Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
2002-01-29
2004-06-15
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
C416S09700R
Reexamination Certificate
active
06749395
ABSTRACT:
FIELD OF THE INVENTION
The invention generally relates to a gas turbine and method for controlling cooling of a gas turbine.
BACKGROUND OF THE INVENTION
An air-cooled gas turbine blade appliance is known from EP 0 768 448 A1. The rotor blades are inserted on rotatable carrier disks. Due to the hot air supplied for the operation of the gas turbine, temperature-sensitive regions of the gas turbine are also heated and can be subjected to damage by this. The rotor blades, which are inserted on the rotatable carrier disks driven by the hot air, are cooled by cooling air supplied from the carrier disk. For cooling purposes, cooling air supplied radially from the outside flows through the stationary guide blades. This is used, inter alia, for cooling carrier disk lateral spaces located between the rotor blades and the guide blades.
For feeding the cooling air to the carrier disk lateral spaces at the radially inner end of a guide blade, the guide blade has an opening through which the cooling air, which is led through an external cooling air supply duct, is fed. The discharge of the rest of the cooling air takes place, essentially, through a large number of small openings, so-called film cooling holes, in a so-called blade nose into the hot air flow, so that a cooling air film is formed on the outside of the gas turbine blade.
In the case of an unrestricted cooling air supply with the objective of maximum cooling, the efficiency of the gas turbine, which is essentially determined by the temperature of the hot gas introduced, is greatly reduced by the large quantities of cooling air supplied and the energy consumption of the gas turbine is essentially increased.
Control valves are inserted to combat this. In general, these are commercial valve shapes and are located radially outside on the guide blade or further upstream in the supply path of the cooling air, in the cooling air supply duct.
Although, on the one hand, this makes the valve easily accessible in order, for example, to carry out possible repairs or adjustments, it means, on the other hand, that only a simultaneous adjustment is possible of the pressure of the cooling air for the carrier disk lateral space and of the pressure of the cooling air which flows through the film cooling holes onto the blade nose. Where adjustment takes place to a very low cooling air pressure, this can easily lead to break-down of the cooling air film on the blade nose and, in consequence, there is no longer adequate cooling of the guide blade surface. If, on the other hand, the cooling air pressure is adjusted to be strong to produce an adequate cooling film, a powerful cooling air flow is produced in the hot air and this leads to a reduction in the power of the gas turbine and a high consumption of energy.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a control of a cooling air flow. In the case of a gas turbine, in particular, an automatic gas turbine, adequate cooling of the carrier disk lateral space by a supply of cooling air should be reliably ensured independently of the operating conditions. Further, at the same time, a high gas turbine efficiency should be achieved.
This object is achieved by providing an appliance for controlling a gas turbine cooling air flow through a flow duct. In one embodiment, it includes, a control fluid flow which is introduced into the cooling air flow, in the region of the flow duct, with a flow component transverse to the flow direction of the cooling air flow through the flow duct. In one embodiment, it is possible to adjust the flow rate of the cooling air flow as a function of control parameters of the control fluid flow and/or by the introduction geometry of the control fluid flow into the cooling air flow and/or by the geometry of the flow duct.
This type of control is well suited for difficult access locations on machines or the like, which are also subjected to severe loads. The appliance operates almost independently of dirt or other environmental influences such as, for example, aggressive chemical attacks due to a corresponding cooling air flow. The control element is not subject to any wear and erosion-free switching is possible because of the contactless adjustment without, for example, electrical current or mechanical appliances. Such a control appliance therefore requires very little maintenance because the control of the cooling air flow takes place exclusively by way of a specially adjusted supply of a control fluid flow. In the case of a failure of the control system, the originally adjusted cooling air flow takes place at its basic setting in any event. Independently of the function of the control flow, the cooling air flow can be adjusted before the appliance is put into operation in such a way that it is sufficient for the desired function.
The control fluid flow intervenes in the flow behavior of the cooling air in such a way that it either accelerates or retards the flow, respectively increasing or lowering the flow rate. This essentially takes place by changes in the type of the active fluid flow in specified boundary or central regions of the cooling air flow in the flow duct. This is, in particular, also directed toward converting the flow from a laminar flow to a turbulent flow. The precondition is that the control fluid flow should have a flow component suitable for influencing the flow when flowing into the cooling air flow. This refers to a component of its main flow direction which is directed transverse to the flow direction of the cooling air flow through the flow duct. By this, the flow behavior of the cooling air flow is influenced in a predetermined manner.
The control fluid is advantageously air. It is also conceivable to supply to the active fluid a control fluid with a composition which is, to a certain extent, “neutral” with respect to the cooling air flow, such as an aqueous solution water.
The control fluid flow can, on the one hand, be adjusted in strength, or in its flow rate, and exerts, by this, a control influence on the cooling air flow. On the other hand, its introduction geometry, for example the angular position of the control fluid flow relative to the cooling air flow, or the arrangement of the control fluid flow relative to the cooling air flow, can be changed. Influence can also be effected by changing the geometry of the flow duct through which the cooling air flows. The possibilities mentioned for the control can be combined with one another, the flow rate or strength of the control fluid flow being adjusted after the installation of an appliance according to the invention in a machine. In the case of a fixed geometry, the control fluid flow is controlled by means of control parameters of the control fluid flow which, however, depend on the respectively selected geometry.
The flow rate of the cooling air flow can preferably be adjusted by adjusting the pressure of the control fluid flow. Stepless and very accurate adjustment of the control fluid flow can be achieved by this, which adjustment can be undertaken with little complexity. This appliance also requires very little maintenance because a control flow is flowing almost continuously so that the supply ducts of the control flow are kept free.
The flow rate of the control fluid is preferably small relative to the flow rate of the cooling air flow because, in this way, no changes are undertaken to the physical and chemical properties of the cooling air flow, for example pressure or temperature changes or changes to the chemical composition or to a cooling function. In the event of a failure of the control fluid flow, furthermore, the cooling air flow continues to be sufficient to satisfy the envisaged duties so that the system, in which the appliance is inserted for control purposes, is not subject to any essential disturbance due to the failure of the control system. The proportion of the control fluid flow which is introduced into the cooling air flow is, in total, preferably smaller than 50% and, in particular, smaller than 10% of the total flow. The overall flow result
Lieser Dirk
Reichert Arnd
Harness & Dickey & Pierce P.L.C.
Look Edward K.
McAleenan J. M.
Siemens Aktiengesellschaft
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