EP0161954B1 - Intermediate channel for a device feeding fuel and a combustion-supporting medium to a pulsating combustion chamber - Google Patents

Abstract

An intermediary chamber associated to a device for feeding a pulsatory combustion chamber with fuel and comburent includes a heat tube l65 defining with the inner channel wall 125 a recirculation zone for the burnt gases issuing from the combustion chamber. The intermediary channel located between the combustion chamber for pulsatory combustion of a mixture of fuel and a combustive agent and an injection chamber includes the heat tube being directly communicated with the combustion chamber, wherein an internal wall of the intermediary channel and an outer surface of the heat tube define a recirculation zone for the recirculaton of burn gases issuing from the combustion chamber, the recirculation zone being at least partially open at an upper end thereof.

Description

The present invention relates to an intermediate channel for a device for supplying a pulsating combustion chamber with oxidant and fuel, that is to say which is situated between the chamber where the injection takes place and the chamber where a place the pulsating combustion.

PCT patent application number 8 101 454 "Starting method and device for combustion apparatus" describes a system for pulsed combustion which comprises a combustion chamber surmounted by a supply device between which is interposed an intermediate channel which is located substantially at the second conical part of the tube which surrounds the injection head. According to this same patent application, the intermediate channel is provided with an internal tube, also called a heat tube. The inner wall of the intermediate channel and the heat tube define an annular space which is open in its lower part, but closed in its upper part.

This heat tube essentially allows the vaporization of the fuel before it enters the combustion chamber, but it must therefore remain relatively hot. However, a possible drawback of such a device lies in the fact that soot deposits are produced, in particular at the level of the injection head. These deposits are generally due to excessively high temperatures.

It has been proposed, in DE-A-2 508 770, to provide, in the heat tube, openings perpendicular to its axis, as well as a transverse slot. However, this device still does not make it possible to combat the deposit of soot.

The object of the present invention is to provide an intermediate channel provided with a heat tube maintained at a high temperature, but which also makes it possible to avoid the formation of soot in the chamber where the injection takes place, and to create a tube effect. which favors the acceleration of the burnt gases towards the combustion chamber.

For this, the invention provides an intermediate channel between, on the one hand a chamber for the pulsed combustion of a mixture of fuel and oxidizer and on the other hand an injection chamber for the injection of said mixture, comprising a heat tube defining with the inner wall of the channel a recirculation zone for the burnt gases coming from the combustion chamber, said zone being open at its upper end, said channel comprising a lower part located near the combustion chamber and an upper part located near the injection chamber, said heat tube being located in the lower part. This intermediate channel is characterized in that its two parts are cylindrical, the lower part having a diameter larger than the upper part, and in that said two parts are joined by a flange opposite which is located l 'upper end of said heat tube.

The collar may be flat or rounded and preferably, it has in its peripheral part of smaller diameter, a circular projection whose largest diameter is less than the inside diameter of the heat tube.

According to different embodiments of the invention, this projection can be vertical and inclined towards the outside or the inside of the intermediate chamber.

In its lower part, the intermediate channel may include an insulation sleeve coaxial with the heat tube made of a thermally insulating material.

According to another characteristic of the invention, the upper part of the intermediate channel comprises a cylindrical sleeve with an outside diameter smaller than that of said heat tube and the lower edge of which constitutes the projection of the collar.

The sleeve can be held in place by a series of rings arranged inside a cylindrical outer jacket, said rings resting on a flat annular surface of said jacket.

Preferably, some of these rings are made of a thermally insulating material and / or define at least one annular insulation space.

• la figure 1 est une vue en coupe partielle d'un dispositif de combustion pulsatoire comportant un canal intermédiaire réalisé selon l'invention,
• la figure 2 est une vue de détail d'une variante de réalisation du dispositif représenté figure 1,
• la figure a est une variante de réalisation du détail représenté figure 2,
• la figure 3 est une vue en coupe d'un deuxième mode de réalisation de l'invention,
• les figures 4a et 4b représentent des détails du mode de réalisation de la figure 3,
• la figure 5 est une vue partielle d'une variante de réalisation du dispositif selon l'invention,
• la figure 6 représente un détail de la partie inférieure du canal,
• la figure 7 représente une variante de réalisation de la figure 1.

However, the invention and its advantages will appear more clearly on reading the following description made, in an illustrative but in no way restrictive manner, with reference to the drawings in which:

• FIG. 1 is a partial section view of a pulsating combustion device comprising an intermediate channel produced according to the invention,
• FIG. 2 is a detailed view of an alternative embodiment of the device shown in FIG. 1,
• FIG. a is an alternative embodiment of the detail shown in FIG. 2,
• FIG. 3 is a sectional view of a second embodiment of the invention,
• FIGS. 4a and 4b show details of the embodiment of FIG. 3,
• FIG. 5 is a partial view of an alternative embodiment of the device according to the invention,
• FIG. 6 represents a detail of the lower part of the channel,
• FIG. 7 represents an alternative embodiment of FIG. 1.

The device shown in Figure 1 comprises a body (2) mounted on the neck (3) of a chamber (4) of pulsed combustion. The interior of the body (2) has an injection chamber (150) of the fuel and oxidant mixture, in which is located an injection head. The injection chamber (150) is bounded at the bottom by the circular surface (5), the annular surface (6) and the wall (10) which define a cylindrical bore (39) for the insertion of a disc ( 7).

This disc (7) has two coaxial cylindrical parts (43) and (44), a central bore (45), a second central bore (46) and a circular groove (48). The lower cylindrical part (44) has a diameter greater than the upper part (43) and it is fitted into a bore (30) of a sleeve (55). The disc (7) is therefore held in place between the sleeve (55) and the lower part of the injection chamber (150).

The upper part (43) of the disc (7) and its central bore (45) constitute the upper part of the intermediate channel, this upper part being connected to the lower part by the groove (48) which defines a junction flange between the two parts.

The central bore (45) is conical and its upper diameter is equal to the lower diameter of the injection chamber.

The walls of the groove (48) and the central bore (45) are interconnected by a flat annular surface so as to define a circular projection (162).

The cylindrical sleeve (55) is disposed inside the neck (3) and it has an upper bore (56) and a flange (57) which is embedded in a complementary bore (58) of the neck (3). The outside diameter of the sleeve (55) is equal, apart from the play tolerances, to the inside diameter of the neck (3).

Inside the cylindrical sleeve (55) is placed a heat tube (165) which is in the form of a cylindrical jacket (70), held in place by a series of four fixing lugs such as (71) which are crimped in a support ring (52) interposed between the bore (56) and a circular groove (72) of the disc (7).

In the device shown in Figure 1, the disc (7) is made of graphite, the sleeve (55) is of insulating ceramic, the other parts are essentially metallic.

In normal operation, that is to say outside of the combustion initiation phase, the device operates in the following manner. The fuel is injected into the injection chamber, in a manner known per se by an injector, having a cone of a spray such that the impact of the drops of fuel takes place mainly below the upper level. of the shirt (70).

The lower part of this then constitutes the zone for mixing the fuel and the oxidizer although it is possible that part of this mixture has already taken place in the lower zone of the manifold, or injection chamber, or at the opposite in the combustion chamber (4).

As is conventional in pulsed combustion processes, the explosion phase causes an increase in the pressure in the combustion chamber, followed by the expulsion of the burnt gases to the exhaust system. However, part of the burnt gas is discharged towards the top of the device, in the direction of the injection chamber (150). The invention makes it possible to use this part of the burnt gases to bring the heat tube to a sufficiently high temperature. Indeed, the outer surface (123) of the jacket (70), the inner wall (125) of the sleeve (55) and the groove (48) define an annular gas recirculation channel.

This channel is convergent towards the inside of the groove (48). During recompression, the burnt gases are therefore accelerated upwards, then deflected downwards. The acceleration of these gases downwards is favored by the presence of the circular projection (162) which makes it possible to create a proboscis effect at the outlet of the bore (45).

Due to this recirculation of the burnt and hot gases, the heat tube is brought to a temperature allowing it to maintain the evaporation of the drops of fuel which have been impacted on it. Indeed, without this vaporizing effect, such drops agglomerated as they descend to the combustion chamber and would penetrate therein in a form unsuitable for perfect combustion. To this effect of vaporization due to the high temperature of the tube, is added that provided by the recirculation of the gases which come to lick the internal wall (120) of the jacket (70) so as to limit the impact of the fuel droplets liquid against the wall.

In addition, as can be seen in FIG. 1, the upper part of the heat tube is flared so that, at the outlet of the circular groove (48), the zone of change of direction of the recirculated gases constitutes substantially a convergent towards the wall. inside (120) of the heat tube (165).

There is shown in Figure 2, a detailed view of an alternative embodiment of the device of Figure 1. In Figures 1 and 2, the same parts are referenced by the same numbers. According to this embodiment, the central bore (45) of the disc (7) is cylindrical and it ends in a projection (170) whose external (171) and internal (172) surfaces are conical and oriented inwards. of the heat tube (165). The disc (7) has an annular recess (175) of rectangular section. The lower part of the injection chamber (150) is also provided with an annular recess of the same width (176). The recesses (176) and (175) are located opposite each other so that they define a closed empty annular chamber (178). This chamber (178) constitutes a thermal insulation cushion which limits the heat transfers from the heat tube (165) to the upper part of the device. In this FIG. 2, it can be seen that the neck (3) does not include a sleeve so that the flue gas recirculation channel is defined directly by the internal wall of the neck (3). The support ring (52) on which the fixing lugs (71) are fixed is held in place in the groove (72) by an intermediate disc (183) which itself comes to bear on the annular surface (184) neck (3).

Finally, we note in this figure that the same wall (185) of the heat tube (165) is cylindrical at least in its lower part.

On the device shown in Figure 2 and as has been said above, the ring (7) is made of graphite or ceramic. Due to the nature of this ring and the small dimensions of the fixing lugs (71), thermal transfers upwards, coming from the sleeve, are limited. The sleeve is therefore kept at a high temperature.

However, an embodiment can be provided which keeps the upper part of the recirculation channel warm so that the recirculated gases are not cooled. This embodiment is shown in Figure 2a. Opposite the heat tube (165), the ring (7) - ceramic or graphite - is provided with a ring (173) made of conductive material, for example stainless steel. The jacket (70) constituting the heat tube is directly fixed to the ring (173) by stainless steel fixing lugs (375).

There is shown in Figure 3 a second embodiment of the invention more specifically adapted to the case where the air injection is done in a vertical movement. The parts common to the embodiments of Figures 1, 2 and 3 are identified by identical reference numbers.

The lower part of the injection chamber (150) in which the injector (115) is placed is delimited by a first ring (200) of substantially triangular section, the lower surface (201) of which is planar and has an annular projection ( 202). An O-ring (203) is placed in a groove (204) and abuts with the neck (3).

Below the ring (200) is placed a cylindrical sleeve (205) comprising an annular upper flange (206) whose external diameter is equal to that of the ring (200) and which comprises a circular notch (207) of which the section corresponds to the projection (202). The sleeve (205) is fitted into a second sleeve (210) whose internal diameter is slightly greater than the external diameter of the sleeve (205) and which has an annular collar (211 Between the annular collar (211) and the collar (206) a flat ring (220) is inserted between the sleeve (205). The lower end (221) of the second sleeve (210) is bent towards the first sleeve (205) and comes to bear thereon. is therefore surrounded by an air jacket (225). Its outside diameter is less than the inside diameter of the heat tube.

The lower end (222) of the sleeve (205) is located at a level slightly lower than that of the lower end (221) of the second sleeve (210). This end (222) is narrowed so as to define an inwardly converging crown.

The sleeve (210) is held in place in the neck (3) by the disc (226) which is blocked between the annular flange (211) and the annular surface (184) by means of the rings (230) and (231 ) and washers (232), (233) and (234), which define annular insulation spaces (300).

The heat tube (70) which is cylindrical above all its height comprises a collar (235) which comes to bear on the washer (234).

The washer (234) is shown in detail in Figures 4a and 4b. Its outside diameter is substantially equal to the inside diameter of the neck (3) and its inside diameter is greater than the outside diameter of the jacket (70) but less than the largest diameter of the collar (235). The washer (234) is provided with a series of radial and elongated openings (240) which extend from its inner periphery. These openings define between them tongues (242) bearing on the flange (235) (Figure 4b).

In this embodiment shown in Figure 3, the following materials have been chosen for the different parts. The sleeves (205) and (210) as well as the two rings (230) and (231) and that the disc (226) are made of graphite while the flat ring (220) and the washer (232) are made of asbestos. There is thus obtained a very good limitation of heat transfers by conduction towards the top of the device, that is to say towards the injection chamber.

It can be noted that in FIG. 3, the lower end of the sleeve (205) is located above the entry face of the heat tube and that the smallest internal diameter of this sleeve is less than the internal diameter of the tube. of heat so that all of these parts, in combination with the lower disc (226) define the upper part of the zone for recirculation of the burnt gases coming from the combustion chamber.

Finally, there is shown in Figure 5, an alternative embodiment of the device according to the invention, more particularly of the device shown in Figure 1. According to this variant, the jacket (70) of the heat tube (165) extended at the bottom by a series of four legs (350) which extend towards the interior of the combustion chamber (4). These tabs make it possible to facilitate the temperature rise of the tube (165) during the combustion initiation phase since they make it possible to ensure a thermal transfer between the central part of the chamber (4) and the jacket (70) you heat tube.

FIG. 6 shows another embodiment of the lower part of the intermediate channel. We see in this figure that the neck (3) is welded to the combustion chamber (4). The jacket (70) and the sleeve (55) extend inside the neck to the upper level of the combustion chamber (4) so that the lower faces of the sleeve and the jacket are contained in the plane (60) containing the intersection of the chamber (4) and the interior volume of the neck.

FIG. 7 illustrates another embodiment of the disc (7). The central bore (45) of the disc is cylindrical. It is fitted into the ring (200). The disc (7) bears directly against the internal surface of the neck (3) and it has an annular recess (250) which constitutes a closed chamber of thermal insulation. Note that in this FIG. 7, as in FIG. 3, the connecting flange between the upper part of the intermediate channel and the lower part is not in the form of a rounded groove, but in the form of a prismatic section groove whose upper face (260) is horizontal. Any other shape can be provided for this groove, in particular it can be produced with an inclined upper face so as to define a divergent volume downwards.

Claims (11)

1. An intermediary channel between a chamber (4) for the pulsatory combustion of a mixture of combustive agent and fuel and an injection chamber (150) for the injection of said mixture, said intermediary chamber comprising a heat tube, said heat tube and the internal wall of said channel defining a recirculation zone for the burned gases from said combustion chamber, said zone being open at its upper end, said channel being provided with a lower portion (44) in proximity to the combustion chamber and an upper portion (43) in proximity to said injection chamber, said heat tube being located in said lower portion, characterized in that said both portions are cylindrical, said lower portion having a diameter larger than that of said upper portion, and in that said two portions are connected to each other by a flange (48) in front of which is located the upper end of said heat tube.

2. An intermediary channel according to claim 1, charactereized in that said flange is flat or rounded and comprising at its minimum diameter peripheral zone a circular protusion (162), the diameter of the lowermost portion of which is greater than the inner diameter of said heat tube.

3. An intermediary channel according to claim 2, characterized in that said circular protusion is vertical.

4. An intermediary channel according to claim 2, characterized in that said circular protusion is inclined toward the inside of said intermediary channel.

5. An intermediary channel according to claim 2, characterized in that said circular protusion is inclined outwardly of said intermediary channel.

6. An intermediary channel according to claim 1, characterized in that its upper portion comprises a cylindrical sleeve (205) the outer diameter of which is smaller than the inner diameter of said heat tube and the lower edge of which forms said protusion of said flange.

7. An intermediary channel according to claim 6, characterized in that said cylindrical sleeve is maintained in place in a jacket integral with said combustion chamber by at least one ring (230, 231) which bears on an annular flat surface of said jacket.

8. An intermediary channel according to claim 7, characterized in that said sleeve is maintained in place by two rings that define annular isolating spaces (300).

9. An intermediary channel according to claim 7, characterized in that said cylindrical sleeve is surrounded by a second cylindrical sleeve (210) that defines with said cylindrical sleeve an insulating jacket.

10. An intermediary channel according to claim 1, characterized in that said heat tube comprises at least one pad which axtends toward the central portion of said combustion chamber.

11. An intermediary channel according to claim 1, characterized in that said flange defines a downwardly diverging space.

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