozen Rotor and the Mixing Plane ones, helps to keep the computational cost low, it can be not for an exhaust hood optimization process, which requires a significant number of CFD simulations to identify the most performing geometry configuration. For these reasons, a simplified model of the exhaust hood must be adopted to analyse all the possible design variants within a feasible time. The purpose of this work is to present a strategy for the exhaust hood design based on the definition of a simplified CFD model. A parametric model has been developed as a function of key geometrical parameters of both the exhaust hood and the diffuser, taking into account the strong fluid-dynamic coupling between these components. A periodic approximation has been introduced to model the exhaust hood domain, thus allowing to augment the number of the geometrical parameters of the DOE, while keeping the computational effort low. A response surface has been achieved as a function of the key geometrical parameters, therefore an optimization method has allowed identifying the best performing configuration. A 3D model of the optimized periodic geometry has been then generated to assess the effectiveness of the procedure here presented. Finally, the presented procedure has been applied in several off-design operating conditions, in order to find out an optimal geometry for each operating point, evaluating how much they differ from that one got for the design point.

District Heating Network Modelling for the Analysis of Low-Exergy Sources

2017 ◽  
Author(s):  
Vittorio Verda ◽  
Elisa Guelpa
Keyword(s):  
Power Plants ◽  
Waste Heat ◽  
Fluid Dynamic ◽  
Renewable Energy Sources ◽  
Variable Mass ◽  
District Heating ◽  
Conservation Equation ◽  
Operating Conditions ◽  
Heat Sources ◽  
District Heating System

One of the main advantages of district heating system technology is the possibility of integrating multiple heat sources for domestic heating. In particular, it is often possible exploit low-exergy sources, such as waste heat recovered from industry or from renewable energy sources, that are often affected by time variation of the temperature. A very convenient and useful opportunity for predicting and analyzing district heating network behavior is modelling. Modelling allows to quantify opportunities related to changes in DH (district heating) network design or management, before real implementation. Therefore an important point is the creation of models able to simulate network, also very large and linked to many power plants, working at variable heat production conditions (i.e. variable mass flow rates and temperatures). The goal of this work is to propose a novel approach which combines exergy analysis with a DH network model for evaluating the best DH operating conditions. A thermo-fluid dynamic model based on conservation equation has been adapted for the discussed aims and applied to a network involving different low-exergy heat sources with variable temperatures. An evaluation of the implementation of these sources is provided for the Turin district heating network, which is the largest network in Italy.

scholarly journals CFD Modeling and Experimental Validation of an Alkaline Water Electrolysis Cell for Hydrogen Production

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1634
Author(s):  
Jesús Rodríguez ◽  
Ernesto Amores
Keyword(s):  
Fluid Dynamics ◽  
Hydrogen Production ◽  
Current Density ◽  
Fluid Dynamic ◽  
Water Electrolysis ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Electrolysis Cell ◽  
Alkaline Water Electrolysis ◽  
Alkaline Water

Although alkaline water electrolysis (AWE) is the most widespread technology for hydrogen production by electrolysis, its electrochemical and fluid dynamic optimization has rarely been addressed simultaneously using Computational Fluid Dynamics (CFD) simulation. In this regard, a two-dimensional (2D) CFD model of an AWE cell has been developed using COMSOL® software and then experimentally validated. The model involves transport equations for both liquid and gas phases as well as equations for the electric current conservation. This multiphysics approach allows the model to simultaneously analyze the fluid dynamic and electrochemical phenomena involved in an electrolysis cell. The electrical response was evaluated in terms of polarization curve (voltage vs. current density) at different operating conditions: temperature, electrolyte conductivity, and electrode-diaphragm distance. For all cases, the model fits very well with the experimental data with an error of less than 1% for the polarization curves. Moreover, the model successfully simulates the changes on gas profiles along the cell, according to current density, electrolyte flow rate, and electrode-diaphragm distance. The combination of electrochemical and fluid dynamics studies provides comprehensive information and makes the model a promising tool for electrolysis cell design.

THE INFLUENCE OF OPERATION CONDITIONS OF HYDROELECTRIC POWER PLANTS THE CHOICE OF THE MAIN PARAMETERS OF THE SUCTION PIPES

2015 ◽  
Vol 5 (4) ◽  
pp. 86-92 ◽  
Author(s):  
Mikhail Ivanovich BALZANNIKOV
Keyword(s):  
Power Plants ◽  
Draft Tube ◽  
Operating Conditions ◽  
Hydroelectric Power Station ◽  
Geometrical Parameters ◽  
Hydroelectric Power ◽  
Operation Conditions ◽  
Hydropower Plants ◽  
Large Water ◽  
Run Of River

Considered run-of-river hydropower plants (HPP). Notes the importance of technical-economic calculations in the justifi cation of large water-conducting elements of the path these types of HPP. The methodology of economic substantiation of the expediency of increasing the length of the draft tube. Using the technique of the calculations for lowpressure hydroelectric run-of-river type. The results of the analysis of the influence of the operating conditions of the hydroelectric power station on basic geometrical parameters of draft tube.

Magnus-Effect Rotors for Solar Chimney Power Plants

2010 ◽  
Author(s):  
Mohamed A. Serag-Eldin ◽  
Mohammed A. Abdul Latif
Keyword(s):  
Power Plants ◽  
Operating Conditions ◽  
Circular Cylinders ◽  
Cfd Modeling ◽  
Solar Chimney ◽  
Magnus Effect ◽  
Expected Performance ◽  
Circular Track ◽  
Force Components ◽  
Axial Turbines

The paper proposes the use of spinning and rotating cylinders to replace the axial turbines of Solar Chimney power plants. A large number of circular cylinders are placed equidistant, on a circular track concentric with the solar chimney axis. The cylinders spin around their own axis while simultaneously rotating about the chimney axis. By virtue of the Magnus effect, Lift forces arise which create force components tangential to the track in the direction of motion of the cylinders; thus mechanical work is produced. Using CFD modeling, the paper analyzes the resulting flow pattern and presents the expected performance of the hypothetical design for different geometric parameters and operating conditions. It is demonstrated that the design is indeed promising, and worthy of further investigation and development. It is also revealed that good performance of the proposed rotor is highly dependent on the proper choice of operating parameters.

Development of Enertech’s Advanced Normally Open NozzleCheck Valves for Generation III+ Nuclear Power Plants

2014 ◽  
Author(s):  
Haykaz Mkrtchyan
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Reverse Flow ◽  
Flow Direction ◽  
Fluid Dynamic ◽  
High Capacity ◽  
Check Valve ◽  
Operating Conditions ◽  
Flow Conditions ◽  
Valve Design

Enertech introduced the first Normally Open NozzleCheck valves to the nuclear power industry nearly 20 years ago. This passive valve design was developed to address reoccurring maintenance and reliability issues often experienced by various check valve types due to low or turbulent flow conditions. Specifically, premature wear on the hinge pins, bushings and severe seat impact damage had been discovered in several applications while the systems were in steady state operating conditions. Over the last two decades, Enertech has continued to improve upon the design of the valve, with the culmination coming most recently in support of Generation III+ passive reactor requirements. This entirely new valve is designed with minimal stroke, ensuring quick closure under low reverse flow conditions which no other check valve design could support. Additionally, features such as first in kind test ports, visual inspection points, and the ability to manually stroke the valve in line have resolved many of the short comings of previous inline welded flow check valves. Most importantly, advanced test based methodologies and models developed by Enertech, allow for accurate prediction of NozzleCheck valve performance. This paper presents the development of Enertech’s advanced Normally Open NozzleCheck Valve for Generation III and III+ nuclear reactor designs. The Valve performance was initially determined by using verified and validated computational fluid dynamic (CFD) methods. The results obtained from the CFD model were then compared to the data gathered from a prototype valve that was built and tested to confirm the performance predictions. Enertech has fully tested and qualified the Normally Open NozzleCheck valve which is specifically designed for applications that require a high capacity in the forward flow direction and a quick closure during low reverse flow condition with short stroke to minimize the hydraulic impact on the system.

Design and Optimization of Turbomachinery Components for Parabolic Dish Solar Hybrid Micro Gas Turbine

2020 ◽  
Author(s):  
Maulana Arifin ◽  
Markus Schatz ◽  
Damian M. Vogt
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Renewable Energy Sources ◽  
Computational Cost ◽  
Three Dimensional ◽  
Cycle Performance ◽  
Small Scale ◽  
Micro Gas Turbine ◽  
Parabolic Dish ◽  
Fully Coupled

Abstract The application of power plants based on renewable energy sources is attractive from an ecological viewpoint. Micro Gas Turbine (MGT) combined with solar energy is a highly promising technology for small-scale electric power generations in remote areas. In MGT state-of-the-art development, the necessity of the numerical optimization in turbomachinery components becomes increasingly important due to its direct impact on the MGT cycle performance. The present paper provides the multidisciplinary design optimization (MDO) of a radial turbine and radial compressor for a 40 kW Solar Hybrid Micro Gas Turbine (SHGT) with a 15m diameter parabolic dish concentrator. The objectives of MDO are to maximize the stage efficiency, to minimize the maximum stress and the inertia, and to enhance the operational flexibility. Preliminary design and performance map prediction using one-dimensional (1D) analysis are performed for both turbine and compressor at various speed lines followed by full three-dimensional (3D) Computational Fluid Dynamics (CFD), Finite Element (FE) analyses and 3D parameterization in the MDO simulations. The purpose of 1D analysis is to set the primary parameters for initial geometry such as rotor dimensions, passage areas, diffuser and volute size. The MDO has been performed using fully coupled multi-stream tube (MST), 3D CFD and FE simulations. MST is used for calculating the load on the blade and the flow distribution from hub to shroud and linearized blade-to-blade calculations based on quasi-three dimensional flow. Thereafter, 3D CFD simulations are performed to calculate efficiencies while the structural stresses are simulated by means of FE analyses. In the current studies, Numeca Fine/Turbo is used as a CFD solver and Ansys Mechanical as a FEA solver, together with Axcent™ as an interface to Fine/Design 3D for geometry parameterization. Furthermore, the cycle analysis for SHGT has been performed to evaluate the effect of the new turbomachinery components from the MDO on the SHGT system performance. It is found that using the MST fully coupled with CFD and FE analysis can significantly reduce the computational cost and time on the design and development process.

CFD Modeling and Performance Analysis of a Thermoacoustically Driven Thermoacoustic Refrigerator

2021 ◽  
pp. 2150029
Author(s):  
Zahra Bouramdane ◽  
Abdellah Bah ◽  
Mohammed Alaoui ◽  
Nadia Martaj
Keyword(s):  
High Performance ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Geometrical Parameters ◽  
Pressure Amplitude ◽  
Cfd Analysis ◽  
Thermoacoustic Engine ◽  
Simulation Results ◽  
And Performance ◽  
Thermoacoustic Refrigerator

Although thermoacoustic devices comprise simple components, the design of these machines is very challenging. In order to predict the behavior and optimize the performance of a thermoacoustic refrigerator driven by a standing-wave thermoacoustic engine, considering the changes in geometrical parameters, two analogies have been presented in this paper. The first analogy is based on CFD analysis where a 2D model is implemented to investigate the influence of stack parameters on the refrigerator performance, to analyze the time variation of the temperature gradient across the stack, and to examine the refrigerator performance in terms of refrigeration temperature. The second analogy is based on the use of an optimization algorithm based on the simplified linear thermoacoustic theory applied for designing thermoacoustic refrigerators with different stack parameters and operating conditions. Simulation results show that the engine produced a high-powered acoustic wave with a pressure amplitude of 23[Formula: see text]kPa and a frequency of 584[Formula: see text]Hz and this wave applies a temperature difference across the refrigeration stack with a cooling temperature of 292.8[Formula: see text]K when the stacks are positioned next to the pressure antinode. The results from the algorithm give the ability to design any thermoacoustic refrigerator with high performance by picking the appropriate parameters.

Burner Component Upgrades for Wall-Fired Coal Burners: RPI Results and Experiences

2011 ◽  
Author(s):  
Stephen W. Black ◽  
Murat Yaldizli
Keyword(s):  
Second Generation ◽  
Fluid Dynamic ◽  
Cost Effective ◽  
Operating Conditions ◽  
Cfd Modeling ◽  
Nox Emissions ◽  
Effective Components ◽  
Utility Companies ◽  
Boiler Operation ◽  
First And Second Generation

Improving the operation and emissions performance of coal fired utility boilers equipped with first and second-generation wall fired low NOx coal burners is of significant interest to many utility companies today. The recent development of cost effective components for existing first and second-generation wall fired burners permits better combustion performance, increased wear life reliability, and decreased NOx emissions. Existing air register systems can typically remain in place, resulting in reduced capital cost and reduced outage time for installation. Computational fluid dynamic (CFD) modeling is used to assist in the design of key burner components and operating conditions that enable further reduction of NOx emissions. Results include better flame attachment, better airflow recirculation patterns, and early ignition and pyrolysis of the coal in a more controlled primary combustion zone. NOx reductions of 10–20% have been demonstrated using burner component upgrades with improved overall boiler operation. This paper gives a brief description of the component-only retrofit design methodology that Riley Power Inc., a Babcock Power Inc. company developed for other OEM’s low NOx burners in wall-fired furnaces. The numerical modeling to assist in the design of these low NOx systems and the corresponding CFD results are also discussed.

scholarly journals Design Methodology for Supersonic Radial Vanes Operating in Nonideal Flow Conditions

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Nitish Anand ◽  
Salvatore Vitale ◽  
Matteo Pini ◽  
Gustavo J. Otero ◽  
Rene Pecnik
Keyword(s):  
Shock Wave ◽  
Fluid Dynamic ◽  
Dynamic Performance ◽  
Computational Cost ◽  
Organic Rankine Cycle ◽  
Suction Side ◽  
Rankine Cycle ◽  
Computational Effort ◽  
Design Guidelines ◽  
Boundary Layer Interaction

The stator vanes of high-temperature organic Rankine cycle (ORC) radial-inflow turbines (RIT) operate under severe expansion ratios and the associated fluid-dynamic losses account for nearly two-thirds of the total losses generated within the blading passages. The efficiency of the machine can strongly benefit from specialized high-fidelity design methods able to provide shapes attenuating shock wave formation, consequently reducing entropy generation across the shock-wave and mitigating shock-wave boundary layer interaction. Shape optimization is certainly a viable option to deal with supersonic ORC stator design, but it is computationally expensive. In this work, a robust method to approach the problem at reduced computational cost is documented. The method consists of a procedure encompassing the method of characteristics (MoC), extended to nonideal fluid flow, for profiling the diverging part of the nozzle. The subsonic section and semibladed suction side are retrieved using a simple conformal geometrical transformation. The method is applied to design a supersonic ORC stator working with Toluene vapor, for which two blade shapes were already available. The comparison of fluid-dynamic performance clearly indicates that the MoC-Based method is able to provide the best results with the lowest computational effort, and is therefore suitable to be used in a systematic manner for drawing general design guidelines.

scholarly journals Proposal of a new simplified fluid dynamic model for aerospace servovalves

2019 ◽  
Vol 304 ◽  
pp. 04014
Author(s):  
Matteo D.L. Dalla Vedova ◽  
Pier Carlo Berri
Keyword(s):  
Numerical Model ◽  
Flight Control ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Computational Effort ◽  
Operating Conditions ◽  
System Level ◽  
Simplified Models ◽  
System Level Simulation ◽  
Detailed Computer

Highly detailed computer models are required for design and development of modern flight control systems, capable of emulating with high accuracy the behaviour of on-board equipment. At the same time, different simplified models are needed, specifically intended for operations such as the optimization of preliminary design and the development of diagnostic or prognostic strategies. These simplified models are required to combine sufficient levels of accuracy and reliability with reduced computational costs, to minimize the computational burden associated with prognostic and optimization algorithms. In this work, we focus on electro-hydraulic actuators, since they are critical subsystems in terms of safety and availability of the aircraft. Advanced monitoring and prognostic algorithms require new numerical models, combining an acceptable computational effort with a satisfying ability to simulate their performance and dynamics. To this purpose, this paper proposes a new simplified numerical model of the servovalve fluid-dynamic behaviour. This numerical algorithm, based on a very compact semi-empirical formulation, is intended to take into account in a simplified but sufficiently accurate way several typical effects related to the SV spool geometry and the operating conditions. To evaluate the approximations introduced by this model into a system-level simulation, it has been integrated into a dedicated numerical model simulating a simple electrohydraulic on-board actuator, and compared with a higher fidelity servovalve model.

Sign in / Sign up

Export Citation Format

Share Document