GB1572336A - Combustion equipment - Google Patents

Description

(54) COMBUSTION EQUIPMENT (71) We, LUCAS INDUSTRIES LIMITED, a British Company, of Great King Street, Birmingham B19 2XF, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be per formed to be particularly described in and by the following statement: This invention relates to combustion equipment of the type in which fuel is injected by means of a plurality of fuel injectors into an annular flame tube via respective openings in an annular baffle.

It has been proposed in such combustion equipment to provide an annular baffle formed of a plurality of circumferentially spaced baffle segments. Each baffle segment has a central opening in a rear thereof and a frustoconical surface extending around the opening and projecting forwardly thereof, i.e. away from an end wall of the flame tube through which the fuel injectors extend. With such a proposed arrangement, four corners at the front of the baffle segment are defined by planar portions which merge with the frustoconical surface so as to provide an overall continuity to the annular baffle.

It has now been found that, with such a construction, there is a tendency for the corners of each baffle segment to become overheated.

Upon further investigation, the Applicants found that the overheating was caused by the discontinuity in the surface of the baffle segment since the cooling effect of the air entering the flame tube via the central opening in each baffle segment did not extend to the comers of the baffle segment.

It is an object of the present invention to obviate or mitigate the above disadvantage.

According to the present invention, there is provided combustion equipment comprising an annular flame tube having an annular end wall, a plurality of circumferentially spaced openings for fuel injectors in the end wall, and an annular baffle disposed in the flame tube adjacent said end wall, said annular baffle being defined by a plurality of circumferentially spaced baffle segments each having a central rear opening therein which is aligned with a respective one of the fuel injector openings in the end wall, wherein each baffle segment has a frusto-conical surface extending continuously from the central rear opening away from said end wall to four corners at a front of the baffle segment.

By extending the frusto-conical surface continuously from the rear opening to the four corners at the front of each baffle segment, an improved cooling of the baffle occurs because of the avoidance of discontinuities in the surface of the baffle segment.

In order to enhance the cooling at the corners of each segment, it is preferred to provide a multiplicity of cooling holes through each corner of the baffle segment.

Preferably, each baffle segment is provided with a curved lip around the front thereof, said curved lip defining inner and outer circumferentially directed edges and a pair of radially directed edges.

In order to enhance further the cooling at the front of each baffle segment, it is preferred to provide a row of cooling holes through the lip, said row extending around each baffle segment.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial section through part of one embodiment of combustion equipment according to the present invention, Figure 2 is a front view of a baffle segment forming part of the combustion equipment of Figure 1, Figure 3 is a view in the direction of arrow 3 in Figure 2, and Figure 4 is a view in the direction of arrow 4 in Figure 2.

Referring first to Figure 1 of the drawings, the combustion equipment illustrated therein comprises an annular flame tube 10 of which only an inlet section thereof is illustrated in Figure 1. The flame tube 10 comprises an outer peripheral wall 11, an inner peripheral wall 12 and an annular end wall 13 joining the outer and inner periphery walls 11 and 12. The end wall 13 has a plurality of circumferentially spaced openings 14 therein for the reception of respective fuel injectors 15. A portion of the end wall 13 around each opening 14 extends inwardly of the flame tube 10 to define a sleeve 16. An inner end of each sleeve 16 is in slidable engagement with a surrounding sleeve 17 which is integral with an annular upstream baffle 18. The upstream baffle 18 is integral with parts of the outer and inner peripheral walls 11 and 12.The upstream baffle 18 has rings of inner and outer orifices 19 and 20 therethrough for passage of co5linjir which passes, in use, through apertures 21 in the end wall 13. Secured in each sleeve 17 is one end of a further sleeve 22 which forms part of a respective primary baffle seg- ment 23. The baffle segments 23 are peripherally spaced apart within the flame tube 10 so as to define an annular baffle within the flame tube 10. Disposed in and fixed to each sleeve 22 is a ring of inclined swirler blades 24 which are themselves disposed around and fixed to a sleeve 25 which, in use, supports a forward end of the respective fuel injector 15.

The outer and inner peripheral walls 11 and 12 are provided with secondary air holes 26 therein which are fed, in use, with air from an air passage surrounding the walls 11 and 12.

As can be seen from Figure 1, a passage 27 is defined between the upstream baffle 18 and the primary baffle defined by the baffle segments 23 for passage of air from the orifices 19 and 20 across the back of the primary baffle and into a combustion zone C of the flame tube 10 passed the inner and outer peripheries of the primary baffle.

Referring now to Figures 2 to 4 of the drawings, one of the baffle segments 23 is shown. The baffle segment 23 has a central rear opening 28 which is surrounded by the sleeve 22, and a frusto-conical surface 29 extends continuously from the opening 28 forwardly, i.e. away from the end wall 13, to four corners 30 to 33 respectively at the frong of the baf fle segment 23. Around the front of the baffle segment 23, there is provided a curved lip 34.

As can be seen from Figure 1, the lip 34 is curved so that its end remote from the frusto conical surface 29 extends substantially paral lel to the axis of the flame tube 10. The lip 34 thus defines inner and outer circumferentially extending edges and a pair of radially extending edges to each baffle segment 23. As can be seen from Figures 1,3 and 4, the inner and outer edges and the radial edges of the front of each baffle segment 23 are each concavely curved so that the centre of each edge lies nearer to the back of the segment 23 than the end of each edge. This is in constrast to a construction in which the annular primary baffle is formed of a plurality of baffle segments having flats at the corners.In such a construction, the inner and outer and the radial edges of each baffle segment are not curved in this manner and so such edges appear as straight lines when viewing the segment in directions corresponding to those indicated by arrows 3 and 4 in Figure 2.

Although not shown in relation~to corners 30 and 33, each baffle segment 23 has a multiplicity of holes 35 therethrough at each corner 30 to 33. As can be seen from Figure 2, there are more holes 35 provided through the corners 30 and 31 than there are provided through the comers 32 and 33. Thisis because the dimension of each segment 23 along its outer edge is greater than along its inner edge. The baffle segment 23 is also provided with a row of further holes 36 around its perimeter, the holes 36 being located in the lip 34.

In use, fuel or a mixture of air and fuel is ejected by each fuel injector 15 in the form of a conical discharge into the combustion zone C.

At the same time, air enters the flame tube 10 via the openings 14 and has a swirl imparted thereto by the respective air swirler blades 24. This swirling air pattern increases the angle of the conical discharge of the fuel or fuel and air from the respective fuel injector 15 and the primary baffle defined by the baffle segments 23 assists in setting up a circulation of fuel and air in the com bustion zone C. Cooling of the internal surface of each baffle segment 23 is effected by means of the air from the openings 14 via the swirler blades 24.

Air also enters the flame tube via the apertures 21, the orifices 19 and 20 in the upstream baffle 18 and the passage 27. From the passage 27, the air passes around the inner, outer and radial edges of each baffle segment to effect a cooling of the external surface thereof. Air which enters the combustion zone via the outer and inner edges of each baffle segment 23 alsoassist in cooling of the adjacent portion of the outer and inner peripheral walls 11 of the flame tube 10. Some of the air passing along the passage 27 passes through the holes 35 and 36 in the baffle segments 23 to effect further cooling thereof.

Secondary air enters the - combustion zone C via the openings 26 in the outer and inner peri pheral walls 11 and 12 of the flame tube 10 to take part in the combustion process. Dilution holes shown) are alsoprovided in the outer and inner peripheral walls 11 and 12 downstream of the openings 26 in a manner known per se.

Because the frusto-conical surface 29 in each baffle segment 23 extends continuously from the respective opening 28 to the corners 30 to 33, an effective cooling of all of the primary baffle is effected. In fact even with an air inlet temperature of 400 C., with the above described construction, it is found that there is nowhere on the primary baffle which reaches a temperature higher than 650"C. even under full load conditions, whereas a construction wherein the baffle segments have corners which are flattened reaches temperatures as high as 9000C. under the same conditions.

WHAT WE CLAIM IS: 1. Combustion equipment comprising an annular flame tube having an annular end wall, a plurality of circumferentially spaced openings for fuel injectors in the end wall, and an annular baffle disposed in the flame tube adjacent said end wall, said annular baffle being defined by a plurality of circumferentially spaced baffle segments each having a central rear opening therein which is aligned with a respective one of the fuel injector openings in the end wall, wherein each baffle segment has a frusto-conical surface extending continuously from the central rear opening away from said end wall to four corners at a front of the baffle segment.

2. Equipment as claimed in claim 1, wherein a multiplicity of cooling holes are provided through each corner of the baffle segment.

3. Equipment as claimed in claim 1 or 2, wherein each baffle segment is provided with a curved lip around the front thereof, said curved lip defining inner and outer circumferentially directed edges and a pair of radially directed edges.

4. Equipment as claimed in any preceding claim, wherein a row of cooling holes is provided through th lip, said row extending aroud vided through the lip, said row extending around each baffle segment.

5. Combustion equipment substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. the respective opening 28 to the corners 30 to 33, an effective cooling of all of the primary baffle is effected. In fact even with an air inlet temperature of 400 C., with the above described construction, it is found that there is nowhere on the primary baffle which reaches a temperature higher than 650"C. even under full load conditions, whereas a construction wherein the baffle segments have corners which are flattened reaches temperatures as high as 9000C. under the same conditions. WHAT WE CLAIM IS:

1. Combustion equipment comprising an annular flame tube having an annular end wall, a plurality of circumferentially spaced openings for fuel injectors in the end wall, and an annular baffle disposed in the flame tube adjacent said end wall, said annular baffle being defined by a plurality of circumferentially spaced baffle segments each having a central rear opening therein which is aligned with a respective one of the fuel injector openings in the end wall, wherein each baffle segment has a frusto-conical surface extending continuously from the central rear opening away from said end wall to four corners at a front of the baffle segment.

2. Equipment as claimed in claim 1, wherein a multiplicity of cooling holes are provided through each corner of the baffle segment.

3. Equipment as claimed in claim 1 or 2, wherein each baffle segment is provided with a curved lip around the front thereof, said curved lip defining inner and outer circumferentially directed edges and a pair of radially directed edges.

4. Equipment as claimed in any preceding claim, wherein a row of cooling holes is provided through th lip, said row extending aroud vided through the lip, said row extending around each baffle segment.

5. Combustion equipment substantially as hereinbefore described with reference to the accompanying drawings.