Abstract:
A rotor ( 10 ) for a power plant, in particular an aero engine or a gas turbine, whereby the rotor ( 10 ) includes at least two bonded rotor discs ( 12, 14 ). The rotor ( 10 ) has an inlet opening ( 30 ) for inlet of fluid from around the rotor ( 10 ) into a chamber ( 26, 44 ) in one or between two adjacent rotor discs ( 12, 14 ) and at least one interrupter element ( 38 ) with at least one fluid passage ( 40 ) is arranged in the chamber ( 26 ).

Description:
The present invention relates to a rotor for an engine, in particular a rotor for a compressor of an aircraft engine or a gas turbine. 
     BACKGROUND 
     Rotors for compressors of gas turbines or aircraft engines are for the most part constructed in such a way that air is diverted at the compressor of the engine and is conducted preferably with low loss to the inside to a consumer, in particular for cooling. As the cooling air mass flow is conducted, considerable pressure losses occur as early as when the air is diverted from the compressor drum and conducted to the disk hub on which the compressor disks are mounted. Therefore, an air mass flow of the magnitude necessary for generating sufficient cooling of the turbine is not made possible. 
     As a rule, apertures or bore holes are provided on the outside of the rotor so that air from the compressor drum may reach the disk hub. For example, these apertures are provided on disk vanes or flanges of the disks. A radial mass flow of compressor air from the compressor drum may enter the rotor, in particular between the disks, via these apertures. Flow losses occur since conducting the air via a bore hole into a chamber formed between the disks causes a turbulence or a swirl in the flow. A system of a free vortex and Ekman layers develops after a flow through the aperture. These flow conditions cause a great pressure drop which makes it impossible to reach the required mass flow of (0.7% to 1.5%), for example. 
     In order to avoid this flow pattern and the resulting pressure losses, devices, which are supposed to conduct the radial flow, are used in some engines. For example, radially directed tubes are used which are also referred to as “giggle tubes.” Using these tubes, a rigid vortex which generates only a small pressure drop may be forcibly produced. Although the required flow rate for cooling may be achieved in this way, the approach of the related art has a number of disadvantages. On the one hand, mounting these tubes poses a problem. Moreover, the weight of the rotor is a disadvantage which is increased by these tubes and the mounting device. Finally, these tubes are subject to friction wear, the so-called fretting, and are exposed to vibrations. 
     SUMMARY OF THE INVENTION 
     Therefore, it is the object of the present invention to create a rotor in which a sufficient mass flow of air from the drum to the disk hub may be implemented and the further problems of the related art may be eliminated at the same time. 
     The present invention is based on the finding that the object may be achieved by separating the vortex, which occurs when air is conducted into the inside of the rotor, into multiple sub-vortexes. 
     The present invention provides a rotor for an engine, in particular an aircraft engine or a gas turbine, the rotor having at least two rotor disks connected to one another. The rotor is characterized in that an inlet aperture is provided for the entry of fluid from the area surrounding the rotor into a chamber in one rotor disk or between two adjacent rotor disks and at least one interrupting element having at least one fluid passage is situated in the chamber. 
     As defined in the present invention, an area surrounding the rotor is the area outside of a radius on which the outermost connection point between adjacent rotor disks is provided. In particular, this area represents the compressor drum in which the blades of the compressor disks run and which is surrounded by the compressor housing. 
     By providing an interrupting element which disturbs, i.e., interrupts the air flow, a vortex, which would form during entry through the inlet aperture without an interrupting element, cannot fully develop. The flow is changed by passing through the passage in the interrupting element. Two sub-vortexes occur when one single interrupting element is provided, one vortex forming downstream from the inlet aperture and one vortex forming downstream from the passage. This flow characteristic makes it possible to optimize the pressure drop and thus the air mass flow to the hub and further to the turbine. 
     In one specific embodiment, the rotor is designed in such a way that at least two adjacent chambers are formed by the at least one interrupting element which are connected to one another via the fluid passage. 
     Within the scope of this invention, a space is defined as a chamber whose dimension in the axial direction of the rotor is greater over at least part of the height of the space than the dimension of the inlet aperture and the outlet aperture. 
     This rotor design makes it possible that suitable flow patterns may form in the individual chambers and that overall a flow may be achieved which results in a very low pressure drop and along with it an optimum mass flow for cooling air. 
     If only one interrupting element is provided, only a low turbulence may develop in the flow in the first chamber due to the radial limitation by the interrupting element. The same is true for the second chamber which faces the hub of the rotor. 
     The rotor is made up of at least two rotor disks which are rigidly connected to one another via suitable connecting means. The connection may be established via screws or by welding, for example. 
     The rotor disks are preferably connected to one another in such a way that there is a gap between the individual rotor disks which form the rotor. In one specific embodiment, the at least one interrupting element is provided in this gap between two adjacent rotor disks, thereby forming two chambers in the gap. In contrast to the specific embodiment in which the at least one interrupting element is positioned in the rotor disk itself and thus forms the chambers in the disk, this specific embodiment has the advantage of simpler manufacturing. The disks do not have to be manufactured using a complex hollow casting method or subjected to a complex drilling process. 
     The interrupting element preferably represents a connecting element. This makes it possible to further enhance the rotor&#39;s stability. At least one connecting element is mandatory for producing a disk packet which is jointly supported. This connecting element represents a disk flange, for example. The inlet aperture may be provided in this connecting element. The connecting element lends itself to this since the wall thickness of the connecting elements, such as disk flanges, for example, is as a rule smaller than the wall thickness of the disk. Due to this fact, introducing a bore hole or another aperture into the connecting element is simpler than introducing a bore hole through the disk. The stability of the rotor packet may be further enhanced by designing the interrupting element as an additional connecting element. A passage may also be introduced into this additional connecting element in a simple manner. 
     Both the inlet aperture and the at least one passage are particularly preferably designed in such a way that they have a length which conducts the flow. This is achieved in particular by introducing the inlet apertures into components having a small wall thickness and thereby providing the required hydraulic conditions for generating at least two sub-vortexes with a low pressure drop. 
     The inlet aperture and the at least one passage are preferably positioned radially. This alignment ensures that the flow entering the outer chamber, for example, is able to exit again without extreme turbulences. The inlet aperture and the passage are particularly preferably aligned with each other. The outlet aperture of the second, inner chamber is formed by the gap between the adjacent disks at their inner radius. As a rule, the disks are reinforced at the inner radius. A taper of the inner chamber is thereby formed at its outlet via which the air exits from the chamber. 
     The interrupting element and the connecting element, in which the inlet aperture is provided, are preferably designed in one piece with one of the disks and represent in particular disk flanges or disk wings. This specific embodiment has the advantage that the manufacture of the disk packets may be simplified since a separate process of attaching the connecting element and the interrupting element to both adjacent disks may be omitted. In addition, the one-piece design improves the stability. 
     The interrupting element is provided in an area in which, due to the inlet aperture, a system of a free vortex and Ekman layers would develop. By interrupting the flow in this area, the flow pattern may be improved overall. A swirl, which is formed in the first chamber, has a certain vortex circumferential velocity which is reduced by passing through the passage. A pressure drop occurring due to an angular flow toward the passage is low compared to a pressure drop which occurs during further development of the vortex. 
     The rotor according to the present invention is preferably used in the high pressure compressor of the engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is explained in greater detail in the following with reference to the appended figures. 
         FIG. 1  shows a section of a rotor according to the related art in a schematic sectional view; 
         FIG. 2  shows a section of an additional rotor according to the related art in a schematic sectional view, and 
         FIG. 3  shows a section of a specific embodiment of a rotor according to the present invention. 
     
    
    
     The approaches and problems of the related art are explained in the following with reference to  FIGS. 1 and 2 . 
     DETAILED DESCRIPTION 
       FIG. 1  shows a section of a rotor  10 . Depicted are two rotor disks  12  and  14  in whose bore hole there is a shaft  16 . Disks  12  and  14  have grooves on their outer circumference in which root  18  of a blade  20  is fixed. Blades  20  are compressor blades in the depicted embodiment. In the depicted specific embodiment, rotor disk  12  has disk flanges  22  which extend on a radius Ra in the axial direction from disk  12 . These disk flanges  22 , also referred to as disk wings, are provided at a distance to the outer circumference of disk  12 . This means that the disk flanges are provided on a radius Ra which is smaller than the radius on which the grooves for receiving blade roots  18  are provided. Disk flanges  22  are connected at their free ends to an additional rotor disk  14 . The connection is implemented via a screw construction  24  in the depicted embodiment. 
     A chamber  26  is formed by the sidewalls of disks  12  and  14 , shaft  16  and disk flange  22 . A bore hole  30  is provided in disk flange  22  as the inlet for air from compressor drum  28  in which blades  20  are situated. The outlet of chamber  26  is formed by the gap between both disks  12  and  14  in the area of shaft  16 . 
     Air, which enters chamber  26  via bore holes  30 , which act as inlet apertures, is going to form a system of a free vortex and Ekman layers as schematically indicated in the drawing by the rectangles. The ratio of radius Ra, on which disk flanges  22  are situated, to radius Ri on shaft  16 , on which the air is conveyed to the turbine, is relevant for the vortex formation. At given edge pressures P 1  in the compressor drum and P 2  on shaft  16 , the necessary mass flow is, as a rule, not achievable with the ratio Ra/Ri because of the great pressure drop in the vortex system. 
       FIG. 2  shows an alternative to the related art. The construction corresponds essentially to the one of rotor  10  in  FIG. 1 . The same components are indicated using the same reference numerals as in  FIG. 1  and their function is not explained again. 
     From bore hole  30  on disk flange  22 , a tube  32 , in the following also referred to as a giggle tube, extends into chamber  26 . End  34  of tube  32 , situated opposite bore hole  30 , is mounted on projections  36  on the sidewalls of rotor disks  12  and  14 . From end  34  of tube  32 , the air flow from compressor drum  28 , which has been conducted through tube  32  and forced into a rigid vortex, may be introduced into the area between rotor disks  12  and  14 . The air may be diverted from there and conveyed to a downstream low-pressure turbine (not shown) for cooling. 
       FIG. 3  shows a specific embodiment of a rotor according to the present invention. Here also, components which correspond to those in  FIGS. 1 and 2  are indicated using the same reference numerals and their construction and function are not explained again. 
     As is apparent in  FIG. 3 , an interrupting element  38 , which extends axially between rotor disks  12  and  14 , is provided in chamber  44  of rotor  10  according to the present invention. In the depicted specific embodiment, interrupting element  38  is mounted on the sidewalls of rotor disks  12  and  14 . A passage  40  is provided in interrupting element  38  which may be designed as a ring which is inserted between rotor disks  12  and  14 . This passage  40  may be designed as a bore hole or may represent a nozzle. 
     Due to interrupting element  38 , the flow in chamber  26  is interrupted and two radially adjacent chambers  42  and  44  are formed. The flow which enters chamber  44  from compressor drum  28  is subject to a certain turbulence also in this rotor. However, the vortex circumferential velocity is reduced at this point due to interrupting element  38  provided in chamber  26  and passage  40  provided therein. For vortex formation, the ratio of radius Ra 1 , on which blade flanges  22  are provided, to radius Ra 2 , on which interrupting element  38  is provided, and to radius Ri on the hub, is relevant in the rotor according to the present invention. The ratio of Ra/Ri given from the related art is thereby reduced. A vortex, which would occur without interrupting element  38 , is thus divided into two sub-vortexes, thereby reducing the pressure drop. 
     The present invention is not limited to the depicted specific embodiment. For example, it is within the scope of the present invention to provide more than one interrupting element in chamber  26 . The difference between radius Ra 1  and Ra 2  may be selected according to the requirements and may be smaller than indicated in  FIG. 3 . In this case, the interrupting element would be situated displaced in the direction of the disk wing compared to the position shown in  FIG. 3 . 
     The interrupting element is provided over the entire circumference of the rotor. A suitable number of fluid passages is provided over this circumference, in particular corresponding to the number of inlet apertures in the disk flange.