DE2234589A1 - PRE-EVAPORATION DEVICE FOR LIQUID FUEL - Google Patents

Description

! • ATENTANWKLTE

DR. E. WIEGAND DIPUlNG. W. NiEMANN

DR.M. KÖHLER DlPL-ING. C GERNHARDT 2 23 4 5

MDNCHEN HAMBURG

TELEPHONE: 395314 '2000 HAMBU RG 5Q,

TELEGRAMS: KARPATENT '■ KDNI GSTRASSE 28 12, 7,

W «25 369/72 12 / bl

r *

Societe Nationale d ^f E- £ ude et de Construction de Moteurs d ¹ Aviation »

Paris, France)

Pre-evaporation device for liquids Fuel*

The invention relates to a device for pre-evaporating liquid fuel intended for a combustion device comprising a combustion chamber, a source of liquid fuel and a source of oxygen carrier such as air. The pre-evaporation device comprises in the combustion chamber as a protrusion a hollow or tubular design, which has the general shape of a T and a body which forms the base of the ΐ and is connected to the fuel source and to the oxygen carrier source, and two transverse arms which branch off from the tubular body and each end in an outlet opening which opens into the combustion chamber and at which, during operation, a flow of a mixture of fuel and oxygen carrier emerges , which is at least partially evaporated "

The combustion device under consideration can in particular for a gas turbine engine such as

Turbo reactor be determined.

It has been found that in certain cases the operation of the device, and in particular if the load is low, there are zones of incomplete combustion in the combustion chamber result in such a way that the efficiency in the area of the combustion chamber is deteriorated.

It has also been observed that under the same conditions the arms of the hollow or tubular T-shaped design are sometimes subject to local overheating in such a way that their good behavior in the company is impaired.

In accordance with the present invention, it has been found that the two aforementioned disadvantages may have the same cause or origin have what is not obvious, namely a poor evaporation process in the tubular or hollow version.

It has been found that at low loads, the inside of the tubular design the prevailing temperature, although it may be high under certain special conditions, not always is sufficient for a complete evaporation of the whole entering the tubular design To enable fuel. Part of this fuel thus remains in the form of large ones Drops such that the fuel distribution in the the current flowing through the cross arms is not as regular as when all the fuel evaporates were.

The air-fuel mixture emerging from the tubular design is accordingly not homogeneous, which is aljt explanation for the occurrence of Y9 $ Zones of incomplete combustion, like si, e above mentioned, could serve.

Regarding the local overha ^ tsuiigfii || t to be rememberedj> da | 3 4ig Jiühlffektunj; according to äep

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Evaporation of the fuel in the tubular design originally serves to provide thermal protection of the walls of this tubular design that is immersed in the combustion chamber. It is therefore important for this cooling effect to be effective that all inner surfaces of the tubular Execution of the flow of the air-fuel mixture, which flows through the tubular design, correctly be "moistened". Furthermore, result from the changes in direction, which the current at his Passage in the transverse arms is subjected, especially under the action of centrifugal force a stratification or stratification of this stream. In each arm the big drops of it are still liquid fuel rubbed against one of the walls of the arm while on the on the other side or on the opposite wall there is practically only air. The not "moistened" Walls are thus adequately cooled, which explains the abovementioned local Overheating offers what seems paradoxical at first, since it is a phenomenon that is less Load occurs "

In accordance with the foregoing, it should be noted in particular that the "arch" of the Poor adjacent area is particularly difficult to 'cool'.

The present invention aims generally the. to eliminate the disadvantages in question.

According to the invention, the body of the hollow or tubular design is: i ^ Gestai't ^ near the Arches of the transverse arms of the tubular design are partially blocked by a "thin-walled screen, which is formed from two thin partitions whose, each presents a sharp edge which is against the axis of the body of the tubular design and

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against the corresponding 'sharp edge of the other Partition is directed. The partitions define a scaled-down one between the relevant edges Passage connecting the body of the tubular design to each of the cross arms.

The presence of the thin partitions has two consequences. The first thing is a local one Narrowing of the cross-section of the body of the tubular design and, accordingly, a corresponding one Acceleration of the air flow flowing through the tubular design, which causes the air atomization of the fuel and its intimate mixing with the air is favored. The further consequence is in the fact that at the two sharp edges of the partition walls a mechanical atomization - by impact - of the fuel.

Under the effect of this double atomization, the liquid that is still in the liquid state is distributed Fuel downstream of the membrane in the stream flowing through the tubular design is more homogeneous. All the walls of the arms will accordingly be properly "moistened" or wetted, and out of the tubular Execution, an air-fuel mixture emerges, which has a substantially uniform fuel content Has.

The thermal insulation of the walls is guaranteed in this way, and at the same time the degree of efficiency is increased the combustion chamber improved.

The thin wall panel according to the above Description can be located exactly at the level of the arches of the transverse arms or slightly downstream of these arcs with respect to the direction of flow of the fuel-oxidizer mixture in the Body of the tubular design, ι According to a preferred embodiment, the is applicable in the latter case, the precedence includes

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evaporator-additional passages, soft connect the body of the tubular design to each of the arms. These additional through, gähge begin in the body of the tubular design upstream of the thin-walled screen, and they open into the transverse arms directly in the zone of the arches of the arms. These additional passes can be beneficial be oriented in a direction having a transverse component to the axis of the body of the tubular Represents execution.

A certain proportion of the amount of liquid fuel, which is injected into the body of the tubular design can accordingly cover the area of Wet the arches of the arms of the tubular design directly, which favors the cooling of this area and accordingly the thermal behavior of the tubular design is improved;

According to another preferred embodiment of the invention, each of the thin partition walls is with at least one opening is provided which is oriented in a direction that is parallel to the one component represents the axis of the body of the tubular design. The opening or openings allow lent that a small fraction of the amount of the mixture from oxygen carriers and fuel feeds the vortex zone, which is located downstream of the partition walls forms.

Tests on T-shaped tubular pre-evaporation devices, The throws were partly equipped with partitions and partly not with partitions, made it possible to localize differences To show the temperature of the sheet, whereby the differences can be several 100 °, and although in favor of tubular designs that are provided with such partitions.

The invention is explained below with reference to the drawing, for example.

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Fig. 1 is an axial half-sectional view of a combustion device having T-shaped tubular pre-evaporation devices is equipped.

Fig. 2 is "a partial cross-sectional view according to Line II - II of FIG. 1.

Fig. 5 is a line sectional view on an enlarged scale III - III of Fig. 2, a T-shaped tubular pre-evaporation device known type.

FIG. 4 is a view similar to FIG. 3

a pre-evaporation device according to a first embodiment of the invention.

FIG. 5 is a cross-sectional view taken along line V-V of FIG. 4.

FIG. 6 is a view similar to FIG. 4 of a pre-evaporation device according to FIG a second embodiment of the invention.

In Figs. 1 and 2, the devices for pre-evaporation of liquid fuel are a combustion device for example, a gas turbine engine is designated by 7.

The known combustion device comprises, for example, a combustion chamber with an axis X ¹ - X delimited by an outer lining or wall 1a and by an inner lining or wall 1b which are substantially coaxial. The two claddings 1a, 1b define an annular space in which two walls 2a, 2b, which are arranged essentially coaxially to the two claddings 1a, 1b, delimit an annular flame tube which represents the actual combustion chamber. The combustion chamber is at its upstream part by a

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Ring wall 3 or a dome closed, in the interior of which an annular support structure 4 is arranged. The dome 3 and the ring structure 4 are provided with openings 5 »6, which are ^{evenly distributed around the axis X 1} - X of the combustion chamber. Each opening 6 is in the extension of an opening

5 arranged. A pre-evaporation device 7 is with play along the axis of each of the openings

6 arranged. The combustion chamber is at its upstream part with an oxygen carrier source, for example a compressed air source, which is schematically connected by a line 8 is indicated. The air flows around in the annular spaces, each between the cladding 1a and the Wall 2a, and the cladding 1b and the wall 2b are present, and it occurs in the form of primary air through the openings 5 and in the form of secondary air for distribution and dilution Openings 9a, 9b, 10a, 10b, 11a, 11b into the combustion chamber a. Each pre-evaporation device 7 comprises in a known manner a hollow or tubular one Execution that has a general T-shape and in. the combustion chamber from the opening 6 forms a protrusion. The base of the T is formed by a tubular body 12 leading to the opening 6 runs coaxially and is divided into two transverse arms 13, 14, which form the wings or legs of the T. The cross arms 13, 14 are in the direction bent against the dome 3, and each arm ends in an outlet opening 15 ors. 16 included in the Combustion chamber is directed upstream. The body 12 has an access opening which is connected to a source of liquid fuel, which is shown by a line 17 schematically is.

The opening 6 has a larger cross section

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on than the body 12, so that a sleeve 18 can be arranged around the body 12, which optionally can be connected to the body 12. The sleeve 18 is extended by two branches 19, 20, limit the two ring passages 21, 22 through which a certain proportion of the Primary air is fed directly into the combustion chamber.

During operation, the greater part of the primary air volume occurs at the same time as the liquid fuel into the pre-evaporation device 7, the walls of which are subjected to the action of the flame on their outer surface become such that the fuel evaporates. The mixture of primary air and vaporized fuel emerges essentially axially from the openings 15, 16, namely in the opposite direction to the general direction of flow of the combustion gases, i.e. in a direction in Fig. 1 is indicated by the arrow G. The smaller amount of air that is at 21 around the body 12 enters, serves mainly to provide some thermal insulation for the upstream part of the To ensure evaporation device 7.

The openings 9a-9b allow the entry of two jet groups Fa-Fb, essentially radial and in the opposite direction. These rays meet near the exit opening 15 or 16. Part of their flow rate then flows in the upstream direction of the chamber, so that a vortex zone is formed in the area near the dome 3, around ignition and the start of combustion to facilitate, while the other part according to the flow rate of these jets directly downstream the arrow G flows, for example in the direction of a gas turbine, not shown.

As mentioned above, there is a problem with a combustion device of the type described in FIG

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the thermal protection of the walls of the pre-evaporation devices 7, the high temperatures during operation be subjected to that in the upstream Rule part of the combustion chamber.

This thermal protection is to a certain extent for the upstream part of the pre-evaporation device 7 Extent guaranteed by the presence of a gas layer, which is formed by a part of the amount of air which flows through the passage 21.

In contrast, for the downstream part of the pre-evaporation device, the arms 13, 14 of the T-shape, the walls of which are more exposed to the effect of the heat prevailing in the combustion chamber the only effective protection in a cooling of the walls due to the evaporation of the im Inside the pre-evaporation device 7 existing fuel.

It has also been found that in certain operating states of the combustion device, Local overheating of the arms 13, 14 of the pre-evaporation device occurs particularly with low loads 7, especially in a critical zone near the "arcs" of the arms. This critical zone is designated by the reference numeral 50 in FIG. 3. Fig. 3 shows on an enlarged scale the current ' downstream part of a known T-shaped pre-evaporation device 7th

It has further been found that this Appearance may be accompanied by it being in the upstream part of the combustion chamber Zones incomplete. Form burn.

As already mentioned, it has been found according to the invention that overheating of the pre-evaporation devices 7 and irregular combustion rinr have a common cause, at least at low levels Load, namely an incomplete evaporation

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of the fuel. Part of the fuel remains in the form of large droplets, the movement of which they move is indicated schematically by flow lines 5'I.

As a result of inertia and the effect of centrifugal force, the fuel is still liquid directed against the walls 13a and 14a of the arms 13 and 14 so 'that the walls 13a and 14b are practical not be wetted or moistened. Thus, these walls are insufficiently cooled, and they can experience harmful overheating.

In addition, the flow of the air-fuel mixture, which emerges from the openings "15, 16, not homogeneous, and one of the proportions for this Stroms contains considerably more fuel than the other part fp. The fuel content of the air-fuel mixture is accordingly not uniform in the upstream part of the combustion chamber, which can serve to explain the observed irregularities in the combustion.

4 and 5 is a pre-evaporation device 7 shown, which is designed according to the invention so that the disadvantages described do not occur.

The pre-evaporation device 7 according to FIG. 4 is for beer with two thin partition walls 52 and which extend transversely to the axis Y '- Y of the tubular body 12 and each one present sharp edge 52a or 53a. These edges face each other and determine between them a narrowed passage 54 communicating between the tubular body 12 and each of the Arms 13, 14 represents.

The air flow present in the pre-evaporation device 7 becomes close to the narrowed passage 54 subject to a considerable acceleration

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thrown, which is known to be the pneumatic atomization the liquid fuel and its mixing with the air are favored. Continue to be the large droplets of fuel by impact mechanically atomized at the sharp edges 52a and 53a.

The liquid fuel then enters the arms and 14 in the form of a mist of fine droplets, which are much lighter and, as a result, are less subject to stratification or stratification. The curved surfaces 13b and 14b of the arms 13 *. 14 can accordingly properly wetted or humidified, so that the risk of overheating is considerably reduced or avoided. Finally, the flow f of the air-fuel mixture from the Openings 15 »16, exits, - much more homogeneous than at known pre-evaporation devices of this type, so that the performance of the combustion chamber improves can be. In addition, it has been established that by the distribution that the fuel due to the presence of the thin partitions 52 and 53, its pre-evaporation is accelerated.

The effectiveness of the device according to the invention can be further improved if the Partition walls 52, 53 are provided with small openings 55, 56, which allow a smaller Proportion of the amount of the air-fuel mixture - shown schematically by the rays 57 and 58 directly enters the vortex zone which is formed downstream of the partitions 52, 53, so that the manufacture satisfactory aerodynamic flow conditions is favored.

Fig. 6 shows another embodiment a pre-evaporation device according to the invention, this device is also generally T-shaped.

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The base of the T is formed by a tubular body 12, which is divided into two transverse arms 13, 14 branches, which form the wings or legs of the T. The arms 13, 14 are in the upstream direction of the combustion chamber and each arm terminates in an outlet opening 15 and 16, respectively. The body 12 has an inlet opening 25, which is connected to the source of liquid fuel, schematically represented by an injector 17, and is in communication with the air source.

A sleeve 18, 19 surrounds the tubular body 12 with play, so that an annular channel 21 is formed is that at its upstream part with the air source is in communication and at its downstream part directly into the combustion chamber flows out.

In operation, a certain amount of primary air a ^ occurs simultaneously with the liquid fuel in the pre-evaporation device 7, the walls of which are exposed on their outer surface to the action of the flame in the combustion chamber, so that the fuel evaporates. The mixture of primary air and vaporized fuel exits the openings 15 and 16 substantially axially, as shown by arrows f, in a direction opposite to the general direction of flow of the combustion gases in the combustion chamber. A quantity of primary air & 2 enters the combustion chamber directly through the annular duct 21. This amount ap, which is much smaller than the amount a ^, mainly serves to ensure a certain thermal insulation of the upstream parts of the pre-evaporation device 7.

The arcs of the arms 13 and 14 of the pre-evaporation device 7 are denoted by the reference numeral 13x or 14x designated.

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The body 12 is partially close to the arches 13x and 14x by means of a thin-walled screen or the like blocked, which is formed by two thin partitions 52, 53, each of which has a sharp edge 52a or 53a * These edges are against each other and against the axis Y'-Y of the body 12 directed towards the pre-evaporation device 7 and define a narrowed passage 54 between them, of the body 12 with each of the cross arms 13 and 14 the pre-evaporation device 7 connects.

The air flow passing through the vaporization device 7 becomes narrowed near the Passage 54 subjected to a considerable acceleration, through which the pneumatic atomization the liquid fuel and its mixture with the air are favored. Also, the big ones Fuel drops due to impact on the sharp edges 52a and 53a mechanically atomized.

The liquid fuel then enters the arms 13 and 14 in the form of a mist of fine droplets, which are much lighter and accordingly one Stratification or stratification are much less subject to stratification. The walls of the arms 13 * 14 v / ground on this way completely wetted or moistened with a mixture, which at least some Contains proportion of fuel in the course of evaporation. The risk of overheating these walls is reduced or prevented accordingly. In addition, the flow f of the air-fuel mixture, the emerges from the openings 15 and 16, much more homogeneously than in known pre-evaporation devices of this type, so that the performance of the combustion chamber can be improved.

It has been found that nevertheless in the pre-evaporation device 7 a critical zone is present, which to some extent the cooling

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can withdraw effect that is caused by the evaporation of the fuel in the Air-fuel mixture is contained, which passes through the narrowed passage 54. This zone is formed by the arcs 13x and 14x of the arms 13 and 14 and by those adjacent to these arcs Areas shown or formed.

As a result of the sharp changes in direction, which .the flow of the air-fuel mixture in the Pre-evaporation device 7 experiences, they run Parts of the pre-evaporation device risk of being in a vortex zone with a relatively low risk Amount of flow, so that as a result of this fact it is insufficiently wetted or humidified by the fuel can be.

In order to at least partially overcome this disadvantage, according to the invention, a minor one Modification of the evaporation device 7 according to FIG. 4 proposed, by means of which a more effective Cooling of said critical zone is enabled.

According to the invention is the thin partition

52, 53 offset in such a way that they are related to the .Strömungsrichtung of the air-fuel mixture in the body 12 of the pre-drying device 7, downstream of the arches 13x, I4x of the arms 13, 14 is located. For this purpose, the partition wall 52, 53 is supported by a part 12a of the body 12, which is supported by a Bushing of suitable length is shown disposed in the body 12 and secured thereto.

According to the invention, passages 60 oriented in a direction which is a ^{transverse component to the axis Y 1} -Y of the body 12, 12a are also formed transversely through the side wall of the sleeve 12a, upstream of the partition 52,

53, but slightly downstream of the arcs 13x »I4x.

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These passages, which begin in the body 12, 12a, accordingly open directly into the aforementioned critical zone.

During operation, part of the flow of the air-fuel mixture, which the body 12, 12a of the pre-evaporation device 7 flows through, on the partition walls 52, 53 and becomes the passages 60 deflected so that the arc zone 13x, I4x the arms 13, 14 is fed directly. It is formed accordingly, in this zone, satisfactory aerodynamic flow conditions, thereby facilitating the wetting or humidification of the walls of this zone will. The thermal behavior of the pre-evaporation device 7 is consequently improved.

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Claims (7)

Claims (1. Device for pre-evaporation of liquid Fuel for a combustion device, having a combustion chamber, a source of liquid fuel and a source of an oxidizer like air, the pre-evaporation device in the combustion chamber having a protrusion in the form of a T-shaped hollow or tubular design which has a base of the body representing T, the one with the source of liquid fuel and with the oxygen carrier source is connected, and has two cross arms which branch off from the body and each of which in an outlet opening which opens into the combustion chamber and from which in operation a stream of a mixture of oxidizer and fuel that is at least partially vaporized, emerges, characterized in that the body (12) of the pre-evaporation device (7) near the Arches (13b, 14b or 13x, 14x) of the arms (13 * 14) is partially blocked by means of a thin screen, which is formed from two thin partitions (52, 53) is, each of which has a sharp edge (52a or 53a) facing in the direction against the axis of the Body (12) and is directed against the corresponding sharp edge of the other partition, and that the partitions between the sharp edges constricted passage (54) forming the body (12), the pre-evaporation device (7) with each the cross arms (13, 14) connects, 2. Device according to claim 1, characterized in that that the thin partitions (52, 53) at the level of the arches (13b, 14b or 13x, I4x) of the , Cross arms (13 # 14) are arranged. 209884/1 OA1 3. Apparatus according to claim 1, characterized in that the thin partitions (52, 53) with Relation to the direction of flow of the mixture of oxygen carrier and fuel in the body (12) downstream of the arches (13x, 14x) of the transverse arms (13, 14) are arranged. 4. Device according to. Claim 3, characterized in that that additional passages (60) are provided which the body (12) of the pre-evaporation device (7) connect with each of the cross arms (13, 14) and which in the body £ 12) start upstream of the thin partitions (52, 53) and directly into the zone of the arch (13x or 14x-} of the one in question Open the cross arm (13 or 14). 5. Apparatus according to claim 4, characterized in that the additional passages (60) are oriented in a direction which is a transverse component to the axis of the body (12) of the pre-evaporation device (7) represents. 6. Device according to one of claims 1 to 5, characterized in that each of the thin Partition walls (52, 53) is provided with at least one opening (55 and 56) which in one direction is aligned or -are which one component represents parallel to the axis of the device body (12). 7. Device according to one of claims 1 to 6, characterized in that it is in a gas turbine engine is used. 209884/104 Blank page