Abstract: A fuel injector has a number of groups of nozzles. The groups are generally concentric with an injector axis. Each nozzle defines a gas flowpath having an outlet for discharging a fuel/air mixture jet. There are means for introducing the fuel to the air. One or more groups of the nozzles are oriented to direct the associated jets skew to the injector axis.

Abstract: A method for operating a furnace with a multi-burner system for generating a hot gas is provided. The furnace has a combustion chamber with a plurality of burners, each having a fuel feed. The method includes regulating a first fuel feed to at least one of the plurality of burners as a function of pressure pulsations that occur in the combustion chamber so as to achieve a steady operation of the furnace. The multi-burner system may be a gas turbine, preferably of a power plant.

Abstract: A dual channel ignition circuit (Channel A and a Channel B). In a start sequence in which a successful ignition event occurs, an exciter controller first energizes only a primary ignition channel (Channel A). Once the exciter controller recognizes a success light-off, the alternate channel (Channel B) will also then be excited as the gas turbine engine is accelerated to a self-sustaining speed. The exciter controller will then switch the primary alternative designation of the channels for the next start attempt. In a start sequence in which an unsuccessful ignition event occurs, the exciter controller sets a fail-to-start on the primary ignition channel on a failure to start A/B counter such that a failed ignition channel is diagnosed without dedicated electronic diagnostic circuits while still attempting to excite both circuits to enhance the dependability of a successful engine light-off.

Abstract: The present invention relates to an improved multi-point injector for use in a gas turbine engine or other types of combustors. The multi-point fuel injector has a plurality of nozzles arranged in at least two arrays such as concentric rings. The injector further has different fuel circuits for independently controlling the fuel flow rate for the nozzles in each of the arrays. Each of the nozzles include a fluid channel and one or more swirler vanes in the fluid channel for creating a swirling flow within the fluid channel. A method for injecting a fuel/air mixture into a combustor stage of a gas turbine engine is also described. At least one zone has a flame hot enough to stabilize the entire combustor flame.

Abstract: A staged fuel injector is disclosed that includes a main fuel circuit for delivering fuel to a main fuel atomizer and a pilot fuel circuit for delivering fuel to a pilot fuel atomizer located radially inward of the main fuel atomizer. The pilot fuel circuit is in close proximity to the main fuel circuit enroute to the pilot fuel atomizer so that the pilot fuel flow cools stagnant fuel located within the main fuel circuit during low engine power operation to prevent coking.

Abstract: An auxiliary electrical power supply includes a fuel combustor passively sourced with fuel for combusting fuel and a thermoelectric generator close-coupled to the combustor for converting the heat from the combustor to electric power.

Abstract: A swirler assembly. The swirler assembly may include a hub, a vane positioned on the hub, and a fuel supply passageway extending from the hub through the vane. The fuel supply passageway may include a substantially triangular shape.

Abstract: A method for operating a firing plant with at least one combustion chamber and with at least one burner for producing hot gas, especially a gas turbine, preferably of a power generating plant, includes an operating characteristic for operating the combustion chamber close to the lean extinction limit defined in the form of a burner group staging ratio (BGVRich). The pressure pulsations (PulsActual) which are measured in the combustion chamber are processed by a filter device (2) and converted into corresponding signals (PulsActual,Filter(t)). An exceeding/falling short of at least one pulsation limiting value (PulsLimit) is monitored by a monitoring device (3) and adapts a pulsation reference value (PulsRef) in dependence upon the monitoring.

Abstract: A gas turbine engine augmentor includes an externally fueled annular trapped vortex cavity having a cavity opening open to an exhaust flowpath and a sole source of fuel located upstream of the trapped vortex cavity and being operable for injecting fuel into the exhaust flowpath such that at least a portion of the fuel flows into the cavity through a cavity opening. An exemplary sole source of fuel includes fuel holes in fuel tubes within spray bars operable for injecting the fuel through heat shield openings in heat shields surrounding the tubes wherein the fuel holes are located in a radially outermost portion of the exhaust flowpath. The sole source of fuel may include circumferentially spaced apart radial spray bars and/or integral spray bars integral with radial flameholders and extending radially inwardly into the exhaust flowpath wherein the radial flameholders and radial spray bars are interdigitated.

Abstract: A method of distributing fuel in a fuel nozzle comprises: providing at least two helical channels in the fuel nozzle, each having a channel exit port, providing a fuel inlet cavity in fluid communication with the helical channels, and flowing fuel in the fuel inlet cavity, the helical channels and the channel exit ports.

Abstract: The invention relates to a pre-mix burner for burning a low-calorie combustion gas, said burner comprising an air duct which extends along an axis of the burner and can be used to supply combustion air. A swirling device is arranged in the air duct and is used to apply a swirling motion to the combustion air. An injection device for the low-calorie combustion gas is provided downstream of the swirling device. The injection device comprises inlets for the combustion gas, such that the formation of wake regions in the air channel is prevented. The invention also relates to a method for burning a low-calorie combustion gas, according to which a swirling motion is applied to the combustion air, low-calorie combustion gas is injected into the swirled combustion air and intensively mixed therewith, and the mixture is then burned.

Abstract: A turbofan gas turbine engine augmenter includes a fuel/air swirler disposed between an axially extending bypass flowpath and an axially extending exhaust flowpath. A swirler inlet is axially open to and positioned substantially normal to the bypass flowpath and a swirler outlet is open to and positioned substantially parallel to the exhaust flowpath. A swirl chamber within the fuel/air swirler is between the swirler inlet and the swirler outlet. A swirl axis of the fuel/air swirler extends through the swirler outlet substantially normal to the exhaust flowpath. An air swirler may be centered about the swirl axis within the fuel/air swirler. The air swirler may be a louvered or have a plurality of swirling vanes. The swirler inlet may be radially offset with respect to the swirl axis. An air scoop may lead from the swirler inlet to a rounded swirler housing within which the air swirler is disposed.

Abstract: A method for operating a combustion chamber (1) for a gas turbine. The combustion chamber (1) has a combustion space (2) and a plurality of burners (3), which are each arranged at an inlet (13) of the combustion space (2). The burners (3) are divided into two burner groups (4I, 4II). A common oxidant supply (5) is provided for all the burners (3). A common first fuel supply (7) is provided for the burners (3I) belonging to the first burner group (4I). A common second fuel supply (9) and a common additional fuel supply (11) are provided for the burners (3II) belonging to the second burner group (4II). A first fuel stream (8) is fed to the burners (3I) belonging to the first fuel group (4I), in such a manner that a lean fuel/oxidant mix is established. A second fuel stream (10) is fed to the burners (3II) belonging to the second burner group (4II) in such a manner that a lean fuel/oxidant mix is established.

Abstract: A method of operating a thermal power plant, such as a gas turbine power plant, in which a rotary unit, such as at least one gas turbine stage, is driven by burning gaseous fuel inside a combustion chamber, with hot gases being formed, the rotary energy of which rotary unit is converted into another form of energy, such as electrical energy. A load set point (L) of the thermal power plant is set by regulating the quantity of gaseous fuel fed to the combustion process. The thermal power plant is operated at a load set point (L), provided the gaseous fuel is fed to the combustion process through a gas line at a gas pressure pgas, with pgas>paction limit(L), where paction limit (L) represents a pressure value which depends on a system internal pressure psystem requirement (L) set in the region of the combustion chamber by the load set point (L) of the thermal power plant, with paction limit(L)>psystem requirement(L).

Abstract: A pulse detonation device contains a pulse detonation combustor which detonates a mixture of oxidizer and fuel. The fuel is supplied through fuel ducts and the fuel flow is controlled by fuel flow control devices. Oxidizer flow is provided through a main inlet portion and a flow control device directs the oxidizer flow to either the combustor or to a bypass duct, or both. The combustor further contains an ignition source. Each of the flow control devices, fuel flow control devices and ignition source are controlled by a control system to optimize performance at different thrust/power settings for the device.

Abstract: A method of generating power and a fuel for use in a gas turbogenerator power system are disclosed. The method comprises injecting lignin residue derived from the enzymatic hydrolysis of a biomass feedstock and natural gas into a combustor of a gas turbine power generator; combusting the lignin residue and natural gas with compressed air; inputting the resultant gases into a gas turbine to rotate a turbine shaft and generate rotational energy; and converting the rotational energy into electrical energy. The lignin residue is preferably derived from a process of simultaneous sachrification and fermentation of the biomass feedstock. The lignin residue is preferably transported to the combustor in a pipeline with pressurized air. The fuel comprises a mixture of lignin residue derived from the enzymatic hydrolysis of a biomass feedstock and natural gas. Preferably, the lignin residue is derived from a process for the simultaneous sachrification and fermentation of the biomass feedstock.

Abstract: Guide vanes include a first flange connected with a casing of a gas turbine engine, a second flange connected with the casing, a first airfoil disposed between the first and second flanges and connected thereto, and a second airfoil disposed between the first and second flanges and connected thereto so as to form a gap extending radially between a first trailing portion of the first airfoil and a second leading portion of the second airfoil, the hollow portion being in flow communication with the gap so as to allow a gaseous fuel to flow from the hollow portion through the gap and into a fluid flowing over the guide vane. Gas turbines that use the guide vanes and methods for injecting a gaseous fuel for combustion in a gas turbine engine are also disclosed.

Abstract: A method for operating a gas turbine uses a first fuel at full load. An improved emission behavior is achieved by operating the gas turbine (11) at partial load with a second fuel, which has a richer mix of higher-value hydrocarbons (C2+) with 2 and more carbon atoms per molecule like ethane (C2H6) and propane (C3H8).

Abstract: A method to control the output of a turbine engine pulses individual fuel injectors completely on and then completely off in selectable groups rather than in unison. The operation of the groups are staggered in time to minimize the periods of no fuel flow to the engine. Simplicity in the control of individual injectors is achieved by electrically controlling individual injectors rather than mechanically controlling the fuel supplied to all injectors, and, in addition, offers the advantage of minimizing the periods of no fuel flow to maintain combustion stability at low loads. Electrically controlling injectors positioned at the point of fuel usage improves upon fuel atomization and eliminates the problem of unequal distribution of fuel from multiple injection points connected to a common fuel metering system.

Abstract: A fuel-air mixer includes an annular shroud, inner and outer counter-rotating swirlers, a hub separating the inner and outer swirlers, a center body extending axially along the annular shroud, a fuel shroud disposed radially outwardly from the outer swirler circumferentially around the annular shroud, and a radial swirler disposed downstream of the inner and outer swirlers, the radial swirler being configured to allow an independent radial rotation of a second gas stream entering the annular shroud from a region outside a wall of the annular shroud separately from a stream flowing through the inner and outer swirlers, the radially rotating second gas stream entering the annular shroud at a region adjacent an outer wall of the annular shroud.

Abstract: A method to control the output of a turbine engine pulses individual fuel injectors completely on and then completely off in selectable groups rather than in unison. The operation of the groups are staggered in time to minimize the periods of no fuel flow to the engine. Simplicity in the control of individual injectors is achieved by electrically controlling individual injectors rather than mechanically controlling the fuel supplied to all injectors, and, in addition, offers the advantage of minimizing the periods of no fuel flow to maintain combustion stability at low loads. Electrically controlling injectors positioned at the point of fuel usage improves upon fuel atomization and eliminates the problem of unequal distribution of fuel from multiple injection points connected to a common fuel metering system.

Abstract: A gas combustor has a peripheral premix burner, and a central diffusion burner whose nozzle defines an eccentric first channel housing an ignition device, an axial second channel, and a third channel interposed radially between the first and second channel; the gas combustor is controlled, at a first start-up step, to keep the peripheral burner off and to feed a fuel gas stream along the third channel; at a second step, after a given load is exceeded, the peripheral burner is activated, and the gas stream in the central burner continues to be fed along the same channel as at the first step, and is regulated to reduce its flow to a value greater than zero.

Abstract: A pulse detonation engine system (1) for driving a turbine is comprises a detonation generator section (5) including a detonation tube (7) having a tubular hollow section for permitting detonation to be generated therein during combustion stage of a mixture gas combined with a gas and a fuel, a gas supply section (17) for feeding the gas into the tubular hollow section of the detonation tube (7) at given time intervals, a fuel valve (19) for feeding the fuel into the tubular hollow section of the detonation tube (7) at the given time intervals, and an ignition plug (15) for igniting the mixture gas in the tubular hollow section of the detonation tube (7), and a pulse detonation driven turbine (9) driven directly or indirectly by energy of detonations that are intermittently generated in the tubular hollow section of the detonation tube (7).

Abstract: A method is provided for performing a transfer from gas fuel operation to liquid fuel operation in a gas turbine with a dual fuel system. The method includes initiating a predetermined uncontrolled liquid fuel prefill flow rate through the liquid fuel system, sensing an onset of the uncontrolled liquid fuel flow to the combustor nozzles, and initiating transfer from gas fuel operation to liquid fuel operation when the flow of uncontrolled liquid fuel at the combustor nozzles is sensed. The onset of uncontrolled liquid fuel flow to the combustor nozzles is determined by monitoring changes of Fuel Normalized Power (FNP), a parameter sensitive to uncontrolled liquid fuel flow, and determining when FNP exceeds a threshold algorithm value.

Abstract: A method of lowered NOx combustion is taught wherein the kinetic rate of NOx formation is reduced for a given combustion temperature in a gas turbine combustor. A supply of fuel is provided along with a supply of ambient air in sufficient quantity to form a fuel/air mixture having an equivalence ratio greater than about 0.55 when mixed with the fuel. The fuel/air mixture is mixed with a supply of cooled combustion gases in sufficient quantity such that the oxygen content of the resulting air mixture is less than about 18 percent. The resulting air mixture is then passed into the combustor.

Abstract: A combustor nozzle is provided. The combustor nozzle includes a first fuel system configured to introduce a syngas fuel into a combustion chamber to enable lean premixed combustion within the combustion chamber and a second fuel system configured to introduce the syngas fuel, or a hydrocarbon fuel, or diluents, or combinations thereof into the combustion chamber to enable diffusion combustion within the combustion chamber.

Abstract: A method for operating a combustion system is provided. The method includes coupling the main swirler to the pilot swirler such that the main swirler substantially circumscribes the pilot swirler, supplying fuel to a first fuel circuit defined in the main swirler, and inducing swirling to the supplied fuel via a first set of swirler vanes positioned within the main swirler. The method also includes supplying fuel to a second fuel circuit defined in the main swirler, inducing swirling to the supplied fuel via a second set of swirler vanes positioned within the main swirler, each of the second set of swirler vanes comprising at least one second fuel passage defined therein, and coupling a shroud in flow communication to at least one of the first set of swirler vanes and the second set of swirler vanes, the shroud comprising at least one third fuel passage defined therein.

Abstract: A method of operating a gas turbine engine is provided. The method includes discharging pilot fuel into a combustion chamber from a nozzle through at least one pilot fuel outlet defined in a tip of the nozzle, discharging steam from the nozzle through a plurality of steam outlets that are spaced circumferentially about the plurality of pilot fuel outlets, and discharging primary fuel from the nozzle through a plurality of primary fuel outlets that are circumferentially aligned with the plurality of steam outlets. To facilitate mixing the primary fuel with the steam, the primary fuel is discharged from the nozzle tip at an oblique angle with respect to a centerline extending through the nozzle tip.

Abstract: Conventional swozzle-type burners are modified so as to be capable of selectively running on liquid fuel without requiring water injection for NOx abatement or dedicated air supply for atomizing liquid fuel.

Abstract: A fuel/oxidant premixing device for a gas turbine includes an annular array of Coanda profiled fuel injected airfoils configured to receive a fluid stream containing the oxidant, wherein each one of the airfoils comprises a leading edge, a trailing edge and a fuel injection opening configured for introducing fuel at about the leading edge to provide a Coanda effect. Also disclosed herein are methods for its operation.

Abstract: A method for controlling a temperature distribution within a combustor having a plurality of chamber sections comprising controlling a fuel-to-air ratio in the chamber sections. At least two chamber sections have different fuel-to-air ratios to create a non-uniform temperature distribution within the combustor to reduce thermoacoustic instabilities.

Abstract: A gas turbine combustor has a combustion chamber into which fuel and air are supplied, wherein the fuel and the air are supplied into said combustion chamber as a plurality of coaxial jets.

Abstract: A scalable power generator is described. A scalable, portable pulsed detonation engine is coupled to a turbine which drives a generator and using commonly available fuels, electric energy is provided. Additional embodiments incorporate a mechanical compressor at the intake of the pulsed detonation engine which is driven by a second turbine, the second turbine drives a shaft that powers the mechanical compressor. Other enhancements to the invention and additional embodiments are described.

Abstract: A gas turbine engine is piloted with a pilot flow of fuel delivered to a combustor as a liquid. A first additional flow of the fuel is also delivered to the combustor as a liquid. A second additional flow of the fuel is vaporized and delivered to the combustor as a vapor. A fuel injector may have passageways associated with each of the three flows.

Abstract: A method of operating a gas turbine is provided, wherein the gas turbine engine is coupled to an electrical grid operating at a standardized grid frequency value, and the gas turbine includes a combustor coupled in flow communication with a plurality of independent fuel circuits and a compressor. The method includes determining a deviation of a grid frequency from the standardized grid frequency value and adjusting fuel flow from a portion of the plurality of fuel circuits while maintaining a substantially constant air flow from the compressor to facilitate controlling a fuel to compressor discharge pressure ratio such that a combustor state does not lag changes in airflow when the combustor responds to the grid frequency deviation.

Abstract: Variable rate ignition method and system that take advantage of knowledge and analysis of environmental conditions and/or operational conditions. A variable ignition rate for igniting the engine permits an optimal use of the igniters and thereby prolongs their life as well as its associated maintenance schedule. Operating costs and durability are also enhanced. Furthermore, flexibility is enhanced since any changes to the method of determining the best spark rate can be made through update in the software of the engine controller instead of change in the hardware (e.g., the exciter).

Abstract: A gas stream with a reduced oxygen concentration relative to ambient air is used to vaporize a liquid fuel or liquefied higher hydrocarbon gas, or is mixed with a vaporized gas, and the reduced oxygen vaporized fuel gas is fed to a combustion device such as a premixed or diffusion combustor. Preferably, the oxygen content of the gas stream is less than the limiting oxygen index. By mixing the fuel with a gas stream that has an appropriately reduced oxygen content, auto-ignition prior to the desired flame location in the combustor can be avoided. In some embodiments, the reduced oxygen stream is generated from an air separator or taken from the exhaust of the combustion device.

Abstract: A fuel modulation system usable in can-annular combustor systems of turbine engines for more efficiently managing fuel flow to reduce the amount of NOx while maintaining appropriate combustor flame temperatures. The fuel modulation system controls individual inline modulation valves in cooperation with a overall stage control valve to bring a turbine engine through the startup phase and to maintain operating conditions at a load set point while reducing NOx variability between baskets by using individual combustor dynamic pressure measurements. The fuel modulation system may be managed such that individual inline modulation valves remain within a predetermined range of positions relative to a nominal position to reduce NOx variability.

Abstract: A steady-state detonation combustor and a steady-state detonation wave generating method, in which a stabilized detonation wave can be generated by generating a hypersonic and unburned premixed gas. An rich premixed gas whose gas fuel is rich is combusted in a rich premixed gas combustion chamber (11) to generate a fist high-temperature and high-pressure burned gas, while at the same time, a lean premixed gas whose oxygen is rich is combusted in a lean premixed gas combustion chamber (12) to generate a second high-temperature and high-pressure burned gas, and subsequently, after each high-temperature and high-pressure burned gas is accelerated to hypersonic speed and at the same time mixed together through an interpenetrating nozzle (40), a premixed gas obtained by the mixture and containing the gas fuel and the oxygen which are unreacted is impinged on a steady-state detonation stabilizer (60), so that a stabilized detonation wave is generated.

Abstract: A combustion apparatus (10) incorporating a dry low NOx (DLN) combustor (20) that uses two different fuels (30, 40) simultaneously. One fuel (30) is premixed with air (22) for a primary combustion zone (25), and a second fuel (40) supplies a diffusion pilot flame (29). Each fuel may be selected for its specialized role, maximizing overall combustion efficiency while lowering emissions. A primary fuel (30) such as natural gas (NG) may be chosen for its economy and combustion characteristics in a lean premix. A pilot fuel (40) may be chosen for having a low diffusion flame temperature and a clean burn. An oxygenated pilot fuel such as dimethyl ether (DME) has a lower flame temperature than natural gas, thereby reducing NOx from the pilot flame. The pilot fuel (40) may be produced from the primary fuel (30) by a reformer (50) associated with the combustion apparatus.

Abstract: The present invention discloses an apparatus and method for reducing the carbon monoxide emissions emitted by a pilot injector of a gas turbine combustor. Multiple embodiments of a means for establishing a recirculation zone are disclosed whereby a portion of the fuel and air mixture from the pilot injector recirculates and a flame is held, thereby increasing the local reaction temperature at the desired location and lowering carbon monoxide emissions.

Abstract: A secondary combustion system for a stage one turbine nozzle. The secondary combustion system may include a supply tube extending into the stage one nozzle, a number of injectors extending from the supply tube to an outer surface of the stage one nozzle, and an air gap surrounding each of the number of injectors.

Abstract: A fuel heating system for fuel usable in a turbine engine. The fuel heating system may include at least one fuel heating chamber in communication with an exhaust stack of a turbine engine. The fuel heating chamber may be configured to allow exhaust gases to flow through the at least one fuel heating chamber. The fuel heating system may also include at least one conduit positioned in the fuel heating chamber. The conduit may be configured to receive fuel from a fuel source at a first temperature, allow the fuel to flow through the conduit, and exhaust the fuel at a second temperature that is higher than the first temperature.

Abstract: An apparatus for actively controlling fuel flow from a fuel pump to a mixer assembly of a gas turbine engine combustor, where the mixer assembly includes a pilot mixer and a main mixer. The pilot mixer further includes an annular pilot housing having a hollow interior, a primary fuel injector mounted in the pilot housing and adapted for dispensing droplets of fuel to the hollow interior of the pilot housing, a plurality of axial swirlers positioned upstream from the primary fuel injector. The fuel flow control apparatus further includes: at least one sensor for detecting dynamic pressure in the combustor; a fuel nozzle; and, a system for controlling fuel flow supplied by the fuel nozzle through the valves. The fuel nozzle includes: a feed strip with a plurality of circuits for providing fuel to the pilot mixer and the main mixer; and, a plurality of valves associated with the fuel nozzle and in flow communication with the feed strip thereof.

Abstract: A mapping device maps each burner mode at various bleed settings to generate control schedules for a combustion controller that ensure combustion dynamic (acoustic) pressures, and emissions limits and ring flame temperatures are within operational limits. In general, a method of combustor mapping involves adjusting the bulk ring flame temperature to meet emissions and acoustic requirements. The dome (ring) ring flame temperature is then adjusted to determine maximum and minimum ring flame temperature boundary limits. At both the maximum and minimum ring flame temperatures, the emissions levels and acoustic pressures are checked to see that they are within specification limits. If they are not, the bulk ring flame temperature is adjusted, and the entire process is repeated for that bleed setting and burner mode. If the emissions levels and acoustic pressures are within specification limits, then the power is increased to a different mode and bleed setting combination, and the process is again repeated.

Abstract: A low-emission method for producing power using a gas turbine includes premixing a plurality of fuel and air mixtures, injecting the fuel and air mixtures into a combustion chamber using a plurality of fuel nozzles, and adjusting a ratio of fuel and air injected by at least one of the nozzles to control a fuel/air concentration distribution within the combustion chamber.

Abstract: A variable geometry pre-mixing fuel injector (50) for injecting a fuel/air mix in a downstream direction, comprising: an air inlet (60); a fuel inlet (58) positioned downstream of the air inlet (60); a duct (56) extending at least downstream of the fuel inlet (58) to define a fuel and air pre-mixing zone (62), that narrows to form an opening (64); and means for varying the flow of fuel/air mix from the pre-mixing zone (62) through the opening (64).

Abstract: A method of operating a combustor (10), to provide intimately mixed hot combusted gas (44) for a gas turbine (46), includes feeding gaseous oxidant (12) and gaseous fuel (16) into the combustor (10) near a combustion flame (28) which has a tip end (39) and a root end (29), where corona discharge occurs through adjustment of an electric field (34), and where the corona discharge causes ionized particles (36) to form and also causes intimate turbulent mixing of the gases.

Abstract: The present invention provides a mixer for a gas turbine combustor comprising a plurality of generally annular walls interconnected by at least a plurality of first vanes. The vanes are oriented at angles, so as to create a shear layer between the two flows. A fuel is then injected so as to penetrate the shear layer for enhanced mixing. The mixture passes through an extended mixing passage to provide sufficient time and distance for improved mixedness prior to ignition. Multiple embodiments of the present invention are disclosed comprising a plurality of first vanes and a plurality of first and second vanes.

Abstract: A combustion chamber 10 for a gas turbine that operates in a highly diluted mode of combustion has a substantially toroidal plenum 30. At least one combustion fluid injector is located at the periphery of the plenum. The shape of the plenum and the disposition of the combustion fuel injectors are such that a vortex flow 2 is established in the combustion chamber in use. Gasses are entrained in the vortex which provides high enough levels of flue gas re-circulation to allow for the onset of highly diluted combustion.