Reduction of NOx̳ for a Lean Direct-injection Combustor Using High Shear Mixing PDF Download
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Author: Stuart Scott Hay
Publisher:
ISBN:
Category :
Languages : en
Pages : 158
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Author: Stuart Scott Hay
Publisher:
ISBN:
Category :
Languages : en
Pages : 158
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Author: Rodrigo Villalva Gómez
Publisher:
ISBN:
Category :
Languages : en
Pages : 288
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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: 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: Wade H. Shafer
Publisher: Springer Science & Business Media
ISBN: 1461303931
Category : Science
Languages : en
Pages : 427
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Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS)* at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dis semination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all concerned if the printing and distribution of the volumes were handled by an international publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Corporation of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 39 (thesis year 1994) a total of 13,953 thesis titles from 21 Canadian and 159 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this impor tant annual reference work. While Volume 39 reports theses submitted in 1994, on occasion, certain uni versities do report theses submitted in previous years but not reported at the time.
Author: Arnaud Lacarelle
Publisher: Univerlagtuberlin
ISBN: 9783798323810
Category :
Languages : en
Pages : 317
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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: Shigeru Hayashi
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Presented at the International Gas Turbine and Aeroengine Congress and Exposition, Houston, Texas - June 5-8, 1995.
Author: H Zhao
Publisher: Elsevier
ISBN: 1845697456
Category : Technology & Engineering
Languages : en
Pages : 761
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Book Description
Volume 2 of the two-volume set Advanced direct injection combustion engine technologies and development investigates diesel DI combustion engines, which despite their commercial success are facing ever more stringent emission legislation worldwide. Direct injection diesel engines are generally more efficient and cleaner than indirect injection engines and as fuel prices continue to rise DI engines are expected to gain in popularity for automotive applications. Two exclusive sections examine light-duty and heavy-duty diesel engines. Fuel injection systems and after treatment systems for DI diesel engines are discussed. The final section addresses exhaust emission control strategies, including combustion diagnostics and modelling, drawing on reputable diesel combustion system research and development. Investigates how HSDI and DI engines can meet ever more stringent emission legislation Examines technologies for both light-duty and heavy-duty diesel engines Discusses exhaust emission control strategies, combustion diagnostics and modelling
Author: J. P. Gore
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: R. R. Tacina
Publisher:
ISBN:
Category :
Languages : en
Pages :
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