Patent Application
20200103113
This application claims priority to German Patent Application DE102018216807.5 filed Sep. 28, 2018, the entirety of which is incorporated by reference herein.
The present invention concerns a combustion chamber assembly for an engine, with a combustion chamber and several heat shields and/or burner seals arranged next to each other in the circumferential direction, to each of which at least one fuel nozzle is assigned for introduction of fuel into the combustion chamber.
One or more heat shields of a combustion chamber assembly protect heat-sensitive components from the high temperatures prevailing in the combustion space of the combustion chamber. The heat shield or shields are here arranged on a head plate of the combustion chamber. Burner seals on a heat shield or several heat shields in turn serve for mounting a fuel nozzle. A burner seal is normally mounted so as to float relative to a head plate and heat shield in order to allow movement of the fuel nozzle relative to the combustion chamber, but at the same time guarantees a seal between the fuel nozzle and the head plate or heat shield.
The geometric design of the burner seal and/or heat shield is known to influence the technical attributes of the combustion chamber, in particular the characteristics of the combustion taking place in the combustion chamber. Thus an aerodynamic design of the burner seal for example influences the occurrence of emissions, e.g. soot and CO, the operability, i.e. the ignition and extinction behaviour, and the susceptibility to thermoacoustic excitation. A burner seal and/or a heat shield are here typically designed accordingly such that no attribute of the combustion chamber becomes unacceptably poor. The respective design is however always a compromise, since none of the attributes may be selected optimally without negatively influencing another attribute.
It is therefore an object of the proposed invention to provide a combustion chamber assembly for an engine which is improved in this respect.
This object is achieved by a combustion chamber assembly according to claim 1.
Accordingly, a combustion chamber assembly for an engine is proposed in which at least two different types of heat shield and/or burner seal are provided along the circumferential direction of the combustion chamber. In the context of the proposed invention therefore, at least two different designs of heat shields and/or burner seals are provided along the circumferential direction of the combustion chamber. This takes better account of the locally differing requirements, whereas for example solutions previously implemented in practice always provided identically configured burner seals as identical components for a combustion chamber.
The proposed solution includes in particular that a heat shield is used which is configured as a disc, ring or ring segment, and this is combined with at least two different types of burner seal. In particular, it is included that (in each case) several passage openings for several burner seals are provided on several heat shields or on a single heat shield, and for example burner seals of at least two different types are provided on a heat shield.
The phrase “different types of heat shields and/or burner seals” means in particular that heat shields and/or burner seals of a first type differ geometrically, i.e. with regard to form, at least in portions, from heat shields and/or burner seals of at least one other second type.
In principle, the number of first types of heat shield and/or burner seal may be different from the number of second types of heat shield and/or burner seal. In one embodiment variant for example, the number of first types of heat shield and/or burner seal is at least twice as great as the number of second types of heat shield or burner seal. In such an embodiment variant, for example, a heat shield and/or a burner seal of the second type is deliberately combined with a plurality of heat shields and/or burner seals of the first type, in order to take account of peripheral conditions which deviate locally, for example because of local structural and/or functional differences on the combustion chamber. A burner seal of modified shape or a heat shield of modified shape of the second type may thus influence a flow into the combustion chamber locally differently from adjacent regions of the combustion chamber along the circumference.
Thus a combustion chamber for an engine typically comprises at least one spark plug, typically several (at least two) spark plugs which are each provided in the region of the fuel nozzle. In one embodiment variant, a heat shield and/or a burner seal of a second type is assigned to the fuel nozzle, in the region of which at least one spark plug is provided. In a region without spark plug lying adjacent thereto in the circumferential direction however, at least one heat shield and/or at least one burner seal of the first type is provided. In such an embodiment variant therefore, in the region of a spark plug of the combustion chamber assembly, one fuel nozzle is mounted for example on a burner seal of the second type while several further fuel nozzles in regions without spark plugs are each mounted on a burner seal of a first type of different design. An aerodynamically differently designed burner seal may be provided via the respective burner seal, depending on the presence of a spark plug downstream, and hence depending on whether or not a spark plug is provided downstream of the respective fuel nozzle, in order to improve the mixture formation and the susceptibility to thermoacoustic excitations.
In a refinement, at least two spark plugs are distributed along the circumference of the combustion chamber, and a heat shield and/or a burner seal of the second type is provided in the region of each of these at least two spark plugs.
In principle, evidently more than two different types of heat shield and/or burner seal may be provided on a proposed combustion chamber assembly. In view of the complexity of mounting of the combustion chamber assembly however, it may be suitable to provide only two different types, in particular only one other type in the region of a spark plug.
In one embodiment variant, a number N of fuel nozzles is provided along the circumference of the combustion chamber, and 1 to N fuel nozzles are assigned to 1 to N sectors along the circumference of the combustion chamber. A circumference along which the fuel nozzles of the combustion chamber are arranged is thus (virtually) divided into 1 to N sectors corresponding to the number N of fuel nozzles. With a view to efficient distribution of heat shields and/or burner seals of different types along the circumference of the combustion chamber, it may be suitable to assign the different types by sectors. For example, in one embodiment variant it is provided that a heat shield of a second type and/or a burner seal of a second type is provided in an Nth sector, whereas at least one heat shield of a first type and/or a burner seal of a first type is provided in each of at least two adjacent sectors along the circumference.
The N fuel nozzles may be arranged next to each other in the circumferential direction along a circular path, in particular for an annular combustion chamber configured as a ring in cross-section. The Nth sector with the heat shield of the second type and/or with the burner seal of the second type may then for example lie on an upper intersection point of the circular path with a vertical running centrally relative to the circular path or offset to the right or left in the circumferential direction to this upper intersection point in a sector adjacent to the intersection point. A heat shield of the second type and/or a burner seal of the second type thus for example lies in a sector in the region of a top dead centre or TDC. With an odd number N of sectors distributed over the circumference therefore, the Nth sector lies precisely at top dead centre. With an even number N of sectors distributed evenly over the circumference, the Nth sector with the burner seal and/or heat shield of the second type would lie to the left or right of the top dead centre, in a back view onto the fuel nozzles.
Alternatively or additionally, an embodiment variant of the proposed solution provides that the combustion chamber assembly comprises a number Z of spark plugs, and a number N of fuel nozzles is provided along the circumference of the combustion chamber, wherein 1 to N fuel nozzles are assigned to 1 to N sectors along the circumference of the combustion chamber, and a heat shield of a first type and/or a burner seal of a first type is provided in N−Z−1 sectors, and a heat shield of a second type and/or a burner seal of a second type is provided in each of Z+1 sectors. For example, with 16 fuel nozzles and 2 spark plugs, the configuration explained above may mean that, along the circumference of the combustion chamber, 13 heat shields and/or burner seals of a first type and 3 heat shields and/or burner seals of a second type are provided. The heat shield and/or the burner seal of the second type, which is not provided in the region of the spark plug, lies for example in the Nth sector, in particular in the region of a top dead centre. Such a configuration may for example have the advantage that the extinction stability of the combustion chamber is improved, since usually the sector in the region of the top dead centre is the first to be extinguished.
In principle, the heat shields and/or the burner seals of different types, on at least one portion facing the combustion chamber, extending into the combustion chamber and/or influencing a flow into the combustion chamber, are geometrically different from each other. A corresponding portion, which is provided with heat shields and/or burner seals of different types, thus differs from type to type.
For example, burner seals of different types, in the form of a flow guidance element provided on the burner seal and extending into the combustion chamber for guiding the fuel-air mixture, are geometrically different from each other. In a refinement based thereon, it is provided for example that a flow guidance element comprises a flow guidance hopper, and the flow guidance hoppers of different types of burner seals have differently greatly inwardly curved, differently thick and/or differently greatly inclined wall portions.
A flow guidance hopper of a combustion chamber seal may in principle widen in the direction of the combustion chamber and thus diverge. The wall portions which are differently greatly inwardly curved, differently thick and/or differently greatly inclined, are here typically provided at the end of the burner seal, i.e. each at an end of a flow guidance hopper lying in the flow direction. Thus, locally, the flow may be influenced in targeted fashion via the differently designed wall portions, so that on the combustion chamber, identical burner seals are provided which are not merely designed for the best possible compromise.
The proposed solution also provides an engine with an embodiment variant of a combustion chamber assembly proposed, in particular an engine with an annular combustion chamber.
The appended figures illustrate exemplary possible design variants of the proposed solution.
In the figures:
The air fed into the primary flow duct via the compressor V enters a combustion section BK of the core engine, in which the driving energy for driving the turbine TT is generated. For this purpose, the turbine TT has a high-pressure turbine 13, a medium-pressure turbine 14 and a low-pressure turbine 15. Here, the energy released during the combustion is used by the turbine TT to drive the rotor shaft S and thus the fan F in order to generate the required thrust by means of the air conveyed into the bypass channel B. Both the air from the bypass channel B and the exhaust gases from the primary flow channel of the core engine flow out via an outlet A at the end of the engine T. In this arrangement, the outlet A generally has a thrust nozzle with a centrally arranged outlet cone C.
In principle, the fan F can also be coupled to the low-pressure turbine 15, and can be driven by the latter, via a connecting shaft and an epicyclic planetary transmission. It is furthermore also possible to provide other gas turbine engines of different configurations in which the proposed solution can be used. For example, engines of this type can have an alternative number of compressors and/or turbines and/or an alternative number of connecting shafts. As an example, the engine can have a split-flow nozzle, meaning that the flow through the bypass duct B has its own nozzle, which is separate from and situated radially outside the core engine nozzle. However, this is not limiting, and any aspect of the present disclosure may also apply to engines in which the flow through the bypass channel B and the flow through the core are mixed or combined before (or upstream of) a single nozzle, which may be referred to as a mixed-flow nozzle. One or both nozzles (whether mixed flow or split flow) may have a fixed or variable region. Whilst the described example relates to a turbofan engine, the proposed solution may be applied, for example, to any type of gas turbine engine, such as an open-rotor (in which the fan stage is not surrounded by a nacelle) or turboprop engine, for example.
The heat shield 5 also has cooling holes 50 for cooling, and is connected to the head plate 4 by a fixing device 64. The head plate 4 also comprises cooling holes 40 in a known fashion.
For introduction of fuel into the combustion space of the combustion chamber 3, a fuel nozzle 2 is inserted in the combustion space. A combustion chamber head 7 surrounds the fuel nozzle 2 outside the combustion space. This combustion chamber head 7 is attached to the head plate 4 and/or to the combustion chamber wall 30.
In order to mount the fuel nozzle 2 suitably relative to the combustion space of the combustion chamber 3, a floatingly mounted burner seal 6 is situated between the head plate 4 and the heat shield 5. This burner seal 6 allows movement of the fuel nozzle 2 relative to the combustion space. Furthermore, the burner seal 6 serves to position the fuel nozzle 2 such that no leakage occurs between the fuel nozzle 2 and the head plate 4 or heat shield 5. For this, the burner seal 6 has a sealing face 60 towards the fuel nozzle 2.
In addition, the burner seal 6 is formed aerodynamically favourably upstream towards the combustion chamber head 7, and has an inlet lip 61 so that a flow is guided from the combustion chamber head 7 to the fuel nozzle 2.
Downstream in the direction of the combustion space of the combustion chamber 3, the burner seal 6 is also formed so as to guide a flow of an air-fuel mixture from the fuel nozzle 2 in targeted fashion. In the embodiment variant shown, at its end on the combustion space side, the burner seal 6 comprises a flow guidance element in the form of a flow guidance hopper 62. This flow guidance hopper 62 widens in the flow direction and hence into the combustion space. The wall portions of the burner seal 6 adjacent to the flow guidance hopper thus extend radially outward in order to conduct a flow, emerging into the combustion space, radially outward.
Discrete cooling holes 63 are provided for cooling the burner seal 6 and in particular the flow guidance hopper 62. These discrete cooling holes 63 in the burner seal 6 are configured such that an (air) flow from the combustion chamber head 7 is guided between the fuel nozzle 2 and burner seal 6 by means of the inlet lip 61, and then continues radially outward from the inside of the burner seal 6 to its outside. The flow is then guided from behind onto the flow guidance hopper 62 so that the flow guidance hopper 62 is cooled from behind, and the cooling air flow passes between the heat shield 5 and burner seal 6 into the combustion space of the combustion chamber 3.
The aerodynamic design of the burner seal 6 influences all technical attributes of the combustion chamber 3, i.e. in particular the emissions, operability and susceptibility to thermoacoustic excitation. In configurations according to
A spark plug 8 is provided in the region of a respective fuel nozzle 2 in sectors SK numbered “6” and “10” along the circumference, and hence at an angle of 120° and 210° viewed starting from a top dead centre TDC. The identically formed burner seals 6, each with a flow guidance hopper 62, thus constitute the best possible compromise for guiding the fuel-air mixture favourably from the respective fuel nozzle 2 even in the region of sectors SK numbered “6” and “10” at which a spark plug 8 is present.
In the context of the proposed invention, it is now proposed that two different types of heat shield 5 and 5′, and/or at least two different types of burner seal 6 and 6′, are provided along the circumferential direction U. By using different types, the heat shield and/or burner seal may be adapted locally to different environmental conditions and/or circumstances. Thus unidentically formed heat shields 5 and/or burner seals 6 are provided along the circumferential direction U.
With reference to
According to the depiction of
For an odd number N of sectors SK and also an odd number N of fuel nozzles 2, accordingly the burner seal on the vertical running through the top dead centre TDC is a burner seal 6′ of the second type. For an even number N of sectors SK and hence fuel nozzles 2, the burner seal is a burner seal 6′ of the second type which lies to the right or left of the top dead centre TDC, i.e. in the exemplary embodiment shown, the sector SK of
Alternatively, said sectors SK arranged next to each other along a circular path K may also, instead or in addition to different burner seals 6′, be fitted with heat shields 5′ with an alternative heat shield geometry. In particular in the sectors SK to which a spark plug 8 is assigned, thus a heat shield 5′ of geometrically different design may be provided. In the other sectors SK however, in each case (by sector) a single heat shield 5 of a first type or a heat shield 5 of the first type extending as a ring segment (and spanning several sectors SK) is present.
Via the proposed use of at least two different types of heat shield 5, 5′ and/or at least two different types of burner seal 6, 6′ along the circumferential direction U of the combustion chamber 3, here configured as a ring, measures may be taken which are adapted to the local circumstances and locally vary the attributes of the combustion chamber 3, without having to significantly change the overall configuration of the combustion chamber 3. This may be advantageous generally, and in particular in view of the emissions, operability and susceptibility to thermoacoustic excitation at the combustion chamber head 7 and combustion chamber 3.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 216 807.5 | Sep 2018 | DE | national |
