The present invention relates to a device for guiding an element, such as a spark plug or a fuel injector, extending into an orifice or in the vicinity of an orifice of a combustion chamber wall of a turbomachine.

An annular combustion chamber of a turbomachine is defined by two coaxial walls of revolution which extend (relative to axis34below) one inside the other and which are connected to each other at their upstream ends by an annular chamber bottom wall.

The chamber bottom wall has openings for the passage of a mixture of air and fuel inside chamber, with air from a compressor of the turbomachine and fuel supplied by injectors.

The upstream side is the side where the mixture of air and fuel reaches the annular combustion chamber.

(In relation to axis38below), the injection means, or injectors, extend substantially radially from their outer ends fixed to an outer chamber housing to their heads axially aligned with the holes in the chamber bottom wall.

The outer wall of revolution of the chamber has at least one through-hole for one end of a spark plug, the other end of which can be fixed to an outer casing of the chamber, this spark plug being adapted to initiate combustion of the air/fuel mixture in the chamber.

During operation of the turbomachine, the walls of the combustion chamber expand thermally, causing relative movements between the outer wall of the chamber and the spark plug and between the bottom wall of the chamber and the fuel injectors.

To compensate and allow these relative displacements, spark plug guiding devices and injectors are used, each comprising a substantially coaxial floating ring and flange mounted inside each other. The ring is adapted to be axially traversed by the element and has an external flange guided transversely in an internal groove of the flange. The flange is adapted to be attached to an edge of the combustion chamber wall opening. This flange comprises a sleeve provided with a dropped edge where the sleeve is brazed or welded with a cup, so as to define between them said annular groove. The device has at least one preferred transverse direction of movement of the ring.

The applicant's patent application EP-A1-1 770 332 describes a guiding device of this type. The relative displacements between the outer wall of the chamber and the spark plug mainly take place in a direction parallel to the longitudinal axis of the chamber. During operation, the flange on the chamber wall is therefore essentially displaced in this longitudinal direction relative to the spark plug guide ring supported on the outer housing. The relative displacements of the ring in the flange groove in the other transverse directions are of smaller amplitudes. The axial or longitudinal direction is therefore the preferred direction of movement of the spark plug guide ring in relation to the flange carried by the chamber. The relative movements between the chamber bottom wall and the injectors are mainly in radial directions in relation to the longitudinal axis of the chamber, the preferred direction of relative movement of the ring mounted around an injector is therefore a radial direction in relation to the longitudinal axis of the chamber.

In today's technology, the two parts, cup and flange, forming the flange of a guiding device are fixed to each other at their external peripheries by one or more weld beads extending around the entire circumference of the bushing.

The term weld covers both brazing and actual soldering.

Although maximum care is taken by the operator in charge of making this weld, the weld beads may protrude into the annular guide groove of the ring and locally block the external periphery of this groove, thus reducing or preventing the ring from moving transversely in the flange groove. The welding operation of the flange parts is therefore delicate to carry out and does not allow to control these weld overflows. In addition, there is a risk of jamming of the device and/or damage to the welds, or even breakage, every time the rim of the ring comes into contact with a weld bead that protrudes into the flange groove.

The invention more particularly aims at providing a simple, efficient and cost-effective solution to this problem.

A device is therefore provided for guiding an element in an orifice in a combustion chamber wall of a turbomachine, the device comprising a floating ring and a substantially coaxial flange mounted one inside the other, the ring being adapted to have an element passing axially through it (axis520a) and comprising an external flange guided transversely (to said axis520a) in an internal annular groove of the flange, which is adapted to be fixed to an edge of the orifice in the combustion chamber wall, the flange comprising a bushing provided with a fallen edge where the bushing is brazed or welded with a cup, so as to define, between them, said groove, the device having at least one preferred transverse direction of movement of the ring, this device being characterised in that, parallel to said axis (520a), between the welds or brazes and the trajectory (path) of the rim of the ring when the latter is displaced with respect to the bushing in the preferred direction, an intermediate space is reserved, as an extension of said groove.

Thus, said welds or brazes will overflow into this intermediate space; and the welds or brazes will be outside the trajectory of the ring rim.

The solution is simple to implement and economical. With the solution of the invention, said welds or brazes may only protrude into said intermediate space, and thus only into the latter.

One way of moving the intermediate space, and hence the overflow of welds or brazes, away from said trajectory very effectively is to provide for said space to extend around a part of the cup, transversely to said axis (520a), between said part of the cup and the fallen edge.

The desired axial offset will be achieved around said part of the cup.

An effective way of creating this intermediate space, avoiding deformation of the bushing, is to provide for the cup to be stepped by means of a shoulder provided with an external rim by which the cup will have been brazed or welded with an axially elongated end of the fallen edge.

Thus, the shoulder will act as an obstacle or screen between the area of the ring rim trajectory and the overflow area.

Furthermore, rather than shaping the cup with, for example, an inverted U-shaped peripheral shape, oriented, parallel to said axis (520a), towards said groove, it may be preferable that, parallel to this axis, the height (H10below) of said fallen edge is at least equal to the height (H30below) of said protrusion plus the thickness of said flange and a clearance J (below) allowing said flange to move in the internal groove of the flange.

Thus, compared to a known situation as shown inFIG. 2below, the fallen edge will have been “simply” raised along said axis (520a).

And, if, transversely to said axis (520a), the rim sets the shoulder away from the fallen edge, as said part of the cup, thus creating said intermediate space reserved for the overflow of welds or brazes, it will be possible to obtain, transversely to this axis520a, the most appropriate compromise between the optimal volume for overflow and the smallest space requirement.

Also concerned by the invention is a combustion chamber of a gas turbomachine for an aircraft, the combustion chamber extending annularly around an axis (34below) and being provided with a guiding device as aforesaid, with all or some of the characteristics mentioned, this guiding device defining a spark plug guide, the element guided in the orifice of said combustion chamber wall being a spark plug which communicates with an interior volume of the combustion chamber through this orifice, the wall in which said orifice is formed being an annular wall radially outer with respect to said axis (34).

In particular, this combustion chamber may further comprise an annular chamber bottom wall connecting said radially outer annular wall to a radially inner annular wall with respect to said axis (34), said annular chamber bottom wall having orifices for mounting systems for injecting a mixture of air and fuel into the combustion chamber.

Thus, an efficient combustion chamber can be offered.

The invention will be better understood, if need be, and other details, characteristics and advantages of the invention will appear upon reading the following description given by way of a non restrictive example while referring to the appended drawings.

