Rotary kinetic fluid motors or pumps – Method of operation
Reexamination Certificate
2002-08-09
2004-09-07
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Method of operation
C415S116000
Reexamination Certificate
active
06786694
ABSTRACT:
This application claims priority under 35 U.S.C. §119 on European Application No. EP 01119261.4 which has a filing date of Aug. 9, 2001, the entire contents of which are hereby incorporated by reference.
FIELD OF THE INVENTION
The invention generally relates to a gas turbine, having a number of turbine blades/vanes respectively combined to form blade/vane rows. Preferably, each of the turbine blades/vanes has an integrated cooling air duct. It also generally relates to a method of operating a gas turbine.
BACKGROUND OF THE INVENTION
Gas turbines are employed in many fields for driving generators or machinery. In this process, the energy content of a fuel is used to generate a rotational motion of a turbine shaft. For this purpose, the fuel is burnt in a combustion chamber, with compressed air being supplied from an air compressor. The working medium at high pressure and at high temperature generated in the combustion chamber by the combustion of the fuel is conducted, in this process, via a turbine unit connected downstream of the combustion chamber, where the gas expands with an output of work.
In order to generate the rotational motion of the turbine shaft in this process, a number of rotor blades, which are usually combined into blade groups or blade rows, are arranged on this turbine shaft and these rotor blades drive the turbine shaft by means of a transfer of inertia from the flow medium. In order to conduct the flow medium within the turbine unit, furthermore, guide vane rows connected to the turbine casing are usually arranged between adjacent rotor blade rows.
In the design of such gas turbines, a usual design objective—in addition to the achievable power—is a particularly high efficiency. For thermodynamic reasons, an increase in the efficiency can fundamentally be obtained by increasing the outlet temperature at which the working medium flows out of the combustion chamber and into the turbine unit. In consequence, temperatures of approximately 1200° C. to 1300° C. are an objective for such gas turbines and are also achieved.
In the case of such high temperatures of the working medium, however, the components and structural parts exposed to this working medium are subjected to high thermal stresses. In order, nevertheless, to ensure a comparatively long life of the components affected whole maintaining a high level of reliability, cooling is usually provided for the components affected, in particular for the rotor blades and/or guide vanes of the turbine unit. The turbine blades/vanes are therefore usually designed so that they can be cooled, it being particularly necessary to ensure an effective and reliable cooling of the first blade/vane rows, viewed in the flow direction of the working medium. For cooling purposes, the respective blade/vane in this arrangement usually has a coolant duct, which is integrated into the blade/vane aerofoil or the blade/vane profile and from which a coolant can be specifically conducted to the thermally stressed zones, in particular, of the turbine blade/vane.
In this arrangement, cooling air is usually employed as the coolant. This cooling air is usually supplied to the respective turbine blade/vane, in the manner of an open cooling system, via an integrated coolant duct. After emerging from the latter, the cooling air flows, in branch ducts, through the respectively provided regions of the turbine blade/vane. At the outlet end, these ducts are left open so that, after flowing through the turbine blade/vane, the cooling air emerges from the latter and, in the process, mixes with the working medium conducted in the turbine unit.
In this way, it is possible to make a reliable cooling system for the turbine blade/vane available with comparatively simple means, it being also possible to admit coolant, in an appropriate manner, to thermally particularly stressed zones of the turbine blade/vane. With respect to the introduction of the cooling air into the working medium conducted in the turbine unit, on the other hand, it is however necessary to pay attention to ensuring that its characteristic parameters, such as pressure and temperature, are consistent with or are compatible with the corresponding parameters of the working medium. In particular, only limited heating of the cooling air is permissible during the cooling of the turbine blades/vanes so that, precisely in the case where comparatively high outlet temperatures are desired for the working medium, a particularly large quantity of cooling air is necessary. This, in turn, has the effect of limiting the efficiency of the gas turbine.
An economy in the cooling air requirements, which is desirable for these reasons, can be achieved by configuring the cooling system as a closed cooling system. In a closed cooling system of this type, the used cooling air is returned to the combustion process. Particularly in the case of such a closed cooling system, however, in which the cooling air can be subject to a comparatively high pressure loss, it is usually necessary to provide cooling air which is matched to the location and requirement and has a comparatively high pressure, which depends on the injection location provided. In this arrangement, the pressure loss in the conduction of the cooling air through a closed system has inter alia also to be taken into account. Precisely in the case of comparatively long, extended systems, the pressure loss can contribute to a substantial extent to the requirements with respect to the cooling air which has to be provided. Precisely the provision of cooling air with comparatively high pressure does, however, involve a comparatively complicated design of the associated systems; particularly in the case of high pressure requirements, the cooling air compressor necessary for providing the cooling air can, depending on the operating conditions, partially or indeed completely counterbalance the efficiency and power advantages attainable due to the closed cooling system.
SUMMARY OF THE INVENTION
An embodiment of the invention is therefore based on an object of providing a gas turbine in which, while maintaining reliable cooling of the turbine blades/vanes, the cooling air requirement is kept particularly low. In addition, a particularly suitable method for operating such a gas turbine with a comparatively small cooling air requirement overall is to be provided.
With respect to the gas turbine, an object may be achieved, according to an embodiment of the invention, by the turbine blades/vanes forming a first turbine blade/vane row and the turbine blades/vanes forming a second blade/vane row connected downstream of the first blade/vane row, viewed in the flow direction of the working medium, being connected one behind the other on the cooling air side with the intermediate connection of an injection device for water.
An embodiment of the invention then takes into consideration that the cooling air requirement for reliable cooling of the turbine blades/vanes can be kept particularly small by employing the cooling air to a particularly intensive extent for cooling the turbine blades/vanes. With respect to the necessary operating pressure of the cooling air, this is, in particular, possible in the case of the cooling air which has to be made available at a comparatively high pressure in any case for the turbine blade/vane rows located comparatively far forward, viewed in the flow direction of the working medium. The cooling air for these turbine blade/vane rows has to be made available, for operational reasons, at such a high pressure that this pressure level is sufficient for conducting cooling air over a plurality of turbine blades/vanes or blade/vane rows connected on the cooling air side in sequence, even taking account of comparatively high pressure losses when cooling the blades/vanes.
In order to utilize this pressure potential, provision is made for employing the still available pressure of the cooling air flowing out of the first blade/vane row, which has now been cooled, for feeding the second blade/vane row which still has to be cooled. In this arrangem
Harness & Dickey & Pierce P.L.C.
Look Edward K.
McCoy Kimya N.
Siemens Aktiengesellschaft
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