Numerical Investigation on Channel Vortex in a Francis Turbine

2011 ◽  
Author(s):  
Maojin Zhang ◽  
Shuhong Liu ◽  
Yulin Wu ◽  
Demin Liu ◽  
Lefu Zhang
Keyword(s):  
Guide Vane ◽  
Vortex Motion ◽  
Leading Edge ◽  
Suction Side ◽  
Hydraulic Turbine ◽  
Francis Turbine ◽  
Computational Domain ◽  
Flow Passage ◽  
Runner Blade ◽  
Steady Simulation

When a Francis hydraulic turbine operates under different working heads at small flow condition, the fluid in the flow passage will generate vortex shedding near the blade leading-edge and form the channel vortex in the blade passages due to the mismatch between the outlet angle of guide vane and the inlet angle of runner blade. The severity of channel vortex will trigger high-frequency vibration or generate unit resonant vibration, affecting the operational stability of the turbines. In this paper some typical operation points were chosen out for the steady simulation of a model turbine according to a unit hill-chart. The computational domain was chosen as the whole flow passage from the inlet of the volute to the outlet of the draft tube. Based on RNG k–ε turbulence model, the internal flows was simulated, and the occurrence of vortex between the turbine runner blades was discussed. The numerical results show that the vortex motion near the development-line (IVDL) is stronger than that near the channel vortex inception-line (IVIL) in channel vortex zone marked in the hill-chart. The velocity triangle is used to explain the reasons that channel vortex occur in the suction side at high working head while in the pressure side at the low working head, and two different forms and formation mechanism of the channel vortex were analyzed.

scholarly journals Numerical Study of Sediment Erosion Analysis in Francis Turbine

2019 ◽  
Vol 11 (5) ◽  
pp. 1423 ◽  
Author(s):  
Md Rakibuzzaman ◽  
Hyoung-Ho Kim ◽  
Kyungwuk Kim ◽  
Sang-Ho Suh ◽  
Kyung Kim
Keyword(s):  
Erosion Rate ◽  
Cavitation Erosion ◽  
Numerical Study ◽  
Leading Edge ◽  
Suction Side ◽  
Hydraulic Turbine ◽  
Francis Turbine ◽  
Trailing Edge ◽  
Sand Erosion ◽  
Turbine Design

Effective hydraulic turbine design prevents sediment and cavitation erosion from impacting the performance and reliability of the machine. Using computational fluid dynamics (CFD) techniques, this study investigated the performance characteristics of sediment and cavitation erosion on a hydraulic Francis turbine by ANSYS-CFX software. For the erosion rate calculation, the particle trajectory Tabakoff–Grant erosion model was used. To predict the cavitation characteristics, the study’s source term for interphase mass transfer was the Rayleigh–Plesset cavitation model. The experimental data acquired by this study were used to validate the existing evaluations of the Francis turbine. Hydraulic results revealed that the maximum difference was only 0.958% compared with the CFD data, and 0.547% compared with the experiment (Korea Institute of Machinery and Materials (KIMM)). The turbine blade region was affected by the erosion rate at the trailing edge because of their high velocity. Furthermore, in the cavitation–erosion simulation, it was observed that abrasion propagation began from the pressure side of the leading edge and continued along to the trailing edge of the runner. Additionally, as sediment flow rates grew within the area of the attached cavitation, they increased from the trailing edge at the suction side, and efficiency was reduced. Cavitation–sand erosion results then revealed a higher erosion rate than of those of the sand erosion condition.

scholarly journals CFD Investigation of a High Head Francis Turbine at Speed No-Load Using Advanced URANS Models

2018 ◽  
Vol 8 (12) ◽  
pp. 2505 ◽  
Author(s):  
Jean Decaix ◽  
Vlad Hasmatuchi ◽  
Maximilian Titzschkau ◽  
Cécile Münch-Alligné
Keyword(s):  
Power Plants ◽  
Turbulence Modeling ◽  
Suction Side ◽  
Hydraulic Turbine ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Hydroelectric Power ◽  
Electrical Grid ◽  
Runner Blade ◽  
Pumped Storage

Due to the integration of new renewable energies, the electrical grid undergoes instabilities. Hydroelectric power plants are key players for grid control thanks to pumped storage power plants. However, this objective requires extending the operating range of the machines and increasing the number of start-up, stand-by, and shut-down procedures, which reduces the lifespan of the machines. CFD based on standard URANS turbulence modeling is currently able to predict accurately the performances of the hydraulic turbines for operating points close to the Best Efficiency Point (BEP). However, far from the BEP, the standard URANS approach is less efficient to capture the dynamics of 3D flows. The current study focuses on a hydraulic turbine, which has been investigated at the BEP and at the Speed-No-Load (SNL) operating conditions. Several “advanced” URANS models such as the Scale-Adaptive Simulation (SAS) SST k - ω and the BSL- EARSM have been considered and compared with the SST k - ω model. The main conclusion of this study is that, at the SNL operating condition, the prediction of the topology and the dynamics of the flow on the suction side of the runner blade channels close to the trailing edge are influenced by the turbulence model.

scholarly journals Derivation of Global Parametric Performance of Mixed Flow Hydraulic Turbine Using CFD

1970 ◽  
Vol 7 ◽  
pp. 60-64 ◽  
Author(s):  
Ruchi Khare ◽  
Vishnu Prasad Prasad ◽  
Sushil Kumar
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Solutions ◽  
Guide Vane ◽  
Hydraulic Turbine ◽  
Francis Turbine ◽  
Mixed Flow ◽  
Flow Equations ◽  
Laboratory Setup ◽  
Wide Range

The testing of physical turbine models is costly, time consuming and subject to limitations of laboratory setup to meet International Electro technical Commission (IEC) standards. Computational fluid dynamics (CFD) has emerged as a powerful tool for funding numerical solutions of wide range of flow equations whose analytical solutions are not feasible. CFD also minimizes the requirement of model testing. The present work deals with simulation of 3D flow in mixed flow (Francis) turbine passage; i.e., stay vane, guide vane, runner and draft tube using ANSYS CFX 10 software for study of flow pattern within turbine space and computation of various losses and efficiency at different operating regimes. The computed values and variation of performance parameters are found to bear close comparison with experimental results.Key words: Hydraulic turbine; Performance; Computational fluid dynamics; Efficiency; LossesDOI: 10.3126/hn.v7i0.4239Hydro Nepal Journal of Water, Energy and EnvironmentVol. 7, July, 2010Page: 60-64Uploaded date: 31 January, 2011

Based on CFX Numerical Simulation of Francis Turbine Runner

2013 ◽  
Vol 456 ◽  
pp. 207-210
Author(s):  
Fang He
Keyword(s):  
Numerical Simulation ◽  
Guide Vane ◽  
Prediction Method ◽  
Internal Flow ◽  
Francis Turbine ◽  
Flow State ◽  
Hydro Turbine ◽  
Runner Blade ◽  
Vibration Prediction ◽  
Turbine Runner

This paper presents a vibration prediction method for Francis turbine: Provided with advanced CFX software, Numerical simulation of movable guide vane and Turbine runner’s internal flow state. From the source of hydraulic vibration, Focus on numerical analysis, numerical simulation for the cutting thickness of the runner blade. After analysis of the influence of the blade of hydraulic vibration. To explore new ways for the hydro turbine control hydraulic vibration.

A New Test Facility to Investigate Film Cooling on a Non-Axisymmetric Contoured Turbine Endwall: Part I — Introduction and Aerodynamic Measurements

2015 ◽  
Author(s):  
Franz Puetz ◽  
Johannes Kneer ◽  
Achmed Schulz ◽  
Hans-Joerg Bauer
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Pressure Distribution ◽  
Film Cooling ◽  
Gas Turbines ◽  
Guide Vane ◽  
Leading Edge ◽  
Suction Side ◽  
Test Facility ◽  
Endwall Contouring

An increased demand for lower emission of stationary gas turbines as well as civil aircraft engines has led to new, low emission combustor designs with less liner cooling and a flattened temperature profile at the outlet. As a consequence, the heat load on the endwall of the first nozzle guide vane is increased. The secondary flow field dominates the endwall heat transfer, which also contributes to aerodynamic losses. A promising approach to reduce these losses is non-axisymmetric endwall contouring. The effects of non-axisymmetric endwall contouring on heat transfer and film cooling are yet to be investigated. Therefore, a new cascade test rig has been set up in order to investigate endwall heat transfer and film cooling on both a flat and a non-axisymmetric contoured endwall. Aerodynamic measurements that have been made prior to the upcoming heat transfer investigation are shown. Periodicity and detailed vane Mach number distributions ranging from 0 to 50% span together with the static pressure distribution on the endwall give detailed information about the aerodynamic behavior and influence of the endwall contouring. The aerodynamic study is backed by an oil paint study, which reveals qualitative information on the effect of the contouring on the endwall flow field. Results show that the contouring has a pronounced effect on vane and endwall pressure distribution and on the endwall flow field. The local increase and decrease of velocity and the reduced blade loading towards the endwall is the expected behavior of the 3d contouring. So are the results of the oil paint visualization, which show a strong change of flow field in the leading edge region as well as that the contouring delays the horse shoe vortex hitting the suction side.

Effect of Runner Blade Thickness on Flow Characteristics of a Francis Turbine Model at Low Flowrates

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Seung-Jun Kim ◽  
Young-Seok Choi ◽  
Yong Cho ◽  
Jong-Woong Choi ◽  
Jin-Hyuk Kim
Keyword(s):  
Stokes Equations ◽  
Guide Vane ◽  
Vortex Formation ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Hydroelectric Power ◽  
Runner Blade ◽  
Blade Thickness ◽  
Interblade Vortices

Abstract Francis turbines are often used for generating hydroelectric power, but their performance characteristics significantly depend on the operating conditions. In particular, interblade vortices in the passages between runner blades can occur at low flowrates, which can degrade performance, and increase vibrations and instability during operation. In a previous study, we showed that the hydraulic performance and flow characteristics depend on the flow passage area of runner blades under low-flowrate conditions. Under such operating conditions, the runner blade thickness can affect the interblade vortex characteristics, and in turn, affect the performance of the turbine. In this study, we investigated the effect of runner blade thicknesses in the presence of interblade vortices under low flowrates; steady- and unsteady-state Reynolds-averaged Navier–Stokes equations were solved using a shear stress transport as a turbulence model. The interblade vortices were described well at the near leading and trailing edges near the hub. These vortex regions showed flow separation and stagnation flow, and the interblade vortex characteristics were dependent on the high-magnitude unsteady pressures at the low-frequency region. For the same guide vane opening, at lower flowrates, higher blockage ratios reduced interblade vortex formation and unsteady pressure.

Experimental and Numerical Conjugate Investigation of the Blowing-Ratio Influence on the Showerhead Cooling Efficiency

1998 ◽  
Author(s):  
Dieter E. Bohn ◽  
Volker J. Becker ◽  
Karsten A. Kusterer ◽  
Agnes U. Rungen
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Guide Vane ◽  
Leading Edge ◽  
Suction Side ◽  
Computer Code ◽  
Inlet Temperature ◽  
Cooling Efficiency ◽  
Blowing Ratio ◽  
Turbine Guide Vane

This paper presents the experimental investigation of the flow and the numerical analysis of the flow and heat transfer in a turbine guide vane with showerhead cooling for two different blowing ratios. The aerodynamic results are compared with those of the experiments. Starting with a showerhead design of two rows of ejection holes, two additional rows have to be used in an enhanced design due to hot gas contact in the leading edge area. Thus, the cooling gas mass flow is doubled when keeping the blowing ratio constant at m = 1.5. Lowering the amount of cooling gas needed whilst still guaranteeing sufficient cooling is the motivation for the analysis of the influence of a lower blowing ratio on the cooling efficiency. The investigated blowing ratios are m = 1.5 and m = 1.0. The experiments are conducted using a non-intrusive LDA technique. The numerical results are gained with a conjugate heat transfer and flow computer code that has been developed at the Institute of Steam and Gas Turbines. The results show that the blowing ratio has to be chosen carefully as the leading edge flow pattern and the heat transfer are strongly influenced by the blowing ratio. Lower blowing ratios lead to a better attachment of the cooling film and thus they hardly disturb the main flow. With the lower blowing ratio, the material temperature increases up to 1.5% of the total inlet temperature in the leading edge area on the pressure side, whereas it decreases locally for about 0.8% for the lower blowing ratio on the suction side. This is due to the enhanced attachment of the cooling gas film.

Effects of an Axisymmetric Contoured Endwall on a Nozzle Guide Vane: Convective Heat Transfer Measurements

2010 ◽  
Author(s):  
A. A. Thrift ◽  
K. A. Thole ◽  
S. Hada
Keyword(s):  
Heat Transfer ◽  
Guide Vane ◽  
Leading Edge ◽  
Critical Factor ◽  
Suction Side ◽  
Leakage Flow ◽  
Cross Sectional ◽  
Nozzle Guide Vane ◽  
Linear Slope ◽  
Nozzle Guide

Heat transfer is a critical factor in the durability of gas turbine components, particularly in the first vane. An axisymmetric contour is sometimes used to contract the cross sectional area from the combustor to the first stage vane in the turbine. Such contouring can lead to significant changes in the endwall flows thereby altering the heat transfer. This paper investigates the effect of axisymmetric contouring on endwall heat transfer of a nozzle guide vane. Heat transfer measurements are performed on the endwalls of a planar and contoured passage whereby one endwall is modified with a linear slope in the case of the contoured passage. Included in this study is upstream leakage flow issuing from a slot normal to the inlet axis. Each of the endwalls within the contoured passage presents a unique flowfield. For the contoured passage, the flat endwall is subject to an increased acceleration through the area contraction while the contoured endwall includes both increased acceleration and a turning of streamlines due to the slope. Results indicate heat transfer is reduced on both endwalls of the contoured passage relative to the planar passage. In the case of all endwalls, increasing leakage mass flow rate leads to an increase in heat transfer near the suction side of the vane leading edge.

Combustor Turbine Interface Studies: Part 1 — Endwall Effectiveness Measurements

2002 ◽  
Author(s):  
W. F. Colban ◽  
K. A. Thole ◽  
G. Zess
Keyword(s):  
Film Cooling ◽  
Total Pressure ◽  
Large Scale ◽  
Guide Vane ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Profile ◽  
Secondary Flows ◽  
Adiabatic Wall ◽  
Combustor Liner

Improved durability of gas turbine engines is an objective for both military and commercial aeroengines as well as for power generation engines. One region susceptible to degradation in an engine is the junction between the combustor and first vane given that the main gas path temperatures at this location are the highest. The platform at this junction is quite complex in that secondary flow effects, such as the leading edge vortex, are dominant. Past computational studies have shown that the total pressure profile exiting the combustor dictates the development of the secondary flows that are formed. This study examines the effect of varying the combustor liner film-cooling and junction slot flows on the adiabatic wall temperatures measured on the platform of the first vane. The experiments were performed using large-scale models of a combustor and nozzle guide vane in a wind tunnel facility. The results show that varying the coolant injection from the upstream combustor liner leads to differing total pressure profiles entering the turbine vane passage. Endwall adiabatic effectiveness measurements indicate that the coolant does not exit the upstream combustor slot uniformly but instead accumulates along the suction side of the vane and endwall. Increasing the liner cooling continued to reduce endwall temperatures, which was not found to be true with increasing the film-cooling from the liner.

Loss assessment of the NASA SDT configuration using URANS with phase-lagged assumption

2021 ◽  
pp. 1-14
Author(s):  
Maxime Fiore ◽  
Majd Daroukh ◽  
Marc Montagnac
Keyword(s):  
Numerical Simulations ◽  
Data Storage ◽  
Rotational Speed ◽  
Guide Vane ◽  
Leading Edge ◽  
Low Noise ◽  
Computational Domain ◽  
Compression Method ◽  
Loss Assessment ◽  
High Rotational Speed

Abstract This paper presents the study of the Source Diagnostic Test fan rig of the NASA Glenn (NASA SDT). Numerical simulations are performed for the three different Outlet Guide Vane (OGV) geometries (baseline, low-count and low-noise) and three rotational speeds. Unsteady Reynolds Averaged Navier Stokes (URANS) approach is used. The in- and out-duct flow including the nacelle are considered in the numerical simulations and results are compared against available measurements. Due to the blade count of the fan and OGVs, the simulation can only be reduced to half the full annulus simulation domain using periodic boundary conditions that still represents a significant cost. To alleviate this issue, a URANS with phase-lagged assumption is used. This method allows to perform unsteady simulations on multistage turbomachinery configurations including multiple frequency flows with a reduced computational domain composed of one single blade passage for each row. The large data storage required by the phase-lagged approach is handled by a compression method based on a Proper Orthogonal Decomposition. This compression method improves the signal spectral content especially at high frequency. Based on the numerical simulations, the flow field is described and used to assess the losses generated in the turbofan architecture based on an entropy approach. The results show different flow topologies for the fan depending on the rotational speed with a leading edge shock at high rotational speed. The fan boundary layer contributes strongly to losses with the majority of the losses being generated close to the leading edge.

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