GB2402714A

GB2402714A - Cannular combustor with directly associated nozzle guide vanes

Info

Publication number: GB2402714A
Application number: GB0313543A
Authority: GB
Inventors: Michael Whiteman; Michael Andrew Macquisten; Anthony John Moran
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2003-06-12
Filing date: 2003-06-12
Publication date: 2004-12-15
Also published as: GB0313543D0

Abstract

A cannular arrangement of combustors is used in a turbine engine for a stationary or industrial environment. The combustors discharge a combustion flow 33 through an exit nozzle 31 which is guided by nozzle guide vanes 34. Thus the discharge flow 33 is rendered annular by the guide vanes 34. The invention provides a direct association between the guide vanes 34 and the exit 31. A continuous discharge path eliminates the gap (6, figure 1) which allows circumferential thermo acoustic flows which cause efficiency as well as noise problems.

Description

24027 1 4 Turbine Engine The present invention relates to a turbine engine

and more particularly to the combustion discharge of a static turbine engine.

Operation of turbine engines is well known and involves in principal the stages of suck, squeeze, combustion and blow. The present invention relates to discharge from the combustion process through nozzle guide vanes in a turbine engine. Use of turbine engines with respect acting as a primary mover for electricity generation and pumping purposes is known and the relatively high efficiency of such turbine engines makes them attractive for these purposes. Clearly, with regard to any engine operation efficiency as well as environmental effects such as noise are important.

Previously a combustion discharge nozzle in a turbine engine has taken the form of a cannular which discharges through a nozzle and subsequently nozzle guide vanes to turbines upon a shaft to cause rotation of that shaft which in turn drives compressor blades for engine operation.

Previously a cannular combustion system has been incorporated in the turbine engine as an adjunct to an existing nozzle guide vane arrangement for that engine. In such circumstances the cannular combustor can be readily installed and removed as necessary for assembly as well as maintenance.

Unfortunately, such an arrangement of a distinct unitary combustion cannular causes a gap between the discharge nozzle exit of the combustor and the nozzle guide vanes. This gap causes a thermo acoustic resonance which spins around the gap between the discharged nozzle of the cannular combustor and the nozzle guide vanes. This À:. .e Age...: À:e:e acoustic resonance causes problems in terms of noise levels as well as flow control.

In accordance with the present invention there is provided a turbine engine including a cannular combustor associated with nozzle guide vanes to guide combustion discharge to turbines for engine operation, the engine characterized in that the combustor incorporates a discharge exit which includes guide vanes directly associated with that discharge exit for a continuous discharge path.

Preferably, the guide vanes are integrally formed within a discharge nozzle of the cannular combustor.

Possibly, the engine is reinforced about mountings normally associated with guide vanes for the engine.

Typically, the discharge exit defines a conduit incorporating the guide vanes and that conduit is smooth to avoid flow turbulence and deflection.

Possibly, the guide vanes are provided by an insert secured within the discharge exit.

Also in accordance with the present invention there is provided a cannular combustor for a turbine engine as described above. Furthermore, there is provided in accordance with the present invention a discharge exit for a cannular combustor of a turbine engine.

An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: Fig. 1 is a schematic illustration of an existing cannular combustor and nozzle guide vane arrangement for a turbine engine; Fig. 2 is a cross section of a cannular discharge exit in accordance with the present invention; and, e. es.. ... a:: Àe e. ce Fig. 3 is a schematic illustration of a plan cross section depicting a discharge exit in accordance with the present invention.

Fig. 1 provides a cross section illustrating a combustor cannular discharge exit 1 associated with a nozzle guide vane assembly 2. It will be appreciated that the exit 1 and assembly 2 are associated in use with a turbine engine in order that combustion discharge in the direction of arrowhead 3 passes through the exit 1 and is guided by vanes 4 in the assembly 2 for incidence upon turbine blades 5 which rotate in accordance with known turbine engine practice. Generally, the discharge nozzle or exit 1 is used to merge the combustion flows leaving the combustor of the turbine engine so that these flows enter the turbine 5 with an annular flow profile.

As can be seen the nozzle exit 1 in previous arrangements is spaced from the nozzle guide vane assembly 2. There is a gap 6 which is generally in the order of 30mm.

This gap 6 creates thermo acoustic resonance particularly as a result of circumferential mode spinning around the gap 6 between the discharge exit nozzle 1 and the guide vanes 4 of the assembly 2. In terms of noise abatement and efficiency it is desirable to remove the acoustic path created in the gap 6.

Fig. 2 illustrates a cross section of a discharge nozzle exit 21 in accordance with the present invention.

This exit 21 incorporates direct flow to nozzle guide vanes 24. In such circumstances, a combustion flow in the direction of arrow head 23 passes through the nozzle 21 and is guided by the vanes 24. There is no gap between the exit and the vanes 24 so that there is a continuous discharge path and therefore no possible acoustic pathway with circumferential mode spinning for thermo acoustic resonance. Further, as illustrated, the vanes 24 are integrally formed with the exit nozzle 21 in order to create a smooth path or conduit within the exit 21 to the vanes 24. Such a smooth path will avoid turbulence due to surface protrusions and ribbing.

The exit nozzle 21 incorporating vanes 24 in accordance with the present invention will be mounted within a turbine engine utilising existing mountings or specific mounting arrangements. Where existing mountings are utilised, it would be appreciated that the exit nozzle 21 will typically be secured by those mountings previously provided for a previous discharge nozzle or an independent guide vane assembly and then the security of this mounting will be supplemented by mountings typically provided by a separate exit nozzle.

As an alternative to integrally forming the guide vanes within the exit nozzle 21 it will be appreciated that a couplable vane assembly may be provided which is directly coupled with an outlet part of the exit nozzle 21 such that there is no gap that is to say there is a substantially continuous exit nozzle discharge path is provided. In such circumstances, there is no gap and therefore circumferential thermo acoustic swirl cannot occur in that gap.

As a further alternative it will be appreciated that distinct guide vanes in the form of an insert grille or cassette may be manufactured. This guide vane insert cassette will then be located within the exit nozzle of the cannular combustor in order to provide direct flow to those guide vanes for nozzle guide vane operation.

As indicated above, the purpose of the nozzle guide vanes is to ensure annular flow. In such circumstances, direct operation of guide vanes either integrally formed or directly secured or in the form of an insert cassette within a discharge exit nozzle will release annular discharge flow. In such circumstances, the guided air flow as a result of the direct guide vanes now incorporated directly in the exit nozzle in accordance with the present invention will inhibit circumferential thermo acoustic flow by constraining and directing that flow towards the existing engine turbines.

Normally, within an engine the nozzle guide vanes provide some structural support. Thus, as the previous nozzle guide vane assembly, at least in terms of the vanes, is removed it is generally necessary to reinforce the engine about the mountings for these guide vanes or assembly to retain structural strength.

Fig. 3 is a schematic plan view illustrating a nozzle discharge exit 31 in accordance with the present invention.

As can be seen the exit nozzle 31 comprises a cannular conduit 32 from a combustor (not shown). A combustion discharge flow in the direction of arrowhead 33 passes through the cannular conduit 32. This discharge flow 33 is 0 presented to guide vanes 34 which essentially guide that flow 33 for appropriate presentation to a turbine (not shown) downstream of the exit nozzle 31. Vanes 34 ensure an annular flow downstream of the exit nozzle 31 which is appropriate for coupling to the turbines for turbine engine operation in accordance with known practice.

It can be seen that an exit wall 34 of the exit nozzle 3 is continuous. Thus, there is no gap within which turbine acoustic flow can occur.

Normally, there is a cannular combustor arrangement about the engine whereby exit nozzles are presented and d scharged flow is appropriately guiding for turbine rotation and therefore engine function.

It will be understood that an exit nozzle in accordance with the present invention may be manufactured 1 À À . : . : . as an integral unit by casting or as described above nozzle guide vane cassettes as inserts may be located in a generally open nozzle exit to create the direct vane guiding without a gap required to avoid potential circumferential thermo acoustic mode pathways. It will also be understood that a nozzle guide vane grating may be secured directly to the end of the exit conduit pathway such that there is direct flow to the guide vanes without a gap therebetween.

Generally, the shape and configuration in terms of dimensions, angles and path lengths will be determined for particular installations of exit nozzles for cannular combustors. These dimensions, vane angles as well as path lengths will be chosen for particular turbine engine performance, size and output requirements. Nevertheless, removal of the gap between the exit nozzle and previous guide vane assemblies will eliminate circumferential thermo acoustic flow with consequent improvements in engine performance.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

At: ::: cese, :: '. e I e e e e CLAIMS

1. A turbine engine including a cannular combustor associated with nozzle guide vanes (2) to guide combustion discharge (3) to turbines for engine operation, the engine characterized in that the combustor incorporates a discharge exit (21, 31) which includes guide vanes (24, 34) directly associated with that discharge exit (21, 31) for a continuous discharge path.

2. An engine as claimed in claim 1, wherein the guide vanes (24, 34) are integrally formed within a discharge nozzle (21, 31) of the cannular combustor.

3. The engine is reinforced about mountings normally associated with guide vanes (2) for the engine.

4. An engine as claimed in any preceding claim, wherein the discharge exit (21, 31) defines a conduit incorporating the guide vanes (24, 34) and that conduit is smooth to avoid flow turbulence and deflection.

5. An engine as claimed in any claims 1 to 3, wherein the guide vanes (24, 34) are provided by an insert secured within the discharge exit (21, 31).

6. A turbine engine substantially as hereinbefore described with reference to the accompanying drawings.

7. A cannular combustor for a turbine engine, the combustor characterized in that a discharge exit (21, 31) includes guide vanes (24, 34) directly associated with that discharge exit (21, 31) for a continuous discharge path.

8. A cannular combustor substantially as hereinbefore described with reference to Figs. 2 and 3.

9. A discharge exit (21, 31) for a cannular combustion of a turbine engine, the exit (21, 31) characterized in that it includes guide vanes (24, 34) directly associated with that discharge exit (21, 31) for a continuous discharge path.

10. A discharge exit substantially as hereinbefore described with reference to Figs. 2 and 3.

11. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.