Dynamics and stability of lean-premixed swirl-stabilized combustion

Lean blowout (LBO) of a partially premixed swirl flame is studied using chemiluminescence imaging and simultaneous stereo-PIV and OH-PLIF measurements at repetition rates up to 5 kHz. The flame, which is operated with methane and air in a gas turbine model combustor at atmospheric pressure, features a pronounced precessing vortex core (PVC) at the inner shear layer. In the first part of the study, the stabilization mechanism of the flame close to LBO is investigated. The fields of velocity and OH show that near LBO there are essentially two regions where reaction takes place, namely the helical zone along the PVC and the flame root around the lower stagnation point. The zone along the PVC is favorable to the flame due to low strain rates in the vortex center and accelerated mixing of burned and fresh gas. The flame root, which is located close to the nozzle exit, is characterized by an opposed flow of hot burned gas and relatively fuel-rich fresh gas. Due to the presence of high strain rates, the flame root is inherently unstable near LBO, featuring frequent extinction and reignition. The blowout process, discussed in the second part of the study, starts when the extinction of the flame root persists over a critical length of time. Subsequently, the reaction in the helical zone can no longer be sustained and the flame finally blows out. The results highlight the crucial role of the flame root, and suggest that well-aimed modifications of flow field or mixture fraction in this region might shift the LBO limit to leaner conditions.

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Dynamics of lean blowout of a swirl-stabilized flame in a gas turbine model combustor

The attainment of very low pollutant emissions, in particular oxides of nitrogen (NO{sub x}), from gas turbines is not only of considerable environmental concern but has also become an area of increasing competitiveness between the different engine manufacturers. For stationary engines, the attainment of ultralow NO{sub x} has become the foremost marketing issue. This paper is devoted primarily to current and emerging technologies in the development of ultralow emissions combustors for application to aircraft and stationary engines. Short descriptions of the basic design features of conventional gas turbine combustors and the methods of fuel injection now in widespread use are followed by a review of fuel spray characteristics and recent developments in the measurement and modeling of these characteristics. The main gas-turbine-generated pollutants and their mechanisms of formation are described, along with related environmental risk and various issues concerning emissions regulations and recently enacted legislation for limiting the pollutant levels emitted by both aircraft and stationary engines. The impact so these emissions regulations on combustor and engine design are discussed first in relation to conventional combustors and then in the context of variable-geometry and staged combustors. Both these concepts are founded on emissions reduction by control of flame temperature. Basicmore » approaches to the design of dry low-NO{sub x} and ultralow-NO{sub x} combustors are reviewed.« less

The Role of Fuel Preparation in Low-Emission Combustion

To provide a semiconductor device in which a layer to be peeled is attached to a base having a curved surface, and a method of manufacturing the same, and more particularly, a display having a curved surface, and more specifically a light-emitting device having a light emitting element attached to a base with a curved surface. A layer to be peeled, which contains a light emitting element furnished to a substrate using a laminate of a first material layer which is a metallic layer or nitride layer, and a second material layer which is an oxide layer, is transferred onto a film, and then the film and the layer to be peeled are curved, to thereby produce a display having a curved surface.

Vehicle, display device and manufacturing method for a semiconductor device

Methods and systems for low emission power generation in hydrocarbon recovery processes are provided. One system includes integrated pressure maintenance and miscible flood systems with low emission power generation. An alternative system provides for low emission power generation, carbon sequestration, enhanced oil recovery (EOR), or carbon dioxide sales using a hot gas expander and external combustor. Another alternative system provides for low emission power generation using a gas power turbine to compress air in the inlet compressor and generate power using hot carbon dioxide laden gas in the expander. Other efficiencies may be gained by incorporating heat cross-exchange, a desalination plant, co-generation, and other features.

Low emission power generation and hydrocarbon recovery systems and methods

A new approach for low emission gas turbines was investigated by modifying a typical production high-swirl injector (HSI) for gas turbine combustors to operate in a novel low-swirl mode (LSI). This LSI (S = 0.5) was configured in the laboratory and investigated by particle image velocimetry at firing rates of 9–87 kW (1

A comparison of the flowfields and emissions of high-swirl injectors and low-swirl injectors for lean premixed gas turbines

Present gas turbine engines fail to effectively and efficiently control the emission emitted therefrom. Many existing systems estimate the amount of constituents emitted within the exhaust gas verses measuring the actual quantity of constituent emitted within the exhaust gas. The present exhaust gas monitoring system has the ability to measure the actual quantity of an emission constituent, such as carbon monoxide (CO), sends a signal to a control box, interprets the signal, sends a second signal to an actuation device controlling a fluid flow to the combustion section resulting in the controlling of emissions emitted from the gas turbine engine within the exhaust gas.

Emission control for a gas turbine engine

The low-swirl injector (LSI) is a simple and cost-effective lean premixed combustion method for natural-gas turbines to achieve ultralow emissions (<5 ppm NO x and CO) without invoking tight control of mixture stoichiometry, elaborate active tip cooling, or costly materials and catalysts. To gain an understanding of how this flame stabilization mechanism remains robust throughout a large range of Reynolds numbers, laboratory experiments were performed to characterize the flowfield of natural-gas flames at simulated partial load conditions. Also studied was a flame using simulated landfill gas of 50% natural gas and 50% CO 2 . Using particle image velocimetry, the nonreacting and reacting flowfields were measured at five bulk flow velocities. The results show that the LSI flowfield exhibits similarity features. From the velocity data, an analytical expression for the flame position as function of the flowfield characteristics and turbulent flame speed has been deduced. It shows that the similarity feature coupled with a linear dependency of the turbulent flame speed with bulk flow velocity enables the flame to remain relatively stationary throughout the load range. This expression can be the basis for an analytical model for designing LSIs that operate on alternate gaseous fuels such as slower burning biomass gases or faster burning coal-based syngases.

Laboratory Studies of the Flow Field Characteristics of Low-Swirl Injectors for Adaptation to Fuel-Flexible Turbines

An injector nozzle (66, 190) having a central axis (68), said injector nozzle (66, 190) comprising means (179) for passing a pilot fuel through the injector nozzle (66, 190) during operation thereof; means (186) for introducing a supply of pilot air through the injector nozzle (66, 190), said supply of pilot air being mixed with the pilot fuel only after exiting the injector nozzle (66, 190) during operation thereof; means (133) for introducing a primary supply of air through the injector nozzle (66, 190) during operation thereof, said means (133) for introducing the primary supply of air including a main air passage (132) being defined by a portion of the inner surface (90) of the wall (88) and a portion of the shell (126); and means (160) for passing a main source of fuel through the injector nozzle (66, 190) during operation thereof, said means (160) for passing the main source of fuel including a plurality of spoke members (150) disposed within respective ones of the plurality of holes (148) and being partially positioned within the main air passage (132) and having a plurality of passages (156) therein exiting into the main air passage (132).

Low emission combustion nozzle for use with a gas turbine engine

Solar Turbines Incorporated, under U.S. government sponsored programs, has been evaluating ceramic matrix composite combustor liners in test rigs and Solar's Centaur® 50S gas turbine engines since 1992. The objective is to evaluate and improve the performance and durability of CMCs as high-temperature materials for advanced low emissions combustors. Field testing of CMC combustor liners started in May of 1997 and by the end of 2004, over 67,000 operating hours had been accumulated on SiC/SiC and oxide/oxide CMC liners. NO X and CO emissions have been consistently <15 ppmv and <10 ppmv, respectively. Maximum test durations of 15,144 h and 13,937 h have been logged for SiC/SiC liners with protective environmental barrier coatings. An oxide/oxide CMC liner with a Friable Graded Insulation coating has been tested for 12,582 h. EBCs significantly improve SiC/SiC CMC liner life. The basic three-layer EBC consists of consecutive layers of Si, mullite, and BSAS. The durability of the baseline EBC can be improved by mixing BSAS with mullite in the intermediate coating layer. The efficacy of replacing BSAS with SAS has not been demonstrated yet. Heavy degradation was observed for two-layer Si/BSAS and Si/SAS EBCs, indicating that the elimination of the intermediate layer is detrimental to EBC durability. Equivalent performance was observed when the Hi-Nicalon fiber reinforcement was replaced with Tyranno ZM or ZMI fiber. Melt infiltrated SiC/SiC CMCs have improved durability compared to SiC/SiC CMCs fabricated by Chemical Vapor Infiltration of the matrix, in the absence of an EBC. However, the presence of an EBC results in roughly equivalent service life for Ml and CVI CMCs. Results to date indicate that oxide/oxide CMCs with protective FG1 show minor degradation under Centaur® 50S gas turbine engine operating conditions. The results of, and lessons learned from CMC combustor liner engine field testing, conducted through 2004, have been summarized.

Kenneth O. Smith

Papers

A comparison of the flowfields and emissions of high-swirl injectors and low-swirl injectors for lean premixed gas turbines

Emission control for a gas turbine engine

Laboratory Studies of the Flow Field Characteristics of Low-Swirl Injectors for Adaptation to Fuel-Flexible Turbines

Low emission combustion nozzle for use with a gas turbine engine

Ceramic Matrix Composite Combustor Liners: A Summary of Field Evaluations