On the Unsteady Interaction Between the Leakage and the Main Passage Flow in a High Pressure Turbine Rig: CFD URANS Investigations and Comparison With the Rig Test Data

2016 ◽  
Author(s):  
Giulio Zamboni ◽  
Paolo Adami
Keyword(s):  
Test Data ◽  
Fluid Dynamic ◽  
Flow Path ◽  
Complex Flow ◽  
Complex Flows ◽  
Design Work ◽  
Flow Interactions ◽  
Present Design ◽  
Unsteady Interaction ◽  
Urans Cfd

The flow path of modern turbine stages is highly influenced by the interaction of the main passage flow with the secondary leakages used for sealing purposes. The interaction between these two flows significantly influences the topology of the overturning passage secondary flow and therefore with the performance of the turbine itself. During the aerodynamic design phase, this complex interaction is usually assessed using RANS and URANS CFD calculations. This paper reports on the use of CFD calculations to predict the complex fluid dynamic interaction between the leakage at the inner platform upstream of a single stage HPT blade and the generation of the secondary overturning passage flow within the aerofoil. Rig test data are presented for a direct comparison with the CFD considering two different rim sealing geometric configurations. The first aim of this paper is to show how the prediction of similar complex flows can be addressed to quantify the performance improvement and what results can be expected when using industrial mature simulation technology based on RANS/URANS CFD. The second objective is to support the understanding of accuracy improvements requirements and limitations still observed when comparing these flow path predictions with rig test data. This work shows that despite the ability to capture trends, the details of these complex flow interactions still represent a challenge for the state of the art RANS and URANS solvers used in the design of the gas path of the HPT turbine stages. The understanding of the accuracy in prediction capability through the comparison with rig test data is not only essential to support present design work, but also for the developments and assessment of the next generation of modelling capabilities.

Numerical Analysis on the Impact of Interstage Flow Addition in a High-Pressure Steam Turbine

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Soo Young Kang ◽  
Jeong Jin Lee ◽  
Tong Seop Kim ◽  
Seong Jin Park ◽  
Gi Won Hong
Keyword(s):  
High Pressure ◽  
Pressure Drop ◽  
Computational Analysis ◽  
Fluid Dynamic ◽  
Geometric Model ◽  
Flow Path ◽  
Complex Flow ◽  
Flow Paths ◽  
Single Passage ◽  
The Impact

This study analyzes the fluid dynamic characteristics of an ultrasupercritical (USC) high-pressure turbine with additional steam supplied through an overload valve between the second and third stages. The mixing between the main and admission flows causes complex flow phenomena such as swirl and changes of velocity vectors of the main flow. This causes a pressure drop between the second-stage outlet and third-stage inlet, which could potentially affect the performance of the turbine. First, a single-passage computational analysis, which is usually preferred in predicting the performance of multistage turbomachines, was performed using a simple model of an admission flow path and a single passage (SP) for the second and third stages of the turbine. However, the actual flow in the overload valve is supplied through the admission flow path, which has the shape of a casing that circumferentially surrounds the turbine, after flowing in two directions perpendicular to the turbine axis. This necessitates full-passage computational analyses of the two stages and the flow paths of the admission flow. To achieve this, we implemented a full three-dimensional (3D) geometric model of the admission flow path and conducted a full-passage computational analysis for all the flow paths, including those of the second and third stages of the turbine. The focus of analysis was on the pressure drop due to the admission flow. The results of the single and full-passage analyses were compared, and the effects of two different methods were analyzed.

scholarly journals Analysis and Control of Complex Flows in U-Bends Using Computational Fluid Dynamics

2014 ◽  
Author(s):  
Yiğitcan Güden ◽  
Mehmet Metin Yavuz
Keyword(s):  
Fluid Dynamic ◽  
Computation Time ◽  
Radius Of Curvature ◽  
Complex Flow ◽  
Complex Flows ◽  
Dean Number ◽  
Mean Velocity ◽  
Dean Vortices ◽  
Numerical Studies ◽  
And Control

Analysis and control of flow structure in U-bends are crucial since U-bends are used in many different engineering applications. As a flow parameter in U-bends, the ratio of inertial and centrifugal forces to viscous forces is called as Dean number. The increase of Dean number destabilizes the flow and leads to a three-dimensional flow consisting of stream wise parallel counter-rotating vortices (Dean vortices) stacked along the curved wall. Due to the curvature in U-bends, the flow development involves complex flow structures including Dean vortices and high levels of turbulence that are not seen in straight duct flows. These are quite critical in considering noise problems and structural failure of the ducts. In this work, computational fluid dynamic (CFD) models are developed using ANSYS FLUENT to simulate these complex flows patterns in square sectioned U-bend with a radius of curvature Rc/D=0.65. The predictions of mean velocity profiles on different angular positions of the U-bend are compared against the experimental results available in the literature and previous numerical studies. Performance of six different turbulence models are evaluated, namely: the standard k-ε, the k-ε Realizable, the k-ε RNG, the k-ω SST, the Reynolds Stress Model (RSM) and the Scale-Adaptive Simulation Model (SAS), to propose the best numerical approach with increasing the accuracy of the solutions while reducing the computation time. Numerical results show remarkable improvements with respect to previous numerical studies and good agreement with the available experimental data. The best turbulence model for this application is proposed considering both the computation time and the result accuracy. In addition, different flow control techniques are still under investigation to eliminate Dean vortices and to reduce turbulence levels in U-bends.

scholarly journals Large Temperature Fluctuations due to Cold-Air Pool Displacement along the Lee Slope of a Desert Mountain

2017 ◽  
Vol 56 (4) ◽  
pp. 1083-1098 ◽  
Author(s):  
Matthew E. Jeglum ◽  
Sebastian W. Hoch ◽  
Derek D. Jensen ◽  
Reneta Dimitrova ◽  
Zachariah Silver
Keyword(s):  
Low Frequency ◽  
Temperature Fluctuations ◽  
Atmospheric Modeling ◽  
Large Temperature ◽  
Complex Flow ◽  
Near Surface ◽  
Cold Air ◽  
Flow Interactions ◽  
Initial Drop ◽  
Program Temperature

AbstractLarge temperature fluctuations (LTFs), defined as a drop of the near-surface temperature of at least 3°C in less than 30 min followed by a recovery of at least half of the initial drop, were frequently observed during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program. Temperature time series at over 100 surface stations were examined in an automated fashion to identify and characterize LTFs. LTFs occur almost exclusively at night and at locations elevated 50–100 m above the basin floors, such as the east slope of the isolated Granite Mountain (GM). Temperature drops associated with LTFs were as large as 13°C and were typically greatest at heights of 4–10 m AGL. Observations and numerical simulations suggest that LTFs are the result of complex flow interactions of stably stratified flow with a mountain barrier and a leeside cold-air pool (CAP). An orographic wake forms over GM when stably stratified southwesterly nocturnal flow impinges on GM and is blocked at low levels. Warm crest-level air descends in the lee of the barrier, and the generation of baroclinic vorticity leads to periodic development of a vertically oriented vortex. Changes in the strength or location of the wake and vortex cause a displacement of the horizontal temperature gradient along the slope associated with the CAP edge, resulting in LTFs. This mechanism explains the low frequency of LTFs on the west slope of GM as well as the preference for LTFs to occur at higher elevations later at night, as the CAP depth increases.

Conjugate Heat Transfer Analysis for Gas Turbine Cooled Stator

2012 ◽  
Author(s):  
Kuo-San Ho ◽  
Christopher Urwiller ◽  
S. Murthy Konan ◽  
Jong S. Liu ◽  
Bruno Aguilar
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Test Data ◽  
Conjugate Heat Transfer ◽  
Fluid Dynamic ◽  
Thermal Analyses ◽  
Convection Heat Transfer ◽  
Heat Transfer Analysis ◽  
Engine Test ◽  
Adiabatic Wall

This paper explores the conjugate heat transfer (CHT) numerical simulation approach to calculate the metal temperature for the gas turbine cooled stator. ANSYS CFX12.1 code was selected to be the computational fluid dynamic (CFD) tool to perform the CHT simulation. The 2-equation RNG k-ε turbulence model with scalable modified wall function was employed. A full engine test with thermocouple measurement was performed and used to validate the CHT results. Metal temperatures calculated with the CHT model were compared to engine test data. The results demonstrated good agreement between test data and airfoil metal temperatures and cooling flow temperatures using the CHT model. However, the CHT calculations in the outer end wall had a discrepancy compared to the measured temperatures, which was due to the fact that the CHT model assumed an adiabatic wall as a boundary condition. This paper presents a process to calculate convection heat transfer coefficient (HTC) for cooling passages and airfoil surfaces using CHT results. This process is possible because local wall heat flux and fluid temperatures are known. This approach assists in calibrating an in-house conduction thermal model for steady state and transient thermal analyses.

Numerical investigation of particle trapping in various groove configurations in straight and bent flow channels

SIMULATION ◽  
2020 ◽  
Vol 96 (8) ◽  
pp. 679-699
Author(s):  
LA Florio
Keyword(s):  
High Speed ◽  
Particle Interaction ◽  
Flow Path ◽  
Particle Flow ◽  
Computational Technique ◽  
Straight Channel ◽  
Particle Trapping ◽  
Flow Interactions ◽  
Groove Configurations ◽  
Channel Configuration

A novel computational technique is applied to investigate particle trapping in straight and bent channel flow paths with various groove configurations in high-speed compressible, particle laden flow. The technique is valid for particle sizes of the same order of magnitude as the groove dimensions and where the particle–flow path, particle–particle, and particle–flow interactions play significant roles in determining the particle motion. The sacrificial grooves within the flow path can remove particles from the flow to reduce particle impact-induced wear. The feasibility of the trapping grooves and the conditions for which they are most beneficial can be gleaned from analysis of the model results. Three groove configurations are studied: a straight groove, a flared groove, and a 45 degree angle groove, for the same groove entrance size, groove depth, and spacing in a straight channel and a channel with a 90 degree bend. A transient maximum of 22% of the particles were trapped for the flared groove for the bent channel and a transient maximum of 15% of the particles for the straight channel configuration. The second groove of the bent channel produces the greatest single groove particle holding of 8.25% of all of the particles for the flared grove configuration. The contributions of the groove positioning, groove shape, gas flow, and particle interaction conditions to the trapping characteristics can be readily obtained from examination of the model results since the modeling technique includes detailed treatment of particle–flow path and flow interactions, allowing for the study of the mechanisms acting to trap the particles within the grooves.

Semiempirical Analysis of Liquid Fuel Distribution Downstream of a Plain Orifice Injector Under Cross-Stream Air Flow

1982 ◽  
Vol 104 (4) ◽  
pp. 788-795 ◽  
Author(s):  
Ming-hua Cao ◽  
Hong-kun Jiang ◽  
Ju-shan Chin
Keyword(s):  
Ambient Temperature ◽  
Test Data ◽  
High Velocity ◽  
Liquid Fuel ◽  
Air Flow ◽  
Liquid Sheet ◽  
Flow Path ◽  
Preliminary Design ◽  
Fuel Injector ◽  
Fuel Distribution

An improved semiempirical analysis is presented for the liquid fuel distribution downstream of a plain orifice fuel injector under a cross-stream air flow of uniform high velocity and constant ambient temperature. The analysis is based on a simplified “flat-fan spray” model (ε–ψ model). A ε–ψ model is proposed which assumes that the fuel injected through the orifice forms a flat-fan liquid sheet with an average fan angle 2ψ0. Once the droplets have been formed, the trajectory of individual droplets determines the fuel distribution downstream. The validity of the analysis is confirmed by comparison of calculations based on the ε–ψ model and test data obtained from fuel distribution experiments under cross-stream air flow of ambient temperature. The agreement is shown to be very good. The semiempirical analysis presented offers a very useful approach in the preliminary design of the fan air flow path portion of turbofan afterburners.

Development and Preliminary Validation of a STH-CFD Coupling Method for Multiscale Thermal-Hydraulic Simulations of the MYRRHA Reactor

2016 ◽  
Author(s):  
A. Toti ◽  
J. Vierendeels ◽  
F. Belloni
Keyword(s):  
Research Reactor ◽  
Fluid Dynamic ◽  
Domain Decomposition Method ◽  
Test Facility ◽  
Research Centre ◽  
High Tech ◽  
Primary System ◽  
Complex Flow ◽  
Transient Event ◽  
Flow Mixing

MYRRHA (Multi-purpose hybrid research reactor for high-tech applications) is a lead-bismuth eutectic (LBE) cooled research reactor currently under development at SCK•CEN, the Belgian Nuclear Research Centre. The compact design of the pool-type primary system implies the presence of pronounced 3D thermal fluid-dynamic phenomena, which can affect the evolution of certain accidental transients such as loss of flow (LOF). System thermal-hydraulics (STH) codes, conceived to carry out global NPP safety analyses, present severe limitations in taking into account local 3D phenomena including flow mixing, thermal stratification, etc. To overcome this limitation, a promising solution is coupling STH codes with CFD codes, which can calculate complex flow fields but result, on the other hand, in too expensive computational resources for whole-plant simulations. A domain decomposition method that couples the STH code RELAP5-3D and the CFD code Ansys FLUENT has been developed and implemented. Proof-of-principle tests on simple configurations have been carried out to demonstrate its validity and to identify modeling and numerical issues. The experimental campaign carried out at the test facility TALL-3D, operated by the KTH Royal Institute of Technology in Sweden, has been selected for preliminary verification and validation (V&V) of this method. This paper presents the results of the coupled 1D-3D simulation of a forced-to-natural circulation transient event, whose evolution results to be strongly affected by flow mixing and stratification phenomena. The experimental validation, based on a high-quality set of experimental data, is currently on-going. Further development and validation activities will be carried out in the experimental facility ESCAPE, under commissioning at SCK•CEN, within the recently launched EU project MYRTE (Horizon 2020 programme).

Simulations of the PC boiler equipped with complex swirling burners

2014 ◽  
Vol 24 (4) ◽  
pp. 845-860 ◽  
Author(s):  
Wojciech P. Adamczyk ◽  
Pawel Kozolub ◽  
Gabriel Węcel ◽  
Arkadiusz Ryfa
Keyword(s):  
Fluid Dynamic ◽  
Exchange Process ◽  
Combustion Process ◽  
Accurate Solution ◽  
Flue Gases ◽  
Discrete Phase Model ◽  
Complex Flow ◽  
Content Type ◽  
Combustion Technology ◽  
The Impact

Purpose – The purpose of this paper is to show possible approaches which can be used for modeling complex flow phenomena caused by swirl burners combined with simulating coal combustion process using air- and oxy-combustion technologies. Additionally, the response of exist boiler working parameter on changing the oxidizer composition from air to a mixture of the oxygen and recirculated flue gases is investigated. Moreover, the heat transfer in the superheaters section of the boiler was taken into account by modeling of the heat exchange process between continuum phase and three stages of the steam superheaters. Design/methodology/approach – An accurate solution of the flow field is required in order to predict combustion phenomena correctly for numerical simulations of the industrial pulverized coal (PC) boilers. Nevertheless, it is a very demanding task due to the complicated swirl burner construction and complex character of the flow. The presented simulations were performed using the discrete phase model for tracking particles and combustion phenomena in a dispersed phase, whereas the Eulerian approach was applied for the volatile combustion process modeling in a gaseous phase. Findings – Applying the air- to oxy-combustion technology the temperature in the combustion chamber, decreased for investigated oxidizer compositions. This was caused by the higher heat capacity of flue gases which also influences on the level of the heat flux at the boiler walls. Simulations shows that increasing the O2 concentration to 30 percent of volume base in the oxidizer mixture provided the similar combustion conditions as those for the conventional air firing. Moreover, the evaluated results give a good overview of differences between approaches used for complex swirl burners simulations. Practical implications – Nowadays, the numerical techniques such as computational fluid dynamic (CFD) can be seen as an useful engineering tool for design and processes optimization purposes. The application of the CFD gives a possibility to predict the combustion phenomena in a large industrial PC boiler and investigate the impact of changing the combustion technology from a conventional air firing to oxy-fuel combustion. Originality/value – This paper gives good overview on existing technique, approaches used for modeling PC boiler equipped with complex swirl burners. Additionally, the novelty of this work is application of the heat exchanger model for predicting heat loses in convective section of the boiler. This usually is not taken into account during simulations. The reader can also find basic concept of oxy-combustion technology, and their impact on boiler working conditions.

Validation of URANS Simulation of Truck Cooling Fan Performance

2014 ◽  
Author(s):  
Sassan Etemad ◽  
Peter Gullberg
Keyword(s):  
Test Data ◽  
Industrial Applications ◽  
Ideal Gas ◽  
Computational Time ◽  
Constant Density ◽  
Cfd Simulations ◽  
Simulation Accuracy ◽  
Cooling Fan ◽  
Density Assumption ◽  
Urans Cfd

The performance of an axial heavy duty truck cooling fan was investigated by measurements in a test rig and by CFD simulations. In order to account for the unsteadiness of the flow, URANS simulations were employed. Good agreement was achieved between the simulation and test data, in particular in the axial regime, despite the constant density assumption. To improve the simulation accuracy in the radial and transitional regime it is most likely insufficient to assume constant density. New simulations with ideal gas assumptions for these regimes are believed to give better agreement with the test data. The simulations show that URANS CFD can produce results very close to the ones obtained in the test facilities and thereby can be used for the industrial applications when flow unsteadiness has to be taken into account. The fact that it requires long computational time and is CPU-demanding can no longer be regarded as a major preventing factor for its application in the industry. In addition, it provides valuable information about the details of the flow which can contribute to the optimization of the geometry for improved efficiency and higher performance.

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