SYSTEM FOR PURGING A FUEL HAVING REACTIVE GAS

Abstract

This system for purging a fuel containing hydrogen comprises a gas turbine. The gas turbine comprises at least one combustion chamber (20) provided with at least one injector (52) of the fuel, an exhaust section and a hot gas circuit going from the combustion chamber (20) to the exhaust section. The system comprises at least one point of injection (A, A′) of air and/or of inert gas positioned on the hot gas circuit.

Claims

1. A system system for purging a fuel containing hydrogen, comprising: a gas turbine, said gas turbine comprising at least one combustion chamber provided with at least one injector of said fuel, an exhaust section and a hot gas circuit, going from said combustion chamber to said exhaust section, wherein at least one point of injection of air and/or of inert gas and/or of combustion inhibitor positioned on said hot gas circuit.

2. The purging system according to claim 1, wherein said at least one injection point is located downstream of the combustion zone of said at least one injector of said fuel.

3. The purging system according to claim 1, additionally comprising a cooling circuit having fixed blades located on said hot gas circuit, wherein said at least one injection point is located on said cooling circuit (50).

4. The purging system according to claim 1, wherein said system additionally comprises a distribution ring placed inside an exhaust downstream of said exhaust section, said at least one injection point being located on said distribution ring.

5. The purging system according to claim 3, wherein said at least one injection point is connected to an external feed source.

6. The purging system according to claim 1, wherein said inert gas is nitrogen.

7. The purging system according to claim 1, wherein said inert gas is carbon dioxide.

8. The purging system according to claim 1, wherein said inert gas is steam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Other aspects and advantages of the invention will become apparent on reading the detailed description below of specific embodiments, given by way of examples which are in no way limiting, with reference to the appended drawings, in which:

[0044] FIG. 1 is a graph representing detonation and flammability curves for a combustible mixture of air and of hydrogen as a function of an added percentage of inert gas in a specific embodiment of the purging system in accordance with the invention where the inert gas added is nitrogen.

[0045] FIG. 2 is a graph representing detonation and flammability curves for a combustible mixture of air and of hydrogen as a function of an added percentage of inert gas in a specific embodiment of the purging system in accordance with the invention where the inert gas added is carbon dioxide.

[0046] FIG. 3 is a diagrammatic view in longitudinal section of a conventional gas turbine with its main components and the hot gas circuit.

[0047] FIG. 4 is a diagrammatic view of a detailed description of the hot gas passages in the expansion turbine.

[0048] FIG. 5 is a diagrammatic view illustrating a first embodiment of the invention.

[0049] FIG. 6 is a diagrammatic view illustrating a second embodiment of the invention.

[0050] FIG. 7 is a diagrammatic view illustrating a third embodiment of the invention.

DESCRIPTION OF EMBODIMENT(S)

[0051] In the graph of FIG. 1, the axis of the abscissae is the percentage by volume of nitrogen added in a combustible mixture of air and of hydrogen, the percentage by volume of hydrogen of which is shown on the axis of the ordinates.

[0052] The curve as continuous lines represents the limits of the flammability zone and the curve in dashes represents the limit of the detonation zone.

[0053] At point D, the combustible mixture comprises 30% by volume of hydrogen and 70% by volume of air. It is seen, at point C, that it is possible to exit from the detonation zone if the hydrogen concentration is reduced to 13% by volume, by the addition of 58% by volume of nitrogen, in which case the mixture comprises 29% by volume of air.

[0054] In the graph of FIG. 2, the axis of the abscissae is the percentage by volume of carbon dioxide added in a combustible mixture of air and of hydrogen, the percentage by volume of hydrogen of which is shown on the axis of the ordinates.

[0055] The curve as continuous lines represents the limit of the flammability zone and the curve in dashes represents the limit of the detonation zone.

[0056] At point D, the combustible mixture comprises 30% by volume of hydrogen and 70% by volume of air. It is seen, at point C, that it is possible to exit from the detonation zone if the hydrogen concentration is reduced to 13% by volume, by the addition of 30% by volume of carbon dioxide, in which case the mixture comprises 57% by volume of air.

[0057] FIG. 3 diagrammatically represents a view in longitudinal section of a conventional gas turbine 10. The main components of the gas turbine 10 are as follows: a compression section 12 comprising a compressor 16, an air inlet 14 and a compressed air outlet 38; a section of the combustion system 18, from where combustion gas streams, known as hot gases, 40 escape; an expansion section or turbine 22 comprising fixed blades and moving blades fitted to a rotor 26 of axis of rotation 28, the rotor 26 connecting the compression section 12, the expansion turbine 22 and one or more combustion chambers 20, the flow of hot gases 40 traversing the stages of the expansion turbine 24 (in the expansion section 22) up to the inlet of an exhaust section 30.

[0058] FIG. 4 shows a detailed description of the upper part of the expansion turbine 24 traversed by the hot gases 40. Stages of blades 32A, 32B and 32C are fixed to the stator, while moving blades 34A, 34B and 34C are fixed to the rotor 26 illustrated in FIG. 3. Thus, a passage and cavities for hot gases exiting from the combustion chamber 20 illustrated in FIG. 3 are formed upstream of the exhaust section 30 illustrated in FIG. 3.

[0059] FIG. 5 illustrates a first embodiment of the invention, where the purging system comprises a point of injection “A and A′” of air and/or of inert gas and/or of combustion inhibitor into the combustion system, preferably downstream of the flame or combustion zone in the combustion chamber.

[0060] A fuel containing a predetermined part of hydrogen is considered.

[0061] The purging system in accordance with the invention comprises a gas turbine of the type of the gas turbine 10 described above with reference to FIG. 3. In particular, the gas turbine 10 comprises at least one combustion chamber 20 provided with at least one injector 52 of the abovementioned fuel. The gas turbine 10 also comprises an exhaust section 30 (see FIG. 3) and a hot gas circuit 40 going from the combustion chamber 20 to the exhaust section 30.

[0062] The combustion chamber 20 illustrated in FIG. 5 is typically limited, on the one hand, at the inlet, by a cover 51 where inlet connections for fuel injectors 52 are found and, on the other hand, at the outlet, by a transition piece 53 emerging toward the stages of the expansion turbine 24 (not represented in FIG. 5 but visible in FIG. 3).

[0063] Inside the combustion chamber 20, a liner 56 makes possible the passage of compressed air 57 originating from the compressor 16 (illustrated in FIG. 3) to the intake of the fuel injectors 52. Inside the combustion chamber 20, a combustion zone 54 and a dilution zone 55 can be formed in operation.

[0064] The references A and A′ denote, in this first embodiment, at least one point of injection of air and/or of inert gas and/or of combustion inhibitor. This injection point is on the hot gas circuit, immediately downstream of the zone where the flame is supposed to be, in the case of lighting on starting. The injection points A and A′ are thus located downstream of the fuel injectors 52.

[0065] In the specific embodiment of FIG. 5, the injection points A and A′ are located at the combustion zone 54. Thus, as the gas turbine is equipped with a controller (not represented), the latter makes possible the opening of the valve for controlling the reactive gas flow making possible the starting of the combustion system. At the same time as this starting, the controller also provides for the purging system to be active, either before or at the same time, for an injection of air and/or of inert gas creating a flow F which mixes with the hydrogen-based fuel which is in the combustion chamber 20 and in the hot gas circuit of the turbine.

[0066] FIG. 6 illustrates a second embodiment of the invention, in which the gas turbine comprises a cooling circuit having fixed blades. In this second embodiment, the injection of air and/or of inert gas can be carried out through the cooling circuit. It is sufficient for this to have available at least one point of injection of air and/or of inert gas on the cooling circuit 50.

[0067] The cooling circuit 50 comprises a plurality of fixed blades, including those denoted by the references S1N and S2N in FIG. 6. These blades are fixed to the stator at the hot gas passage and cavities 40. Furthermore, the source to be injected into the cooling circuit can be air withdrawn from the compressor 16 or an external source 60 of air and/or of inert gas and/or of combustion inhibitor.

[0068] FIG. 7 illustrates a third embodiment of the invention, in which the gas turbine comprises a distribution ring 75 placed inside the exhaust section 74 located immediately downstream of the expansion turbine 24. In this third embodiment, the injection of air and/or of inert gas and/or of combustion inhibitor can be carried out through the distribution ring 75. For this, it is sufficient to have available at least one injection point on the distribution ring 75. Furthermore, the source to be injected into the distribution ring 75 can be an external source 77 of air and/or of inert gas and/or of combustion inhibitor.

[0069] In all the embodiments described above, as nonlimiting examples, the inert gas used for the purging can be nitrogen or carbon dioxide or also steam.

[0070] Of course, in all the embodiments described above, the volume and the flow of air and/or of inert gas and/or of combustion inhibitor chosen to be injected depend on the hydrogen fraction in the fuel and on the volume of fuel injected for false starting, or also on the volume in the hot gas circuit of the turbine.

[0071] Furthermore, the three embodiments described can be combined in order to provide an effective solution making it possible to mix the air and/or the inert gas with the fuel comprising a hydrogen fraction.