EP1223308A2 - Cooling of a turbo machine component - Google Patents

Abstract

The present invention relates to a component of a turbomachine, in particular a turbine blade, which has a cooling channel (9, 10) through which a cooling medium can flow, with at least one deflection formed by the wall (11, 12) of the cooling channel, through which the flow of the cooling medium is prevented by one first channel section (9) is deflected into a downstream second channel section (10). In the area of the deflection, at least one flow guide element (8) is arranged in the cooling channel, through which the cooling channel is divided into an inner (13) and an outer flow channel (14). The inner flow channel (13) has a constriction in the flow cross section in the present component. The proposed design of the cooling duct deflection minimizes the pressure loss caused by the deflection and at the same time achieves a significantly more homogeneous heat transfer to the cooling medium without local temperature peaks. <IMAGE>

Description

The present invention relates to a component a turbomachine, in particular a turbine blade, which can be flowed through by a cooling medium Cooling channel with at least one through the wall of the cooling channel formed deflection through which the flow of the cooling medium from a first Canal section into a downstream second Channel section is deflected, being in the area of Deflecting at least one flow guiding element in the Cooling channel is arranged through which the cooling channel in the diversion into an inner and an outer Flow channel is divided.

In the field of fluid machines, in particular of gas turbines, are used to increase the Performance increasingly higher turbine inlet temperatures aspired and realized. The higher temperatures are on the one hand through advances in materials technology towards higher permissible material temperatures and on the other hand through an improved Cooling of the components achieved the high Exposed to temperatures. Especially in the area of There is a need for gas turbines here Cooling for new generations of gas turbine blades continue to improve.

A known cooling method for cooling gas turbine blades is internal, convective cooling. In this cooling technique, cooling air is introduced through the rotor shaft into the blade root and from there is guided into cooling channels running inside the blade blade, in which it absorbs the heat from the turbine blade. The heated cooling air is finally blown out of the turbine blade through suitably arranged bores and slots.
An exemplary course of the cooling air ducts in a gas turbine blade (according to: Thalin et al. 1982: NASA CR 1656087) is shown in FIG. 1. The cooling air enters the turbine blade via the blade root 1, is guided via a cooling channel 2 to the rear of the blade and is finally blown out via corresponding opening slots 3. In the example shown in FIG. 1, a separate cooling duct 2a is additionally provided, via which part of the cooling air is guided to the front and tip of the blade in order to exit there via corresponding openings 4. The flow pattern of the cooling air within the airfoil is indicated by the arrows.
In the case of a typical course of the cooling air duct, 180 ° deflections 5 are required in the vicinity of the blade tip or the blade root, which connect the different sections of the cooling air duct 2 to one another. In the area of these deflections 5, however, complicated flow patterns with dead water areas develop, which lead to large pressure losses over the length of the cooling air duct 2 and thus require an increased pumping capacity for the transport of the cooling air. Furthermore, areas of low heat transfer to the turbine blade arise in these areas, which lead to local temperature peaks on the outer skin of the turbine blade.
FIG. 2 shows schematically a section of a cooling air duct 2 with a deflection 5, in which the recirculation areas, ie the areas that generate the high pressure loss, are identified by reference number 6. The flow of the cooling medium is again shown by the arrows. In addition to the pressure loss, the recirculation areas have only a low flow, which is why there are areas with low heat transfer.

State of the art

In the previously known technical developments, the pressure loss over the length of the cooling channel could be reduced in part by suitable arrangement of flow-guiding elements, as can be seen, for example, in FIG.
An arrangement is known from US Pat. No. 5,073,086 in which a flow guiding element is arranged in the cooling duct in the region of the deflection, through which the cooling duct in the deflection is completely divided into an inner and an outer flow duct. Through this complete division of the flow, the pressure loss caused by the deflection can be reduced, but a significantly more homogeneous dissipation of the heat from the region of the deflection is not achieved. Rather, new areas of low heat transfer arise in the area of the flow guide element designed as a deflection baffle.

The object of the present invention is in having a component of a turbomachine to provide improved cooling, in the area of Redirection of the cooling channel reduces the pressure loss and a homogeneous heat transfer is achieved.

Presentation of the invention

The task is performed using the component Claim 1 solved. Advantageous configurations the component are the subject of the subclaims.

The proposed component of the fluid machine, usually a turbine blade, has in a known manner through which a cooling medium can flow Cooling channel with at least one through the wall of the cooling channel formed by the deflection Flow of the cooling medium from a first channel section into a downstream second channel section is redirected. In the area of this redirection is also a flow control element in the present component, for example in the form of a baffle, arranged in the cooling duct through which the cooling duct in the deflection completely into an inner and an outer flow channel is divided. The this component is characterized in that the inner flow channel is constricted in the Has flow cross-section. Through this Constriction, i.e. a narrowing and subsequent renewed widening of the flow cross-section occurs a nozzle effect in the inner flow channel, which the Heat transfer due to the acceleration of the flow in advantageously increased and homogenized at the same time. The constriction is preferably by a suitable shaping or contouring of the flow guiding element and / or the wall of the cooling channel in Area of the deflection formed.

The proposed solution is therefore a Reduction of pressure losses in the redirection simultaneous homogenization of the heat transfer between the cooling medium and the wall material of the Component reached. The present design is regardless of the further configuration of the Component, in particular regardless of the rib configuration in the first and second channel section, in Hereinafter also referred to as the inlet and outlet duct, as well as possible curves on the outer Edge areas of the deflection. Such details, that with a variety of gas turbine blades occur do not affect the beneficial Effect of the present invention.

In a very advantageous further embodiment of the component, one or more outlet bores for the cooling medium are additionally formed in the wall of the cooling channel in the outer flow channel of the deflection, through which a small part of the cooling medium can exit the cooling channel. This so-called cooling air blow-out - in the case of air as the cooling medium - in conjunction with the features already explained, again contributes to a significant improvement in the heat transfer, so that a component is obtained in which on the one hand there are no longer local temperature peaks in the area of the deflection and on the other high mean values of heat transfer to the cooling medium can be achieved. By arranging these outlet bores in corner areas of the deflection, in which otherwise dead water areas occur, a significantly improved heat transfer is achieved there. The drilling leads to the dissolution of the dead water areas and thus contributes to a homogenization of the heat transfer. Furthermore, these bores can bring about the desired side effect that dust particles in the cooling medium are blown out through the bores. To reinforce this side effect, the longitudinal axes of the bores are aligned approximately in the direction of the local streamlines of the flow of the cooling medium in the cooling channel.
Due to the low adjacent flow velocity, the additional bores only make a small contribution to the global pressure loss via the cooling channel, which, due to the advantageous effect mentioned above, is hardly noticeable to minimize the pressure loss.

The constriction of the flow cross section required for the best possible function of the present invention in the inner flow channel of the deflection, that is to say in the flow channel which has the shorter flow path in the deflection, can be achieved, on the one hand, by appropriate design of the flow guide element, for example by a thickening, and, on the other hand, by a corresponding one Formation of the channel wall opposite the flow guide element in the inner flow channel can be achieved. Of course, the constriction can also be achieved by a corresponding shaping of both elements or the further wall areas surrounding the inner flow channel.
In an advantageous embodiment, in which the first and second duct sections run approximately parallel on both sides of a partition wall, which forms one side of the wall of the cooling duct, the thickness of the partition wall increases in the region of the deflection, in order to reduce the corresponding constriction within the region due to this increase in thickness inner flow channel. The shape of the contour of this partition wall, which separates the outlet duct from the inlet duct, can be different in order to bring about the effect mentioned.

The flow control element that the cooling channel in the Redirection into an inner and an outer flow channel divides, is usually as a flow baffle educated. This preferably extends Flow control element over a certain distance up to into the second duct section or outlet duct. The distance that the flow guide element in the extends into the second channel section preferably approximately the distance between the Flow control element and that in the inner flow channel opposite wall of the cooling duct at the inlet or outlet of the diversion. By extending the Flow control element is an extension of Division of the cooling channel into an inner and an outer flow channel reached. At the exit of the inner flow channel can be a slight constriction or widening of the channel cross section can be provided, so that the wall of the flow guide in this Area not necessarily parallel to the duct wall of the second channel section or outlet channel got to.

The flow guide element is preferably such trained and arranged within the deflection, that about 25 to 45% of the mass flow from the Inlet channel into the flow entering the deflection the area within the flow guide element, i.e. into the inner flow channel, enters and the rest outside the baffle, i.e. in the outer flow channel, flows. The mass flow ratio corresponds to that Entry cross-sectional area ratio of the outer and inner flow channel. The area ratio on The outlet duct should be roughly the same as the inlet duct correspond, i.e. it shouldn't be more than 20% deviate from this ratio. Of course can usually the round baffle vary in thickness, or even again with Guide devices should be provided.

In a further preferred variant of the invention the flow guide has means which a Accumulation of dust or dirt in one of the Prevent flow channels. For example can be achieved by using the flow guide Provide passage openings or otherwise on suitable Way is designed.

By the sum of those in the training courses Measures or features listed, i.e. through the Optimization of the geometry and by blowing out the cooling air at critical points, an optimized Cooling in the area of the deflecting element with minimized Pressure loss reached. The individual measures are regardless of the specific geometry of the Component and the cooling channel and can for example, also use for cooling duct deflections, whose deflection angle is not equal to 180 °. Still is the present invention neither on turbine blades still limited to gas-cooled components, but can also be used with components use other flowing cooling media.

Brief description of the drawings

Fig. 1

einen Schnitt durch eine Turbinenschaufel mit Kühlkanalumlenkungen gemäß dem Stand der Technik;

Fig. 2

eine schematische Darstellung der Ablösegebiete innerhalb einer Kühlkanalumlenkung;

Fig. 3

schematisch ein Ausführungsbeispiel für die erfindungsgemäße Ausgestaltung einer Kühlkanalumlenkung;

Fig. 4

ein Beispiel für eine Anordnung zusätzlicher Auslassbohrungen in der Kühlkanalumlenkung;

Fig. 5

die in Figur 3 dargestellte Konfiguration, mit Massnahmen zur Vermeidung einseitigen von Staub- und Schmutzansammlungen;

Fig. 6

Eine Ausgestaltung des Strömungsleitelementes zur Vermeidung von einseitigen Staub- und Schmutzansammlungen.

The present invention is briefly explained again below without restricting the general inventive concept using an exemplary embodiment in conjunction with the drawings. Show here

Fig. 1

a section through a turbine blade with cooling channel deflections according to the prior art;

Fig. 2

a schematic representation of the separation areas within a cooling channel deflection;

Fig. 3

schematically an embodiment for the inventive design of a cooling channel deflection;

Fig. 4

an example of an arrangement of additional outlet bores in the cooling channel deflection;

Fig. 5

the configuration shown in Figure 3, with measures to avoid one-sided accumulation of dust and dirt;

Fig. 6

An embodiment of the flow guide element to avoid one-sided accumulation of dust and dirt.

Ways of Carrying Out the Invention

Figures 1 and 2 have already been related explained with the description of the prior art, the problem of pressure loss occurring there and the areas of low heat transfer within the To show redirection of a cooling channel.

Figure 3 shows a schematic representation Embodiment for the design of the cooling channel deflection 5 the component of a turbomachine according to the present invention. The flow direction of the cooling medium is in turn through in this figure thick arrows indicated. The cooling medium overflows a first channel section 9 in the deflection 5 and thence to a second canal section 10. The two Channel sections 9 and 10 are used in this example separated from each other by a partition 11, the Is part of the cooling channel wall 12. Such one Cooling channel can be in a usual gas turbine blade, as shown for example in FIG. 1, be arranged.

A shaped flow or deflection baffle 8 is formed within the deflection 5, which divides the cooling channel within the deflection 5 into a radially inner flow channel 13 and a radially outer flow channel 14. Both flow channels are completely separated from one another by the deflection baffle 8. In the present example, the deflection baffle 8 also extends into the second channel section 10. The distance by which the deflection baffle 8 projects into the second channel section 10 corresponds approximately to the width B 'or B "of the distance between the partition 11 and at the inlet or outlet channel and the baffle 8.
In this example, the deflection baffle is designed such that approximately 25 to 45% of the mass flow of the flow entering the deflection 5 from the inlet duct 9 flows into the area of the inner flow channel 13 and the rest flows into the area of the outer flow channel 14. The mass flow ratio corresponds to the inlet area ratio A '/ B'. The area ratio at the outlet duct A "/ B" in this example corresponds to the area ratio at the inlet duct and should not deviate more than ± 20% from A '/ B'.

In the present example, the partition 11 is in the Area of the deflection 5, i.e. on their redirection side End contoured so that it becomes a Constriction of the flow cross section inside Flow channel 13 leads. The contouring is in this example with a thicker partition 11 reached. By the shown in Figure 4 linear increase in the thickness of the partition 11 and at the same time on the rounded course of the flow guide plate 8 adapted deflection end or Edge becomes a nozzle-like constriction at the inlet inner flow channel 13 and a corresponding shaped widening at the outlet in the second Channel section 10 reached. Through this configuration there is a nozzle effect that prevents heat transfer between the cooling medium and the component in it Area increased by the acceleration of the flow and thus homogenized at the same time. Without one such constrictions would reduce areas Heat transfer within the baffle 8, i.e. in the inner flow channel 13 occur. The constriction the cross-sectional area of the inner flow channel 13 should be about 5 to 20%.

In addition to the flow guide plate 8 and the constriction caused by the partition 11 inner flow channel 13 are in the present Figure 3 two holes 15 in the corner areas of the Recognize deflection 5. Through these additional Bores 15 is a small part of the cooling air in the external flow blown outside the component. This advantageously leads to a Acceleration of the flow in the area of the detachment or Dead water areas on the outer corners, and enforces a convective flow through the dead water areas 6 with coolant so that the dead water areas fill, leading to further homogenization of the Contributes heat transfer.

Preferably, the holes 15 depending on location with its axis of drilling approximately in Direction of the streamlines of the flow of the cooling medium aligned so that - as an additional side effect - the discharge of small particles or dust in the Cooling air can take place via the bores 15.

Figure 4 shows a possible arrangement of the Bores 15 and a favorable orientation of the associated bore axes (through the dash-dotted Lines indicated). The representation corresponds to one Vertical section through a gas turbine blade tip to the viewing level of FIG. 3.

Figure 5 shows another preferred Embodiment of the invention shown in Figure 3. The flow guide element 8 has a number of bores 16, which contribute to dust and Dirt accumulation in the outer 14 or inner 13 Avoid flow channel. Figure 6 shows another Possibility to achieve this effect. The Flow guide element is in several sub-elements, 8a and 8b, divided between which a gap is trained, which has the same effect as the bores 16 in FIG. 5.

LIST OF REFERENCE NUMBERS

1

blade

2,2a

cooling channel

3

Exit slots, rear edge blow-out

4

outlet openings

5

redirection

6

Dead water or recirculation area, area with high pressure loss

8th

Flow guiding element, flow or Umlenkleitblech

8a, 8b

partial elements

9

First, upstream, channel section

10

Second, downstream, channel section

11

partition wall

12

Kühlkanalwandung

13

Inner flow channel

14

Outer flow channel

15

outlet bores

16

Hole, passage opening

Claims (13)

Component of a turbomachine, in particular a turbine blade, which has a cooling channel (2) through which a cooling medium can flow, with at least one deflection (5) formed by the wall (11, 12) of the cooling channel (2) through which the flow of the cooling medium flows from a first channel section (9) is deflected into a downstream second duct section (10), at least one flow guide element (8) being arranged in the cooling duct (2) in the region of the deflection (5), through which the cooling duct (2) in the deflection (5) is divided into an inner (13) and an outer flow channel (14),
characterized in that the inner flow channel (13) has a constriction in the flow cross section. Component according to claim 1,
characterized in that the constriction is brought about by the shape or contouring of the flow guide element (8) and / or the wall (11, 12) of the cooling channel (2). Component according to claim 2,
characterized in that the first (9) and second duct section (10) run on both sides of a partition (11) as part of the wall (11, 12) of the cooling duct, the thickness of the partition (11) increasing in the region of the deflection (5) to effect the constriction of the flow cross section in the inner flow channel (13). Component according to one of Claims 1 to 3,
characterized in that the flow guide element (8) extends into the second channel section (10). Component according to claim 4,
characterized in that the flow guide element (8) extends over a distance into the second channel section (10), which is approximately the distance between the flow guide element (8) and the wall (11) of the cooling channel opposite in the inner flow channel (13) (2) at the transition from the first (9) or second channel section (10) to the deflection (5). Component according to one of Claims 1 to 5,
characterized in that the flow guide element (8) is arranged in the cooling channel (2) such that approximately 25 to 45% of the mass flow of cooling medium arriving via the first channel section (9) flows through the inner flow channel (13). Component according to one of claims 1 to 6,
characterized in that the flow guide element (8) and / or the wall (11, 12) of the cooling channel (2) are designed in such a way that they constrict the flow cross section in the inner flow channel (13) by approximately 5-20%. Component according to one of Claims 1 to 7,
characterized in that one or more outlet bores (15) are formed in the wall (12) of the cooling channel (2) in the outer flow channel (14), via which a small part of the cooling medium can escape from the cooling channel (2). Component according to claim 8,
characterized in that the outlet bores (15) extend at least approximately in the direction of local streamlines of the flow of the cooling medium. Component according to Claim 8 or 9,
characterized in that the outlet bores (15) are arranged in corner regions of the deflection (5). Component according to one of Claims 8 to 10,
characterized in that the outlet bores (15) are dimensioned such that they enable dust to be removed from the cooling medium. Component according to one of Claims 8 to 11,
characterized in that the outlet bores (15) are arranged in dead water areas (6) of the cooling channel with low flow, and there ensure the maintenance of a convective flow of cooling medium. Component according to one of Claims 1 to 12,
characterized in that the flow guide element (8) has suitable means (16) and / or a suitable configuration in order to avoid one-sided dust accumulation.

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