GB2596305A

GB2596305A - Burner of a reheat gas turbine engine

Info

Publication number: GB2596305A
Application number: GB2009568.3A
Authority: GB
Inventors: Yang Yang; Baibuzenko Igor; Myatlev Alexander; Rubekin Evgeny
Original assignee: Ansaldo Energia Switzerland AG
Current assignee: Ansaldo Energia Switzerland AG
Priority date: 2020-06-23
Filing date: 2020-06-23
Publication date: 2021-12-29
Also published as: GB202009568D0

Abstract

A burner 1 of a reheat gas turbine engine has a body 2 that may be annular and includes an inner wall 7 and an outer shell 8. The burner further includes a front panel 5a, 5b which may include a damper 10 to dampen thermo-acoustic oscillations during the combustion process in the combustion zone 6. The burner can include a mixing zone 4 downstream of fuel injection heads 3, and the inner wall and outer shell are provided with convective cooling, i.e. a cooling air flow is provided sweeping over the wall and shell in a counter current direction. The inner wall and outer shell can have a hollow structure, with a chamber or a number of axial channels, and can include ribs and/or turbulators for cooling heat transfer enhancement. In use, cooling air is then exhausted in the hot gas via film cooling holes 20 provided close to the trailing edge of the injector heads. The arrangement reduces the required cooling air mass flow consumption and minimizes the cold near wall layer at the inner wall and outer shell. This improves emission performance and increases the flame temperature.

Description

BURNER OF A REHEAT GAS TURBINE ENGINE

The present invention relates to a burner of a reheat gas turbine engine.

A reheat gas turbine engine comprises a compressor, a first combustion chamber, a second combustion chamber fed with hot gas generated in the first combustion chamber and a turbine. In different examples, between the first and the second combustion chamber, a high pressure turbine can be provided; alternatively, between the first and the second combustion chamber a mixer, for injecting air into the hot gas generated in the first combustion chamber, can also be provided. During operation, air is compressed at the compressor and fed together with a fuel in the first combustion chamber, where the fuel is combusted generating hot gas. The hot gas, partially expanded in the high pressure turbine (if the high pressure turbine is foreseen) or diluted with air (if the mixer is foreseen) is then fed in the second combustion chamber where further fuel is supplied and combusted by auto combustion after a given delay time with residual air still present in the hot gas. The hot gas emerging from the second combustion chamber is finally expanded in the turbine.

The second combustion chamber is provided with burners having tubular body and a combustion area; the burners receive the hot gas from the first combustion chamber, inject fuel in this hot gas and mix the fuel with the hot gas, to provide the zo mixture to the combustion area.

Since the fuel is combusted by auto ignition, in order to reach an acceptable level of flashback margin, the hot gas must have a high velocity when moving through the mixing zone of the burners. This causes high convective heat transfer to the walls of the tubular body at the mixing zone.

Traditionally, the walls of the tubular body are provided with effusion cooling holes, through which cold air, which is contained in a plenum housing the second combustion chamber, is fed in such a way that it forms a layer of cold air over the wall of the second combustion chamber, in order to counteract heat exchange.

It was found that the layer of cold air causes non-uniformity of both hot gas temperature and mixing quality; this negatively affects the emission performance of the gas turbine engine.

It is an aspect of the invention to provide a gas turbine engine with improved emission performance over traditional gas turbine engines.

This and further aspects are attained by providing a gas turbine engine in accordance with the accompanying claims.

Further characteristics and advantages will be more apparent from the description of a preferred but non-exclusive embodiments of the burner, illustrated by way of non-limiting example in the accompanying drawings, in which: Figure 1 shows an example of a burner according to the invention.

Figure 1 shows the second burner of the gas turbine engine. The second burner 1 has a tubular or annular body 2 having one or more fuel injection heads 3 at one of its ends and a mixing zone 4 at a second end; the second end of the burner is connected to an inner front panel 5b and an outer front panel 5a that delimit a zo combustion zone 6.

In the following reference to an annular second combustion chamber is made such that the body 2 is defined by an inner wall 7 and an outer shell 8.

The inner wall 7 and outer shell 8 are highly thermally loaded by the hot gas generated in the first combustion chamber and passing through the burners of the second combustion chamber.

Traditionally effusion holes are distributed over the front panel 5a, 5b, inner wall 7 and outer shell 8 for cooling them. This causes a large air consumption and also non-uniformity of the hot gas temperature and mixing quality.

According to the invention, the inner wall 7 and the outer shell 8 are convectively cooled, i.e. a cooling air flow is provided sweeping over them in counter current. In this respect, the inner wall 7 and outer shell 8 can have a hollow structure, with a chamber extending over (substantially) all the inner wall 7 and outer shell 8 or a number of channels directed axially or along a direction inclined with respect to an axial axis.

The inner wall 7 and outer shell 8 have a similar structure and may comprise ribs and/or turbulators for cooling heat transfer enhancement.

Cooling air is then exhausted in the hot gas via film cooling holes 20 provided as upstream as possible, i.e. close to the trailing edge of the injector heads.

This solution reduces the required cooling air mass flow consumption and minimizes the cold near wall layer at the inner wall 7 and outer shell 8, with a beneficial effect on the emission performance, also in view of a possible increase of the flame temperature.

The inner and/or outer front panels (in the figure the outer front panel 5a) can carry a damper 10 for damping thermo-acoustical oscillations that may be generated during operation of the gas turbine engine; the inner and preferably also outer front panels 5b, 5a can be produced using additive manufacturing and can have near wall cooling channels. Near wall cooling channels are uniformly distributed within the front panel and are oriented substantially radially.

The invention thus provides for a combination of near wall cooling for the front panel and convective cooling for the inner wall and outer shell, with exhaust of the cooling air in the hot gas close to the injector head trailing edge.

The front panel near wall cooling channels minimize the cooling air mass flow consumption. Near wall channels have curved shape and are arranged evenly for uniform cooling and are oriented radially from the center to mitigate for hot gas ingestion caused by the secondary flow structured of the hot gas in the combustion chamber.

Convective cooling air of the inner wall and outer shell minimizes the layer of cold air at the surfaces of the inner wall 7 and outer shell 8; this is beneficial for combustion and emission performance for future increase of flame temperature.

Naturally the features described may be independently provided from one another.

In practice the materials used and the dimensions can be chosen at will according to requirements and to the state of the art.

Claims

CLAIMS1. A burner of a reheat gas turbine engine comprising a body with an inner wall and an outer shell and a front panel, wherein the inner wall and outer shell are provided with convective cooling only.
2. The burner of claim 1, wherein the inner wall and outer shell have a hollow structure, with a chamber extending over all the inner wall and outer shell or a number of channels directed axially or along a direction inclined with respect to an axial axis.
3. The burner of any of the previous claims, wherein the front panel carries at least a damper for damping thermo-acoustical oscillations that may be generated during operation of the gas turbine engine.
4. The burner of any of the previous claims, wherein the front panel is produced by additive manufacturing and has near wall cooling channels.
5. The burner of the previous claim, wherein the near wall cooling channels are uniformly distributed within the front panel and are oriented radially.