An Experimental/Computational Study of Airflow in the Combustor–Diffuser System of a Gas Turbine for Power Generation

1998 ◽  
Vol 120 (1) ◽  
pp. 24-33 ◽  
Author(s):  
A. K. Agrawal ◽  
J. S. Kapat ◽  
T. T. Yang
Keyword(s):  
Gas Turbines ◽  
Computational Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Strong Interactions ◽  
Test Model ◽  
Computational Fluid Dynamic Analysis ◽  
Flow Measurements ◽  
Venturi Effect

This paper presents an experimental/computational study of cold flow in the combustor–diffuser system of industrial gas turbines employing can-annular combustors and impingement-cooled transition pieces. The primary objectives were to determine flow interactions between the prediffuser and dump chamber, to evaluate circumferential flow nonuniformities around transition pieces and combustors, and to identify the pressure loss mechanisms. Flow experiments were conducted in an approximately one-third geometric scale, 360-deg annular test model simulating practical details of the prototype including the support struts, transition pieces, impingement sleeves, and can-annular combustors. Wall static pressures and velocity profiles were measured at selected locations in the test model. A three-dimensional computational fluid dynamic analysis employing a multidomain procedure was performed to supplement the flow measurements. The complex geometric features of the test model were included in the analysis. The measured data correlated well with the computations. The results revealed strong interactions between the prediffuser and dump chamber flows. The prediffuser exit flow was distorted, indicating that the uniform exit conditions typically assumed in the diffuser design were violated. The pressure varied circumferentially around the combustor casing and impingement sleeve. The circumferential flow nonuniformities increased toward the inlet of the turbine expander. A venturi effect causing flow to accelerate and decelerate in the dump chamber was also identified. This venturi effect could adversely affect impingement cooling of the transition piece in the prototype. The dump chamber contained several recirculation regions contributing to the losses. Approximately 1.2 dynamic head at the prediffuser inlet was lost in the combustor–diffuser, much of it in the dump chamber where the fluid passed though narrow pathways. A realistic test model and three-dimensional analysis used in this study provided new insight into the flow characteristics of practical combustor–diffuser systems.

scholarly journals Computational Fluid Dynamic Analysis of a Vibrating Turbine Blade

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Osama N. Alshroof ◽  
Gareth L. Forbes ◽  
Nader Sawalhi ◽  
Robert B. Randall ◽  
Guan H. Yeoh
Keyword(s):  
Gas Turbine ◽  
Turbine Blade ◽  
Moving Boundary ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Commercial Software ◽  
Computational Fluid Dynamic Analysis ◽  
Current State ◽  
Blade Tip ◽  
The One

This study presents the numerical fluid-structure interaction (FSI) modelling of a vibrating turbine blade using the commercial software ANSYS-12.1. The study has two major aims: (i) discussion of the current state of the art of modelling FSI in gas turbine engines and (ii) development of a “tuned” one-way FSI model of a vibrating turbine blade to investigate the correlation between the pressure at the turbine casing surface and the vibrating blade motion. Firstly, the feasibility of the complete FSI coupled two-way, three-dimensional modelling of a turbine blade undergoing vibration using current commercial software is discussed. Various modelling simplifications, which reduce the full coupling between the fluid and structural domains, are then presented. The one-way FSI model of the vibrating turbine blade is introduced, which has the computational efficiency of a moving boundary CFD model. This one-way FSI model includes the corrected motion of the vibrating turbine blade under given engine flow conditions. This one-way FSI model is used to interrogate the pressure around a vibrating gas turbine blade. The results obtained show that the pressure distribution at the casing surface does not differ significantly, in its general form, from the pressure at the vibrating rotor blade tip.

Thermal Mixing Downstream of a 90-Degree T-Junction: Laminar and Turbulent Flows

2019 ◽  
Author(s):  
Bakhtier Farouk
Keyword(s):  
Turbulent Flows ◽  
Thermophysical Properties ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Inlet Temperature ◽  
Horizontal Pipe ◽  
Thermal Mixing ◽  
Large Eddy ◽  
Inlet Conditions

Abstract A three-dimensional time dependent computational fluid dynamic (CFD) study of laminar and turbulent thermal mixing of two flows entering a 90° T-junction pipe is presented. The two incoming flows (both liquids) in the T-junction enter the flow domain with different inlet velocities, and temperatures. Water flow is considered in both the horizontal pipe and the vertical pipe. Inlet temperature differences and temperature dependent thermophysical properties are considered. Large eddy simulations (LES) with sub-grid scale (SGS) modeling were considered for the simulation of the turbulent cases. The flow characteristics, and thermal mixing behaviors and detailed mixing structures were simulated, and they showed that thermal mixing of the two streams are closely affected by the inlet conditions of the two streams and the inlet thermophysical properties of the two streams.

Fluid Dynamic Study in a Femoral Artery Branch Casting of Man With Upstream Main Lumen Curvature for Steady Flow

1985 ◽  
Vol 107 (3) ◽  
pp. 240-248 ◽  
Author(s):  
M. R. Back ◽  
Y. I. Cho ◽  
L. H. Back
Keyword(s):  
Steady Flow ◽  
Fluid Transport ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Pressure Distributions ◽  
Flow Investigation ◽  
Measured Pressure

An in-vitro, steady flow investigation was conducted in a hollow, transparent vascular replica of the profunda femoris branch of man for a range of physiological flow conditions. The replica casting tested was obtained from a human cadaver and indicated some plaque formation along the main lumen and branch. The flow visualization observations and measured pressure distributions indicated the highly three-dimensional flow characteristics with arterial curvature and branching, and the important role of centrifugal effects in fluid transport mechanisms.

Comparison of Left Anterior Descending Coronary Artery Hemodynamics Before and After Angioplasty

2005 ◽  
Vol 128 (1) ◽  
pp. 40-48 ◽  
Author(s):  
S. D. Ramaswamy ◽  
S. C. Vigmostad ◽  
A. Wahle ◽  
Y.-G. Lai ◽  
M. E. Olszewski ◽  
...  
Keyword(s):  
Shear Stress ◽  
Coronary Artery ◽  
Fluid Dynamic ◽  
Critical Role ◽  
Three Dimensional ◽  
Cardiac Contraction ◽  
Local Geometry ◽  
Arbitrary Lagrangian Eulerian ◽  
Computational Fluid Dynamic Analysis ◽  
Before And After

Coronary artery disease (CAD) is characterized by the progression of atherosclerosis, a complex pathological process involving the initiation, deposition, development, and breakdown of the plaque. The blood flow mechanics in arteries play a critical role in the targeted locations and progression of atherosclerotic plaque. In coronary arteries with motion during the cardiac contraction and relaxation, the hemodynamic flow field is substantially different from the other arterial sites with predilection of atherosclerosis. In this study, our efforts focused on the effects of arterial motion and local geometry on the hemodynamics of a left anterior descending (LAD) coronary artery before and after clinical intervention to treat the disease. Three-dimensional (3D) arterial segments were reconstructed at 10 phases of the cardiac cycle for both pre- and postintervention based on the fusion of intravascular ultrasound (IVUS) and biplane angiographic images. An arbitrary Lagrangian-Eulerian formulation was used for the computational fluid dynamic analysis. The measured arterial translation was observed to be larger during systole after intervention and more out-of-plane motion was observed before intervention, indicating substantial alterations in the cardiac contraction after angioplasty. The time averaged axial wall shear stress ranged from −0.2to9.5Pa before intervention compared to −0.02to3.53Pa after intervention. Substantial oscillatory shear stress was present in the preintervention flow dynamics compared to that in the postintervention case.

Validated Unsteady Computational Fluid Dynamic Analysis of an Oscillating Bio-Inspired Airfoil

2015 ◽  
Vol 799-800 ◽  
pp. 698-706 ◽  
Author(s):  
Tim Flint ◽  
Wei Hua Ho ◽  
Tze How New ◽  
Mark Jermy
Keyword(s):  
High Pressure ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Flow Characteristics ◽  
Complex Flow ◽  
Computational Fluid Dynamic Analysis ◽  
Pressure Region ◽  
Lift And Drag ◽  
High Pressure Zone ◽  
Oscillating Motion

An unsteady, two-dimensional numerical study was conducted to investigate the aerodynamic and flow characteristics of a bio-inspired corrugated airfoil oscillating at 2Hz with an amplitude of 10°. The upstream flow was set such that the chord Re = 14,000. The computational results were validated against experimental results from a 2D particle image velocimetry (PIV) experiment on the same airfoil geometry. Complex flow structures such as the formation and shedding of trailing edge vortices have been revealed to have significant impacts on the lift and drag characteristics of the airfoil in oscillating motion. The shed vortices provide a low pressure region on the top surface of the airfoil throughout the period of oscillation, thus increasing lift of the airfoil. In particular, vortices formed and shed from the rear-most corrugation appear to have the largest effect. The pitch-down motion produces a lower absolute peak lift as compared the pitch-up motion which may be explained by the disruption of the high pressure zone on the top surface of the airfoil by a vortex forming in the corrugations. This results in a relatively lower high pressure region on the advancing side as compared to the pitch-up motion. In addition to the lift calculations, drag calculations indicate that net thrust is being produced during the oscillations and more thrust is produced on the pitch-up than the pitch-down motion.

Effect of Pitch Chord Ratio and Side Wall Expansion Angle on Flow Through Vane Swirlers

2006 ◽  
Author(s):  
R. Thundil Karuppa Raj ◽  
V. Ganesan
Keyword(s):  
Computational Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Side Wall ◽  
Reynolds Stress Model ◽  
Swirl Flow ◽  
Expansion Angle ◽  
Turbulence Effects ◽  
Flow Field Characteristics ◽  
Flow Through

This paper is concerned with the computational study of steady flow through the vane swirlers. Swirl flow field characteristics for various pitch chord ratio (s/c) at swirler mean radius are studied for a 45° vane swirler under both sudden and gradual expansions with side-wall expansion angles of 90° and 45° respectively. In the computational study the geometry and meshing is done using pre-processor GAMBIT. Three-dimensional flow within the geometry and through the swirler has been simulated by solving the appropriate governing equations viz. conservation of mass and momentum using FLUENT code. Turbulence effects are taken care of by the Reynolds stress model and shear stress transport k-ω model for high swirls and standard k-ε model for low and medium swirls. The effect of pitch to chord ratio (s/c) on flow characteristics have been studied. The predicted results are validated with the experimental data available in the literature for s/c ratio of 1. The numerical results of axial velocity profiles downstream of the swirler at various axial planes are found to be in close agreement with the experimental results. It is found that the s/c ratio of 1 provides good turning efficiency.

A Numerical Investigation of Rotating Instability in Steam Turbine Last Stage

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
L. Y. Zhang ◽  
L. He ◽  
H. Stüer
Keyword(s):  
Steam Turbine ◽  
Dynamic Instability ◽  
Computational Study ◽  
Fluid Dynamic ◽  
Pressure Ratio ◽  
Separated Flow ◽  
Test Model ◽  
Steam Turbines ◽  
Last Stage ◽  
Rotating Instability

The unsteady flow phenomenon (identified as rotating instability) in the last stage of a low-pressure model steam turbine operated at very low mass flow conditions is numerically studied. This kind of instability has been observed previously in compressors and can be linked to the high structural stress levels associated with flow-induced blade vibrations. The overall objective of the study is to enhance the understanding of the rotating instability in steam turbines at off design conditions. A numerical analysis using a validated unsteady nonlinear time-domain CFD solver is performed. The 3D solution captures the massively separated flow structure in the rotor-exhaust region and the pressure ratio characteristics around the rotor tip of the test model turbine stage in good comparison with the experiment. A computational study with a multi-passage whole annulus domain on two different 2D blade sections is subsequently carried out. The computational results clearly show that a rotating instability in a turbine blading configuration can be captured by the 2D model. The frequency and spatial modal characteristics are analyzed. The simulations seem to be able to predict a rotating fluid dynamic instability with the similar characteristic features to those of the experiment. In contrast to many previous observations, the results for the present configurations suggest that the onset and development of rotating instabilities can occur without 3D and tip-leakage flows, although a quantitative comparison with the experimental data can only be expected to be possible with fully 3D unsteady solutions.

Computational Fluid Dynamic Analysis of Compressible Flow across a Complex Geometry Carburettor Venturi

2018 ◽  
Vol 6 (7) ◽  
pp. 83
Author(s):  
Arvind .T ◽  
Swaminathan M. R
Keyword(s):  
Compressible Flow ◽  
Static Pressure ◽  
Cfd Simulation ◽  
Complex Geometry ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Valve Design ◽  
Computational Fluid Dynamic Analysis ◽  
Throttle Valve ◽  
Fuel Tube

A commercial computational fluid dynamics package could be used to develop a three dimensional, fully turbulent model of the compressible flow across a complex geometry venturi, such as those found in small engine carburettors. The results of the CFD simulation can be used to understand the effect of the different obstacles in the flow on the mass flow rate and the static pressure at the tip of the fuel tube. This would be helpful to analyze the pressure loss in the throat area. Analysis would be performed to study airflow across carburettor venturi by locating fuel tube at the diverging nozzle of the venturi and for various positions of throttle valve in the present paper, fuel tube and throttle plate would be modelled and analyze in order to have better understanding of the flow in complex venturi. The results of this study necessitate for modification throttle valve design. The carburettor body is remodelled with two throttle bodies replacing conventional throttle. Analysis has been performed to study flow field with modified design and results have been discussed.

A Numerical Investigation of Rotating Instability in Steam Turbine Last Stage

2011 ◽  
Author(s):  
L. Y. Zhang ◽  
L. He ◽  
H. Stu¨er
Keyword(s):  
Steam Turbine ◽  
Dynamic Instability ◽  
Computational Study ◽  
Fluid Dynamic ◽  
Pressure Ratio ◽  
High Stress ◽  
Test Model ◽  
Steam Turbines ◽  
Last Stage ◽  
Rotating Instability

In the present study, the unsteady flow phenomenon (identified as rotating instability) in the last stage of a low-pressure model steam turbine operated at very low mass flow conditions is studied through numerical investigations. This kind of instability has been observed previously in compressors and is believed to be the cause of high stress levels associated with the corresponding flow-induced blade vibrations. The overall purpose of the study is to enhance the understanding of the rotating instability in steam turbines at off design conditions. A numerical analysis using a validated unsteady nonlinear time-domain CFD solver is adopted. The 3D solution captures the massively separated flow structure in the rotor-exhaust region and the pressure ratio characteristics around the rotor tip of the test model turbine stage, which compare well with those observed in the experiment. A computational study with a multi-passage whole annulus domain on two different 2D blade sections is subsequently carried out. The computational results clearly show that a rotating instability in a turbine blading configuration can be captured by the 2D model. The frequency and spatial modal characteristics are analyzed. The simulations seem to be able to predict a rotating fluid dynamic instability with the similar characteristic features to those of the experiment. In contrast to the previous observations and conventional wisdom, the present work reveals that the formation and movement of the disturbance can occur without 3D and tip-leakage flows, even though a quantitative comparison with the experimental data can only be expected to be possible with full 3D unsteady solutions.

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