Metal working – Method of mechanical manufacture – Impeller making
Reexamination Certificate
2002-08-12
2003-10-14
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Impeller making
C029S889720
Reexamination Certificate
active
06631561
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/EP00/10678 which has an International filing date of Oct. 30, 2000, which designated the United States of America, the entire contents of which are hereby incorporated by reference.
FIELD OF THE INVENTION
The invention generally relates to a turbine blade, in particular a gas turbine blade. More preferably, it relates to one having a tip region, a root region and a blade-body region. It may have an inner passage system of individual passages, through which cooling gas can be directed on a flow path inside the turbine blade, and a throttle device influencing the throughflow of the cooling gas. Cooling gas may be directed in the passages from the root region through the blade-body region to the tip region and can be diverted in the opposite direction. Also, it may have outlet openings for discharging the cooling gas from the turbine blade, with these outlet openings being arranged on the outflow side of the turbine blade. The invention may generally relate to a method of producing a turbine blade. In order to achieve a high efficiency during the operation of a turbine with an action fluid, in particular of a gas turbine operated with a gas, the action fluid is heated to a high temperature. In a gas turbine with a combustion chamber for producing the hot gas, the guide and moving blades nearest to the combustion chamber are subjected to a throughflow of cooling gas so that they withstand the high temperatures prevailing there, which are partly above the critical values of the material used for producing the turbine blade. The temperature on and inside the turbine blade is reduced by the cooling gas, so that the mechanical stability and thus the operability of the turbine blade under these conditions are ensured.
BACKGROUND OF THE INVENTION
In this type of cooling, an outer wall of the turbine blade around which an action fluid flows encloses a meander-shaped passage system which repeatedly directs the cooling gas from a root region up to a tip region of the turbine blade and back again to the root region. The region in which the cooling gas is introduced is designated as leading edge region, and the region in which cooling gas is discharged is designated as trailing edge region. A plurality of outlet openings are provided in the trailing edge region, these outlet openings connecting the passage system of the turbine blade to an exterior space through which the action fluid flows. During operation of the turbine, cooling gas from the passage system of the turbine blade discharges from the openings right onto the surface of the outer wall.
In order to save cooling gas and thereby increase the output of the gas turbine, only as much cooling gas as is absolutely necessary in order to avoid overheating is to be used for the blades. Since many assumptions with regard to various heat transfers are made when designing a blade, these assumptions being construed on the conservative side in order to avoid damage to the blades, and since the actual geometrical configuration of the turbine blades also cannot be established until after the casting is complete, the flow of the cooling gas through the blades is set subsequently, after the casting.
This is normally done by providing leading edge holes or aperture plates in the region of the leading edge for the cooling air entering the turbine blade, these leading edge holes or aperture plates throttling the entry of the cooling gas into the blade. A disadvantage in this case, however, is that these throttling devices have a considerable loss factor and may in addition lead to flow separation in the region of the entry of the cooling gas, so that adequate cooling in this region of the turbine blade cannot be ensured. In addition, this configuration also impairs the leading edge region, in which the pressure difference between first cooling chamber and external hot gas decreases.
SUMMARY OF THE INVENTION
An object of an embodiment of the present invention is therefore to design a turbine blade which has a throttle device for setting the throughflow of the cooling gas without influencing the flow of the cooling gas at the leading edge. Another alternative object of an embodiment of the invention is to specify a method of producing such a turbine blade. This method may be simple in terms of design and also being individually adaptable.
An object may also be achieved by the throttle device being arranged upstream of the outlet openings in the rear region of the flow path. By such an arrangement of the throttle device, the throughflow of the cooling gas can be throttled without adverse effects on the flow of the cooling gas. The flow at the leading edge is effected largely undisturbed. The throttling only begins in a rear region of the flow path. The cooling-gas flow has left most of its path behind it and has already fulfilled the tasks of heat dissipation, which are linked with sufficient flow velocity.
The pressure difference between the first cooling chamber and the surrounding hot action fluid is retained, so that no hot gas can enter the blade, a factor which would lead to considerable damage. Reliable cooling of the turbine blade is therefore ensured. At the same time, the consumption of cooling gas is minimized. Only as much cooling gas as is absolutely necessary in order to prevent overheating has to be used. In this way, optimum cooling of the turbine blade and at the same time good efficiency of the turbine are obtained.
Favorable flow control of the cooling-gas flow is possible if the throttle device is attached at a reversing point of a passage. Here, the cross section of the passage and thus the throughflow of the cooling gas can be set to a predetermined degree in a simple manner. Possible dimensional differences which result from the production of the gas turbine can be rendered harmless by the throttle device. Thus the same type of throttle device may also be used on different models of turbine blade. This reduces the number of different components of the turbine blade which are required.
It is especially advantageous if the throttle device is attached at the last reversing point arranged upstream of the outlet openings. At this point, the flow path opens out, so that after that sufficient throttling with high efficiency is no longer possible. At the same time, the cooling gas has a maximum flow path and thus maximum contact with the inner surface of the passage system, a factor which optimizes the cooling effect.
It is especially advantageous if the throttle device is attached in a lead-through opening brought about by the casting process. Lead-through openings, which are produced, for example, by core mounts of the casting core during the casting, can be appropriately utilized in this way. They are normally closed merely by means of plates. The throttle device performs the same closing function and at the same time throttles the cooling-gas flow. By means of this throttle device, it is possible to set the throughflow subsequently and compensate for any possible dimensional inaccuracies after the casting. By utilizing the lead-through openings, production steps can thus be saved, which greatly reduces the production costs.
In order to prevent loss of the throttle device during operation or an undesirable penetration of the throttle device into the passage system, it is advantageous if the lead-through opening is permanently closed by the throttle device. If the throttle device were to be shaken loose and were to get into the passage system, for example during pronounced thermal and mechanical loading of the turbine blade, considerable damage to the turbine blade or complete failure of the cooling could be caused, which would result in breakdown of the turbine within a short time. A throttle device located outside the turbine blade inside the turbine may also cause considerable damage. In addition, the cooling effect would be reduced by the cooling gas being discharged into the environment at an unsuitable point through the lead-throu
Anding Dirk
Scheurlen Michael
Tiemann Peter
Cuda Rosenbaum I
Harness & Dickey & Pierce P.L.C.
LandOfFree
Turbine blade and method for producing a turbine blade does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Turbine blade and method for producing a turbine blade, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Turbine blade and method for producing a turbine blade will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3166547