EP0396554B1 - Burner - Google Patents

Abstract

A burner for combustible mixtures consisting of two fluid components comprises a chamber housing (1), first feed means for the first component, second feed means for the second component and an outlet orifice (15) for the combustion gases. The feed means for the first component is an injector tube (2) which has at the end facing the outlet orifice (15) a rear axial bore (21), at the other end a narrower front axial bore (22), a narrow passage (23) between the two bores (21, 22) and at least one inclined radial channel (241, 242; 243, 244) inclined to the injector axis (i) at an angle alpha, the apex of which is turned towards the rear axial bore (21) and which extends from the inner space of the chamber housing (1) to the narrow passage (23) or along the sides of the front axial bore (22) and ends before the narrow passage (23) in such a way that a part of the second component which flows through the inclined channel into the chamber housing (1) reaches the narrow passage, where it mixes with the first component, which enters through the front axial bore (22), is burnt in the rear axial bore (21) from which it flows into the chamber housing (1).

Description

The invention relates to a combustion device for burning a combustible mixture consisting of two flowable components.

A distinction is made between closed and open systems in combustion processes such as take place in modern internal combustion engines. A closed system is a closed combustion chamber in which fuel and oxidizer are brought together, burn and then do mechanical work or generate heat through the expansion of the combustion gases.

In an open system, fuel and oxidizer are burned in a combustion chamber and the combustion gases exit as a jet from an opening in the combustion chamber. The gas jet can be used, for example, as a drive means in aircraft and spacecraft or turbines, but it can also be used for other purposes, such as heating.
In the open systems, a high flow rate with which the fuel and oxidizer flow into the combustion chamber has an unfavorable effect on the ignition behavior. The range of the mixing ratio of fuel and oxidizer, in which it is ignitable (ignitability range), becomes smaller as the flow rate or the combustion chamber pressure increases.

If the mixture ratio between fuel and oxidizer necessary for the ignitability is not can be observed, so-called blow-out occurs. The flame front breaks off and the media flow unburned through the combustion chamber. With fuels that are extremely inhomogeneous, it is not possible to maintain this ignitability range without complex auxiliary structures and aids. With fuels that burn extremely quickly or even detonate, such as hydrogen, the ignitability range becomes extremely small at higher flow speeds and, depending on them, higher combustion chamber pressures. The thermal influences can already result in the ignitability range being shifted in such a way that blow-out occurs.

In the case of thermally favorable combustion of lean mixtures, there is also a very small ignitability range at higher flow velocities of the media to be burned and, depending on their high combustion chamber pressures. Here, too, there is a very high risk of blowing out. In order to achieve high thermal efficiency, a correspondingly complex construction with a pre-combustion chamber and valves must be used in open systems.

Another solution to eliminate the ignition problems would be to over-grease the mixture far beyond the stoichiometric balance. However, this would lead to poorer thermal efficiencies. A catalytic remedy would be very expensive and possibly also environmentally harmful.

In US Pat. No. 3,733,165 there is a combustion device for burning a combustible mixture of two Flowable component described, at least one of which is supplied at high pressure or high speed, with a housing with a chamber, means for supplying and mixing the first and second components, an outlet opening for the combustion gases, an injector tube, which protrudes through the chamber housing in the direction of its outlet opening, with an axial bore for the supply of the first component, a narrow point in the axial bore and at least one inclined channel running radially and obliquely to the injector axis from the interior of the chamber housing, with its inner end pointing in the direction of the axial bore which flows a part of the second component flowing into the chamber housing and mixes with the first component in the first axial bore. This combustion device does not deal with problems that result from substoichiometric combustion, that is to say from the combustion of a lean mixture, in particular at high flow velocities.

The invention is therefore based on the object of providing a combustion device for burning a flowable fuel with a flowable oxiadator, by means of which ignition problems in particular in the case of lean mixtures are avoided.

This object is achieved according to the invention in that the chamber housing is longer than the part of the injector tube which projects into the chamber housing, the injector tube has a larger rear axial bore at its end oriented towards the outlet opening and a narrower front end at its end facing away from the outlet opening Axial bore, between the two bores the constriction and those running into or near the constriction into the front axial bore, with its inner end in Inclined channel pointing in the direction of the rear axial bore with a variable overall cross-section, whereby this mixture, as a rich mixture with high ignitability, largely pre-burns in the rear axial bore, thereby heating up the wall in the area of the rear axial bore, flowing from it into the rest of the chamber housing, where it co-exists the remaining part of the second component mixes and burns out completely.

The injector tube preferably consists of a Base part with the rear axial bore and a coaxial injector needle which is movable in the base part in the longitudinal direction with the front axial bore, the total cross section of the oblique channels being changeable by moving the injector needle in the axial direction.

In the case of a very high-energy combustion in the injector tube, it may be necessary in a further development of the invention to provide the injector tube on its outside with cooling fins. This results in a higher heat output to the second component flowing along the outside of the injector tube, for example the oxidizer.

In the case of a chamber housing which is open at the front, as is the case, for example, in ramjet engines, in a further development of the invention the injector tube must be angled or curved in an arcuate manner.

In a special embodiment of the combustion device, this consists of a cylindrical chamber housing with a head part, the head part for receiving the injector tube having a central bore, around which nozzles are arranged as supply devices for the second component.

In a special form of the invention, the injector tube consists of a catalytic material or is provided with a catalytic material.

Fig. 1

eine Brenneinrichtung mit einem Kammergehäuse und einem Injektorrohr,

Fig. 2

die Brenneinrichtung nach Figur 1 ohne Injektorrohr,

Fig. 3

ein nicht einstellbares Injektorrohr,

Fig. 4

ein einstellbares Injektorrohr,

Fig. 4A

eine auseinandergezogene Darstellung des einstellbaren Injektorrohres nach Figur 4,

Fig. 4B

das einstellbare Injektorrohr nach Figur 4 mit offenen Schrägkanälen

Fig. 4C

das einstellbare Injektorrohr nach Figur 4 mit fast geschlossenen Schrägkanälen

Fig. 5

ein Injektorrohr mit Kühlrippen und

Fig. 6

ein Brennkammergehäuse mit einem abgewinkelten Injektorrohr.

In the drawings, exemplary embodiments of the invention are shown in perspective, partially cut away.
Show it:

Fig. 1

a combustion device with a chamber housing and an injector tube,

Fig. 2

1 without the injector tube,

Fig. 3

a non-adjustable injector tube,

Fig. 4

an adjustable injector tube,

Figure 4A

4 shows an exploded view of the adjustable injector tube according to FIG. 4,

Figure 4B

the adjustable injector tube according to Figure 4 with open inclined channels

Figure 4C

the adjustable injector tube according to Figure 4 with almost closed inclined channels

Fig. 5

an injector tube with cooling fins and

Fig. 6

a combustion chamber housing with an angled injector tube.

FIG. 1 shows a perspective, partially cut-away representation of a combustion device with a chamber housing 1 and an injector tube 2. The chamber housing 1 is used to burn a flowable fuel with a flowable oxidizer at a high combustion chamber pressure or high inflow velocity The term "flowable substance" is understood to mean all liquids, gases or emulsions, but also mixtures of liquids or gases with solid particles, which, however, have flowable properties. As an exemplary embodiment, a cylindrical chamber housing 1 with a disk-shaped head part 11 is shown in FIGS. 1 and 2, the head part 11 for receiving the injector tube 2 being provided with a central bore 12 (FIG. 2) around which a plurality of nozzles 13 are arranged as supply means for the second component of a combustible mixture. For example, the nozzles 131-136 are visible in FIG. However, the number or position of the nozzles 13 is not of importance for the invention. The combustion gases emerge from the chamber housing 1 as a jet through the outlet opening 15.

The injector tube 2 shown in FIG. 3 serves as a supply means for the first component of the combustible mixture. It has a rear axial bore 21 at its rear end oriented towards the outlet opening 15, a narrower front axial bore 22 at its end facing away from the outlet opening 15 and a narrow point 23 between the two bores 21, 22. In addition, several inclined channels 241, 242 run radially and obliquely to Injector axis i with the apex of the angle α pointing in the direction of the front axial bore 21, from the chamber interior to the constriction 23 or on the side of the rear axial bore 22 just before the constriction 23 the inclined channels 241, 242 a part of the second component flowing into the chamber housing 1 flows into the constriction 23 or shortly before the constriction 23, mixes there with the first component entering through the rear axial bore 22 and burns in the rear axial bore 21. that the inclined channels 241, 242 form an acute angle α with the injector axis i, the second component flowing through the inclined channels 241, 242 to the constriction 23 exerts a suction effect on the first component entering through the front axial bore 22. The cross-sectional area of all inclined channels 241, 242 together with the cross-sectional area of the front axial bore 22 is larger than the cross-sectional area of the constriction 23. The cross-sectional area of all inclined channels 241, 242 is therefore not added to the cross-sectional area of the constriction 23 even if the inclined channels 242, 242 are complete or partially open into the constriction 23.

The combustible mixture is ignited in the chamber housing 1 by an ignition probe 3. For this purpose, in the ignition phase of the combustion device, the two components of the combustible mixture are conveyed into the chamber housing 1 with only low pressure or only a low flow rate. After ignition, the flame strikes back to the narrow point 23 between the two axial channels 21, 22, but not beyond the narrow point. The two components of the combustible mixture only mix at the constriction 23, since there is no ignitable mixture in front of the constriction 23 in the front axial bore 22. With an open burner is, for example, at a combustion pressure of 4 bar in the chamber housing 1,
Air as the second component at 5 to 6 bar was fed to the chamber housing 1 through the nozzles 13 and the fuel as the first component at a pressure of only 0.6 bar to the injector tube 2. There is no back pressure or "stuttering" of the combustion even with these large pressure differences.

For technical and economic reasons, the burning behavior of the combustion device is of particular interest when the second component, for example air, is excessively lean. The use of the injector tube 2 here means that when the pressure and flow velocity in the chamber housing 1 change, there is no change in the combustion behavior with regard to the ignitability of the mixture, but only when the injector tube setting is changed, as is shown in FIGS. 4B and 4C. Thus, the combustion in the injector tube 2 can be influenced by enlarging or reducing the oblique channels 241, 242. The above-described decoupling of the combustion behavior of the combustion device from the leanness of the mixture does not exist if the first component is fed to the chamber housing 1 only through a hollow needle protruding into the chamber housing 1, with or without a nozzle. Mixtures can be so lean that the ignitability falls below.

• Bei Inhomogenität einer oder beider Komponenten. In diesem Fall verändert sich die Verbrennung in der hinteren Axialbohrung 21 in dem Maße, wie die Zusammensetzung der einen oder der beiden Komponenten sich verändert. Bei inhomogenen Brennstoffen wird das Volumenverhältnis der Komponenten so eingestellt, daß auch bei schwächstmöglichem Energiegehalt der jeweiligen Komponenten ein mit Sicherheit im leicht zündbaren Bereich liegendes Gemisch in der hinteren Axialbohrung 21 verbrennen kann.
  Das bedeutet andererseits, daß im Falle des höchstmöglichen Energiegehaltes der ersten Komponente, diese nicht restlos mit der zweiten Kompnente, die durch die Schrägkanäle 241 - 244 in das Injektorrohr 2 gelangt, in der hinteren Axialbohrung 21 des Injektorrohres 2 reagieren kann.
• In einem zweiten Fall können unverbrannte Reste der ersten Komponente auch dadurch entstehen, daß sich die Drücke oder die Strömungsgeschwindigkeiten, und als deren Folge wiederum die Drücke, so verändern, daß sich als weitere Folge die Energiedichte der ersten Komponente verändert.
  Bei Schwankungen der Strömungsgeschwindigkeit bzw. der Drücke, mit denen die Komponenten eingegeben werden, kann es gleichfalls unverbrannte Reste bei der Reaktion in der hinteren Axialbohrung 21 des Injektorrohres 2 kommen.
• Ebenso kann es zu unverbrannten Resten kommen, wenn die Reaktionsgeschwindigkeit der Verbrennung in der hinteren Axialbohrung 21 des Injektorrohres 2 so klein ist, daß die Zeit in der die Komponenten die hintere Axialbohrung 21 durchströmen, nicht für eine vollständige Reaktion ausreicht.
  Dies wäre z.B. bei langsam brennenden Emulsionen denkbar. Die Gestaltung des Injektorrohres 2, insbesondere die Länge der hinteren Axialbohrung 21, hat in solchen Fällen einen wesentlichen Einfluß auf den Ausbrand.

The rear axial bore contains a very rich mixture, since the larger portion of the second component flows past the injector tube 2 on the outside and only the smaller portion of the second component entering the injector tube 2 through the inclined channels 241, 242 reacts with the first component in the injector tube 2 . The portion of the second component flowing along this outside the injector tube 2 acts as a jacket current and thus prevents the heat of the injector tube 2 from being lost to the combustion system. This jacket flow reduces the heat transfer from the hot core stream, which emerges from the injector tube 2, to the outer walls of the chamber housing 1, since only the much smaller temperature gradient between the jacket flow and the outer walls is decisive for the heat losses. This leaves more energy in the combustion gases and the combustion has a better overall efficiency. During the combustion in the rear axial bore 21 of the injector tube 2, those parts of the second component react through the inclined channels 241, 242; 243, 244 enter the injector tube 2 with the first component entering through the front axial bore 22. In this combustion, however, unburned residues can get from the injector tube 2 into the chamber housing 1 for various reasons. At the edge zones of the core flow to the surrounding sheath flow, reactions then occur between the second component in the sheath flow, which has not reached the injector tube 2 through the inclined channels 241-244, and the unburned residues of the first component, which have passed through the injector tube 2 has entered the chamber housing 1. In the following cases, unburned residues of the first component can occur:

• If one or both components are inhomogeneous. In this case, the combustion in the rear axial bore 21 changes as the composition of the one or the two components changes. In the case of inhomogeneous fuels, the volume ratio of the components is set in such a way that even with the weakest possible energy content of the respective components, a mixture which is certainly in the easily ignitable area can burn in the rear axial bore 21.
  On the other hand, this means that in the case of the highest possible energy content of the first component, it cannot react completely with the second component, which enters the injector tube 2 through the inclined channels 241-244, in the rear axial bore 21 of the injector tube 2.
• In a second case, unburned residues of the first component can also result from the fact that the pressures or the flow velocities, and as a result of this the pressure, change in such a way that the energy density of the first component changes as a further consequence.
  In the event of fluctuations in the flow velocity or the pressures with which the components are input, unburned residues can likewise occur during the reaction in the rear axial bore 21 of the injector tube 2.
• Likewise, unburned residues can occur if the reaction speed of the combustion in the rear axial bore 21 of the injector tube 2 is so small that the time in which the components flow through the rear axial bore 21 is not sufficient for a complete reaction.
  This would be conceivable, for example, with slow-burning emulsions. The design of the injector tube 2, in particular the length of the rear axial bore 21, has a significant influence on the burnout in such cases.

When leaving the rear axial bore 21 of the injector tube 2, the unburned residues of the first component have such a high temperature that they react immediately with the second component in the jacket flow.

If one or both fuel components are very inhomogeneous, it is necessary to be able to optimally adjust the mixing ratio of the two components in the injector tube 25. For this purpose, the injector tube 25 shown in FIGS. 4, 4A consists of a base part 26 with the rear axial bore 21 and a coaxial injector needle 27 with the front axial bore 22, which can be displaced longitudinally in the base part 26. Due to the axial displacement of the injector needle 27 in the base part 26 the total cross section of the inclined channels 243, 244 can be changed.

This makes it possible to change the mixing ratio of the two components as desired in the combustion in the rear axial bore 21. FIG. 4A shows an exploded view of base part 26 and injector needle 27. A defined movement of the injector needle 27 in the base part 26 can be carried out, for example, by a thread (not shown in the drawings) between the base part 26 and the injector needle 27.

FIGS. 4B, 4C show the injector tube 25 with two extreme positions of the injector needle 27: in FIG. 4B, the oblique channels 243, 244 are completely open and in FIG. 4C they are almost closed. When different components are burned in the same injector tube 25, when changing from one fuel to another, only the injector needle 27 needs to be changed or readjusted in a predetermined manner.

Only two inclined channels 241, 242 and 243, 244 are shown in the drawings. However, it is understood that the number of inclined channels is not limited to this number, but that as many inclined channels can be present as are required for the supply of a sufficient proportion of the second component or for a spatially uniform distribution.

5 shows an injector tube 2 which has cooling fins 28 on its outside. The number and geometry of the cooling fins 28 must be determined on a case by case basis.

FIG. 6 finally shows a chamber housing 14 which is open at the front and in which the injector tube 2 is supported by an angled projection 29. The first component is also fed through the attachment 29. The extension 29 can also be curved like a circular arc section, so that an injector tube 25 with inclined channels 243, 244 with a variable cross section can be used.

To improve the combustion, the injector tube 2 can consist of a catalytic material or can be provided with a catalytic material.

Reference symbol list

1

Chamber housing

11

Headboard

12

central hole

13

jet

131-136

Nozzles

14

open front chamber housing

15

Outlet opening

2nd

Injector tube

21

rear axial bore

22

front axial bore

23

Constriction

241, 242

Inclined channels with a constant cross-section

243, 244

Inclined channels with a variable cross-section

25th

Injector tube with variable cross-section of the inclined channels

26

Basic part

27

Injector needle

28

Cooling fins

3rd

Ignition probe

Claims (8)

1. Burner device for combustion of a combustible mixture of two flowable components, of which at least one is supplied at high pressure or high speed, comprising a housing (1) with a chamber, means for feeding the first and the second component and for mixing thereof, an outlet opening (15) for the combustion gases, an injector pipe (2), which projects into the chamber housing (1) in the direction of the outlet opening (15) thereof and has an axial bore (21, 22) for the feed of the first component, a constriction (23) in the axial bore (21, 22), and at least one inclined channel (241, 242, 243; 244) which extends radially and obliquely relative to the injector axis (i) from the interior of the chamber housing (1) and with its inner end oriented in the direction of the axial bore (21, 22) and through which a part of the second component flowing into the chamber housing (1) flows and mixes in the axial bore (21, 22) with the first component, characterised in that the chamber housing (1) is longer than the part of the injector pipe (2) that projects into the chamber housing (1), the injector pipe (2) has a larger rearward axial bore (21) at its end oriented towards the outlet opening (15), a narrower forward axial bore (22) at its end remote from the outlet opening (15), the constriction (23) between the two bores (21, 22) and the inclined channel (241, 242; 243, 244) of variable total cross-section and extending, with its inner end oriented in direction of the rearward axial bore (21), into the constriction (23) or into the forward axial bore (22) in the proximity of the constriction, wherein this mixture, as rich mixture with high ignitability, is for the greater part combusted in the rearward axial bore (21), thus heats the wall in the region of the rearward axial bore (21), flows therefrom into the rest of the chamber housing (1), mixes there with the remaining part of the second component and combusts in entirety.
2. Burner device according to claim 1, characterised in that the injector tube (25) consists of a base part (26) with the rearward axial bore (21), and a coaxial injector needle (27) which is movable in longitudinal direction in the base part (26) and is provided with the forward axial bore (22), wherein the total cross-section of the inclined channel (243, 244) is variable through a movement of the injector needle (27) in axial direction. (Fig. 4).
3. Burner device according to claim 1 or 2, characterised in that the injector tube (2) has cooling ribs (28) on its outer side to increase the surface (Fig. 5).
4. Burner device according to claims 1 and 3, characterised in that the injector tube (2) is formed to be angled.
5. Burner device according to claims 1 and 3, characterised in that the injector tube (2) is formed to be arcuately curved.
6. Burner device according to claims 1 and 5, characterised by a cylindrical chamber housing (1) with a head part (11), wherein the head part (11) has a central bore (12), about which several nozzles (131 to 136) are arranged as supply devices for the second component, for the reception of the injector tube (2).
7. Burner device according to claims 1 and 6, characterised in that the injector tube (2) consists of a catalytic material.
8. Burner device according to claims 1 to 6, characterised in that the injector tube (2) is provided with a catalytic material.

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