A gas turbine arrangement

The present invention relates to a gas turbine arrangement.

More particularly the present invention relates to a gas turbine arrangement comprising: a passage, annular in cross section, for conveying combustion gases; located in the passage, turbine blading to be driven by the combustion gases; a diffuser, annular in form, for diffusing the combustion gases following their passage through the turbine blading; and a collector for collecting the combustion gases diffused by the diffuser, the collector comprising an annular main part, and, located at a position around the annular main part, a neck exit, in use of the gas turbine arrangement, combustion gases collected by the collector being conveyed around the annular main part of the collector in opposite senses so as to arrive at the neck exit of the collector travelling in opposed directions.

One known such gas turbine arrangement is shown in Figs 1 to 4 of the accompanying drawings . Fig l is a cut away perspective view of the arrangement, Fig 2 is a partial longitudinal cross section of the arrangement, Fig 3 is a schematic diagram illustrating the passage of combustion gases through the arrangement, and Fig 4 is a cross section on the line IV-IV in Fig 3.

Referring to Figs 1 to 4, the gas turbine arrangement comprises: a passage 1, annular in cross section, for conveying combustion gases; located in the passage 1, turbine blading 3 to be driven by the combustion gases; a diffuser 5, annular in form, for diffusing the combustion gases following their passage through the turbine blading 3; and a collector

7 for collecting the combustion gases diffused by the diffuser 5, the collector 7 comprising an annular main part 9, and, located at a position around the annular main part 9, a neck exit 11.

In use of the gas turbine arrangement, combustion gases travel along passage 1, drive turbine blading 3, are diffused by diffuser 5, and are collected by collector 7. The combustion gases on leaving the diffuser 5 form within the collector 7 first and second opposite sense vortical flows 13a, 13b, see Fig 4. These vortical flows 13a, 13b are formed by virtue of the combustion gas flow separating off the shroud rim 15 of the diffuser 5, and rolling up, see arrows 17 in Fig 3. The flow is then convected around the annular main part 9 of the collector 7, forming the first and second opposite sense vortical flows 13a, 13b. These flows 13a, 13b meet at the top neck exit 11 of the collector 7 travelling in opposed directions .

The separating of the combustion gas flow off the shroud rim 15, and the meeting of the vortical flows 13a, 13b in the neck exit 11, result in the production of significant entropy in the flow. This is detrimental to the efficiency of the gas turbine arrangement .

According to the present invention there is provided a gas turbine arrangement comprising: a passage, annular in cross section, for conveying combustion gases; located in the passage, turbine blading to be driven by the combustion gases; a diffuser, annular in form, for diffusing the combustion gases following their passage through the turbine blading; and a collector for collecting the combustion gases diffused by the diffuser, the collector comprising an annular

main part, and, located at a position around the annular main part, a neck exit, in use of the gas turbine arrangement, combustion gases collected by the collector being conveyed around the annular main part of the collector in opposite senses so as to arrive at the neck exit of the collector travelling in opposed directions, wherein the neck exit of the collector includes a partition device whereby the opposed direction flows at the neck exit are kept substantially separate .

In an arrangement according to the preceding paragraph, it is preferable that the turbine blading rotates about a centre line of the gas turbine arrangement, and the partition device runs parallel to the centre line, and extends radially from the centre line.

In an arrangement according to the preceding paragraph, it is preferable that the diffuser has a mouth whereby combustion gases leave the diffuser and enter the collector, the partition device comprises a first portion that extends over the mouth and a second portion that extends to one side of the mouth, and the second portion extends radially inward to a position closer to the centre line than the mouth.

In an arrangement according to the preceding paragraph, it is preferable that the side of the first portion that faces radially inwardly increases in distance from the centre line as the distance from the second portion increases.

In an arrangement according to any one of the preceding four paragraphs, it is preferable that the partition device comprises a flat plate.

In an arrangement according to any one of the preceding five paragraphs, it is preferable that the diffuser has a curved shroud rim whereat combustion gases leave the diffuser and enter the collector, the shroud rim has an extension operative to increase pressure recovery in the gas turbine arrangement, and the extension comprises a flat rim extension that is generally planar in form and forms a discontinuity with the curved shroud rim.

In an arrangement according to any one of the preceding five paragraphs but one, it is preferable that the diffuser has a curved shroud rim whereat combustion gases leave the diffuser and enter the collector, the shroud rim has an extension operative to increase pressure recovery in the gas turbine arrangement, and the extension comprises a spiral rim extension that continues or extends the curve of the curved shroud rim so as to form a spiral.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig 1, already referred to, is a cut away perspective view of a known gas turbine arrangement;

Fig 2, also already referred to, is a partial longitudinal cross section of the arrangement of Fig 1; Fig 3, also already referred to, is a schematic diagram illustrating the passage of combustion gases through the arrangement of Fig 1;

Fig 4, also already referred to, is a cross section on the line IV-IV in Fig 3; Fig 5 is a cut away perspective view of a gas turbine arrangement in accordance with the present invention;

Fig 6 is a partial longitudinal cross section of the arrangement of Fig 5;

Fig 7 is a schematic diagram illustrating the passage of combustion gases through the arrangement of Fig 5;

Fig 8 is a cross section on the line VIII-VIII in Fig 7;

Fig 9 illustrates in greater detail the form and location of a splitter plate of the arrangement of Fig 5;

Fig 10 illustrates alternative splitter plates to the splitter plate of Fig 9;

Fig 11 illustrates possible extensions to a shroud rim of the arrangement of Fig 5; Figs 12, 13 and 14 illustrate respectively combustion gas flow in three gas turbine arrangements;

Figs 15, 16 and 17 are plan views corresponding respectively to Figs 12, 13 and 14;

Figs 18, 19 and 20 are side views corresponding respectively to Figs 12, 13 and 14;

Figs 21 and 22 are perspective views corresponding respectively to Figs 13 and 14; and

Fig 23 illustrates an alternative form of partition device to the flat plates of earlier Figs.

In Figs 5 to 23, the same elements as appearing in Figs 1 to

4 are labelled with the same reference numerals.

Referring to Figs 5 to 8, the arrangement of Figs 5 to 8 is the same as that of Figs 1 to 4 with the exception that the neck exit 11 of the collector 7 includes a partition device in the form of a splitter plate 19 whereby the opposed direction vortical flows 13a, 13b at the neck exit 11 are kept substantially separate, i.e. the splitter plate 19 isolates the vortical flows 13a, 13b one from the other. The splitter plate 19 runs parallel to the centre line A of the gas turbine arrangement, and extends radially from the centre line A.

Preventing meeting of the vortical flows 13a, 13b, reduces entropy production in the flow of combustion gases through the gas turbine arrangement, consequently improving the efficiency of the arrangement. The splitter plate 19 has the advantage that it is simple in design, and can be retrofitted to current gas turbine arrangement collectors .

Fig 9 illustrates the precise shape and location of the splitter plate 19 in the arrangement of Figs 5 to 8. The diffuser 5 has a mouth 35 whereby combustion gases leave the diffuser 5 and enter the collector 7. The splitter plate 19 comprises a first portion 37 that extends over the mouth 35 and a second portion 39 that extends to one side of the mouth 35. It can be seen from Fig 9 that the second portion 39 extends radially inward to a position 41 closer to the centre line A than the mouth 35. It can also be seen from Fig 9 that the side 43 of the first portion 37 that faces radially inwardly progressively increases in distance from the centre line A as the distance from the second portion 39 increases.

Fig 10 illustrates the precise shape of three alternative splitter plates 21, 23, 25. Plate 21 is the same as plate 19 except that the side 45 of plate 21 corresponding to side 43 of plate 19 remains at a constant distance from the centre line A. Plate 23 may be derived from plate 21 by removing that portion of plate 21 which is radially nearer to the centre line A than side 45 of plate 21. Plate 25 may be derived from plate 23 by removing a further radially inner portion of plate 23. It is to be noted that in the case of both plates 23, 25, the sides 47 of the plates 23, 25 that face radially inwardly remain at a constant distance from the centre line A. It is also to be noted that the sides 47 are

radially further from the centre line A than the mouth 35 of the diffuser 5.

Fig 11 illustrates two possible extensions 29, 31 to the shroud rim 15 of the diffuser 5 of the arrangement of Figs 5 to 8. The extensions 29, 31 operate to increase the pressure recovery in the gas turbine arrangement, over and above that obtained using a splitter plate alone. The extensions 29, 31 diffuse the combustion gas flow in a more controlled manner, weakening the vortices formed in the collector 7. Extension 29 comprises a flat rim extension, and is generally planar in form, and forms a discontinuity with the shroud rim 15. Extension 31 comprises a spiral rim extension, and continues or extends the curve of the shroud rim 15 so as to form a spiral.

Fig 12 illustrates combustion gas flow in the diffuser 5 and collector 7 of the known gas turbine arrangement of Figs 1 to 4. It is to be noted that strong vortices occur in the annular main part 9 of the collector 7, and mixing of the vortical flows 13a, 13b occurs in the neck exit 11 of the collector 7.

Fig 13 illustrates combustion gas flow in the diffuser 5 and collector 7 of a gas turbine arrangement including a splitter plate 19 only, i.e. not including an extension 29, 31 to the shroud rim 15 as shown in Fig 11. It is to be noted that strong vortices still occur in the annular main part 9 of the collector 7, but no mixing of the vortical flows 13a, 13b occurs in the neck exit 11 of the collector 7.

Fig 14 illustrates combustion gas flow in the diffuser 5 and collector 7 of a gas turbine arrangement including a splitter

plate 19 and a flat rim extension 29. It is to be noted that only weak vortices occur in the annular main part 9 of the collector 7, and, in addition, no mixing of the vortical flows 13a, 13b occurs in the neck exit 11 of the collector 7.

Figs 15, 16 and 17 are views taken from above in Figs 12, 13 and 14 respectively. Splitter plate 19 is to be noted in Figs 16 and 17. Flat rim extension 29 is to be noted in Fig 17.

Figs 18, 19 and 20 are views taken from the left side in Figs 12, 13 and 14 respectively. Splitter plate 19 is to be noted in Figs 19 and 20. Flat rim extension 29 is to be noted in Fig 20.

Figs 21 and 22 are perspective views corresponding respectively to Figs 13 and 14. Splitter plate 19 is to be noted in Figs 21 and 22. Flat rim extension 29 is to be noted in Fig 22.

In the above description, the partition device in the neck exit 11 of the collector 7 takes the form of a flat plate. It is to be realised that the partition device could take other forms that achieve the required separation of the opposed direction vortical flows 13a, 13b in the neck exit 11. Fig 23 shows an example of an alternative partition device 33, comprising an upper flat plate part 51 and a lower substantially triangular cross section part 53 having concave sides. It is to be noted that the cross section shown in Fig 23 corresponds to second portion 39 in Fig 9, and that the first portion 37 in Fig 9 remains as it is, i.e. a flat plate. The upper and lower parts 51, 53 of the partition device 33 meet at a height corresponding to the height of the obtuse angle 55 in Fig 9.