Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 233

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Author: Yongqiang Fu
Publisher:
ISBN:
Category :
Languages : en
Pages : 185

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A multipoint lean direct injection (LDI) 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 the high-swirling airflow at the combustor dome that provides a homogenous, lean fuel-air mixture. In order to achieve the fine atomization and mixing of the fuel and air quickly and uniformly, a good swirler design should be studied. The focus of this dissertation is to investigate the aerodynamics and combustion of the swirling flow field in a multipoint lean direct injector combustor. A helical axial-vaned swirler with a short internal convergent-divergent venturi was used. Swirlers with various vane angles and fuel nozzle insertion lengths have been designed. Three non-dimensional parameter effects on non-reacting, swirling flow field were studied: swirler number, confinement ratio and Reynolds number. Spray and combustion characteristics on the single swirler were studied to understand the mechanism of fuel-air mixing in this special configuration. Multi-swirler interactions were studied by measuring the confined flow field of a multipoint swirler array with different configurations. Two different swirler arrangements were investigated experimentally, which include a co-swirling array and a counter-swirling array. In order to increase the range of stability of multipoint LDI combustors, an improved design were also conducted. The results show that the degree of swirl and the level of confinement have a clear impact on the mean and turbulent flow fields. The swirling flow fields may also change significantly with the addition of a variety of simulated fuel nozzle insertion lengths. The swirler with short insertion has the stronger swirling flow as compared with the long insertion swirler. Reynolds numbers, with range of current study, will not alter mean and turbulent properties of generated flows. The reaction of the spray dramatically changes the gas phase velocity distribution, while the convergent-divergent nozzle strongly affects the spray velocity profiles. The multipoint flow field has a very complicated structure, especially for the flow structure near the swirler exit, where very strong interactions exit among the adjacent swirlers. Multipoint swirler arrays with the recessed center swirler will alter flow structure significantly. There is a short strong central recirculation zone in both co-swirler and counter-swirler recessed arrays, which may increase the operability range of the multipoint swirl-venturi LDI combustor.

Author: Derick S. Endicott
Publisher:
ISBN:
Category :
Languages : en
Pages : 105

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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: Jacob Haseman
Publisher:
ISBN:
Category :
Languages : en
Pages : 109

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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: Ritangshu Giri
Publisher:
ISBN:
Category :
Languages : en
Pages : 156

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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: Jushan Chin
Publisher: Nova Science Publishers
ISBN: 9781685071097
Category : Technology & Engineering
Languages : en
Pages : 165

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"The aim of this book is to identify that extra high-pressure ratio (such as about 70) civil aero engine low emissions combustors and extra high fuel air ratio (FAR) (such as FAR greater than 0.051) military aero engine combustors make up the next generation of aero combustors. The aero thermal design of these combustors is very different from previous combustors and the major design points are proposed. Two types of high-pressure low emissions combustor design have been suggested: one is without fuel staging and the other is with fuel staging. The high FAR combustor design is brand new. The layout of the next-generation aero combustor is very different. There are no primary holes, no intermediate holes, and no dilution holes. They all have direct mixing combustion. For low-emissions combustors, it is lean direct mixing (LDM) combustion. For high-FAR combustors, it is stoichiometric direct mixing combustion. Combustion air fraction is very high (such as greater than 75%). That will induce idle condition lean blow out (LBO) issue. The present book has proposed several design approaches to solve idle LBO issue, which are effective. Pilot fuel air combustion is designed at idle condition. For civil combustor, maximum condition is designed for low emissions, while for high FAR combustor, maximum condition is designed for non-visible smoke, low luminous flame radiation and good combustion efficiency. For each type of combustor, the fuel air module configuration is designed, which is the most essential part of combustor design. The brand-new combustor cooling design has used a compound angle tangential inlet cooling hole configuration. Such a cooling design provides high cooling effectiveness. The diffuser configuration is totally new. It is an air bleeding diffuser, directly stretching forward to contact the dome. The bled air flows to the annular channel as cooling air. Aero combustor development is discussed in this book. In particular, the combustor developments from technology readiness level (TRL) 3 to TRL level 6 have been discussed in detail. Also reported is the technology to run combustor development tests correctly. Three topics of related combustion research by the present author are summarized in the brochure. They are: a. Fuel injection and co-flowing air combination. The key point is, for next generation combustor development, the designer should not only think about atomization. The combination of fuel injection and co-flowing air should be considered together as a whole device. b. Fuel spray evaporation calculation, the key is an engineering calculation of multi-component fuel evaporation shall be used. c. Non-luminous flame radiation calculation, which has been significantly updated. The present book is a summary of the author's ten years of study on next-generation aero combustors after retirement. It represents advanced aero combustor technology level"--

Author: Jushan Chin
Publisher: Nova Science Publishers
ISBN: 9781536197242
Category : Aircraft gas-turbines
Languages : en
Pages : 0

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Book Description
"The aim of this book is to identify that extra high-pressure ratio (such as about 70) civil aero engine low emissions combustors and extra high fuel air ratio (FAR) (such as FAR greater than 0.051) military aero engine combustors make up the next generation of aero combustors. The aero thermal design of these combustors is very different from previous combustors and the major design points are proposed. Two types of high-pressure low emissions combustor design have been suggested: one is without fuel staging and the other is with fuel staging. The high FAR combustor design is brand new. The layout of the next-generation aero combustor is very different. There are no primary holes, no intermediate holes, and no dilution holes. They all have direct mixing combustion. For low-emissions combustors, it is lean direct mixing (LDM) combustion. For high-FAR combustors, it is stoichiometric direct mixing combustion. Combustion air fraction is very high (such as greater than 75%). That will induce idle condition lean blow out (LBO) issue. The present book has proposed several design approaches to solve idle LBO issue, which are effective. Pilot fuel air combustion is designed at idle condition. For civil combustor, maximum condition is designed for low emissions, while for high FAR combustor, maximum condition is designed for non-visible smoke, low luminous flame radiation and good combustion efficiency. For each type of combustor, the fuel air module configuration is designed, which is the most essential part of combustor design. The brand-new combustor cooling design has used a compound angle tangential inlet cooling hole configuration. Such a cooling design provides high cooling effectiveness. The diffuser configuration is totally new. It is an air bleeding diffuser, directly stretching forward to contact the dome. The bled air flows to the annular channel as cooling air. Aero combustor development is discussed in this book. In particular, the combustor developments from technology readiness level (TRL) 3 to TRL level 6 have been discussed in detail. Also reported is the technology to run combustor development tests correctly. Three topics of related combustion research by the present author are summarized in the brochure. They are: a. Fuel injection and co-flowing air combination. The key point is, for next generation combustor development, the designer should not only think about atomization. The combination of fuel injection and co-flowing air should be considered together as a whole device. b. Fuel spray evaporation calculation, the key is an engineering calculation of multi-component fuel evaporation shall be used. c. Non-luminous flame radiation calculation, which has been significantly updated. The present book is a summary of the author's ten years of study on next-generation aero combustors after retirement. It represents advanced aero combustor technology level"--

Author: Xiao Ren
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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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:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 868

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Author:
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 440

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