Patent Application
20250198616
The invention relates to a nozzle assembly for a combustion chamber of an engine, having at least one nozzle for injecting gaseous fuel, in particular hydrogen, into a combustion space of the combustion chamber, wherein the nozzle comprises a nozzle main body, which extends along a nozzle longitudinal axis and has a nozzle head, and a nozzle bracket, which is connected to the nozzle main body and has at least one fuel feed line.
Nozzle assemblies for combustion chambers of engines are well known in a wide variety of embodiments. Hitherto conventional nozzles of such nozzle assemblies have focused on the injection of fuels where, in particular in the case of gaseous fuels, mixing of the fuel with air takes place already within the nozzle, in order to thus generate a combustible fuel-air mixture directly downstream of the nozzle end. By contrast, in applications involving operation with liquid fuels such as kerosene or diesel, the air flow through the nozzle is commonly used to atomize (or at least assist the atomization of) the fuels to form sprays within the nozzle or directly downstream thereof. Typically, in both of the aforementioned approaches, the air that is to be admixed has swirl imparted to it already within the nozzle, such that a swirling fuel-air flow with turbulence and recirculation, which is considered to be advantageous for combustion, is created downstream of the nozzle end.
Various such nozzle assemblies are presented in various embodiments in documents U.S. Pat. No. 4,842,509 A, DE 10 62 873 A, GB 2 593 123 A, U.S. Pat. Nos. 5,117,637 A, 4,483,138 A, DE 103 14 941 A1, U.S. Pat. No. 9,488,108 B2 and U.S. Pat. No. 5,636,511 A. For example, in the latter case, an ignition apparatus is arranged coaxially in a central pipe, said ignition apparatus having a ceramic body onto which a hardened platinum wire is wound in the form of a coil. Fuel and air are mixed in the central pipe, wherein openings for the feed of air are formed into the surrounding wall of the central pipe around the ignition apparatus, said air being fed via an annular channel formed by means of an outer coaxial pipe.
More recently, concepts for aircraft engines have increasingly been developed in which the engine is operated partially or entirely with hydrogen or other fuels that are to be injected in gaseous form, as is envisaged for example in U.S. Pat. No. 4,713,938 A1 for a gas turbine for power generation. However, if it is then intended to operate an engine for example with hydrogen instead of kerosene or diesel whilst maintaining the same design as far as possible, a different injection configuration is necessary, because the fuel is introduced into the combustion space in gaseous form and, for example in the case of hydrogen, also exhibits considerably shorter ignition delay times and higher flame speeds.
Against this background, the nozzle assembly of claim 1 is proposed, which comprises in particular a nozzle for injecting hydrogen into the combustion space of a combustion chamber of an engine, but which is also suitable for the injection of other fuels, in particular gaseous fuels.
Here, a proposed nozzle assembly comprises a nozzle having a nozzle main body, which comprises a central fuel pipe extending along the nozzle longitudinal axis. Also provided on the nozzle head are at least two radially mutually spaced air-guiding ducts which each have at least one air outlet opening, such that a central fuel outlet opening of the fuel pipe, and, radially further to the outside, the at least two outlet openings of the two air-guiding ducts, are formed at the nozzle end.
Via air-guiding ducts, air that is intended for mixing with the fuel discharged from the fuel outlet opening can be introduced into the combustion space. Thus, on the nozzle head, there are provided at least two air-guiding ducts which are situated radially further to the outside than the inner or central fuel pipe.
The fuel pipe may protrude with its fuel outlet opening axially, with respect to the nozzle longitudinal axis, beyond the air outlet openings of the air-guiding ducts. Thus, in a flow direction which is defined by the fuel pipe and along which the fuel is conducted within the nozzle main body, the fuel outlet opening lies at least exactly at the same level as, or further downstream than, the air outlet openings of the air-guiding ducts. In particular, in this context, provision may be made whereby the fuel outlet opening is arranged furthest downstream, that is to say each air outlet opening is set back axially, with respect to the nozzle longitudinal axis, in relation to the fuel outlet opening of the fuel pipe. In this way, fuel can be injected into the combustion space further downstream than air via the air-guiding ducts situated radially to the outside. This assists in achieving that the release of heat owing to combustion of the mixture of fuel and air that is created downstream of the nozzle does not place a critical thermal load on the nozzle.
Furthermore, the air that has been caused to flow in via the at least two air-guiding ducts serves to form an air-rich zone in a front region of the combustion chamber around the nozzle end (a so-called outer recirculation zone). The nozzle and a combustion chamber wall, surrounding the nozzle, of the combustion chamber can thus be thermally protected from the combustion zone. Air outlet openings of the different air-guiding ducts may each be in the form of an annular gap, in particular a circular annular gap.
In principle, the at least two radially mutually spaced air-guiding ducts of the nozzle head may supply air flows with different air flow rates, different swirl configurations and in particular also different flow speeds. For this purpose, an outer air outlet opening of a radially outermost air-guiding duct of the at least two air-guiding ducts may have a larger cross-sectional area than an inner air outlet opening of an inner air-guiding duct of the at least two air-guiding ducts, which inner air-guiding duct extends on the nozzle head between the radially outermost air-guiding duct and a portion of the fuel pipe. For example, provision is made whereby an outer air outlet opening of a radially outermost air-guiding duct of the at least two air-guiding ducts has a cross-sectional area (through which air flows during the operation of the combustion chamber or of the engine) which is larger than that of an inner air outlet opening of an inner air-guiding duct of the at least two air-guiding ducts by at least a factor of 2, 4 or 6.
The inner air-guiding duct is provided so as to extend on the nozzle head between the radially outermost air-guiding duct and a portion of the fuel pipe. For example, an air flow supplied via the radially inner air-guiding duct exhibits higher axial momentum and reduced swirl in relation to the outer air-guiding duct, or no swirl. In this context, provision is consequently made for the radially inner air-guiding duct to be designed and provided to supply a non-swirling air flow into the combustion space. Alternatively, whilst the radially inner air-guiding duct may be designed and provided to supply a swirling air flow into the combustion space, the swirl of the air flow from the inner air-guiding duct is configured to be reduced in relation to the swirl of the air flow which (during the operation of the combustion chamber) flows into the combustion space via the radially outer or outermost air-guiding duct. Therefore, although it is not imperative that a swirling air flow can be generated by means of the radially inner air-guiding duct, this is however also possible. Imparting swirl may be advantageous for example with regard to the stability characteristics of the combustor, the flame shape and/or flame position, the rate of pollutant formation, and the thermal load on the nozzle. In particular, the air-guiding ducts may then be designed such that the air flow from the inner air-guiding duct exhibits a swirl that is reduced by a defined amount, for example by more than 50% or by more than 60%, in relation to a swirl of the air flow from the outer air-guiding duct. It is thus for example the case that the air flow from the radially inner air-guiding duct remains predominantly tangential with respect to the inflow of the fuel from the fuel pipe, whilst having at least a greater axial component than an airflow from the outer air-guiding duct. The air flow from the radially inner air-guiding duct that is adjacent to the fuel pipe thus assists in relocating the zones of chemical combustion reactions as far as possible into the combustion space.
In one design variant, the radially outermost air-guiding duct, which has the larger cross section through which flow passes, is thus provided in particular for supplying a swirling air flow into the combustion space. In this way, at the nozzle end, an air flow can be generated which ensheathes the fuel flow, draws it apart radially, and thus creates, downstream of the nozzle end, a recirculation zone in which air and fuel mix and which then forms a swirl-stabilized recirculating combustion zone. The air from the air-guiding channels, which air ensheathes the combustion zone, furthermore provides an air-rich zone in a front region of the combustion chamber around the nozzle (a so-called outer recirculation zone). The nozzle and a combustion chamber wall of the combustion chamber can thus be thermally protected from the combustion zone.
For the formation of an effective recirculation zone, it can furthermore be advantageous if, as discussed, the air flow that is introduced into the combustion space via the outermost air-guiding duct exhibits swirl whilst the air flow from the inner air-guiding duct does not exhibit swirl, or the air flow that is introduced into the combustion space via the outermost air-guiding duct exhibits at least increased swirl in relation to the air flow from the inner air-guiding duct. For example, for this purpose, one or more axial swirl-imparting means or radial swirl-imparting means are provided at least in a radially outermost air-guiding duct of the at least two air-guiding ducts.
To provide an adequate air flow rate, in particular for an outer recirculation zone as discussed above, via the nozzle, one or more radially inwardly pointing inlet lips may be provided at least at a radially outermost air-guiding duct of the at least two air-guiding ducts in order to direct air into the radially outermost air-guiding duct and optionally also into a further air-guiding duct that is situated radially further to the inside. When the nozzle assembly is installed as intended, the one or more inlet lips thus for example also ensure that air, coming from a compressor stage and conducted around the nozzle main body, is conducted radially inward into the radially outermost air-guiding duct, and where applicable also into a further air-guiding duct situated radially further to the inside. The use of inlet lips for one or more air-guiding ducts may be advantageous in particular for a head region of the nozzle, which head region is comparatively thick and thus, under some circumstances, initially obstructs the axial inflow of an adequately high air flow rate into the one or more air-guiding ducts.
In one design variant, a local narrowing of the inner air-guiding duct toward the air outlet opening thereof may be provided. Portions of inner and outer (duct) walls which border the inner air-guiding duct and which are situated opposite one another therefore approach one another in the region of the air outlet opening. Thus, the inner air-guiding duct may for example narrow in the form of a nozzle, whereby an increase of the exit speed of the inflowing air can be achieved. Furthermore, by means of such a narrowing, the air flow can be diverted radially inward, that is to say in the direction of the nozzle longitudinal axis L.
Within the central fuel pipe, there may be provided a centrally arranged flow body, along the outer lateral surface of which fuel that is fed to the fuel pipe can flow in the direction of a fuel outlet opening of the fuel pipe, via which fuel outlet opening the fuel can be introduced into the combustion space. Such a central flow body may in this case be provided in combination with the at least two air-guiding ducts. In principle, however, the use of such a central flow body may also be advantageous in the case of other designs of a nozzle head having a central fuel pipe, for example in combination with only one surrounding coaxial air-guiding duct.
Fuel may flow axially around the centrally arranged flow body, which thus serves to homogenize the fuel flow within the fuel pipe and/or influence the flow direction of the fuel at the fuel outlet opening. In the fuel pipe, fuel fed via at least one fuel feed line in a nozzle bracket of the nozzle can consequently be conducted within the nozzle main body to the fuel outlet opening of the fuel pipe, which is co-defined by an end of the flow body. By means of the (downstream) end of the flow body, the fuel can be injected in particular with a radially outwardly pointing flow component into the combustion space, and/or can positively influence a flow field in the combustion space.
In principle, one end of a flow body provided within the fuel pipe may extend as far as the nozzle end, and thus in particular as far as the fuel outlet opening. For example, at the nozzle end, the flow body may protrude axially beyond an edge, situated radially further to the outside, of the fuel outlet opening, that is to say may project axially at least slightly beyond the edge of the fuel outlet opening. In the case of an axially protruding flow body, provision is for example made for the flow body to project to an extent that amounts to 5% or 10% of the diameter of the central fuel pipe.
In combination with the flow body, one advantageous refinement in conjunction with the central injection of gaseous fuel, namely hydrogen, into the combustion space consists in that an ignition plug is integrated into the fuel pipe, in particular into the flow body, such that the front-side ignition portion of said ignition plug faces toward the combustion chamber. In this way, through the use of an advantageously small ignition plug that can be operated with little expenditure of energy, fine tuning of the fuel flow that is introduced into the combustion space can be achieved, in coordination with optimum ignition conditions.
In an advantageous further embodiment, provision is made for the ignition plug to be received in a central cavity of the flow body. This results in a defined, precise installation process, wherein the cavity in the flow body may be formed for example by a central bore that is formed into the flow body coaxially with respect to the longitudinal axis, for example a blind bore that is open at a front side.
It is also advantageous here that a cable connector for the electrical actuation of the ignition plug is led through the flow body, for example a leadthrough formed on the rear side of the cavity, and optionally through a bearing element, in particular supporting strut, of a bearing structure that holds the flow body in the fuel pipe, and through the nozzle bracket. The ignition plug is installed, and the cable is routed, in leak-tight fashion.
For optimized setting of the fuel flow into the combustion space and of the ignition conditions, provision is advantageously made whereby the flow body that is of blunt form in the direction of the combustion chamber, the region of the fuel outlet opening, and the region of at least one air outlet opening of at least one air-guiding duct that is arranged in particular in the nozzle body, are designed and coordinated with one another such that the feed of air and the feed of gas into the combustion chamber lead to a recirculation of the gas-air mixture toward the ignition portion of the ignition plug.
The installation of the ignition plug in the stated combination with the flow body is based on the consideration that the central injection of the gaseous fuel, in particular hydrogen, has the effect that only little gas-air mixture is distributed outward in the direction of the combustion chamber wall, in particular in operating states with low air mass flow rates and low air speeds, for example for the starting of the engine. However, the ignition plug for igniting the gas-air mixture is conventionally positioned on the combustion chamber wall. This means that ignition is possible only when a suitable quantity of gas-air mixture is present. This can have the effect that a large quantity of ignitable mixture is already present in the combustion chamber before ignition occurs. This can lead to a deflagration. The solution according to the invention specified here results in the ignition device being incorporated, in a manner which is advantageous for optimum ignition conditions, in the aforementioned structure of the nozzle assembly with central injection of the gaseous fuel, in particular hydrogen.
An end of the flow body may define a flow direction for the fuel that is to be injected into the combustion space. For example, for this purpose, the flow body may have at its end a guide element by means of which fuel that emerges at the fuel outlet opening is directed outward radially with respect to the nozzle longitudinal axis. For example, at the end of the flow body, the guide element is formed by a radial widening of the flow body. Here, the injection of fuel into the combustion space with a radially outwardly pointing flow component can influence the properties, such as shape and size, of the flow field of a recirculation zone that forms downstream of the nozzle end, which may be advantageous in particular in the case of gaseous fuel, and in particular hydrogen, with regard to flame stability and relatively low combustion temperatures in the immediate vicinity of the nozzle.
Furthermore, a targeted acceleration of the fuel flow into the combustion space may be achieved by way of a narrowing at the end of the fuel pipe at the fuel outlet opening, which is implemented by way of that end of the flow body which faces toward the combustion space.
In principle, the flow body may be of pin-like or conical form.
Alternatively or additionally, the flow body is of symmetrical form, in particular rotationally symmetrical form, with respect to to the nozzle longitudinal axis, and/or is formed with a blunt, centrally arranged end face that faces toward the combustion space. A blunt, centrally arranged end face on an end of the flow body may for example assist the formation of an inner recirculation zone with a relatively high fuel concentration during the operation of the combustion chamber or engine. Such an inner recirculation zone may however be associated with low combustion temperatures in the vicinity of the nozzle and thus immediately downstream of the nozzle end.
The blunt end face may in principle—depending on the desired flow conditions—be substantially planar, (slightly) convex, or (slightly) concave.
In principle, the flow body may have an upstream end with a convex curvature, which upstream end may also be aerodynamically shaped and is axially spaced from an end wall of the nozzle or from a rear wall of the fuel pipe. In principle, however, some other aerodynamically favorable shape may be provided for the upstream end. For example, the end may be hemispherical, conical (optionally with a truncated or rounded cone tip), ogival or ovoid. Depending in particular on the design of the feed reservoir, it is however also possible, in design variants of the proposed solution, for the flow body to be connected to an end wall of the nozzle or a rear wall of the fuel pipe. The flow body then extends away from the end wall or the rear wall along the nozzle longitudinal axis, and is therefore not axially spaced from the end wall or the rear wall. Whereas, with an axial spacing of the flow body, the flow body has an upstream end, which is impinged on axially by fuel, within the fuel pipe, this is not the case with a flow body that is connected to the end wall or rear wall. Depending on the design and boundary conditions, one or the other form of the flow body may be advantageous, for example with regard to an achievable thickness of the nozzle main body in a head region of the nozzle main body.
If the flow body is not connected to an end wall of the nozzle or to a rear wall of the fuel pipe and runs centrally within the fuel pipe along the nozzle longitudinal axis as far as the fuel outlet opening, then the flow body typically extends over a major part of the length, measured along the nozzle longitudinal axis, of the nozzle main body that has the fuel pipe, for example over at least 85% of said length.
In one design variant, it is also possible for two flow bodies that are mutually spaced axially with respect to the nozzle longitudinal axis to be provided within the fuel pipe. In such a design variant, a pipe portion of the fuel pipe through which fuel can flow over the entire cross section is consequently present centrally between the two flow bodies. For example, a first, upstream flow body is of pin-like form, whereas a further flow body that is provided downstream in the region of the fuel outlet opening is of conical or other aerodynamically favourable form, for example hemispherical, conical (optionally with a truncated or rounded cone tip), ogival or ovoid.
On its outer lateral surface around which flow passes axially during the operation of the combustion chamber, the flow body may comprise a plurality of (at least two) protruding portions. These protruding portions may serve firstly for intensifying a transfer of heat between the material of the flow body, which typically consists of metal, and the fuel, which is relatively cool in particular during the operation of the combustion chamber. If the flow body extends as far as the fuel outlet opening, it is exposed to relatively high temperatures at least at the side facing toward the combustion space, such that the injected fuel can also be used in the region of the flow body for cooling purposes, in particular if the fuel to be injected is hydrogen. The protruding portions on the outer lateral surface may furthermore targetedly serve for influencing the fuel flow within the fuel pipe. For example, the protruding portions are formed by ribs, ridges, pins, studs or fins. Here, the protruding portions may be distributed uniformly on the outer lateral surface around which flow passes axially. In particular, the protruding portions may be distributed over the entire outer lateral surface, or else only in a limited region of the lateral surface (for example in the region of the fuel outlet opening).
In one possible refinement, the protruding portions are arranged on the outer lateral surface such that, by means of said ribs, any swirl that has already been intentionally imparted to the fuel flow is not counteracted, or such a swirl is optionally even assisted. In particular, the protruding portions may be designed and provided to locally influence, and optionally intensify, the swirl. For example, the protruding portions on the lateral surface are of obliquely inclined and/or helical form for this purpose.
Alternatively or in addition, on its outer lateral surface around which flow passes axially, the flow body may comprise a plurality of depressions, for example in the form of bores and/or indentations. Such structures that change the surface area of the flow body may also serve for intensifying the transfer of heat from the flow body to the fuel.
In principle, an end of the fuel pipe in the region of the fuel outlet opening may be designed in a variety of ways. Since it is to be expected when using fuel which exhibits very fast reaction kinetics, such as hydrogen, that a flame will become anchored in the combustion space relatively close to the nozzle, it is also possible in principle that, at certain operating points of the engine, an anchoring point of the combustion zone lies directly at an outflow edge of the fuel pipe. The end of the fuel pipe should therefore be designed such that, firstly, the release of heat in the combustion space in the immediate vicinity of the end of the fuel pipe is kept low, and secondly, adequate robustness with respect to the introduction of heat from the combustion zone is ensured. In this context, it may for example be advantageous for the fuel pipe to be designed, at the fuel outlet opening, with an edge which encircles the nozzle longitudinal axis and which has a radially outwardly inclined bevel.
In one refinement, the bevel may taper to a point, or transition into a blunt end geometry, at an axial end of the fuel pipe. If the bevel tapers to a point, and if the edge of the fuel pipe separates the fuel flow from an air flow of the adjacent air-guiding duct, a bevel which tapers to a point may have the advantage that the fuel flow and the air flow impinge on one another tangentially. A high outflow speed of the two flows from the nozzle can hereby be maintained. The release of heat in the region of the aforementioned anchoring point thus remains low. A disadvantage here may however be that heat that is introduced during the operation of the combustion chamber in the region of an end that tapers to a point cannot be transported away quickly enough by heat conduction within the fuel pipe, and there is therefore the risk of thermal overloading of the end that tapers to a point. Such thermal overloading can however be counteracted through corresponding influencing of the flow, for example by way of the tangential impingement of fuel and air on one another and the resulting effects on the combustion zone, specifically the anchoring point of the flame and the local release of heat at the anchoring point.
If the bevel transitions into a blunt end geometry of the fuel pipe, then under certain circumstances, a small “stagnation zone” or a small (inner) recirculation zone forms directly downstream of the nozzle end, in which zone the fuel and the inflowing air can mix such that, during the operation of the combustion chamber, a locally relatively intense release of heat occurs here as a result of combustion. However, in the case of a blunt end geometry, the heat that is introduced into the pipe edge of the fuel pipe can be transported away more effectively by heat conduction, whereby the risk of thermal overloading can be more easily avoided.
In principle, the central fuel pipe may be sealed off with respect to an inflow of air. In this way, the fuel can be introduced into the combustion space, without mixing with air, via the fuel pipe that extends centrally in the nozzle main body along the nozzle longitudinal axis. When the nozzle assembly has been installed as intended in an engine, the nozzle-side fuel pipe is thus sealed against an inflow of air from a compressor stage of the engine, in particular at an upstream end of the nozzle main body. Therefore, in a nozzle of a proposed nozzle assembly, no premixing of fuel and air takes place within the nozzle. This is advantageous in particular with regard to gaseous fuel to be injected, in particular highly flammable hydrogen, since the risk of flashback or premature autoignition of the fuel that is to be injected can hereby be reduced. Therefore, in a nozzle of a proposed nozzle assembly, the fuel to be injected is mixed with air for the first time downstream of the nozzle end. The fuel is not premixed with air within the nozzle, and therefore the fuel emerges from the nozzle end initially in unmixed form, and it is only downstream of the nozzle end that mixing with (combustion or mixing) air takes place.
In one design variant, the nozzle comprises a feed reservoir which is connected to the fuel feed line and to which fuel can be fed from the fuel feed line and from which fuel can be fed to the fuel pipe. The feed reservoir is thus fluidically connected both to the fuel feed line and to the fuel pipe, so that the fuel coming from the fuel feed line can flow into the fuel pipe via the feed reservoir. The feed reservoir is formed for example as a cavity in the nozzle bracket or in the nozzle main body, for example as a cavity of annular cross section, in particular a circular annular cavity, or a cavity of circular cross section. The feed reservoir can assist in achieving that the fuel is introduced into the fuel pipe as uniformly as possible, for example by virtue of fuel flowing in from the feed reservoir via a plurality of specifically arranged and for example uniformly distributed passage openings.
For example, the feed reservoir is provided in a region of the nozzle which is bordered by an end wall situated upstream with respect to a flow direction defined by the fuel pipe, along which flow direction the fuel is guided within the nozzle main body to the nozzle end. When the nozzle assembly has been installed as intended in an engine, such an end wall faces away from the combustion space of the combustion chamber. For example, such an upstream feed reservoir is then formed in a head region, which is connected to the nozzle bracket, of the nozzle main body. The fuel that is introduced from the feed reservoir into the fuel pipe can thus be conducted in the fuel pipe to the fuel outlet opening over a relatively large part (more than 60%) of the length of the nozzle main body as measured along the nozzle longitudinal axis. The fuel can thus be conducted to the nozzle end in targeted fashion, for example with homogenization of the fuel flow, and optionally with targeted swirling of the fuel flow.
At least one passage opening via which fuel can flow from the feed reservoir into the fuel pipe may for example be configured for a radially inward inflow of fuel into a first pipe portion of the fuel pipe. A substantially radially inwardly directed flow into the first pipe portion of the fuel pipe is thus made possible via the at least one passage opening. Accordingly, one or more fluidic connections provided by one or more passage openings are provided between the feed reservoir and the fuel pipe, via which fluidic connections fuel can flow from the feed reservoir substantially radially inward into the first pipe portion and thus into the fuel pipe.
As an alternative to a substantially radial inflow of fuel from the feed reservoir into the fuel pipe, it is also possible for at least one passage opening to be configured for an inflow of fuel into a first pipe portion of the fuel pipe in a substantially axial direction. For example, the at least one passage opening may extend through a rear wall of the fuel pipe, which rear wall runs substantially or exactly perpendicularly to the nozzle longitudinal axis and borders (delimits) the first pipe portion (upstream), or through a partition that separates the feed reservoir from the first pipe portion.
As already discussed in the introduction, the proposed solution is particularly suitable for the injection of different types of fuel. However, with regard specifically to the injection of gaseous fuel and in particular hydrogen, the central feed of fuel, which is protected against mixing with air, via a nozzle-side fuel pipe has particular advantages.
With nozzle assemblies of the aforementioned design, it is advantageously possible to construct an annular combustion chamber having at least one nozzle assembly, in particular also according to any one of claims 9 to 14, in a combustion chamber ring. Advantageous refinements here consist in that an ignition plug is integrated into at least one nozzle assembly, in particular at the highest point of the combustion chamber ring, or into a plurality of nozzle assemblies or into all nozzle assemblies.
The proposed solution also comprises an engine having at least one design variant of a proposed nozzle assembly. A proposed nozzle assembly may however self-evidently also be used in a (static) gas turbine.
The appended figures illustrate, by way of example, possible design variants of the proposed solution.
In the figures:
The air that is conveyed into the primary flow duct by means of the compressor V enters the combustion chamber assembly BK of the core engine, in which thermal energy for driving the turbine TT is generated by combustion of fuel with air that flows in from the compressor V. For this purpose, the turbine TT has a high-pressure turbine 113, an (optional) medium-pressure turbine 114 and a low-pressure turbine 115. Here, the turbine TT drives the rotor shafts S1, S2 and S3 and thus the medium-pressure and high-pressure compressors and the fan F in order to generate thrust by means of the air that is conveyed into the bypass duct B. Both the air from the bypass duct B and the exhaust gas-air mixture from the primary flow duct of the core engine flow out via an outlet A at the end of the engine T, and both contribute to the total thrust of the engine. Here, the outlet A commonly has a thrust nozzle and a centrally arranged outlet cone C. Also widely used are designs in which, upstream of the exit through the outlet A, the air from the bypass duct and the exhaust-gas-laden air from the primary flow duct are merged to form one single airflow. To achieve this merging, lobed mixers are commonly used, which are arranged within the engine upstream of a common thrust nozzle and the outlet A (not shown).
Conventional nozzles D for an engine T are typically designed for injecting liquid fuel, such as kerosene or diesel, and for this purpose have a central first air-guiding duct, at least one further, second air-guiding duct situated radially to the outside, and a fuel-guiding duct that is provided between the two air-guiding ducts. Fuel that emerges at a fuel outlet opening of such a fuel-guiding duct is then mixed already at the nozzle with air from the first central air-guiding duct and optionally also with the air from the air-guiding duct situated radially further to the outside, such that a fuel-air mixture is provided at a nozzle end of the nozzle D.
Such a configuration of a nozzle D is disadvantageous under certain circumstances, in particular for fuel that is to be injected into a combustion space 1030 of the combustion chamber 1031 in gaseous form, in particular hydrogen. This is remedied by a nozzle assembly having a nozzle D according to the proposed solution, different design variants of which are illustrated in
Here, provision is made in each case whereby, on a nozzle main body DR of the nozzle D, a central fuel pipe 3 is provided which extends along a nozzle longitudinal axis L and which is sealed off to prevent an inflow of air and via which fuel can be conducted within the nozzle main body DR to a fuel outlet opening 33 of the fuel pipe 3, which fuel outlet opening is provided at a nozzle end of the nozzle D. From the fuel outlet opening 33, the fuel can then be introduced into the combustion space 1030 in order to be mixed with air for the first time.
In a first design variant according to
At the end face averted from the combustion space 1030, the fuel pipe 3 is sealed off, by means of a continuous end wall DW of the nozzle D, with respect to air coming from the compressor V of the engine T. Fuel that is fed from the fuel feed line 1 into the fuel pipe 3 is furthermore also conveyed within the nozzle main body DR to the nozzle end of the nozzle D in unmixed form, that is to say without being mixed with air. Here, the fuel that is fed radially from the annular chamber 2A into the fuel pipe 3 flows in an axial direction from the first pipe portion 3A, which defines a prechamber within the fuel pipe 3, into a second pipe portion 3B that has a flow body 30 arranged centrally within the fuel pipe 3. The fuel flows along said flow body 30 to the fuel outlet opening 33 of the fuel pipe 3 at the end face of the nozzle.
In the present case, the central flow body 30 is of pin-like form, thus defining the second pipe portion 3B which in the present case is of annular cross section (and thus defining an annular space axially adjoining the first pipe portion 3A), in which second pipe portion the fuel is conducted along the nozzle longitudinal axis L to the fuel outlet opening 33. By means of the flow body 30, the fuel flow can be homogenized over the cross section. The flow body 30 furthermore has, at a downstream end 301, a guide collar 3010 which serves as a guide element and by means of which the nozzle outlet opening 33 is narrowed in order to accelerate the emerging fuel flow. The emerging fuel flow is furthermore diverted radially outward by means of the guide collar 3010.
The fuel thus injected is mixed with air for the first time within the combustion space 1030 downstream of the fuel outlet opening 33, said air being introduced into the combustion space 1030 via two air-guiding ducts 4 and 5 on a nozzle head DK of the nozzle D. Here, a first air-guiding duct 4 is formed as a relatively narrow annular gap on the nozzle head DK radially to the outside of the central fuel pipe 3. The further air-guiding duct 5 is provided radially further to the outside of this, as a radially outermost air-guiding duct, on the nozzle head DK. Air outlet openings of the two air-guiding ducts 4, 5 are in this case axially set back in relation to the fuel outlet opening 33, such that the end of the fuel pipe 3 and thus the fuel outlet opening 33 protrude axially, with respect to the flow direction of the fuel defined by the fuel pipe 3, beyond the air outlet openings of the two air-guiding ducts 4 and 5 (in this regard, see also
In the design variant of
A swirling fuel flow can likewise be generated by axial fuel-swirling means 31 within the second pipe portion 3B of the fuel pipe 3, which swirling fuel flow enters the combustion space 1030 at the fuel outlet opening 33. Consequently, in the design variant of
The central, sealed-off guidance of the fuel in the fuel pipe 3 having the flow body 30 is advantageous in particular for highly flammable hydrogen, in order to avoid in-stances of flashback and premature autoignition in the vicinity of the nozzle. The airflows supplied via the air-guiding ducts 4 and 5 furthermore ensure advantageous formation of recirculation zones in the combustion space 1030 downstream of the nozzle D.
The first, upstream flow body 30A is in the present case furthermore designed in the manner of a hub journal in the region of the fuel distributor 31 in the fuel pipe. The blunt and in the present case substantially planar end face 301S of the downstream, second flow body 30B faces toward the combustion space 1030. Such a blunt end face 301S is also provided at the downstream end 301 of the continuous flow body 30 in
As can be seen from
This is assisted in particular by means of the inner and outer air-guiding ducts 4 and 5 of the nozzle D, which adjoin the nozzle head DK of the nozzle D to the outside in the radial direction. Thus, air with relatively high axial momentum and little swirl is injected into the combustion space 1030 from the inner air outlet opening, formed as a narrow annular gap, of the radially inner air-guiding duct 4. On the other hand, the air flow from the air outlet opening of the radially outermost air-guiding duct 5, which air outlet opening is likewise in the form of an annular gap (and has a larger cross-sectional area through which flow passes), exhibits an intense swirl. As a result, the air flow thus generated ensheathes the central fuel flow, draws it apart radially, and thus creates, downstream of the nozzle D, a recirculation zone in which air and fuel mix and which then forms the swirl-stabilized recirculating combustion zone VBZ.
The air flow that ensheathes the combustion zone VBZ furthermore generates an air-rich zone in the front region of the combustion chamber 103 around the nozzle end of the nozzle D, and this is denoted in
Different designs of the fuel pipe 3, of the air-guiding ducts 4, 5 and in particular of the flow body 30 or 30B within the fuel pipe 3 may be selected here in order to influence the flow conditions without departing from the proposed solution, for example with regard to the design of the combustion chamber 103, the specification of different operating parameters of the engine T (for example with regard to transient operating states, for example during acceleration and deceleration of the engine T), the setting of particular flame shapes and flame positions, the reduction of pollutants formed, for example of nitrogen oxides, and the reduction of thermal loads placed on parts of the nozzle D and/or on the combustion chamber 103.
For example, in the design variant of
In the design variant of
As shown in
As an ignition plug 20, use may be made of a small, compact design, for example with a plug length LK in the range between 20 mm and 40 mm, for example between 25 mm and 35 mm (typically of approximately 28 mm) and a diameter of between approximately 6 mm and 12 mm, wherein a clear inner diameter DO of the cavity is chosen in coordination with the ignition plug 20 and is for example 8 mm, and a mean diameter D1 at the thread root is for example 9 mm, wherein an outer diameter D2 of the nozzle head DK at the outside around the (in this case only one) air duct 4 is for example 30 mm to 50 mm, for example approximately 36 mm. Here, too, the flow body 30 may be equipped, in the region of the fuel outlet opening 33, with differently designed gas outlet ducts 28, as illustrated for example in
The fuel is thus introduced into the combustion space 1030 through the central fuel pipe 3. In order to optimize and fine-tune the fuel flow that is introduced into the combustion space 1030, the fuel pipe 3 may be equipped, as illustrated, with a combination of different structures in order to form a suitable fuel flow, for example also by means of an axial fuel-swirling means that imparts rotary momentum to the fuel flow. As a hub of the axial fuel-swirling means, use is made, for example, of a body which is rotationally symmetrical as far as into the region of the outlet plane of the fuel pipe 3 (and optionally a few mm beyond this) and which may be formed as an elongation of the hub of the axial fuel-swirling means, and which is provided with additional supporting struts 303 at the end of the central fuel pipe 3 or else with no such struts, as has been discussed for example with reference to
The ignition plug 20 that is inserted into the cavity 27 in the central flow body 30 is sealed off with respect to the surroundings. As can be seen for example from
The ignition plug is suitably axially seated in the flow body 30 so as to achieve optimized interaction with the gaseous fuel and, for ignition purposes, with the gas-air mixture. The in particular blunt flow body 30, the feed of air via the at least one air duct 4, 5, and the feed of the gaseous fuel, in particular hydrogen, cause the gas-air mixture to be recirculated toward the front ignition portion or the tip of the ignition plug 20. This is optimally assisted by the illustrated design, also in coordination with the installation conditions.
In the case of annular combustion chamber having a number of fuel nozzles arranged in a combustion chamber ring R, any desired number of nozzles or nozzle assemblies of the aforementioned construction may be equipped with an ignition plug 20, for example with only one, in particular at or close to the highest point of the combustion chamber 103 (because gas is lighter than air), or with several, for example distributed uniformly over the circumference, arranged in every second nozzle assembly or grouped in the nozzle assemblies, or integrated into all nozzle assemblies.
With regard to the manufacture of a fuel pipe 3 having a central flow body 30 that is intended to have no supporting struts 303 in the region of its end 301 facing toward the combustion space 1030,
Building on the design variant of
Irrespective of whether a single, continuous flow body 30 or two axially mutually offset flow bodies 30A, 30B are used within the fuel pipe 3, provision is made in each of the illustrated design variants whereby the particular flow body 30 or 30B provided in the region of the fuel outlet opening 33 causes a local narrowing of the fuel outlet opening 33 in order to accelerate the fuel flow as it flows into the combustion space 1030. Then, the particular flow body 30, 30B is correspondingly designed such that an end-side widening of the diameter of the fuel pipe 3 for the purposes of diverting the fuel flow radially outward is at least compensated, or even overcompensated, by a widening of the flow body 30 or 30B toward its end. In this way, an annular gap of the fuel outlet opening 33 narrows toward the nozzle end.
The individual illustrations in
It is furthermore clear from the design variant of
In the design variant of
In the design variant of
Irrespective of whether axial swirl-imparting means 51 or radial swirl-imparting means 52 are used, and also irrespective of whether one or more flow bodies 30 or 30A/30B are used, it is expedient for an axial offset between the individual air outlet openings of the first and second air-guiding ducts 4 and 5 and the fuel outlet opening 33 of the fuel pipe 3 to be provided at the nozzle end of a proposed nozzle D. It is then for example the case that an (outflow) edge of the fuel pipe 3 protrudes axially furthest along the nozzle longitudinal axis L, such that the fuel outlet opening thereof lies in the region of a first virtual (outlet) plane E3 that extends perpendicular to the nozzle longitudinal axis L and lies further downstream than further virtual planes E1 and E2, in which the air outlet openings of the radially outermost air-guiding duct 5 and of the inner air-guiding duct 4 lie. The plane E3 of the central fuel pipe 3 thus projects deepest into the combustion space 1030. The outlet plane E2 of the inner air-guiding duct 4 situated adjacently radially further to the outside is aligned therewith or, as illustrated in
The axial offset of the air outlet and fuel outlet openings may for example make it possible to reduce a thermal load on the components of the nozzle D at the nozzle end. In this way, zones in which fuel and air come into contact with one another, and therefore a release of heat can take place owing to a chemical combustion reaction, are first created further downstream of the nozzle D. Furthermore, the axial offset that is created means that an interaction of the individual flow paths with one another, in particular influencing caused by any swirl that is imparted, can be more finely tuned. This can be advantageous in particular for any adaptation of the stability behavior of the combustor, of the flame shape, of the flame position and of the rate of pollutant formation (with regard to nitrogen oxides in the case of hydrogen), and for a thermal load on the nozzle D and on the combustion chamber 103.
In principle, the end of the central fuel pipe 3 at the combustion space side may be geometrically designed in a variety of ways in the region of the fuel outlet opening 33. However, specifically with regard to a gaseous fuel for injection which exhibits fast reaction kinetics, such as hydrogen, it must be taken into consideration that a flame may become anchored very close to the nozzle end of the nozzle D. In particular, at certain operating points of the engine T, a corresponding anchoring point of the recirculation combustion zone VBZ may lie directly at the outflow edge of the fuel pipe 3. Against this background,
In the design variant of
In order to assist the feed of air into the air ducts 4 and 5 on the nozzle head DK of the nozzle D, one possible refinement according to
The detail views in
It is self-evident that the proposed solution is not limited to the exemplary embodiments described above, and various modifications and improvements can be made without departing from the concepts described here. Any of the features may be used separately or in combination with any other features, unless they are mutually exclusive, and the disclosure extends to and includes all combinations and subcombinations of one or more features which are described here.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 202 937.2 | Mar 2022 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/057208 | 3/21/2023 | WO |
