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Author: Jacob Haseman
Publisher:
ISBN:
Category :
Languages : en
Pages : 109
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Book Description
Current trends with swirler/combustor designs tend towards lower emissions in accordance with ICAO standards, with the main problems inherent in common lean-direct-injection (LDI) designs being poor stability and autoignition or flashback issues. The LDI design is meant to combine the good stability and performance of a traditional rich-burn quick-quench lean-burn (RQL) combustor with the ultra-low NOx emissions of a lean-premixed-prevaporized (LPP) combustor. The goal of this research is to investigate the feasibility of using swirlers with varying swirl strengths in an LDI combustor array by performing a series of combustion tests at atmospheric pressure. Three configurations were designed and tested which contained different arrangements of two counter-rotating radial-radial swirler designs with varying swirl strengths in a 3x3 array format. All nine swirlers contained a fuel nozzle with very similar flow numbers and were all set to the same insertion depth with respect to the swirlers' flare exits. Two nozzle insertion depths were investigated to see how the performance changes with changing insertion depth. Three fuel circuits supplied fuel to the nine fuel nozzles to the center, sides, and diagonal swirlers respectively. Testing was conducted by placing the hardware on a horizontally-oriented test rig connected to an air intake manifold, with the inlet air preheated to approximately 400°F and the pressure drop across the swirler set to 4% of atmospheric pressure. These tests investigated fuel staging configurations at various simulated engine throttle settings and flight conditions to gauge the steady-state combustion and LBO characteristics and low- NOx potential of this design. The results of this testing show that all three configurations tested were able to achieve stable-burning with low equivalence ratios for the three simulated flight conditions tested, as well as across a number of other investigated parameters. The two high-strength swirler configurations performed better than the baseline configuration in terms of LBO, stability, and flame uniformity, but all three configurations achieved stable combustion at comparable equivalence ratios to traditional combustor designs currently in use in industry. The low fuel flow rates required for ignition with the larger flow number fuel nozzles also demonstrates the practicality of this design in a real-world scenario. These tests also demonstrate that the deeper nozzle insertion depth performed better than the shallow insertion depth, and that future testing should focus on the high-strength swirler configurations.
Author: Jacob Haseman
Publisher:
ISBN:
Category :
Languages : en
Pages : 109
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Book Description
Current trends with swirler/combustor designs tend towards lower emissions in accordance with ICAO standards, with the main problems inherent in common lean-direct-injection (LDI) designs being poor stability and autoignition or flashback issues. The LDI design is meant to combine the good stability and performance of a traditional rich-burn quick-quench lean-burn (RQL) combustor with the ultra-low NOx emissions of a lean-premixed-prevaporized (LPP) combustor. The goal of this research is to investigate the feasibility of using swirlers with varying swirl strengths in an LDI combustor array by performing a series of combustion tests at atmospheric pressure. Three configurations were designed and tested which contained different arrangements of two counter-rotating radial-radial swirler designs with varying swirl strengths in a 3x3 array format. All nine swirlers contained a fuel nozzle with very similar flow numbers and were all set to the same insertion depth with respect to the swirlers' flare exits. Two nozzle insertion depths were investigated to see how the performance changes with changing insertion depth. Three fuel circuits supplied fuel to the nine fuel nozzles to the center, sides, and diagonal swirlers respectively. Testing was conducted by placing the hardware on a horizontally-oriented test rig connected to an air intake manifold, with the inlet air preheated to approximately 400°F and the pressure drop across the swirler set to 4% of atmospheric pressure. These tests investigated fuel staging configurations at various simulated engine throttle settings and flight conditions to gauge the steady-state combustion and LBO characteristics and low- NOx potential of this design. The results of this testing show that all three configurations tested were able to achieve stable-burning with low equivalence ratios for the three simulated flight conditions tested, as well as across a number of other investigated parameters. The two high-strength swirler configurations performed better than the baseline configuration in terms of LBO, stability, and flame uniformity, but all three configurations achieved stable combustion at comparable equivalence ratios to traditional combustor designs currently in use in industry. The low fuel flow rates required for ignition with the larger flow number fuel nozzles also demonstrates the practicality of this design in a real-world scenario. These tests also demonstrate that the deeper nozzle insertion depth performed better than the shallow insertion depth, and that future testing should focus on the high-strength swirler configurations.
Author: Rodrigo Villalva Gómez
Publisher:
ISBN:
Category :
Languages : en
Pages : 288
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Book Description
Experimental research on lean direct injection (LDI) combustors for gas turbine applications is presented. LDI combustion is an alternative to lean premixed combustion which has the potential of equivalent reduction of oxides of nitrogen (NOx) emissions and of peak combustor exit temperatures, but without some drawbacks of premixed combustors, such as flashback and autoignition. Simultaneous observations of the velocity field and reaction zone of an LDI swirl-stabilized combustor with a mixing tube at atmospheric conditions, with the goal of studying the flame stabilization mechanism, are shown. The flame was consistently anchored at the shear layer formed by the high-speed reactants exiting the mixing tube and the low speed recirculation region. Individual image analysis of the location of the tip of the recirculation zone and tip of the reaction region confirmed previously observed trends, but showed that calculation of the distance between these two points for corresponding image pairs yields results no different than when calculated from random image pairs. This most likely indicates a lag in the anchoring of the flame to changes in the recirculation zone, coupled with significant stochastic variation. An alternate LDI approach, multi-point LDI (MLDI), is also tested experimentally. A single large fuel nozzle is replaced by multiple small fuel nozzles to improve atomization and reduce the total volume of the high-temperature, low velocity recirculation zones, reducing NOx formation. The combustor researched employs a novel staged approach to allow good performance across a wide range of conditions by using a combination of nozzle types optimized to various power settings. The combustor has three independent fuel circuits referenced as pilot, intermediate, and outer. Emissions measurements, OH* chemiluminescence imaging, and thermoacoustic instability studies were run in a pressurized combustion facility at pressures from 2.0 to 5.3 bar.Combustor performance was analyzed for three fuel staging configurations, using local equivalence ratio of the individual circuits as a predictive parameter. Pilot-only mode enabled combustor operation at very low overall equivalence ratios while limiting NOx formation in idle power settings due to its configuration approximating a rich-quench-lean combustor. Pilot and intermediate staging tests demonstrated the range of equivalence ratios that are effective in reducing NOx formation while keeping other pollutants in check; very low equivalence ratio results in high unburned hydrocarbon and carbon monoxide, while very high equivalence ratios result in a detrimental effect as more fuel is routed through the intermediate fuel circuit. Using all three fuel circuits simultaneously in high power operation resulted in very low NOx levels (emissions index at or below 0.5 g/kg), particularly when fuel distribution was such that local equivalence ratio was equal among all circuits. The observed NOx levels compared favorably with other MLDI designs which do not have the operational flexibility of the combustor tested. Thermoacoustic instabilities occurred in the MLDI combustor for some test conditions. The local equivalence ratio of the intermediate fuel circuit was found to be one of the major predictor of the onset of instabilities. Detailed analysis of a two-circuit instability (pilot and intermediate) is presented.
Author: Derick S. Endicott
Publisher:
ISBN:
Category :
Languages : en
Pages : 105
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Book Description
The focus of this research is to investigate the isothermal aerodynamic behavior of three LDI configurations utilizing a 3 x 3 array of radial-radial swirlers. Configurations consisted of varying combinations of two swirlers featuring high and low swirl intensity. Two-dimensional velocity data is presented from the measurement of 37 planes spanning the width of the LDI array. An experimental aerodynamic investigation has been carried out on a preliminary Lean Direct Injection (LDI) combustor to discern the effects on the flow-field resulting from interactions between low and high-swirl counter-rotating radial-radial air swirlers in a 9-swirler array. Particle Image Velocimetry (PIV) was used to take velocity field measurements and to study the inter-swirler interactions. The goal of this work is to improve upon the stability limits of current LDI designs while maintaining the current emissions capabilities established by existing LDI designs. The test setup consisted of 9 swirlers arranged in a 3 x 3 pattern with a spacing of 1 inch between the swirler centers. A square plexiglass chamber with an inner dimension of 4.5 x 4.5 inch was used for flow field confinement. A high-speed PIV system was used to take 2D velocity measurement in a vertical plane parallel to the swirler axes. Measurements were conducted at a total of 37 planes spanning the width of the enclosure in an attempt to completely describe the flow field. Three test cases were studied which utilized a combination of a low and high Swirl Number swirlers: the baseline case utilized 9 low swirl (SN about 0.6) swirlers, the second case used one high swirl (SN about 1.0) swirler in the center of the array, and the third case used 3 high swirl swirlers in a row within the array. The flow field developed by the three experimental cases differed significantly and inter-swirler interaction proved significant and highly complex. The velocity fields developed from swirlers in an array varied from that of the individual swirler, and as such, it should not be expected that the array have the same characteristics of the individual swirler. Placing a high-swirl swirler in a low-swirl array increased swirler interaction and led to substantial favorable changes in velocity fields and the recirculation zones developed downstream of each swirler in comparison to the baseline configuration including the development of a large CTRZ with weakened intensity for increased flame anchoring potential. The aerodynamic data was used to extrapolate implications on combustion performance and recommendations for the LDI design have been developed to move forward in the design process. Careful consideration needs to be given to the aerodynamic interaction between swirlers as it can have substantial impact on the delicate balance between combustor performance, stability and emissions.
Author: Xiao Ren
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
To reduce the environmental impact of aviation, lean direct injection (LDI) combustion is being pursued to achieve very low emissions. LDI utilizes multi-point mixers to achieve low NOx emissions and satisfactory combustion stability. Since the performance of LDI directly depends on design parameters of each single LDI mixer, a series of fundamental investigations into lean-dome-relevant pilot combustor devices are conducted herein. A single LDI mixer typically uses swirlers with converging venturi and diverging flare to generate swirling flows, which facilitate mixing in the combustor dome. This dissertation aims to investigate the impact of LDI mixer design parameters, including swirler vane angle, flare, and relative swirling direction between inner and outer swirlers, on single-mixer LDI combustion. The flow fields, flame structures and responses, radical distributions, emissions, and lean blowout (LBO) limits of methane-fueled LDI combustion are investigated with varying mixer design parameters. Experimentally, a test system of single-mixer LDI combustion has been designed and built to investigate mixer designs via advanced optical diagnostics, including particle image velocimetry, broadband flame imaging, chemiluminescence imaging, and OH-planar laser induced florescence. Compared against experimental data, the best practices of meshing and turbulence and combustion modeling have been established for Computational Fluid Dynamics (CFD) simulations of LDI. Reasonable agreement between experimental and CFD result has been achieved for flow characteristics and flame structure/response. Larger swirler vane angle lowers LBO limits but produces higher NOx levels. Removing flare reduces NOx emissions at a cost of worsening operability. Counter-swirling forms a stronger shear layer than the co-swirling case.
Author: Timothy C. Lieuwen
Publisher: Cambridge University Press
ISBN: 052176405X
Category : Science
Languages : en
Pages : 385
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Book Description
The development of clean, sustainable energy systems is a preeminent issue in our time. Gas turbines will continue to be important combustion-based energy conversion devices for many decades to come, used for aircraft propulsion, ground-based power generation, and mechanical-drive applications. This book compiles the key scientific and technological knowledge associated with gas turbine emissions into a single authoritative source.
Author: Ritangshu Giri
Publisher:
ISBN:
Category :
Languages : en
Pages : 156
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Book Description
A multipoint lean direct injection (MLDI) concept was introduced recently in non-premixed combustion to obtain both low NOx emissions and good combustion stability. In this concept a key feature is the injection of finely atomized fuel into high swirling airflow at the combustor dome that provides a homogenous, lean fuel-air mixture. In order to achieve fine atomization and mixing of fuel and air quickly and uniformly, a well designed swirler system is imperative. The present study aims to investigate non-reacting aerodynamic flow characteristics in one such swirl stabilized multiple lean direct injection (MLDI) nozzle system, using the capabilities of computational fluid dynamics (CFD). The fuel nozzles were designed and provided by United Technologies Aerospace Systems (UTAS). The commercial CFD solver Fluent (Ansys Inc, USA) is incorporated to solve the 3-D Navier-Stokes equations for different CFD numerical formulations and, hence simulate the turbulent swirling flowfield generally associated with such systems. Two separate studies were conducted. The first study analyzed the effect of swirl on a turbulent flowfield in a rectangular chamber with sudden expansion, where the complex nozzle system housing air swirlers and a fuel injector were replaced by simple cylindrical inlets. The second study investigated typical aerodynamic flow features associated with the actual system. The domain for conducting simulations were the entire geometry in both cases. First a trusted grid is developed by carrying out grid refinement analysis for both studies. Then a comparison of different Reynolds-Averaged Navier Stokes (RANS) turbulence model were carried out for both cases. The time averaged Particle Image Velocimetry (PIV) data was used as a basis of comparison and the model most closely matching those values was finalized for further numerical computations. Steady state was employed for both set of problems. For the first problem, different swirl intensities were incorporated at the cylindrical inlet to study the changing structure of flowfield. The second numerical analysis of the actual geometric model was further subdivided into two sections. The first section studied the flowfield changes in this complex model by incorporating different mass flow rates for the same nozzle spacing of S = 1.36d. The solution captures the essential flow features generally associated with a non-reacting swirling flowfield in a LDI combustor. The second section analyzed the change in flowfield structure when the spacing between nozzles were varied from 1.1d to 2.72d. A single nozzle case was also used as a basis for comparison. The results obtained were also compared to the available time averaged PIV data. The effect of inter-nozzle spacing result in flows, where the nozzles interact strongly to a case where nozzles do not interact atleast for most of the axial locations. Thus the results provide a useable CFD model for evaluation of this flowfield while highlighting their areas of uncertainty. In addition to that, they also provide useful prerequisites for conducting further reacting flow analysis for this particular design.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 956
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Book Description
Author: The CleanEra Team
Publisher: IOS Press
ISBN: 1614995915
Category : Technology & Engineering
Languages : en
Pages : 192
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Book Description
The CleanEra project was initiated with the goal of developing revolutionary ideas for civil aviation. These ideas were to offer solutions which would limit and reduce some of the negative aspects of aviation, namely: emissions and the use of resources. This book presents you with the highlights of this journey in search of new technologies for a revolutionary aircraft; an aircraft that not only offers a future of comfortable air travel for the passenger, but a future of sustainable aviation for the planet as well.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721572830
Category :
Languages : en
Pages : 38
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Book Description
The VACCG team is comprised of engineers at Virginia Tech who specialize in the subject areas of combustion physics, chemical kinetics, dynamics and controls, and signal processing. Currently, the team's work on this NRA research grant is designed to determine key factors that influence combustion control performance through a blend of theoretical and experimental investigations targeting design and demonstration of active control for three different combustors. To validiate the accuracy of conclusions about control effectiveness, a sequence of experimental verifications on increasingly complex lean, direct injection combustors is underway. During the work period January 1, 2002 through October 15, 2002, work has focused on two different laboratory-scale combustors that allow access for a wide variety of measurements. As the grant work proceeds, one key goal will be to obtain certain knowledge about a particular combustor process using a minimum of sophisticated measurements, due to the practical limitations of measurements on full-scale combustors. In the second year, results obtained in the first year will be validated on test combustors to be identified in the first quarter of that year. In the third year, it is proposed to validate the results at more realistic pressure and power levels by utilizing the facilities at the Glenn Research Center. Baumann, William T. and Saunders, William R. and Vandsburger, Uri and Saus, Joseph (Technical Monitor) Glenn Research Center NASA/CR-2003-212197, E-13800, NAS 1.26:212197
Author: Timothy C. Lieuwen
Publisher: AIAA (American Institute of Aeronautics & Astronautics)
ISBN:
Category : Science
Languages : en
Pages : 688
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Book Description
This book offers gas turbine users and manufacturers a valuable resource to help them sort through issues associated with combustion instabilities. In the last ten years, substantial efforts have been made in the industrial, governmental, and academic communities to understand the unique issues associated with combustion instabilities in low-emission gas turbines. The objective of this book is to compile these results into a series of chapters that address the various facets of the problem. The Case Studies section speaks to specific manufacturer and user experiences with combustion instabilities in the development stage and in fielded turbine engines. The book then goes on to examine The Fundamental Mechanisms, The Combustor Modeling, and Control Approaches.
