SCREW COOLING FOR A FLUID FLOW MACHINE

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Stage of International Application No. PCT/EP2013/055506 filed Mar. 18, 2013, and claims the benefit thereof. The International Application claims the benefit of European Application No. EP12161469 filed Mar. 27, 2012. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a turbomachine comprising a housing having an upper housing part, a lower housing part and a flow duct arranged in the housing, wherein the flow duct has a flow duct exhaust steam space, wherein the housing part can be connected to the lower housing part by means of bolts, wherein the bolt is configured as a stud bolt and has a cooling duct along the axial direction of the stud bolt, wherein the cooling duct has a cooling duct inlet and a cooling duct outlet.

BACKGROUND OF INVENTION

Steam power stations use steam turbines which are capable of delivering up to 1600 megawatts of electrical power. For thermodynamic reasons, a steam turbine is divided up into what are termed turbine sections having a common shaft.

The high-pressure turbine section generally comprises an inner housing which has an upper part and a lower part and which is held together by means of bolted connections. Time- and temperature-dependent relaxations arise as a consequence of the high temperatures and of the temporal behavior of the temperature change. This can result in the clamping of the housing, and thus the seal, deteriorating during operation, which can lead to leakage and is accompanied by a loss of efficiency.

It would therefore be desirable to have a clamping which is as stable as possible for all steam parameters. This can be made possible by means of an improved design or by means of better—albeit more expensive—bolt materials.

SUMMARY OF INVENTION

It is therefore an object of the invention to propose an improved bolted connection which affords good clamping under various steam parameters.

This object is achieved by a turbomachine comprising a housing having an upper housing part, a lower housing part and a flow duct arranged in the housing, wherein the flow duct has a flow duct exhaust steam space, wherein the upper housing part can be connected to the lower housing part by means of bolts, wherein the bolt is configured as a stud bolt and has a cooling duct along the axial direction of the stud bolt, wherein the cooling duct has a cooling duct inlet and a cooling duct outlet, wherein the cooling duct inlet is fluidically connected to the flow duct, wherein the cooling duct outlet is fluidically connected to the flow duct exhaust steam space.

An aspect of the invention thus proposes employing, in the stud bolts used for the bolted connection, a cooling bore which is known per se and which is supplied on one side with steam present in the flow duct, and which is connected on the other side to the flow duct exhaust steam space via a cooling duct outlet. The steam from the flow duct is at a higher pressure than the steam in the flow duct exhaust steam space, so producing a forced flow through the cooling duct of the stud bolt, leading to a cooling of the bolt overall.

Advantageous developments are indicated in the dependent claims.

Thus, in a first advantageous development, the stud bolt comprises a nut, wherein the nut comprises cooling duct slots which fluidically connect the cooling duct to the flow duct exhaust steam space.

It is thus proposed to machine, into the nut, slots which divert the cooling steam flowing through the cooling duct in the bolt and connect this steam to the flow duct outlet which is connected to the flow duct exhaust steam space. As such, it is thus impossible for cooling steam to escape, which leads to an improvement in the seal.

In one advantageous development, the lower housing part has a bore which connects the cooling duct inlet to the flow duct.

This bore may be executed in an axial direction of the upper housing part and lower housing part. It is important in this context that, at a suitable position, the bore has a fluidic connection which delivers the steam intended for the cooling steam.

Aspects of the invention will now be explained in more detail with reference to an exemplary embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures:

FIG. 1 shows a partial detail of a bolted connection according to aspects of the invention,

FIG. 2 shows the upper housing part,

FIG. 3 shows the lower housing part,

FIG. 4 shows a plan view of a nut according to aspects of the invention,

FIG. 5 shows a schematic side view of the upper housing part and of the lower housing part.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows, schematically, a partial view of an upper housing part 1 and of a lower housing part 2. The upper housing part 1 and the lower housing part 2 together form a housing which is used in a turbomachine (not shown in more detail). A flow duct (not shown in more detail) is arranged between the upper housing part 1 and the lower housing part 2. Rotor blades and guide vanes, which convert the thermal energy of steam into rotational energy of a rotor, are arranged in this flow duct. The upper housing part 1 and the lower housing part 2 are connected to one another by means of bolts 3. To that end, the bolt 3 takes the form of a stud bolt, that is to say that the bolt 3 has no bolt head but a thread at both ends. A cooling duct 4, which is connected on one side to a cooling duct inlet 5 and on the other side to a cooling duct outlet 6, is formed along the axial direction of the stud bolt.

Thus, steam flowing into the cooling duct inlet 5 will flow through the cooling duct 4 in the axial direction through the stud bolt and in so doing cool the stud bolt. Finally, the cooling steam arrives in the cooling duct outlet 6.

In order that the cooling steam can flow from the cooling duct 4 into the cooling duct outlet 6, a slot 8, through which the steam can flow into the cooling duct outlet 6, is arranged in the nut 7. The cooling duct outlet 6 is fluidically connected to the flow duct exhaust steam space (not shown in more detail) via a first fluidic connection 9.

The cooling duct outlet 6 is fluidically connected to the flow duct exhaust steam space via a bolt cooling duct 14 arranged between the stud bolt and the housing, in particular the upper housing part 1.

Similarly, as shown in FIG. 3, the duct inlet is connected to the flow duct via a second fluidic connection 10, wherein a fluidic connection is expediently created after a blade or vane stage in which the steam parameters are ideal for a cooling duct circuit.

FIG. 2 shows the upper housing part 1 with the cooling duct outlet 6 and the first fluidic connection 9.

FIG. 3 shows the lower housing part 2 with the second fluidic connection 10 and the cooling duct inlet 5.

FIG. 4 shows the nut 7 for the bolt 3. The nut 7 has, in the region of the thread 11, at least one slot 8 through which the cooling steam can flow.

FIG. 5 shows a side view in the axial direction 12 of the turbomachine. The arrangement of the flow duct 13, the cooling duct inlet 5 and the cooling duct outlet 6, and the first fluidic connection 9 and the second fluidic connection 10 are shown in FIG. 5.