EP0648979B1 - Method and means for cooling a gas turbine combustion chamber - Google Patents

Description

Technical field

The invention relates to a method and an apparatus for Cooling one by means of impingement and convection cooling or pure convection cooling cooled gas turbine combustion chamber.

State of the art

From GB-A-2 077 635 a gas turbine combustor is known the combustion chamber wall is cooled inside by film cooling. The combustion chamber wall is made up of several layers. A Part of the in the annulus between this combustion chamber wall and the Cooling air flowing along the outer wall flows through openings in spaces within the combustion chamber wall and from there in the downstream direction through parallel cooling channels in the Flame tube into where the air is on the inside of the The combustion chamber wall lays and cools it.

A disadvantage of this film cooling method is that due to the loss of cooling air pressure with a large excess of air must be worked and the NOx emission values are quite high.

In modern gas turbine combustors, cooling methods are therefore increasingly used which require little or no cooling air. Because NO _x emissions should be avoided as much as possible, efforts are made to pass as much air as possible through the burners. For this reason, combinations of impingement and convection cooling systems or pure convection cooling systems are increasingly being used. With an unfavorable design, such systems can have the problematic property that small primary damage, for example a small hole in the combustion chamber wall, can lead to very large consequential damage which endanger the operation of a gas turbine. For example, a hole in a cooling duct can result in the cooling duct not being adequately supplied with air after the hole. This can result in damage to the entire channel after the hole or even further damage.

Presentation of the invention

The invention tries to avoid all these disadvantages. you the task is based on an impact and convection cooling or pure convection cooling cooled gas turbine combustion chamber a method and an apparatus for To create cooling with which it is possible to occur minor local damage, such as holes, in the cooling channel to prevent further enlargement of this damage.

According to the invention, this is the case with a method for cooling the gas turbine combustion chamber according to the preamble of the main claim achieved in that the compensating flow in Cooling duct is guided past the outer wall of the combustion chamber.

According to the invention, this is done in a cooling device the gas turbine combustion chamber according to the preamble of the main claim achieved in that between adjacent cooling channels Connection openings are arranged, the connection openings on the outside wall in each of the cooling fins staggered on opposite sides of a cooling channel are.

The advantages of the invention include that a chain reaction when local damage occurs is avoided in the cooling channel and "self-healing" of the damaged cooling duct. The flow rate in the damaged cooling duct even after the Damage point always a critical limit, so that the temperature falls below a critical limit. If the equalizing flow on the outer wall of the combustion chamber is led along, cooling film flows form on the outer wall, which is the outer wall in the area of the damage point cool intensely and completely.

It is advantageous if the web lengths and the opening lengths of the connection openings are the same size, because of that favorable cooling conditions can be achieved.

It is useful if the connection openings between the cooling ducts are dimensioned so that the product average opening width and cooling channel length based on the Cross-sectional area of the cooling channel in the range between 2 and 8 lies. Then the most effective cooling can be achieved.

Brief description of the drawing

In the drawing is an embodiment of the invention represented by a dense gas turbine combustion chamber.

Fig. 1

eine vereinfachte perspektivische Darstellung der Gasturbinenbrennkammer;

Fig. 2

einen Teil der Kühlkanäle der Brennkammer;

Fig. 3

einen Längsschnitt durch einen Kühlkanal.

Show it:

Fig. 1

a simplified perspective view of the gas turbine combustor;

Fig. 2

part of the cooling channels of the combustion chamber;

Fig. 3

a longitudinal section through a cooling channel.

It is only essential for understanding the invention Elements shown. The direction of flow of the cooling air is marked with arrows.

Way of carrying out the invention

The invention is described below using an exemplary embodiment and Figures 1 to 3 explained in more detail.

A gas turbine combustion chamber is shown in simplified form in FIG. 1. To cool the combustion chamber wall 1 is a convective Cooling system used. The entire cooling air flows in cooling channels 2 between the outer wall 3 and the combustion chamber wall 1 along before being fed to the combustion chamber as combustion air becomes. As can be seen from Fig. 2, there are between the cooling channels 2 cooling fins 4, in which according to the invention Connection openings 5 are present. These connection openings 5 are on opposite sides each a cooling channel 2 arranged offset.

d = Breite der Öffnung

L_O = Öffnungslänge

L_B = Steglänge.

Fig. 3 shows in a partial longitudinal section that the web length L _B and the opening length L _{O are} approximately the same size. The average gap width s between two adjacent cooling channels 2 results from the equation s = L O d L O + L B With

d = width of the opening

L _O = opening length

L _B = web length.

The dimensioning of the connection openings 5 between the cooling channels 2 is advantageously carried out according to the design rule 2 <sL / A <8, that is, the product of the average opening width s between two cooling channels 2 and the cooling channel length L, based on the cross-sectional area A of the cooling channel 2, is in the range greater than 2 and less than 8. If the value falls below the lower limit of this interval, a very large hole can lead to overheating of the cooling channel 2 after the hole. If the upper value is clearly exceeded, then a very large hole or a longitudinal slot in one or more cooling channels can lead to such a high air loss that the burners locally overheat the primary zone of the combustion chamber in full load operation.

In the course of operation of the gas turbine combustor can Cooling channels a local damage to the material occur e.g. can be a local damage in the combustion chamber wall 1 6 in the form of a small hole. Then there is in usual gas turbine combustion chambers, which by combined Impact and convection cooling systems or through pure convection cooling systems cooled according to the state of the art be the danger that this small damage point 6 too major consequential damage, because the cooling channel 2 after the Hole is no longer adequately supplied with cooling air.

This chain reaction is, however, according to the present invention Embodiment prevented because between the cooling channels 2 through the connection openings 5, a compensating flow is generated, which causes the flow velocity the cooling air in the damaged cooling duct 2 a critical one even after the local damage point 6 Never falls below the limit value, so that an excess is exceeded critical limit temperature is prevented.

The staggered arrangement of the connection openings 5 ensures that there is air at least in every axial position flow into an adjacent duct in the damaged cooling duct 2 can. The compensating flow takes place at the Combustion chamber outer wall 3.

If there is a hole in the combustion chamber inner wall 1 are formed on the outer wall 3 along cooling film flows, which the cooling channel 2 and especially the outer wall 3 intensive in the area of the local damage site 6 (hole) and cool completely. This can allow further growth of the hole can be avoided. There is a "self-healing" of the damaged cooling duct. The invention has particular very important for thin combustion chamber walls with high heat loads.

Reference list

1

Combustion chamber wall

2nd

Cooling channel

3rd

Outer wall

4th

Cooling fin

5

Connection opening

6

local damage site

L _O

Opening length

L _B

Bridge length

s

medium opening width

L

Cooling channel length

A

Cross-sectional area of a cooling channel

d

Width of the opening

Claims (4)

1. Method for cooling a gas turbine combustion chamber in which the entire cooling air is guided in cooling ducts (2), which are separated from one another by means of cooling ribs (4), between the combustion chamber wall (1) and the outer wall (3), the gas turbine combustion chamber being cooled by means of impingement and convection cooling or pure convection cooling, and after a local damage location (6) has arisen in the cooling duct (2), a compensating flow of the cooling air is guided out of adjacent cooling ducts (2) into the damaged cooling duct (2), characterized in that the compensating flow in the cooling duct (2) is guided past the combustion chamber outer wall (3).
2. Appliance for carrying out the method according to Claim 1, consisting of a gas turbine combustion chamber cooled by means of impingement and convection cooling or pure convection cooling, in which cooling ducts (2) separated from one another by cooling ribs (4) are arranged between the combustion chamber wall (1) and outer wall (3), characterized in that connecting openings (5) are arranged between adjacent cooling ducts (2), the connecting openings (5) being respectively offset on the opposite sides of a cooling duct (2) in the cooling ribs (4) on the outer wall side.
3. Appliance according to Claim 2, characterized in that the web lengths (L_B) and the opening lengths (L_O) of the connecting openings (5) are of equal size.
4. Appliance according to Claim 2 or 3, characterized in that the connecting openings (5) between the cooling ducts (2) are dimensioned in such a way that the product of the average opening width (5) and the cooling duct length (L), referred to the cross-sectional area (A) of the cooling duct (2), is located in the range greater than 2 and smaller than 8.

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