Patent Application
20120148962
The present application hereby claims priority under 35 U.S.C. Section 119 to European Patent application number 10194320.7, filed Dec. 9, 2010, the entire contents of which are hereby incorporated by reference.
The present invention relates to a combustion chamber and a method for supplying fuel to a combustion chamber. In particular, reference to a combustion chamber of a gas turbine is made.
Combustion chambers are known to comprise a body into which fuel and an oxidiser (typically compressed air) are injected to be combusted and generate hot gases that are expanded in a turbine.
Typically, in order to comply with emissions (NOx, CO, uncombusted hydro carbon), pulsations, power optimisation, etc, the fuel is supplied into the combustion chamber via a plurality of stages.
Each stage (typically comprising a plurality of nozzles) allows a fuel to be injected within the combustion chamber in a particular position according to the current load.
With reference to
The premixed combustion chamber 1 has mixing devices 2 into which fuel is supplied and mixed with the compressed air to form a mixture that in burnt into a combustion device 3.
Each mixing device 2 has a plurality of stages identified by 4a, 4b, 4c (any number of stages is anyhow possible, often they are between two and four) each typically comprising a plurality of nozzles.
In order to supply fuel to these stages, a supply circuit 5 is provided, having manifolds 7a, 7b, 7b for each stage and connected to a main line 8a, 8b, 8c supplying fuel into it; in addition control valves 9a, 9b, 9c are provided, to regulate the fuel flow to the manifolds 7a, 7b, 7c.
During operation the fuel is supplied to the manifolds 7a, 7b, 7c that distribute it.
In particular the mass flow distribution among the stages 4a, 4b, 4c is controlled via the valves 9a, 9b, 9c.
Even if largely used, this structure implies structural and operating constrains.
The supply circuit 5 with a manifold for each stage is complex and expensive; in particular the most expensive components are the manifolds 7a, 7b, 7c, which are made up of rings running over the whole combustion chamber circumference, and the valves 9a, 9b, 9c.
Operation during transient periods is very complex, since the three valves 9a, 9b, 9c must be regulated at the same time; in some cases this regulation can cause instabilities and, in extreme cases, it can also cause flame extinction.
In addition, when one (or more) of these valves 9a, 9b, 9c is closed, the relative manifold 7a, 7b, 7c must be purged with air. During the following operation the air contained within the manifold becomes hot and when the valve must be opened to supply fuel within the manifold again, it is necessary to purge the same manifold with air before fuel is introduced within it (to avoid risks of explosions). For this reason, when the valve is opened, first air enters the combustion chamber and only afterwards the required fuel is injected. It is clear that in some cases this air injection could be very troubling; for example, in case of operation close to the lean blow off, flame extinction could occur.
In addition, when the valves 9a and/or 9b and/or 9c are open, in case their regulation must be changed (for example to counter pulsations or increase flame stability), time is required for the fuel pressure to be adjusted over the whole manifolds 7a and/or 7b and/or 7c and up to the injectors 4a, 4b, 4c; this time interval increases the time required for the regulation.
The present disclosure is directed to a combustion chamber having a body with nozzles to inject a fuel to be burnt therein. The nozzles define a plurality of groups to be fed in parallel, and the nozzles of each group define at least two stages, that are differently operated according to the different operating conditions. The combustion chamber includes a manifold for collecting a fuel to be distributed among the groups, a plurality of supply elements distributing the fuel originating from the manifold to each group; and at least one splitter associated with each group for diverting the fuel coming from the supply elements between the stages.
In another aspect, the disclosure is directed to a method for supplying fuel to a combustion chamber having a body with nozzles to inject a fuel to be burnt therein. The nozzles define a plurality of groups to be fed in parallel, and the nozzles of each group define at least two stages, that are differently operated according to the different operating conditions. The method includes collecting in a manifold the fuel to be distributed among the groups and distributing the fuel originating from the manifold to each group via supply elements. The method also includes diverting, for each group, the fuel coming from the supply elements between the stages.
Further characteristics and advantages of the invention will be more apparent from the description of a preferred but non-exclusive embodiment of the combustion chamber and method, illustrated by way of non-limiting example in the accompanying drawings, in which:
An aspect of the invention therefore includes providing a combustion chamber and a method by which the combustion chamber is simpler and the operating constrains are reduced.
Another aspect of the invention is to provide a combustion chamber wherein the fuel response to valve regulation is very quick.
These aspects are attained by providing a combustion chamber and a method in accordance with the accompanying claims.
With reference to the figures, these show a combustion chamber 10 having a body with nozzles to inject a fuel to be burnt therein.
The nozzles define a plurality of groups 13 to be fed in parallel, and the nozzles of each group 13 define at least two stages 12a, 12b (each stage 12a, 12b generally includes a plurality of nozzles; additional stages in addition to the two stages 12a, 12b described can also be provided, i.e. any number of stages is possible); the stages 12a, 12b are differently operated according to the different operating conditions, for example load.
In addition, a manifold 14, typically in the form of a ring, that collects the fuel to be distributed between the stages 12a, 12b of the groups 13 is provided; advantageously one single manifold 14 is provided, alternatively also more than one manifold can be provided, in this case at least one manifold 14 feeds different stages of different groups.
Connected to the manifold 14, supply elements 15 that distribute the fuel originating from the manifold 14 to each group 13 are provided.
In addition, for each group 13, one or more than one splitter 17 (according to the distribution scheme) for diverting the fuel coming from the supply elements 15 between the stages 12a, 12b is also provided.
One main line 19 to supply fuel into the manifold 14 is provided, the main line 19 has a control valve 20 to regulate the fuel flow within the manifold 14.
For each group 13, each supply element 15 is defined by a duct, and further ducts 22 are provided between the splitters 17 and the nozzles of each stage 12a, 12b (
Splitters 17 can have different configurations, but in all cases they divert the fuel flow between the stages 12a, 12b but cannot control the total flow (i.e. the fuel flow is only regulated via the valve 20).
In an embodiment (
In a different embodiment (
The number of stages can also be greater than only two (
In this case a plurality of supply elements 15 are provided for each group 13, each supply element 15 being connected to another supply element 15.
In particular
The splitters 17 can be locally controlled, for example they can be controlled on the basis of the fuel pressure within the duct 15 that carries them.
Alternatively the splitters 17 can be centrally controlled, i.e. they can be all connected to a control unit that drives them according to the different operating conditions such as, for example, load.
In both cases the following control schemes are possible:
Naturally, also combinations of locally and centrally controlled splitters 17 are possible.
The operation of the combustion chamber is apparent from that described and illustrated and is substantially the following.
In the following reference to the embodiment of
Fuel is supplied via line 19 and valve 20 into the manifold 14; the valve 20 regulates the fuel flow, i.e. the amount of fuel that enters the manifold 14 and that is distributed among the groups 13.
From the manifold 14 the fuel enters the supply elements 15 and reaches the first splitters 17.
Each first splitter 17 can:
It is clear that by appropriately diverting the fuel at the splitters 17, the required fluid distribution among the stages 12a, 12b, 12c for each particular load can be achieved. Advantageously, the combustion chamber in embodiments of the invention is simple, because the most troubling and expensive component are the manifold and the valve 20; the splitters 17 and their control system are not troubling and are generally cheap.
In addition operation is much simpler than with traditional combustion chambers. In fact only one single valve 20 controls the fuel flow within the combustion chamber, thus regulation of a plurality of valves that control the amount of fuel flow to a plurality of manifolds is avoided.
In addition, since the splitters 17 only control the fuel distribution among the stages, the fuel amount to each group 13 is in all cases regulated via the valve 20, i.e. defective controls and risks of providing a fuel amount too large or too low is avoided.
Moreover, during operation the valve 20 is always open (because when it is closed no fuel reaches the nozzles and the flame extinguishes), no manifold purging with air is thus necessary; this further simplifies the structure and reduces possible troubling operating conditions that could be caused by air that enters the combustion chamber when fuel is required instead.
Advantageously, since the fuel regulation is made downstream of the manifold 14, the regulation is very quick.
During operation, it is not mandatory that the staging of different groups of nozzles be the same; i.e. the staging can be the same for all groups of it can be different.
In the following, an example of locally controlled splitters is described.
In this case, each supply element 15 receives (almost) the same amount of fuel; then the splitters 17, on the basis of local conditions that may be different over the circumference of the combustion chamber, regulate the staging, i.e. the amount of fuel supplied to each stage of the group.
In the following an example of centrally controlled splitters is described.
Also in this case each supply element 15 receives (almost) the same amount of fuel; then the splitters 17, on the basis of a signal provided by the control unit, regulate the staging, i.e. the amount of fuel supplied to each stage of the group.
In the following three schematic examples of a premixed combustion chamber (
The premixed combustion chamber (
The mixing devices 31 can be made up of two or more shells defining a cone swirl space; the shells define slots for air introduction within the cone swirl shape. A lance is housed within the cone swirl space.
A first stage 12a is for example defined by nozzles provided at the lance (for example at the tip of the lance, it could be a pilot stage) and a second stage 12b is defined by the nozzles at the shells.
As schematically shown, one single ring shaped manifold 14 is provided with one single supply line 19 and valve 20.
From the manifold 14 the supply elements 15 extend and are connected to the splitters 17; from the splitters 17 the ducts 22 that feed the first and second stages 12a, 12b depart.
In this embodiment the nozzles of each group 13 belong to the same mixing device 31.
As shown, the ring shaped manifold 14 is provided connected to a line 19 provided with the valve 20. From the manifold 14 the supply elements 15 depart, each connected to a first splitter 17 that supplies fuel to a duct 22 feeding the first stage 12a and a further supply element 15 connected downstream of the first splitter 17. This further supply element 15 is connected to a further splitter 17 that fees two ducts 22 connected to the second stage 12b and third stage 12c.
Naturally also different types of combustion chambers are possible, for example a can combustor combustion chamber can implement the structure and the method in embodiments of the present invention.
Each mixing device 31 has the same features already described with reference to the first example and
In particular two stages 12a and 12b are common to two of the mixing devices 31 of each group 13, and one single mixing device has a third and fourth stage 12c and 12d; therefore during operation the two mixing devices operated in common can for example generate a flame with a higher temperature and the other mixing device a flame with a lower temperature. Naturally in different embodiments the groups 13 can include any number of mixing devices operated in common with flame having a higher temperature and any number of mixing device operated with a flame at a lower temperature and the number of stages of each burner can also be any, for example only one. A possible embodiment is thus a combustion chamber with the features shown in
The present invention also refers to a method for supplying fuel to a combustion chamber.
With reference to
It should be understood that the features described may be independently provided from one another.
In practice, the materials used and the dimensions can be chosen at will according to requirements and to the state of the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10194320.7 | Dec 2010 | EP | regional |
