EP3830486A1

EP3830486A1 - Combustion chamber comprising a passage section of a flame tube, which is modified, particularly for a turbine designed to generate power, particularly electrical power

Info

Publication number: EP3830486A1
Application number: EP19734807.1A
Authority: EP
Inventors: Jean-Baptiste Michel; Julien Thiriot
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 2018-07-30
Filing date: 2019-07-01
Publication date: 2021-06-09
Also published as: FR3084450A1; FR3084450B1; WO2020025234A1

Abstract

The invention relates to a combustion chamber (18) of a turbine, particularly a thermodynamic cycle turbine with recuperator, for generating power and particularly electrical power, comprising a casing (112) with a means (152) for injecting at least one combustible fuel, and an intake (132) for hot compressed air and fuel, and a flame holder (154). According to the invention, the flame tube (122) comprises a zone (200, 201) in which the section of said flame tube (122) narrows.

Description

COMBUSTION CHAMBER COMPRISING A PASSAGE SECTION OF A MODIFIED FLAME TUBE, PARTICULARLY FOR A TURBINE INTENDED FOR THE PRODUCTION OF ENERGY, ESPECIALLY ELECTRICAL ENERGY

The present invention relates to a combustion chamber of a turbine, in particular of a thermodynamic cycle turbine with recuperator, for the production of energy, in particular electrical energy.

It relates more particularly to a microturbine with recuperator for the production of electricity from a liquid or gaseous fuel.

Generally, it is understood by microturbine a turbine of small power usually less than 200KW.

A turbine with recuperator generally comprises at least one compression stage with at least one compressor, a combustion chamber (or burner), at least one expansion stage with at least one expansion turbine, a heat exchange device (or recuperator) between the compressor and the combustion chamber making it possible to heat the gases compressed by the compressor to send them with a high temperature to the combustion chamber, this exchange device being traversed by the hot gases coming from the turbine.

As described in French patent application Nos. 3041742 and 3049044 of the applicant, the combustion chamber comprises a housing through which circulates the hot compressed air from the recuperator and a flame tube, located inside this box, in which combustion takes place.

The flame tube includes a primary zone which receives part of the total hot compressed air flow and in which combustion takes place and a dilution zone where the mixture between the burnt gases from the primary zone and the compressed gases takes place. hot from dilution holes on the tube. The primary zone also includes a perforated diffuser allowing the passage of hot compressed air as well as fuel coming from a fuel injection system (liquid or gaseous) placed upstream of the diffuser.

As better described in the aforementioned applications, the flame tube carries a flame stabilizer comprising the perforated diffuser, at least one flue gas recirculation passage and a mixing tube.

This combustion chamber, although satisfactory, nevertheless presents significant drawbacks.

In fact, the compressed air is distributed in this combustion chamber in two flows via the dilution holes. The first air flow is directed to the primary zone where combustion takes place while the second flow will enter directly into the dilution zone via the dilution holes to obtain, at the outlet of the combustion chamber, a homogeneous mixture. temperature and composition.

As a result, the asymmetry of the entry of compressed air into the combustion chamber with respect to the flame tube leads to a significant asymmetry in the flow of air and burnt gases. This can lead to licking of the wall by hot gases from the combustion of fuel in the primary zone. These gases can have very high temperatures (more than 1500Ό) can damage the wall of the flame tube.

This results in a strong limitation of the life of the flame tube, except to realize it in very expensive materials.

In addition, if the flame is not correctly located in the flame tube, the efficiency of the dilution zone is reduced and can lead to significant temperature heterogeneities at the outlet of the combustion chamber, which could reduce the life of the turbine.

In addition, incomplete combustion can occur with the risk of extinction and the production of pollutants.

In order to respond to these drawbacks, French patent application No. 3055403 of the applicant relates to a combustion chamber of a turbine, in particular a thermodynamic cycle turbine with recuperator, for the production of energy, in particular electrical energy, comprising a housing with means for injecting at least one fuel and an inlet for hot compressed air, said housing housing a flame tube with a perforated diffuser for the passage of hot compressed air and fuel, and a flame stabilizer and the chamber comprises an air deflector disposed opposite the intake of hot compressed air for circulate this hot air in one axial direction from this hot air intake.

This configuration thus makes it possible to have a combustion chamber having an improvement in the location of the hot zones by allowing better durability of the parts as well as a better homogeneity of the temperature leaving the combustion chamber and a design at a lower cost.

However, there remain drawbacks notably linked to a counter-current flow in the flame tube which generates beat-type instabilities with the flow of burnt gases. These instabilities can have the following consequences, depending on the conditions:

• licking of burnt gases at very high temperatures against the walls which can be destructive;

• destabilization of combustion in the primary zone, in particular when the flame is stabilized downstream of the flame holder.

FIG. 2a schematically represents the distribution of the flows in a flame tube of the prior art as described above and we thus have:

The burnt gases (Gb) from combustion in the primary zone;

The air (A) entering directly into the chamber via the dilution holes;

The gas mixture (MG) directed to the outlet;

The flow (E) against the current generated by the dilution;

The recirculations (R) of burnt gases around the flame holder.

FIG. 2b which is a simulation of the flow of FIG. 2a, makes it possible to note that the flow against the current generated by the dilution induces an instability of the positioning and a phenomenon of flapping at the level of the holes of dilution represented by the reference 166. This is also due to the fact that the recirculations around the flame catch convect a significant proportion of fresh gas coming from the dilution zone.

The objective of the present invention is to improve the two preceding points and in particular aims to improve the stability of combustion and the disappearance of the beat phenomenon. The invention also aims to have a greater recirculation by burnt gases in order to allow more dilute combustions and a further reduction in NOx emissions.

To do this, a first aspect of the invention relates to a combustion chamber of a turbine, in particular of a thermodynamic cycle turbine with recuperator, for the production of energy, in particular electrical energy, comprising a housing with a means for injecting at least one fuel and one inlet for hot compressed air, said housing housing a flame tube with a perforated diffuser for the passage of hot compressed air and fuel and a flame stabilizer and the The invention is characterized in that the flame tube comprises a region for narrowing the cross section of said flame tube.

According to a characteristic of the invention, the flame tube comprises a primary zone and a dilution zone and said narrowing zone is positioned between the primary zone and the dilution zone.

According to a characteristic of the invention, the flame tube has circumferential rows of radial dilution orifices positioned at the start of the dilution zone and said narrowing zone is positioned upstream (in the general direction of the burnt gases) of said rows circumferential radial dilution holes.

According to a characteristic of the invention, the narrowing zone of the section of said flame tube is formed by an obstacle of symmetry of revolution. According to a characteristic of the invention, the obstacle of symmetry of revolution comprises a ring positioned in the flame tube.

According to a characteristic of the invention, the narrowing zone comprises a change in diameter of the flame tube upstream of the dilution zone.

According to a characteristic of the invention, the combustion chamber comprises an air deflector arranged opposite the intake of compressed hot air.

A second aspect of the invention relates to a turbine, in particular a thermodynamic cycle turbine with recuperator, for the production of energy, in particular electrical energy, comprising at least one compression stage with at least one gas compressor , a heat exchanger, a combustion chamber, and at least one expansion stage with at least one expansion turbine connected by a shaft to the compressor, and the invention is characterized in that it comprises a combustion chamber such that described above.

Other characteristics and advantages of the system according to the invention will appear on reading the following description of nonlimiting exemplary embodiments, with reference to the appended figures described below in which:

FIG. 1 is a diagram illustrating a turbine with a combustion chamber according to the invention for the production of energy, in particular electrical energy,

- Figure 2a, already described, is an axial sectional view showing the distribution of flows in a state-of-the-art combustion chamber;

Figure 2b, already described, is an axial sectional view showing the beating of a flame in a state of the art combustion chamber;

Figure 3 is an axial sectional view of a combustion chamber in a first embodiment according to the invention;

Figure 4 is an axial sectional view of a combustion chamber in a second embodiment according to the invention; Figure 5 is an axial sectional view showing the flame in the first embodiment of the invention.

Detailed description of the invention

In general and as shown in FIG. 1, a turbine 10 comprises at least one compression stage 12 with at least one gas compressor 14, a heat exchanger 16 (or recuperator), a combustion chamber 18 (or burner) supplied with fuel by at least one tank 20, at least one expansion stage 22 with at least one expansion turbine 24 connected by a shaft 26 to the compressor. This turbine also comprises a means of producing energy, here electric, which comprises an electric generator 28 advantageously placed on the shaft 26 between the compressor and the turbine.

Of course, this generator can be alternately connected to the expansion turbine or to the compressor by a shaft other than that connecting the turbine and the compressor.

Preferably, the heat exchanger 16 can be a cross-flow exchanger, for example of the shell-tube or alternating plate type with two inlets and two outlets.

The compressor 14 comprises an inlet 30 for fresh gas containing oxygen, here outside air generally at room temperature, and an outlet for compressed air 32 leading to an inlet for compressed air 34 of the exchanger 16 by a line 36. The hot compressed air outlet 38 of this exchanger is connected by a line 40 to a hot compressed air inlet 42 of the burner 18. The superheated gas outlet 44 of the burner is connected by a line 45 to the 'inlet 46 of the turbine, the outlet 48 of which is connected to another inlet 50 of the exchanger by a line of expanded superheated gases 52. The exchanger 16 also includes an outlet of cooled gases 54 to be directed to all means of evacuation and treatment, such as a chimney (not shown). In a first embodiment of the combustion chamber 18 illustrated in Figure 3, without limitation, it comprises a housing 1 12 of cylindrical shape with a tubular wall 1 14 of substantially circular section. This housing is closed at one of its ends by an injector-carrying partition 116 and at the other of its ends by an annular partition 118 with an opening 120 which is substantially circular.

This combustion chamber also comprises a flame tube 122, also of substantially cylindrical shape, housed coaxially in the housing being of diameter smaller than the housing but of diameter identical to that of the opening 120 of the annular partition. This tube comprises a wall 124 of substantially circular section, one end closed by a diffusion partition 126 facing and at a distance from the injector partition 11 16, and an open end 128 which passes through the annular partition by cooperating with sealing with the internal diameter of this annular partition to form the outlet 130 of this combustion chamber.

The housing carries on its peripheral wall 114, substantially at equal distance between the injector-carrying partition and the annular partition, a hot compressed air intake 132.

An air deflector 134 is placed between the two walls 1 14 and 124 and opposite this air intake to circulate this hot air in a single axial direction from this intake.

More particularly, this deflector comprises a tube 136 open at each of its ends 138, 140. This tube comprises a tubular fixing portion 142 and a tubular air diversion portion 144, of different section, connected to each other by a portion junction 146, here of frustoconical shape.

The section of the tubular portion of larger section 142, which corresponds to the tubular fixing portion, has an outside diameter substantially equal to that of the inside diameter of the housing 1 12 while the section of the tubular portion of smaller section 144, which corresponds to the tubular air bypass portion, has a outside diameter which is larger than the outside diameter of the wall 124 of the flame tube 122 and smaller than that of the inside diameter of the wall 1 14 of the housing 1 12.

This deflector is housed in the combustion chamber in such a way that the tubular fixing portion 142 is housed between the injector bulkhead 1 16 and the diffusion bulkhead 126 by being fixed by any known means (soldering, welding ,. .) at the wall of the housing, that the tubular air bypass portion 144 is located substantially opposite the air intake 132 and that the frustoconical portion 146 is placed near this intake.

Advantageously, the diameter of the tubular air bypass portion is such that it is equivalent to the average of the diameters of the housing 12 and of the flame tube 122. This makes it possible to create circulation passages for the compressed air of same radial height R between this portion and respectively the housing (passage 148) and the flame tube (passage 150).

Likewise, the open end 140 of the tubular air bypass portion 144 is located at a distance from the annular partition 11 so that the distance between this open end and the partition creates a connecting passage 151 of which the axial dimension D is at least equal to the radial height R.

Thus, during the admission of the compressed hot air, the latter circulates in passages without significant dimensional variation.

In FIG. 3, the injector-carrying partition carries a means for injecting at least one fuel 152, here in the form of an injector coaxial with the flame tube, opposite a flame stabilizer 154 which is placed on the bulkhead 126.

This stabilizer comprises a perforated diffuser 156 housed in the diffusion wall 126 and comprising a multiplicity of axial holes 158 regularly distributed circumferentially on the sole and a central axial orifice 160. This sole continues in an axial direction and opposite to the partition by axial arms 162, here three arms arranged at 120 ° from each other, and carrying at their ends of a mixing tube 164 of limited axial extent and of outside diameter smaller than the inside diameter of the flame tube 122.

The flame tube 122 also comprises circumferential rows of radial dilution orifices 166 placed at a distance from the diffusion partition and near the annular partition of the housing, being regularly distributed advantageously on either side of the region of free end of the portion 144.

According to the invention, the flame tube 122 comprises a zone for narrowing the section of said flame tube. The narrowing zone is formed by an obstacle of symmetry of revolution. This obstacle may in particular be a ring 200 inserted in the flame tube and of symmetry of revolution.

This ring 200 has a diameter less than the diameter of the flame tube 122, so that it can be inserted into the flame tube 122. The term “diameter” means the largest diameter of the ring, that is to say the external diameter taken on the periphery thereof. The thickness of the ring 200 is preferably between a few millimeters and a few centimeters.

The combustion chamber thus formed comprises an injection / mixing zone ZM where the hot compressed air is mixed with the fuel and the start of combustion, a primary zone ZP in which combustion takes place, and a zone dilution ZD where the mixing takes place between the burnt gases from the primary zone and the hot compressed air from the dilution holes.

The narrowing zone (the ring 200) is positioned between the primary zone and the dilution zone. This ring is positioned relative to the dilution holes 166 in such a way as to block the counter-current flows in the primary zone, that is to the left of the dilution holes 166 of FIG. 3 (upstream of the dilution holes , according to the general direction of flow of the burnt gases).

In a second embodiment of the flame tube visible in FIG. 4, diagrammatically and in a nonlimiting manner, there is no ring but the tube with flame has a particular geometry which consists in having a shrinking zone 201 where there is a sudden change in diameter of the flame tube. This narrowing zone 201 is positioned upstream of the dilution zone and before the dilution holes so as to block the counter-current flows in the primary zone, that is to say to the left of the dilution holes 166 in the figure. 4. In other words, for this embodiment, the primary zone ZP has an external diameter which is strictly greater than the external diameter of the dilution zone ZD.

In operation, the fuel, here in liquid form, is injected by the injector 152 in the direction of the diffusion wall 126 to pass through the central orifice 160. The hot compressed air coming from the inlet 132 is deflected by the deflector 134 according to arrow F1 in the first place by the frustoconical portion 146 to end up in the passage 148. This air circulates in an axial direction starting from the admission 132 and throughout this passage 148 according to a single direction of circulation, here from left to right considering arrow F2 to arrive at the end passage 151. Arrived at this passage, the air has a radial direction of flow according to arrow F3 then circulates in passage 150, in an opposite axial direction to that of passage 148 according to arrow F4. Part of the air circulating in the passage 150 then enters the flame tube through the dilution orifices (arrow F5) and the other part this air arrives in the mixing zone ZM (arrow F6). This air then passes through the holes 158 of the diffusion wall 126 and is directed into the mixing tube 164 in which the liquid fuel evaporates, then the combustion.

Thanks to the deflector, the flow of air from the intake is directed towards the side opposite to the mixing zone before returning to this mixing zone by surrounding the tubular air bypass portion 144.

In doing so:

- the velocities of arrival of the air in the space located in the tubular air bypass portion 144 are low and more symmetrical (symmetry of revolution) with respect to the central axis of the tubular bypass portion of air, which improves the efficiency of the dilution. Indeed, in each of the different rows of dilution holes 166, the speeds of entry of the air into the dilution zone are close for all the holes;

- the tubular air bypass portion 144, which is the hottest room, is better insulated from the outside by the double air flow;

- the velocities of arrival in the zone located between diffusion partition 126 and the box 1 12 are very low due to the large section of the mixing zone ZM and the relatively low flow (part of the total flow leaves in the zone of ZD broadcast). This zone behaves like a collector making it possible to have entry speeds into the main zone ZP via the diffusion wall which are normal to the wall and which are identical for each concentric row of holes. In this, the flame then generated in the primary zone ZP is located well around the axis of the tubular air bypass portion.

In a second embodiment of the combustion chamber 18, not shown, there is no air deflector 134 disposed opposite the intake of compressed hot air 132. The flame tube 122 nevertheless has a narrowing (200, 201) as previously described.

Thanks to the modification according to the invention, the recirculations do not entail fresh gas from the dilution zone in the recirculations in the primary zone. In this, only burnt gases are recirculated and the recirculation rate (proportion of burnt gases on fresh gases) in the primary zone increases. This will make it possible to achieve more dilute combustion regimes, which are interesting in terms of polluting emissions (notably NOx and HC).

As visible in FIG. 5 which is a simulation of a flow in the context of the first embodiment of the combustion chamber 18, the counter-current flow generated by the dilution at the dilution holes 166 and obtained on the state-of-the-art configuration of FIG. 2b is no longer present. This results in a much more stable flame positioning and a very strong attenuation, even a disappearance of the beat phenomenon. As it goes without saying, the invention is not limited to the sole embodiment of the device described above by way of example, on the contrary it embraces all the variant embodiments.

Claims

1) combustion chamber (18) of a turbine, in particular of a thermodynamic cycle turbine with recuperator, for the production of energy, in particular electrical energy, comprising a housing (1 12) with a means of injection (152) of at least one fuel and an inlet (132) of hot compressed air, said housing housing a flame tube (122) with a perforated diffuser (126) for the passage of hot compressed air and fuel and a flame stabilizer (154) characterized in that the flame tube (122) includes a narrowing region (200, 201) of the cross section of said flame tube (122).

2) Combustion chamber (18) according to claim 1, characterized in that the flame tube (122) comprises a primary zone (ZP) and a dilution zone (ZD) and said narrowing zone (200, 201) is positioned between the primary zone (ZP) and the dilution zone (ZD).

3) Combustion chamber (18) according to claim 2, characterized in that the flame tube (122) has circumferential rows of radial dilution orifices (166) positioned at the start of the dilution zone (ZD) and said the narrowing zone (200, 201) is positioned upstream of said circumferential rows of radial dilution orifices (166).

4) Combustion chamber (18) according to one of the preceding claims, characterized in that the narrowing zone (200) of the section of said flame tube (122) comprises an obstacle of symmetry of revolution.

5) Combustion chamber (18) according to the preceding claim, characterized in that the obstacle of symmetry of revolution comprises a ring positioned in the flame tube (122). 6) Combustion chamber (18) according to one of claims 1 to 3, characterized in that the narrowing zone (201) comprises a change in diameter of the flame tube upstream of the dilution zone (ZD). 7) Combustion chamber (18) according to one of the preceding claims, characterized in that it comprises an air deflector (134) disposed opposite the intake of compressed hot air (132).

8) Turbine, in particular a thermodynamic cycle turbine with recuperator, for the production of energy, in particular electrical energy, comprising at least one compression stage with at least one gas compressor, a heat exchanger, a combustion chamber, and at least one expansion stage with at least one expansion turbine connected by a shaft to the compressor, characterized in that it comprises a combustion chamber (18) according to one of the preceding claims.