FR2626937A1 - FUEL BURNER FOR GAS TURBINE - Google Patents

Abstract

A gas turbine fuel burner 10 suitable for the combustion of gas oil comprises an annular body 11 and a central body 22 placed coaxially within the annular body so that an annular flow path 24 is provided. defined between them. At the upstream end of the burner 10, an annular fuel manifold 15 cooperates with the annular body 11 and the central body 22 to define two coaxial passages 21, 26 which conduct the air inside the annular flow path 24. with minimal turbulence. The low level of turbulence inside the fuel burner 10 reduces the risks of spontaneous combustion occurring within the burner 10.

Description

i} 2626937

  This invention relates to a fuel burner for a gas turbine engine.

  Fuel burners for a gas turbine engine are known in which an annular series of fuel injectors is arranged so as to conduct point jets of fuel towards the radially inner surface of an annular body and to produce a flow of fuel on this surface. A cover is provided at the downstream end of the annular body. It is located at a certain axial distance from the downstream end of the annular body so that a space is defined between them. The air, which flows in service through the annular body, escapes through this space and, therefore, vaporizes the fuel which has been conducted on the interior surface of this body and has flowed there. The resulting vaporized fuel is then directed into the

  combustion associated with the burner, after which the fuel / air mixture is burned.

  With burners of this type, it has been found that zones of turbulence can be generated inside the volume defined by the annular body when the burner operates under high pressures, that is to say when the air supplied at the burner is at elevated pressure and temperature. The turbulence zones thus generated in turn lead to recirculation inside the burner so that regions of fuel / air mixture at low speeds are created. These regions of fuel / air mixture at low speed can finally ignite spontaneously,

  causing appreciable overheating of the burner.

  The object of the present invention is to provide a burner for a gas turbine engine in which such turbulence zones are reduced to a size which avoids

  actually any spontaneous ignition inside the burner.

  According to the present invention, a fuel burner suitable for a gas turbine engine comprises an annular body defining a radially inner annular surface.: The upstream end of the annular body is adapted to receive, in service, an air flow . An annular fuel manifold, disposed at the upstream end of said annular body so as to be coaxial with respect to said annular body and to be at least partially inside this body, is adapted to conduct the fuel on said annular surface. Furthermore, a central body of circular section has at least one main portion arranged coaxially inside said annular body and in general downstream of said manifold so that it cooperates with said annular body to define a flow path. through said burner. The downstream ends of said central body and of said annular body are arranged so as to cooperate and thus define an annular discharge directed in the assembly tadially. The downstream ends of said central body and said annular body finally cooperate with at least part of said fuel manifold to define two coaxial passages serving to direct said air flow. inside said annular flow path through said burner, The invention will now be described with the aid of an example with reference to the accompanying drawing which is a section through a side view of a burner of fuel in accordance with the present invention. According to the drawing, a fuel burner suitable for a gas turbine engine (not shown) has the general reference 10, the fuel burner 1. comprises an annular body 11 which, in use, is fixed to the upstream wall or head 12 of a room

  of combustion (not shown) of a conventional gas turbine engine.

  The annular body 1 1 defines an annular surface 13, radially interior and several fuel jets are oriented towards its downstream region 14, the fuel coming from an annular fuel manifold 15, extending axially. The fuel manifold 15 has a smaller diameter than that of the annular body 11 and includes an annular chamber 16 which is supplied with fuel by a fuel supply conduit 17 formed inside an arm 18 supporting the manifold 15 The fuel manifold is arranged coaxially with respect to the annular body 1 and upstream of the latter. A portion of the downstream end of the fuel manifold 15 extends to the interior of the annular body 11 so that an annular passage 21 is defined between them. Several small nozzles 19 are provided in the fuel manifold 15 in order to connect the annular chamber 16 to the annular space 21 and thus define in service the fuel jets which are represented by lines 20 in dotted lines. The

  fuel jets 20 thus pass through the annular passage 21.

  The annular body 11 carries, by means of several radial aerodynamic spacers 23, a hollow central body 22 of generally circular section. Most of the central body 22 is arranged inside the annular body 1, coaxially with the latter, so that an annular flow path 24 is defined between them. The upstream end 25 of the central body 22 has a smaller diameter than the rest so as to allow the end 25 to be inside the downstream end of the fuel manifold 15 and coaxial with it, L ' upstream end 25 of the central body has a smaller diameter than that of the fuel manifold 15 so that a second annular passage 26 is defined between them. This last

  is coaxial with the first annular passage 21 and of generally comparable section.

  L: upstream end of the fuel burner 10 is exposed in service to a high pressure air flow supplied by the compressor of a gas turbine engine in which it is mounted. This air flow is divided into two flows by the fuel collector 1'5: a first flow through the first annular passage 21 radially inner and a second flow through the second annular passage 26 radially inner. The two flows unite again downstream

  of the fuel manifold 15 to create a minor turbulence region 27.

  However, this turbulence is local and most of the air flow along

  of the path 24 annular flow is not turbulent.

  The downstream end 28 of the central body 22 is provided with a ring 29 generally in the form of a truncated cone disposed at its periphery and cooperating with the downstream end of the annular body I l to define an annular exhaust 31, generally directed

  radially, from the air flow passing through the annular flow path 24.

  Fins 32 extend through almost the entire axial width of the exhaust 31 to ensure that the air flow remains non-turbulent in the exhaust region 31. In the present embodiment, the air flow from the exhaust 31 is directed in a slightly upstream direction. It will however be understood that the actual direction will depend on the characteristics of the

  combustion chamber with which the fuel burner 10 is associated.

  The fuel directed by the spouts 19 on the annular surface 13 flows along this surface 13 and, naturally around the aerodynamic spacers 23, in the form of a film as indicated by the lines 33 in dotted lines. When this fuel film reaches the downstream end of the annular body 11, it is vaporized by the flow of air from the exhaust 31 and mixes with this flow of air to introduce a flammable mixture inside. the combustion chamber

  with which the fuel burner is associated.

  It will therefore be seen that a minimum turbulence occurs inside the fuel burner 10 so that the risks of recirculation and therefore of combustion

  spontaneous are significantly reduced.

  Although, in the present example, the central body 22 is shown fixed to the annular body 11 by means of aerodynamic spacers 23, it will be understood that, in certain cases, the spacers 23 can be eliminated and the fins 32 arranged to be secured at the avsal end of the annular body 11 and thus provide the necessary connection. During a normal service cycle of the fuel burner 10, thermal effects are manifested in the central body 22 and the annular body 11, contracting and expanding axially at different speeds. This is authorized by the following measure: If the spacers 23 are present, the fins 32 do not link

  physically the annular body 11 and the ring 29 frustoconical to the central body 2S.

  However, such differential speeds of contraction and expansion pose another problem associated with the interior 26 and exterior annular passages 21. Also, in order to ensure that the sections of the two interior 26 and exterior 21 annular passages remain constant, the portions surfaces of the annular body 1 1, the central body 22 and the fuel manifold 15 which serve to define these passages 21 and 26, are arranged to be as a whole parallel to each other, It is indeed important to maintain a constant section to ensure in all conditions of

  provides adequate air flow through the fuel burner 10.

  Fuel burners 10 according to the present invention are originally intended to use diesel oil as fuel. It should be noted, however, that other

  fuels can be used if desired.

Claims (8)

Claims:   I.- Fuel burner for a gas turbine engine comprising an annular body having a radially inner annular surface and the upstream end of which is adapted to receive an air flow in service. an annular fuel manifold disposed upstream from said annular body so as to be coaxial with said annular body and at least partially inside said annular body, said fuel manifold being adapted to direct fuel onto said annular surface and a central section body circular, at least a main portion of which is arranged coaxially inside said annular body and generally along said annular body to define an annular flow path through said burner, the downstream ends of said central body and said annular body being configured to cooperate in defining a generally radially oriented exhaust from said annular flow path, characterized in that the upstream ends of said central body (22) and said annular body (I 1) cooperate with at least part of said manifold (15) for define two coaxial passages (21, 26) of generally comparable sections used to direct iger said air flow inside said annular flow path (24) through said burner with turbulence minimum of said air flow.   2.- Fuel burner according to claim 1, characterized in that said   fuel manifold (15) extends axially.   3.- Fuel burner according to claim 2, characterized in that at least one upstream portion of said central body (22) has an outside diameter smaller than the inside diameter of at least a downstream portion of said fuel manifold (15 ), said upstream portion of said central body (22) being inside of said downstream portion of said fuel manifold (15) and separated from it radially so as to define one of said passages (2 1) serving to direct said flow air inside said path   annular flow through said burner (10).   4. Fuel burner according to any one of the preceding claims,   characterized in that said central body (22) is connected to said annular body (1 I) by several aerodynamic spacers (23) extending through said path (24) annular flow.   5. Fuel burner according to any one of the preceding claims,   characterized in that several deflecting fins (31) are provided in said exhaust (31) generally directed radially from said annular flow path (24).   6. Fuel burner according to any one of the preceding claims,   characterized in that the two defined coaxial passages (21, 26) each have wall portions which are at least partly parallel so that any differential axial thermal expansion in said annular body (1 1), said manifold ( 15) of fuel and said central body (22) has a minimal effect on the sections of said coaxial passages.   7.- Fuel burner according to any one of the preceding claims,   characterized in that the downstream end of said central body (22) has a generally frustoconical periphery in order to give an axial component downstream to said exhaust (31) generally directed radially from said annular flow path (24).   8.- Fuel burner according to any one of the preceding claims,   characterized in that said fuel is diesel.