Combustion device with flameless combustion chamber, use of such a device and electricity generation or power-heat coupling device with such a device

Description

Subject of the invention

[0001] The present invention relates to a combustion device and to an apparatus for producing electricity or cogenerating energy comprising said device. A combustion device is understood to mean a device comprising one or more combustion chambers or sub-chambers.

[0002] In particular, the invention relates to a combustion system in "flameless" mode operating for example with a gaseous fuel coupled to a heat recovery unit and integrated into a micro-gas turbine operating on natural gas. Technological background and state of the art

[0003] It is known that a combustion chamber feeding a turbine operating in the so-called "flameless" oxidation regime (or "flameless" or FLOX ®< ) makes it possible to achieve extremely low NOx emissions, for example <10 ppm.

[0004] Flameless combustion, known as “MILD combustion” (acronym for Moderate or Intense Low-oxygen Dilution, or low oxygen dilution, moderate or intense), is a combustion mode capable of providing high combustion efficiency with very low pollutant emissions, even with high air preheating. In addition to the improved energy efficiency associated with the heat recovery process, MILD combustion thus ensures a homogeneous combustion environment, a consequence of the intense recirculation of exhaust gases. This results in a localized reduction in the O 2 level, leading to a distributed reaction zone and a reduction in working temperatures compared to conventional flame combustion. The reduced temperature levels and the homogeneous reactive environment have positive effects on the formation of pollutants (NOx, soot), which are significantly reduced, and on the strength of materials, thanks to the absence of strong temperature gradients.MILD combustion provides high fuel flexibility, making it an ideal technology for the following fuels: low calorific fuels, high calorific industrial waste, hydrogen-based fuels, liquid fuels (e.g. kerosene, gasoline, diesel, fuel oil) and solid fuels.

[0005] From the point of view of turbulence-chemistry interactions, MILD combustion is characterized by a strong coupling between the scales of chemical dynamics and fluid dynamics. The Damköhler number Da (ratio between characteristic time of fluid dynamics and chemical reaction times) in MILD is of the order of unity, indicating that the time of chemical reactions is not negligible compared to the times governing fluid dynamics.

[0006] In conventional combustion, the overall process is controlled by heat and mass transfer, leading to a well-defined reaction region with strong temperature and species gradients and Da values ​​greater than unity. In flameless combustion, exhaust gas recirculation (also called flue gas) therefore leads to a more homogeneous temperature and species distribution.

[0007] Generally, flameless combustion is very stable and quiet and could therefore be used for gas turbine applications, where conventional operations can lead to thermo-acoustic instabilities ("hum") and significant stresses.

[0008] Flameless combustion chamber designs are known for (micro-)gas turbine applications. In a micro-gas turbine application, the flue gas temperature at the combustion chamber outlet is limited by the tolerance of the material used to manufacture the turbine, typically from 800°C to 1050°C, and in particular from 950°C to 1050°C. This condition induces the use of a very large excess of air compared to the stoichiometric quantity of air required to burn the fuel.

[0009] In the applications concerned by the present invention, the lambda ratio (air mass flow rate / stoichiometric air mass flow rate or 1 + excess air) could be very high (significantly greater than 1) in order to allow the gas temperature reduction compatible with the turbine inlet. This results in a large quantity of O 2 available for combustion, which seems antagonistic to the ideal conditions for implementing the flameless combustion regime which mainly depends on the dilution of O 2 in the mixture.

[0010] Furthermore, another favorable condition for the appearance of the flameless combustion regime concerns the preheating of the combustion air to a sufficient temperature to ensure easy self-ignition of the mixture. The use of a heat recovery unit present in the gas turbine cycle with regeneration is advantageous to ensure this functionality.

[0011] Many combustion chamber designs for operating in a flameless regime have been proposed. One example is the gas turbine combustion chamber described in WO 2003 / 091626. This chamber is configured to have an internal guide tube open at both ends and which allows for the recirculation of a significant portion of the combustion gases in the chamber, the other portion of the gases being evacuated downstream of the chamber. This recirculation allows for maintaining a flameless oxidation regime in the chamber. These known solutions certainly allow for low NOx levels, but they are not designed to achieve low CO levels.

[0012] CN105299692A discloses a combustion chamber device of a large-area smoke disinfection and epidemic prevention equipment. The combustion chamber device comprises a flame tube, a diffusion section, an air distribution plate, a cold air jacket and a fuel gas jacket, a cooling (or gas return) tube, and an outer casing. The flame gun is welded to the air inlet end face in the fuel gas jacket via four support plates. The fuel gas jacket is bolted to the air distribution plate. The diffusion section is arranged outside the flame gun by a sleeve and fixedly installed to the air distribution plate and the conditioned air jacket via bolts.Air enters from the diffusion section, with a portion entering the combustion chamber for combustion, a portion entering from the area between the flame tube and the fuel gas jacket, to be mixed with the high-temperature flame, and a portion entering the air distribution port on the air distribution plate and mixing with the high-temperature, high-speed airflow from the gas return tube into the cold air tube to obtain an airflow suitable for spraying. The injected disinfectant then forms a mist that is sprayed out of the device.

[0013] The cooling tube is concentric with the fuel gas jacket so that the fuel gas stroke is lengthened, the mixing time is prolonged with a significantly reduced overall structure length.

[0014] Documents CN 105 299 692 B and CN 203 907 671 U show gas turbines having the characteristics specified in the preamble of claim 1. Purpose of the invention

[0015] The invention aims to overcome at least one of the drawbacks of the aforementioned state of the art, in particular that the exhaust gases leaving the combustion device have not only low NOx levels (for example < 10 mg / kWh 1< preferably < 5 mg / kWh) but also low CO levels (for example < 10 mg / kWh).

[0016] More particularly, the invention aims to provide a stable and highly efficient combustion device, configured to produce combustion gases (exhaust) compatible with 1< mg / kWh at 0% O2. kWh = energy injected based on the PCl of the fuel inlet temperature between 800° and 1050 C°, in particular between 950° and 1050 C° while maintaining low NOx and CO levels such as those mentioned above.

[0017] The invention has even more particularly as an object a design of combustion device making it possible to take into account large lambda values ​​(excess air) while allowing the occurrence of combustion without flame. Main characteristic elements of the invention

[0018] The present invention relates to a combustion device, according to claim 1, for an electricity production or energy cogeneration apparatus, said apparatus comprising a gas turbine, in particular a micro-gas turbine, powered by said device, said device being adapted for a combustion regime of the "flameless" type, and comprising: an outer tube; a combustion tube, forming a combustion zone suitable for flameless combustion of a mixture of combustion air and fuel, said combustion tube being concentric with the outer tube, in communication with fuel injection means and air injection means, arranged at a first end of the combustion tube, called the front end, and closed by a bottom at a second end of the combustion tube, called the rear end, said bottom being integral with said combustion tube and sealed; the fuel injection means comprising at least a first orifice, called the fuel injection orifice; the air injection means comprising at least a second orifice, called the air injection orifice; means for discharging the combustion gases; a closing wall covering the front end of the combustion tube and connected to the air and fuel injection means;the combustion tube being substantially cylindrical in shape in a single internal volume, capable of allowing the recirculation of gases in a flameless combustion regime; the combustion gas evacuation means comprising at least one opening arranged at the front end of the combustion tube being substantially cylindrical in shape, said opening being delimited on the one hand by one end of the longitudinal cylindrical wall of the combustion tube proximal to the closing wall and on the other hand by said closing wall, the flow and evacuation of the combustion gases being ensured between said longitudinal wall and the external tube; ; characterized by

[0019] a tubular jacket arranged concentrically between the combustion tube and the external tube, connected to the closing wall and positioned opposite the opening of the evacuation means, to form an annular zone, called a recombination zone, making it possible to extend the residence time of the combustion gases escaping through the opening.

[0020] Advantageous embodiments of the invention are specified in the dependent claims.

[0021] The invention also relates to a use of the combustion device according to the invention, in which an air flow is injected into the device with a speed of between 60 and 120 m / s, so as to obtain a fluid recirculation rate mE / (mA+mF) greater than 1.3, where mE, mA and mF respectively represent the mass flow rates of the burnt and recirculated gases in the combustion zone, and of the combustion air and fuel introduced into the combustion zone (4).

[0022] The present invention also relates to an apparatus for producing electricity or cogenerating energy comprising a combustion device according to the invention.

[0023] Advantageously, the electricity production or energy cogeneration device comprises a heat exchanger for recovering the thermal energy from the combustion gases produced in the combustion device, to preheat the intake air supplying the combustion device.

[0024] Preferably, the heat exchanger comprises a first circuit in fluid communication with a downstream section of a turbine, in particular a micro-turbine, and a second circuit in fluid communication with an upstream section of the combustion device.

[0025] According to the present invention, the lambda ratio can reach values ​​as high as 6-8, which allows a sufficient temperature reduction of the exhaust gases compatible with the entry into the turbine. The apparent antagonism with the need for a flameless combustion regime is resolved by the optimized geometry of the combustion chamber which allows an efficient dilution of the oxygen in the mixture.

[0026] The characteristics specific to the invention are advantageous in that they make it possible to have a combustion device compatible with the use of different fuels such as natural gas, biogas, gas of synthetic origin (syngas, etc.), etc. In addition, flameless combustion is stable. Brief description of the figures

[0027] Other features and advantages of the present invention will be better understood from the drawings and description below. There figure 1shows a perspective (external) view of a flameless combustion device according to the invention. The figure 2 represents a three-dimensional longitudinal sectional view of the flameless combustion device according to the invention. The figure 3 shows a three-dimensional cross-sectional view of the flameless combustion device according to the invention, taken at the plenum level. The figure 4 shows two perspective views of the fuel and air injection ports of the flameless combustion device according to the invention. The Figure 5 is a schematic representation in longitudinal section of the flameless combustion device according to the invention, in which the flows are represented by arrows. The figure 6 is a schematic representation of the energy cogeneration apparatus (in the form of a cycle) according to the invention. The figure 7 is a longitudinal cross-sectional distribution diagram of the temperature field. The figure 8is a longitudinal cross-sectional distribution diagram of the velocity field. The figure 9 is a longitudinal cross-sectional distribution diagram of the CO field. The figure 10 is a longitudinal cross-sectional distribution diagram of the OH field. Description of preferred embodiments of the invention

[0028] One embodiment of the combustion device proposed in the present invention has been designed specifically to accommodate large lambda values ​​while still allowing flameless combustion to occur. Description of the combustion chamber

[0029] THE figures 1 to 5 show an embodiment for a flameless combustion device 100 that receives preheated air from a heat recovery unit (105, see figure 6 ) connected to a turbine, for example a micro-turbine, via an air supply duct of appropriate dimensions and shape, typically cylindrical, in order to reduce pressure losses.

[0030] The air supply duct may comprise an air supply duct 21 and an adapter duct 10 allowing the junction between this air supply duct 21 and a first end of the combustion device 100. Usually, the adapter duct 10 comprises at one end a clamping flange 22, in particular a V-shaped flange, ensuring the fixing of the air supply duct 21 to the adapter duct 10. The adapter duct 10 may comprise at its other end a so-called main flange 23, which can be welded to a connecting tube. The adapter duct 10 allows access to the interior of the combustion device as illustrated in the figure 2 .

[0031] At its other end, the combustion device 100 can be connected to a volute of the turbine (not shown) by means of a conical tube 24 welded to an external tube 26 of the combustion chamber 100. A V-shaped clamping flange 25 can allow the junction with the volute of the turbine.

[0032] As illustrated in the figure 2 , the combustion device may comprise stiffeners 27 welded to the external tube 26, the stiffeners 27 ensuring the rigidity of said device 100.

[0033] There figure 2also shows that the ignition of the combustion device 100 can be ensured by a heating plug 28. The plug 28 passes through the external tube 26, a tubular jacket 7 and a combustion tube 5, in order to enter an ideal zone for the ignition of the mixture. This zone is preferably located at a distance from orifices 36 of air injection means equivalent to the average diameter defined by an internal surface 31 of an injection ring 40. In addition, this zone is preferably located at a distance from the central axis of the combustion tube 5 of approximately ¾ of the average diameter defined by the internal surface 31 of the injection ring 40.

[0034] The combustion device 100 may comprise a thermocouple 29, preferably of type K, also penetrating into the heart of the combustion device 100 in order to measure the temperature of the combustion zone 4. It serves as a safety device in order to avoid the occurrence of excessively high temperatures inside the combustion tube 5.

[0035] The combustion device 100 comprises fuel injection means comprising a tube 20 passing through the air intake duct 21. This tube 20 can be fixed, preferably welded, to a fuel injection head 33. This tube 20 allows the fuel to be supplied to the injection head 33.

[0036] According to the invention, a technique is used for dividing / separating the air inlet flow into two separate air flows, a primary flow used for combustion and a secondary flow used for cooling the mixture. Thus, the figure 3shows that the combustion device 100 may comprise a plenum 1 serving to divide the air flow into two flows: a primary flow and a secondary flow. The primary air flow may be injected into the combustion tube 5 via the orifices 36 of the air injection means. The secondary air flow passes through the bypass 6 and mixes with the primary flow downstream ( Figure 5 ).

[0037] The bypass 6 allows the secondary flow to pass to the downstream mixing zone. The bypass 6 may include openings 39, for example notches, the surface of which allows the ratio between the primary flow and the secondary flow to be adjusted. Typically, this ratio is equal to 1 in order to achieve a maximum lambda of 4 within the combustion zone 4.

[0038] There figure 4illustrates more precisely how the air and fuel injection means can be combined. In this configuration, the air injection means comprise the injection ring 40 having an internal surface 31 of substantially conical shape. According to this advantageous embodiment, the face of the injection ring 40 facing the combustion tube 5 has a shoulder 34 in order to facilitate fitting into a closing wall 14, for example a plate, of the combustion tube 5. The fuel injection head 33 may have an external surface 41 of conical shape extending over the majority of its length. The fuel injection head 33 may be held in the center of the injection ring 40 by profiled arms 30 connected to the injection ring 40. The external surface 41 of the fuel injection head 33 may at least partially delimit the external surface of the air injection orifices 36.The profiling of the arms 30 makes it possible to reduce the pressure loss produced by the flow of air in the air injection orifices 36. The conical internal surface 31 has an angle such that the primary air flow converges towards the combustion zone. The angles of the internal surface 31 of the injection ring 40 and of the external surface 41 of the injection head 33 ensure the formation of conduits whose section is convergent in the direction of the combustion zone 4. The fuel injection tube 20 is welded to the injection head 33 at a recess or shoulder 32 formed in the latter, in order to ensure a sealed connection. The fuel, preferably gas, is ejected through the injection port 35. Preferably, the means for combined injection (i.e. air and fuel) may be manufactured by an additive 3D printing process (e.g. DMLM, acronym for . Direct Metal Laser Melting,or direct fusion of metal by laser) into refractory material, for example nickel or cobalt based alloys or refractory steels. Alternatively, other processes are possible such as machining, MIM (acronym for Metal Injection Molding , or powder injection molding), etc.

[0039] As illustrated in the figure 4, the air and the fuel are respectively injected via the air orifices 36 and fuel orifices 35 into the combustion tube 5. The latter has a cylindrical shape closed at its end by a bottom 12. To obtain a flameless combustion regime, the speed of the air flow must be between 60 and 120 m / s. The combustion gases escape from the recombination zone 4 through one or more openings 9, for example a slot. However, part of the fluid recirculates in the combustion zone. The recirculation rate calculated on the basis of the formula mE / (mA + mF) greater than 1.3, where mE, mA and mF represent respectively the mass flow rates of the burnt and recirculated gases in combustion zone 4, of air and fuel introduced into combustion zone 4. It is in particular this significant recirculation of the gases which allows the dilution of the oxygen and the fuel and which leads to the appearance of the flameless combustion regime.The size of the openings 9 allows the level of recirculation to be controlled. Metal parts 37, 38 (see . figure 2 ) can be used to ensure the positioning of the combustion tube 5 in the outer tube 26 while fixing the passage section of the openings 9 (in the example shown a slot 9). One of the parts 37, 38 can be welded to the outer tube 26 and thus allow the combustion tube 5 to expand freely.

[0040] It appeared to the inventors, first experimentally and then by numerical verification, that the addition of a tubular jacket 7 makes it possible to significantly reduce the CO level in the combustion gases downstream of the combustion device 100, and this when the combustion device 100 also comprises a bypass 6. The tubular jacket 7 is an open tube concentric with the combustion tube 5. This tubular jacket 7 makes it possible to avoid excessively rapid mixing between the primary flow and the secondary flow. Thus the temperature of the primary flow remains high and the CO recombination reaction into CO 2 can continue further in the so-called recombination zone 8. The CO concentration in the combustion gases can thus be reduced by a factor of approximately 10. The length of the tubular jacket 7 therefore impacts the recombination of CO and can advantageously be optimized by calculation. In any case, it is generally at least 50% of the length of the combustion tube 5.Preferably, the tubular jacket 7 is fixed to the closing wall 14.

[0041] The combustion tube 5 undergoes extreme temperatures of the order of 1050°C to 1150°C. Different metal alloys can be used for the radiant tubes in heat treatment such as 602CA ®< , 310S, Inconel ®< 625, and preferably the ferritic iron-chromium-aluminium alloy Kanthal ®< APM. It should be noted that the combustion tube 5 may also have a hemispherical bottom or another shape making it possible to improve the recirculation of the gases and the pressure drop in the combustion device.

[0042] The other parts of the combustion device 100, including for example the outer tube 26, the adapter pipe 10, the flanges 22, 23 and the tubular jacket 7, may be made of 310S steel. The material must allow, as for any other combustion device, the installation of a protective layer against oxidation and corrosion at high temperatures. The combustion tubes 5 and outer tubes 26 are preferably cylindrical in shape. Description of the electricity production or energy cogeneration device

[0043] The flameless combustion device 100 may be associated with a micro-turbine application and in particular intended for the production of electricity or heat in cogeneration. The electricity production or cogeneration device may comprise several modular elements (see figure 6). The apparatus comprises at least one turbogenerator and a combustion device 100 which are combined with one or more of the following elements: a heat recovery unit 105, a power electronics system (not shown), a gas-water (or air-water) heat exchanger 103, a set of auxiliaries (not shown).

[0044] The turbogenerator comprises a compressor 101, a turbine 104, for example a micro-turbine, an electric generator 102 preferably with a permanent magnet, the assembly fixed on the same shaft. Preferably, the shaft bearings may comprise two radial aerodynamic bearings requiring no lubrication based on a liquid or solid lubricant such as oil. In addition, the turbogenerator may comprise an axial aerodynamic bearing intended to compensate for the axial force of the compressor-turbine couple. The electric generator 102 may be positioned at the front of the compressor 101 in a cantilevered manner (not shown). This configuration makes it possible to obtain a very compact shaft. The electric stator is then fixed to the compressor volute. A sufficient space between the electric generator and the stator finally allows the air to be sucked in by the compressor 101.

[0045] The heat recovery unit 105 may comprise a heat exchanger intended to recover the useful energy present in the exhaust gases of the turbine 104 in order to preheat the air compressed by the compressor 101, which will supply the combustion device 100.

[0046] The power electronics system (not shown) can be configured so that it allows the conversion of high-frequency alternating current produced by the generator 102 (synchronous alternating current motor, in particular permanent magnet) into direct current so that it can be injected into the electrical network via an inverter, for example of the type used for solar applications.

[0047] A gas-water (or air-water) heat exchanger 103 can be placed at the outlet of the cogeneration unit to recover energy from the exhaust gases to heat water or produce steam in cogeneration mode. Several exchangers can be used. In addition, each gas-water heat exchanger can be positioned at other locations in the cogeneration unit requiring cooling.

[0048] The set of auxiliaries ensures the function of compression and regulation of the flow of fuel, for example gaseous fuel, for injection into the combustion device 100 as well as systems for water cooling of the electric stator and possibly of the support of the aerodynamic bearings.

[0049] A micro-turbine is a turbine with a power of 5 kW to 750 kW, preferably 25 to 500 kW. Typically, these turbines are mounted on piston combustion engines to provide supercharging. Simulation results

[0050] The simulation results are presented to the figures 7 , 8 , 9 And 10 . These were carried out with ANSYS 2020 R1 software. The approach consists of solving the axisymmetric Navier-Stokes (RANS) equations assuming a stationary incompressible flow. The numerical modeling uses an incompressible solver of the Pressure Based type, equipped with an adequate turbulence model (for example standard k-ε with the first constant C 1ε equal to 1.6), a radiation model ( Discrete Ordinate Method ), a model of turbulence interaction with the convection-diffusion equations of chemical species specifically adapted to flameless combustion ( Eddy Dissipation Concept coupled to the model Partially Stirred Reactor model, PaSR) and a reactive gas model (e.g. KEE58, GRI 2.11, etc.). The simulations are carried out following a mesh convergence study to demonstrate that the quality of the results becomes sufficiently independent of the mesh used.

[0051] The simulation of the temperature field ( figure 7 ) shows that the maximum temperature reached does not exceed 1380°C, which is well below the threshold triggering the production of NOx. The combustion zone is confined to the bottom of the combustion tube and relatively dispersed as shown by the figure 10 showing the distribution of OH radicals. Furthermore, the very high CO concentration in the combustion zone is reduced very sharply under the effect of the recombination of CO into CO2 ( figure 9 ). The predicted emission values ​​in this case are: NOx = 1,43 ppm ; CO = 0,50 ppm .

[0052] A test bench was set up in parallel to measure the performance of the flameless combustion chamber according to the present invention. This is equipped with a 30kW electric air heater to ensure preheating of the air entering the combustion chamber. Emission measurements are carried out using a Testo 350, which allows measurements of CO (0-10000ppm) and NO (0-4000ppm). The air flow is measured using a GasView volumetric flow meter with ±3% full scale accuracy error. The gas flow is adjusted with an Elflow type flow controller with a full scale accuracy of ±0.5%. The main measurement results are summarized in Table 1. Table 1: Emission measurement Emissions mg measurements / kWh at 0% O2 (1)< CO < 10 (2)< NOx 3,43 (1) Air flow 25g / s, air temperature 650°C (2) Gas test according to EN 437 List of reference symbols

[0053] 1Plenum 2Injector 4Combustion zone 5Combustion tube 6Bypass 7Tube liner 8Recombination zone 9Opening(s), slot 10Air supply duct, adapter duct 12Bottom 14Closing wall, plate 20Fuel injection tube 21Air supply duct, air inlet duct 22Flange 23Main flange 24Tapered tube 25Flange 26Outer tube 27Stiffener(s) 28Spark plug 29Thermocouple 30Profile arms 31Injection ring inner surface 32Recess 33Injection head, guide element 34Shoulder 35Fuel injection port 36Air injection port 37Positioning metal part 38Positioning metal part 39Bypass opening(s), notches 40Injection ring 41External surface of the guide element 100Combustion device 101Compressor 102Electricity generator 103Heat exchanger 104Turbine 105Heat recovery unit (exchanger for preheating)

Claims

1. A combustion device (100) for an electricity production or energy cogeneration apparatus, said apparatus comprising a gas turbine, in particular a micro gas turbine supplied by said device, the combustion device being suitable for a flameless combustion regime, and comprising: - an outer tube (26); - a combustion tube (5) forming a combustion zone (4) for flameless combustion of a mixture of oxidizing air and fuel, the combustion tube (5) being concentric with the outer tube (26), in communication with fuel-injection means and air-injection means arranged at a first end of the combustion tube (5), referred to as a front end, and which is closed by an end wall (12) at a second end of the combustion tube, referred to as a rear end, said end wall (12) being integral with and sealed to said combustion tube (5); - the fuel-injection means comprising at least a first orifice (35), referred to as a fuel-injection orifice; - the air-injection means comprising at least a second orifice (36), referred to as an air-injection orifice; - means for discharging combustion gases; - a closure wall (14) covering the front end of the combustion tube (5) and connected to the air-injection and fuel-injection means, - the combustion tube (5) being substantially a cylinder with a single internal volume configured to allow the combustion gases to recirculate in the flameless combustion regime, - the means for discharging the combustion gases comprising at least one opening (9) arranged at the front end of the combustion tube (5), which is substantially cylindrical in shape, said opening (9) being delimited on one side by an end of the longitudinal cylindrical wall of the combustion tube (5) proximal to the closure wall (14) and on the other side by said closure wall (14), with the flow and evacuation of combustion gases being ensured between said longitudinal wall (5) and the external tube (26); characterized by a tubular sleeve (7) arranged concentrically between the combustion tube (5) and the outer tube (26), connected to the closure wall (14) and positioned facing the opening (9) of the evacuation means so as to form an annular combustion zone (8), to extend a residence time of the combustion gases exhausted via the opening (9).

2. The combustion device (100) of claim 1, wherein the outer tube (26) delimits, at least in part with the combustion tube (7), an annular passage referred to as a bypass (6), allowing passage of a flow of dilution air to mix with the combustion gases downstream of the combustion zone (8), the closure wall (14) comprising one or several openings (39), referred to as bypass openings, formed in a periphery thereof and via which the flow of dilution air enters the bypass (6).

3. The combustion device (100) of claim 1, characterized in that the tubular sleeve (7) extends axially over at least 50% of a length of the combustion tube.

4. The combustion device (100) according to any one of the preceding claims, further comprising: a plenum (1) of cylindrical shape formed in part by a portion of the outer tube (26) and by the closure wall (14), the portion being arranged at a front end of the outer tube (26), the closure wall (14) forming an end wall of the plenum (1).

5. The combustion device (100) according to claim 4, wherein the plenum (1) is fluidically connected to an air-supply duct (10,21).

6. The combustion device (100) according to any one of the preceding claims, characterized in that the opening (9) of the combustion gases discharge means is an annular opening formed between the closure wall (14) and the front edge of the combustion tube (5).

7. The combustion device according to any one of the preceding claims, characterized in that the fuel-injection orifice (35) is an orifice centered with respect to the combustion tube.

8. The combustion device (100) according to any one of the preceding claims, characterized in that the fuel-injection means comprise an injection head (33) in which the fuel-injection orifice (35) is formed.

9. The combustion device (100) according to claim 8, characterized in that the fuel-injection means comprise a fuel-injection tube (20), a rear end of which is secured to the injection head (33).

10. The combustion device (100) according to claim 9 in combination with claim 5, characterized in that the air-supply duct (10,21) and the fuel-injection tube (20) are, over part of their respective lengths, arranged coaxially.

11. The combustion device (100) according to any one of the preceding claims, characterized in that the air-injection orifice (36) comprises several orifices arranged in the closure wall (14).

12. Use of the combustion device (100) according to any one of the preceding claims, in which a flow of air is injected into the combustion device with a velocity of between 60 and 120 m / s, so as to obtain fluid recirculation rate mE / (mA+mF) greater than 1.3, where meE, mA and mF represent the mass flow rates of the burned and recirculated gases in the combustion zone, and of the oxidizing air and fuel introduced into the combustion zone (4), respectively.

13. Electricity generation apparatus comprising a combustion device (100) according to any one of the claims 1 to 11.

14. The electricity-production or energy-cogeneration apparatus of claim 13, further comprising; a heat exchanger (105) configured to recuperate heat energy from the combustion gases produced in the combustion device (100) in order to preheat intake air supplied to the combustion device (100).

15. The electricity-production or energy-cogeneration apparatus of claim 13 or 14 in which the heat exchanger (105) comprises a first circuit in fluidic communication with a section downstream of a turbine (104), in particular a microturbine (104), and a second circuit in fluidic communication with a section upstream of the combustion device (100).