The Effect of Geometry on the Aerodynamics of a Prototype Gas Turbine Combustor

2010 ◽  
Author(s):  
Bassam Mohammad ◽  
San-Mou Jeng
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Flow Structure ◽  
Strong Influence ◽  
Swirling Flow ◽  
Rectangular Cross Section ◽  
Low Velocity ◽  
Significant Difference ◽  
Expansion Angle ◽  
The Asymmetry

The method of admission of the swirling flow to the combustion chamber has a strong influence on the flow field structure in Gas Turbine Combustors (GTC). Two different exit configurations are studied. The first configuration is that of a swirl cup that ends only with a splash plate such that there is a sudden unguided expansion as the flow emanates from the swirl cup. The second is a swirl cup that ends with a splash plate and an asymmetric combustion dome. Laser Doppler Velocimetry (LDV) measurements are conducted in the horizontal plane (X-Y), for both configurations, 5mm from the flare exit. Also, LDV measurements are conducted in two vertical planes passing by the combustor centerline (X-Z and Y-Z). The results reveal a significant difference in the flow structure for both configurations. The combustion dome appears to reduce the turbulence activities close to the exit of the swirl cup. In addition, the presence of the combustion dome eliminates the corner recirculation zone and the low velocity region close to the combustor walls. It is interesting to see that the asymmetry of the combustion dome (9° difference in the expansion angle on both sides) results in a significant asymmetry in the velocity magnitude as well as the turbulence activities. Moreover, the asymmetry in the combustion dome results in a tilting of the CRZ toward the surface with the higher expansion angle. The results highlight the importance of the proper and careful design of the GTC front section. The experiments are conducted in a dump combustor (rectangular cross section). To study the effect of the chamber geometry on the flow field, the base configuration is installed in an annular combustor sector and LDV measurements are conducted in the axial radial plane (X-Z). The flow field as well as the shape of the CRZ are significantly different in both cases. The CRZ height reduced by 40% with the swirl cup installed to the SAC sector. The results emphasize the strong influence of the confinement on the flow structure.

Effect of Dome Geometry on Swirling Flow Field Characteristics of a Counter-Rotating Radial-Radial Swirler

2013 ◽  
Author(s):  
Yi-Huan Kao ◽  
Samir B. Tambe ◽  
San-Mou Jeng
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Aerodynamic Characteristics ◽  
Sudden Expansion ◽  
Reacting Flow ◽  
Clockwise Rotation ◽  
Expansion Angle ◽  
Flow Field Characteristics

An experimental study has been conducted to study the effect of the dome geometry on the aerodynamic characteristics of a non-reacting flow field. The flow was generated by a counter-rotating radial-radial swirler consisting of an inner, primary swirler generating counter-clockwise rotation and an outer, secondary swirler generating clockwise rotation. The dome geometry was modified by introducing dome expansion angles of 60° and 45° with respect to the swirler centerline, in addition to the baseline case of sudden expansion (90°). The flow downstream of the swirler is confined by a 50.8mm × 50.8mm × 304.8mm (2″ × 2″ × 12″) plexiglass chamber. A two-component laser doppler velocimetry (LDV) system was used to measure the velocities in the flow field. The dome geometry is seen to have a clear impact on mean swirling flow structure near the swirler exit rather than the downstream flow field. For the configurations with 60° and 45° expansion, no corner recirculation zone is observed and the swirling flow structure is asymmetric due to the non-axisymmetric dome geometry. The cross-section area of central recirculation zone is larger for dome geometry with 60° expansion angle, as compared to the 90° and 45° cases. The configurations with 60° and 45° expansion have higher magnitudes of negative velocity inside the core of central recirculation zone, as compared to the configuration with 90° expansion angle.

The Impact of Representative Aerodynamic Flow Fields on Liquid Fuel Atomisation in Modern Gas Turbine Fuel Injectors

2014 ◽  
Author(s):  
A. G. Barker ◽  
J. F. Carrotte
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Liquid Fuel ◽  
Swirling Flow ◽  
Subsequent Development ◽  
Potential Effect ◽  
Far Field ◽  
Fuel Injector ◽  
Swirl Vane ◽  
The Impact

In modern gas turbine engines swirl is typically imparted to the airflow as it enters the region of heat release to stabilize the flame. This swirling airstream is often highly turbulent and contains non-uniformities such as swirl vane wakes. However, it is within this environment that fuel atomization takes place. This paper is concerned with the potential effect of these airstream characteristics on the atomization process. Such a flow field is difficult to capture within simplified geometries and so measurements have been made within, and downstream of, injector representative geometries. This is experimentally challenging and required the application of a variety of techniques. The geometry considered is thought typical of an air-blast style injector, as may be used within current or future applications, whereby liquid fuel is introduced onto a pre-filming surface over which an airstream passes. Data is presented which characterizes the atomizing airstream presented to the pre-filming region. This includes significant flow field non-uniformities and turbulence characteristics that are mainly associated with the swirling flow along with the vanes used to impart this swirl. The subsequent development of these aerodynamic features over the pre-filming surface is also captured with, for example, swirl vane wakes being evident through the injector passage and into the downstream flow field. It is argued these characteristics will be common to many injector designs. Measurements with and without fuel indicate the effect of the liquid film, on the non-dimensional aerodynamic flow field upstream of the pre-filming region, is minimal. However, the amount of airflow passing through the pre-filming passage is affected. In addition to characterization of the airstream, its impact on the liquid fuel film and its development along the pre-filming surface is visualized. Furthermore, PDA measurements downstream of the fuel injector (i.e. the injector ‘far-field) are presented and the observed spray characteristics spatially correlated with the upstream aerodynamic atomizing flow field. Hence for the first time a series of experimental techniques have been used to capture and correlate both near and far field atomization characteristics within an engine representative aerodynamic flow field.

Experimental Study of the Swirling Flow in the Internal Volute of a Centrifugal Compressor

1991 ◽  
Author(s):  
E. Ayder ◽  
R. Van Den Braembussche
Keyword(s):  
Flow Structure ◽  
Cross Section ◽  
Mass Flow ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Swirling Flow ◽  
Rectangular Cross Section ◽  
High Mass ◽  
Radial Velocity Component ◽  
The Cross

A detailed study of the swirling flow in a rectangular volute of a centrifugal compressor is presented. The 3D flow field has been measured by means of a five hole probe at six different cross sections for three different operating points of the compressor. For high mass flow, the large radial velocity component at the diffuser exit creates a strong swirling flow with a forced vortex type of velocity distribution. The centrifugal force resulting from this motion is balanced by the increase of static pressure from the swirl center to the volute wall. Due to the effect of circumferential curvature a zone of high through flow velocity occurs next to the volute inner wall. Less swirl is generated for optimum mass flow resulting in smaller pressure gradients over the cross section. Low energy fluid accumulates near the inner wall of the cross section. For low mass flow, a large region of separated flow is observed and more uniform static pressure has been measured over the cross section. The effect of the tongue on the flow structure in the first and last cross section is also discussed. This study is the follow-up of previous studies described in ASME paper 89-GT-183 and 90-GT-49. The results obtained verify the previous studies and provide a better understanding of the flow structure inside internal volutes of rectangular cross section.

Experimental Investigation of Airflow and Spray Stability in an Air-Blast Injector of an Industrial Gas Turbine

2004 ◽  
Author(s):  
Andrei Secareanu ◽  
Dragan Stankovic ◽  
Laszlo Fuchs ◽  
Vladimir Milosavljevic ◽  
Jonas Holmborn
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Swirling Flow ◽  
Laser Sheet ◽  
Front Panel ◽  
Mean Flow ◽  
Air Blast ◽  
Full Cross Section ◽  
Airflow Field ◽  
Industrial Gas Turbine

The airflow field and spray characteristics from an air blast type of injector in an industrial gas turbine (GT) combustor geometry have been investigated experimentally and numerically. The flame in the current combustor is stabilized by a highly swirling flow. The stabilization of the flame is strongly dependent on the stability of the flow field out from the injector and into the combustor. Liquid fuel spray formation in the current type of injector is highly dependent on the airflow from the internal swirler, which supplies the shear to break the liquid film, and form the spray. Experiments were performed in a Perspex model of a 12° sector of the combustor with airflow scaled to atmospheric conditions. The geometry was comprised of the air section including the full primary zone, injector, combustor swirler, front panel and primary air jets. The flow field was visualized using particles that were illuminated by a laser sheet. Quantitative characterization was done using LDA. The airflow field was characterized by the mean flow pattern covering the full cross-section of the flow field and additional long time measurements at a number of locations in order to capture frequency content of the flow. Isothermal spray measurements were performed in an unconfined geometry including the injector, swirl generator and front panel. The spray uniformity was qualitatively investigated using video camera and quantitatively characterized by PDA. The studies of the flow field and fuel atomization (droplet size and density) under different conditions are summarized below.

Numerical Study of Unsteady Flow-Field and Flame Dynamics in a Gas Turbine Model Combustor

2014 ◽  
Author(s):  
Moresh J. Wankhede ◽  
Ferry A. Tap ◽  
Philipp Schapotschnikow ◽  
Wilhelmus J. S. Ramaekers
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Gas Turbine ◽  
Swirling Flow ◽  
Numerical Study ◽  
Swirl Flow ◽  
Detached Eddy Simulation ◽  
Flame Dynamics ◽  
Flamelet Generated Manifold ◽  
Turbine Model

In swirl-stabilized gas turbine combustors, interaction between unsteady flow-field and flame dynamics play a key role in driving several types of combustion instabilities, establishing flame location and its structure and influencing heat release rates. This is challenging to understand and computationally expensive to resolve in detail. In this study, a highly turbulent and swirling flow-flame dynamics in a gas turbine model combustor is characterized numerically using unsteady Reynolds-averaged Navier Stokes (URANS) and detached eddy simulation (DES) based computational fluid dynamics (CFD) methods. From flame representation point of view, the Flamelet Generated Manifold (FGM) method is used to reduce combustion chemistry (which still includes detailed reaction kinetics and species diffusion in reaction layers) and hence computational requirements. The helical precessing vortex core (PVC) instability and its influence on downstream flow/flame dynamics is captured. Further insight is gained into URANS and DES methods capabilities in simulating various coherent swirl flow structures such as central toroidal recirculation zone (CTRZ) and outer recirculation zones (ORZ) as well as fuel-air mixing patterns. NOx emission, which is currently a high-priority design objective due to stringent pollutant regulations, is also computed. The results show that the numerically captured swirling flow-flame dynamics is in accordance with the experimental observations and measurements.

Experimental and Computational Results of Distributed Combustion for Application in Current Gas Turbine Engine Combustor Architectures

2011 ◽  
Author(s):  
Nick Overman ◽  
Jason Ryon
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Swirling Flow ◽  
Numerical Test ◽  
Injection System ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Lean Burn ◽  
Lean Combustion ◽  
Improved Performance

Current development and testing has lead to a fuel/air injection system for application in gas turbine engines that produces ultra low emissions and stable, lean combustion. The system is designed to operate with current combustor architectures similar to existing gas turbine engines. This paper presents both experimental and numerical test results demonstrating the benefits of such technology including extremely low emissions of NOx, CO, and un-burned hydrocarbons (UHC). Primary focus is on experimental results demonstrating reaction distribution and emissions. Numerical confirmation of flow field dynamics was used to develop an understanding of the re-circulation rates within the combustor and impact on reaction behavior. Several design configurations were tested to investigate the effects of aerodynamic stagnation point and fuel placement with respect to the aerodynamic shear layer produced by the swirling flow field. Test conditions were varied, including inlet air temperature and injector pressure drop for monitoring effects on the operating envelope of distributed reaction and on lean blow out limit. Results demonstrate the improved performance of a system capable of operating in a flameless or distributed reaction mode over that of a typical lean burn system.

Gas Turbine Combustor Flow Structure Control Through Modification of the Chamber Geometry

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
B. S. Mohammad ◽  
J. Cai ◽  
San-Mou Jeng
Keyword(s):  
Flow Structure ◽  
Recirculation Zone ◽  
Reverse Flow ◽  
Rectangular Cross Section ◽  
Jet Impingement ◽  
Lessons Learned ◽  
Cross Sectional ◽  
Structure Control ◽  
Expansion Angle ◽  
Primary Jets

As combustors are put in service, problems such as erosion, hot spots, and liner oxidation occur, and a solution based on lessons learned is essential to avoid similar problems in future combustor generations. In the present paper, a combustor flow structure control via combustor geometry alteration is investigated using laser Doppler velocimetry. Mainly, three configurations are studied. The first configuration is that of a swirl cup feeding a dump (rectangular cross section) combustor. The rectangular chamber is configured with a width to breadth (w/b) ratio of 85%. The second configuration is similar to the first one, but a combustion dome is installed. The dome is configured with a 9 deg difference in the expansion angle on both sides (asymmetric dome). The third configuration is that of a swirl cup and a combustion dome installed in a prototype combustor (single annular combustor (SAC) sector), with both primary and secondary dilution jets blocked. The SAC is configured with a cross sectional area that decreases toward the exit through the tilting of the inner combustor liner. The results show that the combustion dome eliminates the corner recirculation zone and the low velocity region close to the combustor walls. The combustion dome asymmetry results in a significant asymmetry in the velocity magnitude, as well as the turbulence activities and the tilting of the central recirculation zone (CRZ) toward the surface with the higher expansion angle. The liner tilting results in a 40% reduction in the length of the CRZ. However, once the primary jets are open, they define the termination point of the CRZ. The chamber w/b ratio results in a CRZ with the same diameter ratio (85%) in all configurations. Interestingly, the maximum reverse flow velocity is roughly constant in all measurement plans and configurations up to a downstream distance of 1R (R is the flare radius). However, with open primary jets, the CRZ strength increases appreciably. It appears that the confinement dictates both the flow field outside the CRZ and the size of the CRZ, while the swirl cup configuration mainly influences the strength of the CRZ. Regarding turbulence activities, the presence of the dome damps the fluctuations in the expanding swirling jet region. On the other hand, the primary jets increase the turbulence activities appreciably in the jet impingement region, as well as the upper portion of the CRZ (60% increase).

Visualization of the Effect of a Shroud on Entrainment of Fluidized Solids into a Gas Jet

2007 ◽  
Vol 5 (1) ◽  
Author(s):  
Craig Hulet ◽  
Jennifer McMillan ◽  
Cedric Briens ◽  
Franco Berruti ◽  
Edward W Chan
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Rectangular Cross Section ◽  
Surrounding Medium ◽  
Flow Patterns ◽  
Transparent Plate ◽  
Significant Difference ◽  
Fundamental Understanding ◽  
Expansion Angle ◽  
Inner Diameter

Submerged gas jets issuing into fluidized beds are used in many different industries and it is important to have a fundamental understanding of how the gas and surrounding medium interact – to understand the flow patterns and how the solids behave in the vicinity of the nozzle jet. Following the discussions of Bohnet and Teifke (1985) and Idelchek (1994) it was decided to qualitatively investigate the effects of altering the region surrounding the contact between the jet and the fluidized bed. Alteration of the flow pattern was accomplished using a semi-cylindrical shroud (0.035 m i.d. and 0.043 m long) that formed a physical barrier around the nozzle tip. The nozzle inner diameter was 0.0016 m i.d. and the motive gas flow rate was supersonic. Videos were recorded of the solids and gas flow patterns via a special transparent plate on the wall of the fluidized bed for a half-jet with and without a shroud at a superficial fluidization gas velocity of 0.11 m/s. Presented below are the original videos and observations derived from the two simple experiments in a fluidized bed with a rectangular cross-section (0.10 by 1.20 m and 2.0 m high). There was a significant difference in the flow patterns of the solids in the vicinity of the nozzle tip when the shroud was present. Furthermore, the jet expansion angle and penetration were observed to decrease by approximately 50% and 43%, respectively.

scholarly journals Aerodynamics of a Fuel Spoke in a Gas Turbine Combustor

1998 ◽  
Author(s):  
Iris Z. Hu ◽  
Sanjay M. Correa
Keyword(s):  
Gas Turbine ◽  
Flow Structure ◽  
Swirling Flow ◽  
Three Dimensional ◽  
Spanwise Direction ◽  
Complex Flow ◽  
Gas Turbine Combustor ◽  
Step Size ◽  
Air Mixing ◽  
Complex Flow Structure

The three-dimensional unsteady flow in a gas turbine combustor was studied using CFD means. The flow structure around a fuel spoke is of interest not only because of pollutant issues, but also because of combustor operating issues such as combustion acoustics and potential flame-holding in the premixer. The CFD model was tested extensively in terms of grid density and lime-marching step size before the final calculation was made. It was shown that when a swirling flow crosses over a cylindrical fuel spoke, wake vortices are formed and a strong secondary flow is generated along the spanwise direction. A secondary vortex existed near the tip of the spoke. This complex flow structure affects the quality of fuel and air mixing and can be addressed by CFD-based design methods.

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