scholarly journals Research on Francis Turbine Modeling for Large Disturbance Hydropower Station Transient Process Simulation

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Guangtao Zhang ◽  
Yuanchu Cheng ◽  
Na Lu
Keyword(s):  
Transient Process ◽  
Process Simulation ◽  
Francis Turbine ◽  
Hydropower Station ◽  
Interpolation Algorithm ◽  
Transfer Coefficients ◽  
Simple Method ◽  
Attractive Option ◽  
Convergence Problems ◽  
Large Disturbance

In the field of hydropower station transient process simulation (HSTPS), characteristic graph-based iterative hydroturbine model (CGIHM) has been widely used when large disturbance hydroturbine modeling is involved. However, by this model, iteration should be used to calculate speed and pressure, and slow convergence or no convergence problems may be encountered for some reasons like special characteristic graph profile, inappropriate iterative algorithm, or inappropriate interpolation algorithm, and so forth. Also, other conventional large disturbance hydroturbine models are of some disadvantages and difficult to be used widely in HSTPS. Therefore, to obtain an accurate simulation result, a simple method for hydroturbine modeling is proposed. By this method, both the initial operating point and the transfer coefficients of linear hydroturbine model keep changing during simulation. Hence, it can reflect the nonlinearity of the hydroturbine and be used for Francis turbine simulation under large disturbance condition. To validate the proposed method, both large disturbance and small disturbance simulations of a single hydrounit supplying a resistive, isolated load were conducted. It was shown that the simulation result is consistent with that of field test. Consequently, the proposed method is an attractive option for HSTPS involving Francis turbine modeling under large disturbance condition.

Switched Model and Dynamic Analysis of a Hydroturbine Governing System in the Process of Load Rejection Transient

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Huanhuan Li ◽  
Diyi Chen ◽  
Feifei Wang ◽  
Hao Zhang
Keyword(s):  
Mathematical Model ◽  
Dynamic Analysis ◽  
Numerical Simulations ◽  
Dynamic Characteristics ◽  
Nonlinear Dynamic ◽  
Hydropower Station ◽  
Transfer Coefficients ◽  
Operational Conditions ◽  
Governing System ◽  
Hammer Impact

In this paper, we pay attention to studying the switched model of the hydroturbine governing system (HTGS) by introducing the concept of the switching of operational conditions. More specifically, utilizing the data of an existent hydropower station in China, we propose six nonlinear dynamic transfer coefficients of the hydroturbine, which can better describe the dynamic characteristics of the HTGS in the process of load rejection transient. Moreover, the elastic water hammer-impact of the penstock system and the nonlinearity of the generator for the process of load rejection transient are considered. Based on the combination of the different regulation modes of the governor and the corresponding running conditions of the hydroelectric generating unit, a novel nonlinear dynamic switched mathematical model of the HTGS is finally established. Meanwhile, the nonlinear dynamic behaviors of the governing system are exhaustively investigated using numerical simulations. These methods and analytical results will provide some theory bases for running a hydropower station.

Heat transfer coefficients for quenching process simulation

2004 ◽  
Vol 120 ◽  
pp. 269-276
Author(s):  
M. Maniruzzaman ◽  
R. D. Sisson
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Process Simulation ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Quenching Process

Quenching heat treatment in a liquid medium is a very complex heat transfer process. Heat extraction from the part surface occurs through several different heat transfer mechanisms in distinct temperature ranges, namely, film boiling, partial film boiling (i.e. transition), nucleate boiling and convection. The maximum heat transfer occurs during the nucleate boiling stage. Experimental study shows that, the effective surface heat transfer coefficient varies more than two orders of magnitude with the temperature during the quenching. For quenching process simulation, accurate prediction of the time-temperature history and microstructure evolution within the part largely depends on the accuracy of the boundary condition supplied. The heat transfer coefficient is the most important boundary condition for process simulation. This study focuses on creating a database of heat transfer coefficients for various liquid quenchant-metallic alloy combinations through experimentation using three different quench probes. This database is a web-based tool for use in quench process simulation. It provides at-a-glance information for quick and easy analysis and sets the stage for a Decision Support System (DSS) and Data Mining for heat-treating process.

Optimization of Two-Stage Closure Law of Turbine Wicket Gates and its Application

2012 ◽  
Vol 249-250 ◽  
pp. 636-641 ◽  
Author(s):  
Sheng Chen ◽  
Jian Zhang ◽  
Xiao Dong Yu
Keyword(s):  
Mathematical Model ◽  
Transient Process ◽  
Field Test ◽  
Hydropower Station ◽  
Two Stage ◽  
The Mathematical Model

Optimization of closure law is the priority selection in solving the guaranteed regulation calculation problems due to its simplicity and economy. This present study deals with the optimization of two-stage closure law of wicket gates, which has more advantages in control pressure and speed rise. The mathematical model of transient process is established by introducing the method of characteristic, whose correctness is validated by the field test. Then the model is applied to a specific hydropower station that only can employ closure law optimization to coordinate the contradiction between pressure and speed rise, for two-stage closure optimization. The achievements of the study can serve as a reference for similar projects.

Boiling Heat Transfer With Freon 11 (R11) in Brazed Aluminum, Plate-Fin Heat Exchangers

1983 ◽  
Vol 105 (3) ◽  
pp. 605-610 ◽  
Author(s):  
J. M. Robertson ◽  
P. C. Lovegrove
Keyword(s):  
Heat Transfer ◽  
Test Section ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Industrial Process ◽  
Heat Fluxes ◽  
Test Fluid ◽  
Transfer Coefficients ◽  
Simple Method ◽  
Wide Range

The results of laboratory experiments with Freon 11 (R11) flowing in an electrically heated, serrated-fin test section to measure local boiling coefficients over a wide range of vapor quality, with mass fluxes up to 150 kg/m2 s, heat fluxes to 4 kW/m2, and pressure from 3–7 bar, are reported. These low mass and heat fluxes reflect the industrial process application of these heat exchangers where exceedingly small temperature differences may exist between streams. Results are compared with the very similar boiling characteristics previously reported elsewhere for the same test section, with liquid nitrogen as a test fluid under comparable flow conditions. A simple method using the Reynolds number of the total flow regarded as a liquid has been used to correlate boiling heat transfer coefficients with quality for both fluids. The use of a liquid-film flow model to produce a nondimensional correlation connecting the Nusselt, Reynolds, and Prandtl numbers of the film is discussed.

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