Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
1999-11-30
2001-12-11
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
With heating, cooling or thermal insulation means
Changing state mass within or fluid flow through working...
C416S224000, C416S22900R
Reexamination Certificate
active
06328532
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to devices for directing the flow of a cooling fluid in a cooling channel of an internally cooled blade of a turbomachine, in particular a gas turbine.
2. Discussion of Background
The efficiency of turbomachines, in particular gas turbines, can be improved via an increase in the pressure and in the temperature of the fluid as parameters determining the cyclic process.
The fluid temperatures which are normal nowadays during the operation of turbomachines, in particular in the turbine inlet region, are already markedly above the permissible material temperatures of the components. In this case, in particular the blading of the turbine is directly exposed to the hot fluid flow. As a rule, the heat dissipation of the turbine blades, which is brought about by the heat conduction of the material, is not sufficient in order to avoid an excess temperature of the blades. Material temperatures which are too high first of all lead to a drop in the strength values of the material. In the process, crack formation often occurs in the components. In addition, in the event of the melting temperature of the material being exceeded, local or even complete destruction of the component occurs. In order to avoid these fatal consequences, it is therefore necessary to additionally cool, in particular, the turbine blades of a turbomachine.
The predominant conventional cooling method used nowadays for the cooling of blades by means of a cooling fluid, usually cooling air, is so-called convection cooling. In this case, the cooling fluid is directed through the blades, which respectively are of hollow design or provided with cooling channels. As a result of the lower temperature of the cooling fluid compared with the temperature of the blade material, a heat transfer occurs between the blade material and the cooling fluid as a result of forced convection in the cooling channels. With efficient cooling, the resulting material temperature is therefore below the maximum permissible temperature of the blade material.
At the end of the cooling channel, the cooling fluid mostly flows out into the main flow via one or more openings in the blade wall. Often, however, the cooling fluid is also directed at the end of the cooling channel into a further, internal chamber and passes from there into a further cooling channel or also into the main flow.
So-called film cooling is another method of cooling blades. In this case, a cooling fluid, usually also cooling air, which is supplied in cooling channels, is blown out through openings in the blade onto the blade surface. In the process, the cooling fluid forms a separating layer, similar to a fluid film, between the blade wall and the hot flow fluid. Thus, no direct heat transfer occurs between the hot fluid of the main flow and the blade.
Both methods have the disadvantage that the blades is not cooled uniformly everywhere. In the case of convection cooling, the heat transfer is directly dependent upon the flow conditions in the cooling channels. Higher flow velocities of the cooling fluid increase the heat transfer. In this case, regions in the blade tip in particular are often at a disadvantage, since here, in particular along the cover wall closing off the blade, there are regions having only very low flow velocities of the cooling fluid or also wake zones. It has been possible to compensate for these disadvantages hitherto only by means of very complicated shapes of the cooling channels in the blade. The production of such blades is extremely complicated and thus expensive. In addition, on account of the production of the blades by casting, one or more openings also generally remain in the blade walls, these openings having been necessary during the casting in order to fix the casting core.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to direct the flow of a cooling fluid to a cooled blade of a turbomachine.
This object is achieved according to the invention in that at least one drawer is arranged in at least one slot of the blade in order to direct the cooling fluid. In addition to at least one cooling channel running in the blade, the blade has at least one feed opening for feeding cooling fluid into the cooling channel and also at least one further opening. The slot and the drawer extend in the blade longitudinal direction only over a section of the blade. In this case, the drawer projects at least partly into at least one cooling channel of the blade. As a result of the arrangement of the drawer, a locally altered path of the cooling channel and thus a locally altered guidance of the cooling fluid in the cooling channel result. It has been found that the heat exchange and thus the component cooling in wall regions previously at a disadvantage are improved by the arrangement of a drawer in a slot of the blade.
The slot and the drawer are preferably made with a rectangular or slit-like cross section. In this case, the cross section to be considered is the cross section perpendicular to the push-in direction of the drawer. It is especially expedient for the slot and the drawer to be dimensioned relative to one another in the form of an interference fit. Consequently, the drawer may be inserted into the slot by means of positive locking. The drawer is expediently also often brazed. Furthermore, it is of advantage to arrange the drawer in the slot perpendicularly to the blade height direction.
Both the slot and the drawer expediently extend from the suction side to the pressure side of the blade. As a result, the slot in particular can be made and machined in a simple manner from the production point of view. The outer contour of the drawer is advantageously adapted to the contour of the blade profile at the location of the slot. Thus turbulence-point-like transitions in the course of the wall contour of the blade are avoided. Such turbulence-point-like transitions would lead to higher flow losses of the main flow of the turbomachine.
In an advantageous refinement, at least the drawer has a step or a continuous cross-sectional reduction. In this case, the cross section of the drawer is advantageously reduced in the direction in which the drawer is pushed into the slot. The slot is expediently made in the same way, so that the drawer can be inserted into the slot by means of positive locking. In particular in the case of rotor blades, it is especially expedient to arranged the step in such a way that the cross section of the drawer is reduced against the direction of rotation of the rotor and the positive locking between the drawer and the slot is provided in the region of the cross-sectional reduction. It has been found that, with such an arrangement, loosening of the drawer in the slot is prevented in an especially effective manner as a result of the inertia forces acting on the drawer during an acceleration of the rotor as well as a result of the fluid-dynamic pressure forces of the flow fluid.
It is especially expedient to arrange the slot and the drawer according to the invention in such a way that the drawer arranged in the slot is directly adjacent to the cover wall and/or at least one side wall of the blade or is at least partly integrated in the cover wall and/or the side wall. In addition, the drawer arranged in this way advantageously has at least one flow channel arranged in the drawer. To this end, a groove is preferably arranged in the drawer in such a way that this groove together with the adjacent cover wall and/or an adjacent side wall of the blade forms the flow channel. The flow channel is connected via at least one opening to the cooling channel and in addition preferably has at least one outlet. In this case, the flow channel is normally made with a smaller cross section of flow than the cooling channel. It is especially expedient to design the outlet of the flow channel as a passage opening in the adjacent cover wall and/or an adjacent side wall. Provided the cooling channel has no further outlets, all the cooling fluid fed to the cooling chan
Alstom
Burns Doane Swecker & Mathis L.L.P.
Look Edward K.
McAleenan James M
LandOfFree
Blade cooling does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Blade cooling, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Blade cooling will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2598882