Investigation of Swirling Air Flows Generated by Axial Swirlers in a Flame Tube

2006 ◽  
Author(s):  
Farhad Davoudzadeh ◽  
Nan-Suey Liu ◽  
Jeffrey P. Moder
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Liquid Fuel ◽  
Recirculation Zone ◽  
Combustion Process ◽  
Civil Aviation ◽  
Single Element ◽  
Fuel Injector ◽  
Flame Tube ◽  
Refined Grid

An unstructured and massively parallel Reynolds-Averaged Navier-Stokes (RANS) code is used to simulate 3-D, turbulent, non-reacting, and confined swirling flow field associated with a single-element and a nine-element Lean Direct Injection (LDI) combustor. In addition, the computed results are compared with the Large Eddy Simulation (LES) results and are also validated against the experimental data. The LDI combustors are a new generation of liquid fuel combustors developed to reduce aircraft NOx emission to 70% below the 1996 International Civil Aviation Organization (ICAO) standards and to maintain carbon monoxide and unburned hydrocarbons at their current low levels at low power conditions. The concern in the stratosphere is that NOx would react with the ozone and deplete the ozone layer. This paper investigates the non-reacting aerodynamics characteristics of the flow associated with these new combustors using a RANS computational method. For the single-element LDI combustor, the experimental model consists of a cylindrical air passage with air swirlers and a converging-diverging venturi section, extending to a confined 50.8-mm square flame tube. The air swirlers have helical, axial vanes with vane angles of 60 degree. The air is highly swirled as it passes through the 60 degree swirlers and enters the flame tube. The nine-element LDI combustor is comprised of 9 elements that are designed to fit within a 76 mm 76 mm flametube combustor. In the experimental work, the jet-A liquid fuel is supplied through a small diameter fuel injector tube and is atomized as it exits the tip and enters the flame tube. The swirling and mixing of the fuel and air induces recirculation zone that anchors the combustion process, which is maintained as long as a flammable mixture of fuel and air is supplied. It should be noted that in the numerical simulation reported in this paper, only the non-reacting flow is considered. The numerical model encompasses the whole experimental flow passage, including the flow development sections for the air swirlers, and the flame tube. A low Reynolds number K-e turbulence model is used to model turbulence. Several RANS calculations are performed to determine the effects of the grid resolution on the flow field. The grid is refined several times until no noticeable change in the computed flow field occurred; the final refined grid is used for the detailed computations. The results presented are for the final refined grid. The final grids are all hexahedron grids containing approximately 861,823 cells for the single-element and 1,567,296 cells for the nine-element configuration. Fine details of the complex flow structure such as helical-ring vortices, re-circulation zones and vortex cores are well captured by the simulation. Consistent with the non-reacting experimental results, the computation model predicts a major re-circulation zone in the central region, immediately downstream of the fuel nozzle, and a second, recirculation zone in the upstream corner of the combustion chamber. Further, the computed results predict the experimental data with reasonable accuracy.

Modelling of Nitric Oxide Formation During Liquid Fuel Combustion

2016 ◽  
Vol 246 ◽  
pp. 279-283
Author(s):  
Stanisław Gil ◽  
Wojciech Bialik
Keyword(s):  
Nitric Oxide ◽  
Experimental Data ◽  
Carbon Monoxide ◽  
Liquid Fuel ◽  
Combustion Process ◽  
Fuel Combustion ◽  
Nitric Oxides ◽  
Oxide Formation ◽  
Nitric Oxide Formation ◽  
The Impact

A liquid fuel combustion process, being a source of many environmentally hazardous pollutants (e.g. nitric oxides, carbon monoxide, polycyclic aromatic hydrocarbons, soot and sulphur oxides), is a subject of extensive research aimed at reduction of their emissions. A high temperature of the combustion air tends to increase the content of NOX in exhaust gases. Based on the experimental data and literature as well as using the CFD tools, a model of light fuel oil combustion has been developed with an emphasis on nitric oxide formation. The model adequately reflects the impact of geometry changes in the flow of combustion substrates on concentrations of carbon monoxide and nitric oxides in the chamber. The quantitative results obtained are comparable to the experimental data.

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.

The Use of Perforated Damping Liners in Aero Gas Turbine Combustion Systems

2011 ◽  
Author(s):  
Jochen Rupp ◽  
Jon Carrotte ◽  
Michael Macquisten
Keyword(s):  
Pressure Drop ◽  
Flow Field ◽  
Gas Turbine ◽  
Analytical Model ◽  
Operating Conditions ◽  
Acoustic Energy ◽  
Fuel Injector ◽  
Flame Tube ◽  
Gas Turbine Combustion ◽  
Combustion Systems

This paper considers the use of perforated porous liners for the absorption of acoustic energy within aero style gas turbine combustion systems. The overall combustion system pressure drop means that the porous liner (or ‘damping skin’) is typically combined with a metering skin. This enables most of the mean pressure drop, across the flame tube, to occur across the metering skin with the porous liner being exposed to a much smaller pressure drop. In this way porous liners can potentially be designed to provide significant levels of acoustic damping, but other requirements (e.g. cooling, available space envelope etc) must also be considered as part of this design process. A passive damper assembly was incorporated within an experimental isothermal facility that simulated an aero-engine style flame tube geometry. The damper was therefore exposed to the complex flow field present within an engine environment (e.g. swirling efflux from a fuel injector, coolant film passing across the damper surface etc.). In addition, plane acoustic waves were generated using loudspeakers so that the flow field was subjected to unsteady pressure fluctuations. This enabled the performance of the damper, in terms of its ability to absorb acoustic energy, to be evaluated. To complement the experimental investigation a simplified 1D analytical model was also developed and validated against the experimental results. In this way not only was the performance of the acoustic damper evaluated, but also the fundamental processes responsible for this measured performance could be identified. Furthermore the validated analytical model also enabled a wide range of damping geometry to be assessed for a range of operating conditions. In this way damper geometry can be optimized (e.g. for a given space envelope) whilst the onset of non-linear absorption (and hence the potential to ingest hot gas) can also be identified.

Study of the Cold Flow Field of a Multi-Injection Combustor

2009 ◽  
Author(s):  
F. Wang ◽  
Y. Huang ◽  
T. Deng
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Gas Turbine ◽  
Recirculation Zone ◽  
Turbulent Model ◽  
Gas Turbine Combustor ◽  
Cold Flow ◽  
Basic Work ◽  
Lining Structure ◽  
Recirculation Zones

Multi-injection combustor (MIC) could extend the steady working range of the whole combustor and reduce emissions therefore, so it is one of the Gas Turbine Combustor (GTC) design direction of future. The cold flow character of MIC is the basic work for MIC designers. Because of the low cost nowadays, the CFD method is a very suitable tool for it. Thus, firstly realizable k-epsilon turbulent model (RKE) and Reynolds stress turbulent model (RSM) were used to simulate the downstream flow field of a double radial swirl-cup amongst a simple tube, and the prediction results are compared with the experimental data which are gained by another researcher in Beihang University. The comparison between the experimental data and the CFD prediction results are shown that in most regions, the prediction results quite agree with the experimental data, and the max error of RKE model and RSM model is about 5% and 3% respectively. So the RKE model can be used for swirl-cup combustor simulation for its low computing cost. Then the RKE model is applied in a single swirl-cup gas turbine combustor and two kinds of multi-injection GTC flow field simulation. In the comparison between one single swirl-cup and nine arranged swirl-cups which all are in the same lining structure, each swirl-cup in MIC has a recirculation zone after its exit. Gradually, the recirculation zones mixed and united together in the downstream region. Finally, the recirculation zones structure turns to be similar to the structure in the single swirl-cup GTC after the primary combustion holes. In the other comparison between two kinds of lining structures which all are fixed with the same multi-injection head, the primary combustion holes affect flow field obviously. All the recirculation zones finished before the former primary combustion holes of the MIC without the primary combustion holes, and the separated recirculation zones form a new recirculation zone close to the primary holes for the MIC with primary holes. So the MIC design should combine with the real combustor lining structure to make a high performance for the whole combustor.

Compressor Exit Conditions and Their Impact on Flame Tube Injector Flows

1999 ◽  
Vol 124 (1) ◽  
pp. 10-19 ◽  
Author(s):  
A. G. Barker ◽  
J. F. Carrotte
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Test Facility ◽  
Fuel Injector ◽  
Turbine Engine ◽  
Flame Tube ◽  
Subsequent Effect ◽  
Injector Flows ◽  
Flow Compressor ◽  
Combustion Processes

Within a gas turbine engine the flow field issuing from the compression system is nonuniform containing, for example, circumferential and radial variations in the flow field due to wakes from the upstream compressor outlet guide vanes (OGVs). In addition, variations can arise due to the presence of radial load bearing struts within the pre-diffuser. This paper is concerned with the characterization of this nonuniform flow field, prior to the combustion system, and the subsequent effect on the flame tube fuel injector flows and hence combustion processes. A mainly experimental investigation has been undertaken using a fully annular test facility which incorporates a single stage axial flow compressor, diffuser, and flame tube. Measurements have been made of the flow field, and its frequency content, within the dump cavity. Furthermore, the stagnation pressure presented to the core, outer and dome swirler passages of a fuel injector has been obtained for different circumferential positions of the upstream OGV/pre-diffuser assembly. These pressure variations, amounting to as much as 20 percent of the pressure drop across the fuel injector, also affect the flow field immediately downstream of the injector. In addition, general variations in pressure around the fuel injector have also been observed due to, for example, the fuel injector position relative to pre-diffuser exit and the flame tube cowl.

Suppression of Instabilities in Liquid Fueled Combustors by Variation of Fuel Spray Properties

2003 ◽  
Author(s):  
J.-Y. Lee ◽  
E. Lubarsky ◽  
B. T. Zinn
Keyword(s):  
Active Control ◽  
Liquid Fuel ◽  
Near Field ◽  
Combustion Process ◽  
Axial Flow ◽  
Fuel Spray ◽  
Fuel Injector ◽  
Combustion Instabilities ◽  
Control Approach ◽  
The Mean

This paper describes an experimental investigation of the feasibility of using “slow” active control approaches, which change liquid fuel spray properties, to suppress combustion instabilities. The objective of this control approach is to break up the feedback between the combustion process heat release oscillations and the combustor oscillations that drives the instability by changing the characteristics of the combustion process (i.e., characteristic combustion time). To demonstrate the feasibility of such control, this study used a proprietary fuel injector (Nanomiser™), which can independently vary its fuel spray properties, and investigated the dependence of acoustics-combustion process coupling, i.e., the driving of combustion instabilities, upon the fuel spray properties. The results of this study showed that by changing the spray characteristics it is possible to significantly damp combustion instabilities. Furthermore, using Abel’s deconvolution, this study showed that the instabilities were mostly driven in regions where the mean axial flow velocity was approximately zero, in the near field of the vortices that were generated in the combustor. The results of this study strongly suggest that a “slow” active control system that employs controllable injectors could be used to prevent the onset and/or damp detrimental combustion instabilities.

Numerical Investigation of a Swirl Stabilized Methane Fired Burner and Validation With Experimental Data

2019 ◽  
Author(s):  
Federica Farisco ◽  
Philipp Notsch ◽  
Rene Prieler ◽  
Felix Greiffenhagen ◽  
Jakob Woisetschlaeger ◽  
...  
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Heat Release ◽  
Reaction Zone ◽  
Gas Turbines ◽  
Combustion Process ◽  
Operating Conditions ◽  
Main Reaction ◽  
Combustion Models ◽  
Flamelet Generated Manifold

Abstract In modern gas turbines for power generation and future aircraft engines, the necessity to reduce NOx emissions led to the implementation of a premixed combustion technology under fuel-lean conditions. In the combustion chamber of these systems, extreme pressure amplitudes can occur due to the unsteady heat release, reducing component life time or causing unexpected shutdown events. In order to understand and predict these instabilities, an accurate knowledge of the combustion process is inevitable. This study, which was provided by numerical methods, such as Computational Fluid Dynamics (CFD) is based on a three-dimensional (3D) geometry representing a premixed swirl-stabilized methane-fired burner configuration with a known flow field in the vicinity of the burner and well defined operating conditions. Numerical simulations of the swirl-stabilized methane-fired burner have been carried out using the commercial code ANSYS Fluent. The main objective is to validate the performance of various combustion models with different complexity by comparing against experimental data. Experiments have been performed for the swirl-stabilized methane-fired burner applying different technologies. Velocity fluctuation measurements have been carried out and validated through several techniques, such as Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV). Laser Interferometric Vibrometry (LIV) provided information on heat release fluctuations and OH*-chemiluminescence measurements have been done to identify the position of the main reaction zone. During the first part of the CFD investigation, the cold flow has been simulated applying different turbulence models and the velocity flow field obtained in the experiments has been compared with the numerical results. As next, the study focuses on the numerical analysis of the thermo-chemical processes in the main reaction zone. Few combustion models have been investigated beginning from Eddy Dissipation Model (EDM) and proceeding with increased complexity investigating the Steady Flamelet Model (SLF) and Flamelet Generated Manifold (FGM). An evaluation of the velocity field and temperature profile has been performed for all models used in order to test the validity of the numerical approach for the chosen geometry. The best option for future investigations of gas turbines has been identified.

The Influence of Geometric and Aerodynamic Boundary Conditions on Fuel Injector Feed and External Aerodynamics for Lean Burn Combustors

2019 ◽  
Author(s):  
Y. Li ◽  
P. A. Denman ◽  
A. D. Walker
Keyword(s):  
Flow Field ◽  
Gas Turbines ◽  
Combustion System ◽  
Fuel Injector ◽  
Flow Uniformity ◽  
Lean Burn ◽  
Fuel Injectors ◽  
Systematic Assessment ◽  
Flame Tube ◽  
External Combustion

Abstract Lean burn combustion is currently a preferred technology to meet the future low emission requirements faced by aero gas turbines. Previous work has shown that the increased air mass flow and size of lean burn fuel injector alters the necessary redistribution of the airflow leaving the high-pressure compressor. This can lead to flow field non-uniformities in the feed to combustor annuli and the fuel injectors which have the potential to impact the overall performance of the combustion system. This paper presents a systematic assessment of the effect of several aerodynamic parameters on the air flow feed to the fuel injectors and the external combustion system aerodynamics for a generic lean burn system. This includes the effect of changes to the flow splits between various combustor cooling features and annulus flows and the effect of a biased compressor exit profile. Flow field data are generated using an isothermal RANS CFD model which is validated against test rig data. The data show that changes in the flow split between the annuli modified the flow uniformity and loss to both the combustor annuli and the fuel injector feed. Changes in the compressor exit profile have a larger effect introducing more notable variations in both flow uniformity and loss. Changes to the angle of the flame tube did not greatly affect the pre-diffuser but did modify annulus loss. Further analysis showed that changes to the combustor annulus flow split, compressor exit profile and flame tube angle modified the location, at compressor exit, of the flow captured by the annuli or each fuel injector passage. The loss to each of these depends on the flow quality (total pressure and uniformity) and from the source more than the flow uniformity delivered.

Numerical Investigation of the Flow Field Around a Low Rise Building Using LES Technique

2010 ◽  
Author(s):  
S. S. Motallebi Hasankola ◽  
O. Abouali
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Recirculation Zone ◽  
Laboratory Data ◽  
Turbulence Models ◽  
Streamwise Velocity ◽  
Building Model ◽  
Rans Models ◽  
Length Width ◽  
Stress Models

In this research the flow field obtained by LES technique is compared with laboratory data measured around a low rise building model with 1:1:0.3 (length: width: height) aspect ratio. The results also are compared with some other turbulence models. The turbulence models include standard k-ε, Durbin’s revised k-ε (DBN), and LRR Reynolds stress models (RSM). Firstly the limitations of the mentioned turbulence models are described for capturing the recirculation zone above and behind of the building model. Among the RANS models, Durbin’s revised model with low Reynolds type of the boundary condition predicts the flow field around the building better compared with other RANS models. The Smagorinski and WALE models among SGS models of LES were employed for the simulation of flowfield around the building. The LES results show generally a better agreement with experimental data compared with RANS models for the streamwise velocity at the roof and behind of building. This improvement is mainly due to the fact that the periodic velocity fluctuation behind the building is well reproduced in LES.

scholarly journals Compressor Exit Conditions and Their Impact on Flame Tube Fuel Injector Flows

1999 ◽  
Author(s):  
A. G. Barker ◽  
J. F. Carrotte
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Test Facility ◽  
Fuel Injector ◽  
Turbine Engine ◽  
Flame Tube ◽  
Subsequent Effect ◽  
Injector Flows ◽  
Flow Compressor ◽  
Combustion Processes

Within a gas turbine engine the flow field issuing from the compression system is non-uniform containing, for example, circumferential and radial variations in the flow field due to wakes from the upstream compressor outlet guide vanes (OGVs). In addition, variations can arise due to the presence of radial load bearing struts within the pre-diffuser. This paper is concerned with the characterisation of this non-uniform flow field, prior to the combustion system, and the subsequent effect on the flame tube fuel injector flows and hence combustion processes. A mainly experimental investigation has been undertaken using a fully annular test facility which incorporates a single stage axial flow compressor, diffuser and flame tube. Measurements have been made of the flow field, and its frequency content, within the dump cavity. Furthermore, the stagnation pressure presented to the core, outer and dome swirler passages of a fuel injector has been obtained for different circumferential positions of the upstream OGV/pre-diffuser assembly. These pressure variations, amounting to as much as 20% of the pressure drop across the fuel injector, also affect the flow field immediately downstream of the injector. In addition, general variations in pressure around the fuel injector have also been observed due to, for example, the fuel injector position relative to pre-diffuser exit and the flame tube cowl.

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