METHOD FOR THE PRODUCTION OF A ONE-PIECE ROTOR AREA AND ONE-PIECE ROTOR AREA

Abstract

The present invention describes a method for the production of a one-piece rotor area, preferably of a jet engine. The rotor area includes an annular base body and several, circumferentially distributed blade elements extending essentially radially from the base body. Residual stresses are imparted to the blade elements in surface-near areas by way of roller compression using a rolling tool introduced between the blade elements. During roller compression, one each area of a blade element is arranged between areas of the rolling tool, with longitudinal sides of the blade element being simultaneously roller-compressed. According to the present invention, the rolling tool is radially introduced between the blade elements and the surfaces of the blade elements are roller-compressed, thus at least the blade elements having a roller-compressed surface.

Description

This invention relates to a method for the production of a one-piece rotor area according to the type more precisely defined in the generic part of patent claim 1 as well as to a one-piece rotor area according to the type more precisely defined in the generic part of patent claim 9.

Downstream of a fan, jet engines known from practical applications are provided with multi-stage compressors, in the area of which the core airflow is incrementally increased to a desired pressure level. The individual compressor stages include blade elements or rotor blades of one-piece rotor areas rotating during the operation of a jet engine and vane elements or stationary guide vanes corresponding therewith.

In the area of the non-rotating stators, mechanical loading is relatively low during the operation of a jet engine since, on the one hand, rotation-due centrifugal loads do not exist and, on the other hand, blade vibrations are minimized by the residual stress of the flow profile in the root and top area.

However, high mechanical loading is present during the operation of a jet engine in the area of the rotor blades. Their total load is composed of several partial loads, with the centrifugal force being the dominant partial load. Since the change of speed is only small during the operation of a jet engine, the centrifugal force, which is superimposed by dynamic partial loads, can be considered as approximately static.

The dynamic partial loads result from the rotation-due vibration excitation of the rotor blades or the blade elements, respectively. Furthermore, the rotor blades are subject to aerodynamically caused loads which are primarily attributable to periodically non-stationary flows. Generally, periodically non-stationary flows are due to the stator-rotor interaction generated by the splitting of the flow as the rotor blades pass the stator vanes. Dynamic loads are further produced by interaction of the flow profiles with the turbulent flow, again resulting in blade vibrations. The dynamic partial loads, in total, lead to high-frequency vibrations occurring in operation primarily in the area of rotor blades of compressors as well as fans or, generally speaking, one-piece rotor areas of jet engines, resulting in highly dynamic stressing of the rotor blades.

Besides mechanical loading, part of the blades is also subject to thermal loading. This applies primarily to the blades of the high-pressure compressor and the rearward blades of the low-pressure compressor where operating temperatures up to 600° C. exist.

Generally, the blades of compressors or fans of jet engines are designed such that the fatigue strength is not, or only in a defined manner, exceeded by the dynamic operating loads and endurance strength or, respectively, a defined level of fatigue strength is ensured. However, premature crack initiation and sometimes even uncontrolled failure of fan and compressor blades, which is predominantly attributable to blade damage by foreign objects, are encountered time and again.

Such foreign object damage is impact damage resulting from the impingement of hard foreign objects. The foreign objects are generally stones and fragments of bolts, nuts, washers and similar items lying on the runway.

Foreign objects frequently fragment upon impingement. These fragments, as well as any object passing the fan area without collision, are entrained further into the engine by the airflow. If the engine features a large bypass airflow, part of the objects may leave the engine via said bypass airflow without causing any major damage. The other part enters the low-pressure compressor together with the core airflow, causing serious collision, primarily with the quickly rotating rotor blades. As a result of kinematics, the main damage location is, similar to the fan, in the area of the inflow edge and the forward concave profile side.

In order to protect the blade elements or, respectively, the rotor blades against foreign object damage and avoid any crack formation resulting therefrom in the area of the blades during the operation of the engine, it is required that the blade elements, as well as the annular base bodies forming an integral part thereof be conceived with suitable solidity. The high material investment involved therewith however increases the total weight and also the manufacturing costs of a jet engine in an undesirable manner.

Therefore, a method of resolidifying rotor blades or blade elements, respectively, of jet engines has been adopted, using appropriate manufacturing processes, and enabling rotor blades to be provided whose component dimensions are smaller than those of non-resolidified rotor blades.

For this purpose, the rotor blades and annular base bodies forming an integral part of the rotor blades are resolidified by means of shot peening, with residual stresses being produced in the shot-peening process in surface-near areas of the rotor blades counteracting crack formation and crack propagation due to foreign object damage or vibratory loading to the extent required.

It is however disadvantageous that the surfaces of rotor blades resolidified by shot peening have inferior surface quality which must be re-improved after shot peening by elaborate and costly rework operations. Moreover, shot peening does not ensure a uniform processing of rotor blades or blade elements, respectively, of one-piece rotor areas, since—for example due to ricochetting or shielding effects—some surface areas are hit by the shot more frequently than others, as a result of which effects detrimental to service life, such as de-solidification, may occur and reproducible processing results are not ensured. Solidification of one-piece rotor areas by means of shot peening is therefore very imprecise and also cost-intensive as it involves the use of compressed air.

It is further known to roll rotor blades in certain areas by means of pliers-type tooling, thereby generating residual stresses in surface-near areas of the rotor blades. In the process, a blade area facing the flow is solidified by roller compression using a rolling tool in the direction of flow or in the axial direction, respectively. Here, usually approx. 20 percent of the surface of a blade element are roller-compressed by simultaneous, both-side rolling of the longitudinal sides in the direction of flow, starting at the leading edge of the blade element, thereby achieving or retaining a high surface quality and avoiding deformation of thin-walled profiles.

This process is, however, disadvantageous in that stress jumps occur at the transition between the surface area of a blade element resolidified by roller compression and the non-resolidified surface area of a blade element. As the blade element is subject to vibratory loads, maximum stress limits are exceeded at this transition area so that plastic flow occurs in the area between the processed area of a blade element and the surface area not processed by roller compression which may result in undesirable crack formation. Cracks once produced will propagate under further vibratory load, ultimately leading to the failure of a blade element.

The present invention, in a broad aspect, provides a method for the production of a one-piece rotor area, preferably of a jet engine, by means of which one-piece rotor areas are producible with high resistance to foreign object damage and vibratory loading and at the same time low component weight. In addition, it is an object of the present invention to provide a one-piece rotor area which, while being cost-effectively producible and having a surface with low roughness, is characterized by high resistance to foreign object damage and vibratory loading.

It is a particular object of the present invention to provide solution to the above problematics by a method in accordance with the features of patent claim 1 and a one-piece rotor area in accordance with the features of patent claim 9.

In the method according to the present invention for the production of a one-piece rotor area, preferably of a jet engine, including an annular base body and several, circumferentially distributed blade elements extending essentially radially from the base body, residual stresses are imparted to the blade elements in surface-near areas by way of roller compression using a rolling tool introduced between the blade elements. During roller compression, one each area of a blade element is arranged between areas of the rolling tool, with longitudinal sides of the blade element being simultaneously roller-compressed.

According to the present invention, the rolling tool is radially introduced between the blade elements and the surfaces of the blade elements are roller-compressed.

Roller compression of the surfaces of the blade elements enables a one-piece rotor area, preferably of a jet engine, including an annular base body and several, circumferentially distributed blade elements, to be provided with—as compared to non-resolidified rotor areas—lower material investment and, thus, lower total weight while at the same time having equal or higher resistance to foreign object damage and vibratory loading.

Moreover, roller compression of the surfaces of the blade elements provides a simple means of avoiding stress jumps and improving the resistance to vibratory loading as compared to blade elements that are resolidified only in certain areas.

As the rolling tool is introduced radially between the blade elements, high resistance to foreign object damage and vibratory loading can easily also be provided to one-piece rotor areas having several blade elements arranged axially one behind the other on the base body. Because of the small spacing between the individual blade element rows, this is not possible using the known practices in which the rolling tool is axially introduced between the blade elements.

In a variant of the method according to the present invention characterized by low control effort, the surfaces of the blade elements are roller-compressed by sequential radial traversing, at least in certain areas.

In a variant of the method according to the present invention, which is also easily feasible, the surfaces of the blade elements are rolled by sequential axial traversing, at least in certain areas.

If the surfaces of the blade elements are roller-compressed by arbitrarily moving the rolling tool along the surfaces of the blade elements at least in certain areas, the latter can be provided with a surface structure required for generating a homogenous flow around the blade elements.

In a further advantageous variant of the method according to the present invention, resistance of a one-piece rotor area is further increased in that the transition areas between the surfaces of the blade elements and the surface of the base body between the blade elements is roller-compressed using a rolling tool.

Resistance to foreign object damage and vibratory loading of a one-piece rotor area characterized by low weight can further be improved in that the surface of the base body between the blade elements is roller-compressed using a rolling tool.

In order to further improve durability of the blade elements, a further advantageous variant of the method according to the present invention provides that a rolling force is variable to enable the surfaces of the blade elements to be provided with specifically the surface-near residual compressive stress which in each case is best for increasing the resistance to foreign object damage and vibratory loading.

The one-piece rotor area according to the present invention features an annular base body and several blade elements distributed over the circumference of the base body and extending essentially radially from the latter. Since at least the blade elements have a roller-compressed surface, the one-piece rotor area according to the present invention—as compared to non-resolidified or only partly resolidified one-piece rotor areas—is characterized by low weight while at the same time having at least equal resistance to foreign object damage and vibratory loading and, additionally, provided in the area of the blade elements in a cost-effective manner, as no extra processing steps are required, with a surface characterized by high surface finish supporting homogenous flow around the blade elements.

If also the joining areas between the surfaces of the blade elements and a surface of the base body are provided with a roller-compressed surface, both resistance to foreign body damage and vibratory loading as well as homogenous flow around the one-piece rotor area are ensured.

In another advantageous embodiment of the one-piece rotor area in accordance with the present invention, resistance to foreign object damage and vibratory loading is improved in that the base body features a roller-compressed surface at least in the area between the blade elements.

In a further advantageous embodiment of the one-piece rotor area, several blade elements axially arranged one behind the other on the base body are provided with a roller-compressed surface.

Both the features cited in the patent Claims and the features specified in the following exemplary embodiment of the subject matter of the present invention are, alone or in any combination, capable of further developing the subject matter of the present invention. The respective combinations of features are in now way limiting the development of the subject matter of the present invention, but essentially have only exemplary character.

Further advantages and advantageous embodiments of the subject matter of the present invention become apparent from the patent Claims and the exemplary embodiment schematically described in the following with reference to the accompanying drawing. In the drawing,

FIG. 1 shows a highly schematized longitudinal sectional view of a jet engine provided with a one-piece rotor area,

FIG. 2 is an enlarged individual representation of a blade element of the one-piece rotor area as per FIG. 1,

FIG. 3 is a side view of a rolling tool, and

FIG. 4 shows the rolling tool as per FIG. 3 in a view IV represented in more detail in FIG. 3.

FIG. 1 shows a longitudinal sectional view of a jet engine 1 provided with a bypass duct 2. The jet engine 1 is further provided with an inlet area 3 downstream of which a fan 4 is arranged in known manner. Again downstream of the fan 4, the fluid flow in the jet engine 1 divides into a bypass flow and a core flow, with the bypass flow passing through the bypass duct 2 and the core flow into an engine core 5 which, again in known manner, is provided with a compressor arrangement 6, a burner 7 and a turbine arrangement 8.

FIG. 2 shows an enlarged individual view of a one-piece rotor area 9 of the compressor arrangement 6 including an annular base body 10 and several circumferentially distributed blade elements 11 extending essentially radially from the base body 10.

The one-piece rotor area 9 is a so-called blisk, i.e. an integrally bladed rotor design. The term blisk is composed of the words “blade” and “disk”. The disk or, respectively, the annular base body 10 and the blade elements 11 are made in one-piece, removing the need for blade roots and disk slots provided on multi-piece rotor areas. The one-piece rotor area 9 is distinct from conventionally bladed compressor rotors by a significant decrease in the number of components and the disk shape of the annular base body 10 is designed for lower rim loads. In combination with the use of lighter materials, this results in a weight saving of the one-piece rotor area 9 of up to 50 percent compared to conventional rotor areas. The amount of weight saving is in each case dependent on the geometry of the compressor arrangement 6.

A further positive effect is that the blade elements 11 of the integrally bladed rotor area 9 are spaceable more closely to each other, thereby enabling best possible compression and enhancement of efficiency.

In order to provide the compressor arrangement 6 or, respectively, the one-piece rotor area 9 with resistance to foreign object damage and also vibratory loading while at the same time keeping the weight low, residual stresses are imparted to the blade elements 11 in surface-near areas by way of roller compression using a rolling tool 14 radially engaging in each case between the blade elements 11 and further shown in FIGS. 3 and 4, with the entire surface of each blade element 11 being roller-compressed in each case. Additionally, the transition areas 12, or fillets, respectively, between the surfaces of the blade elements 11 and a surface 13 of the base body 10 between the blade elements 11 are also roller-compressed by means of a so-called one-finger rolling tool not further shown in the drawing.

Furthermore, the surface 13 or, respectively, the annulus of the base body 10 between the blade elements 11 is preferably also roller-compressed by means of a one-finger rolling tool.

Roller-compressing the surfaces of the longitudinal sides and the edges of the blade elements 11, the transition areas 12 and the surface 13 of the base body 10 in each case solidifies surface-near areas of the one-piece rotor area 9 by increasing dislocation density and hardens the surface layer of the rotor area 9. Hardening the surface layer reduces the risk of cracking resulting from foreign object damage and vibratory loading. Moreover, the residual compressive stresses imparted by roller compression to the material in the area of the rotor area 9 counteract crack propagation after crack formation, thereby positively influencing fatigue strength and, thus, the service life of the jet engine 1.

Furthermore, roller compression provides the one-piece rotor area 9 with high surface finish and low surface roughness, thereby positively influencing the aerodynamic quality of the blade elements 11 and the entire rotor area 9 without the need for a further surface smoothening process to be performed subsequently to the solidification process.

FIG. 3 and FIG. 4 each show a side view of a rolling tool 14 for roller-compressing the longitudinal sides or, respectively, the entire surface of the blade elements 11 of the rotor area 9. The rolling tool 14 includes a tool carrier 15, which can be connected to a carrier spindle 16 of a machine tool to the extent shown. Two pliers-type bodies 17, 18 of the rolling tool 14 are rotatably connected to the tool carrier 15 in the area of a rotating bearing 19, with the pliers-type bodies 17, 18 being coupled via a driving unit 20 provided here as single-acting piston-cylinder unit and a distance between rolling areas 21, 22 being reduced in dependence of a driving unit-side rotational movement of the pliers-type bodies 17 and 18 about the rotating bearing 19. For this, the driving unit 20 is subject to hydraulic pressure and, under the action thereof, a piston element 23 is extended from a cylinder element 24 of the driving unit 20, with a distance between the ends 25 and 26 of the pliers-type bodies 17 and 18 facing away from the rolling areas 21 and 22 being increased during such a change of the operating state of the driving unit 20, while the distance between the rolling areas 21 and 22 is decreased according to the geometric situation in dependence of the rotary movement of the pliers-type bodies 17 and 18 about the rotating bearing 19. The pliers-type bodies 17 and 18 are each rotatably connected to the driving unit 20 in the area of their ends 25 and 26.

Furthermore, the two pliers-type bodies 17 and 18 are additionally rotatably attached to the tool carrier 15 around the rotating bearing 19 about a rotary axis 27 vertically aligned to the drawing plane to enable the pliers-type bodies 17 and 18 to be swivelled upon contact of the rolling areas 21 and 22 with a blade element 11 and avoid distortion of the blade elements 11 resulting from the contact of the rolling areas 21 and 22 with the blade element. During joint rotation of the pliers-type bodies 17 and 18 around the rotating bearing 19 relative to the tool carrier 15, the distance between the rolling areas 21 and 22 remains constant. Joint rotatability of the two pliers-type bodies 17 and 18 around the rotating bearing 19 further ensures that the blade elements 11, each of which being provided with a blade profile, are roller-compressible on their entire surface using the rolling tool 14.

The pliers-type bodies 17 and 18 are operatively connected to the tool carrier 15 via piston elements 28 and 29, with the piston elements 28 and 29 resetting the pliers-type bodies 17 and 18 relative to the tool carrier 15 around the rotating bearing 19 to a zero position defined relative to the tool carrier 15 and shown in FIG. 3 when a rotating force jointly rotating the pliers-type bodies 17 and 18 around the rotating bearing 19 is essentially zero.

Furthermore, a resetting device 32, here including two spring-action devices 30 and 31, is associated to the pliers-type bodies 17 and 18 through which the latter are rotated to enable a distance between the rolling areas 21 and 22 to be changed to a maximum value.

Each of the rolling areas 21 and 22 here includes a ball element 33, 34 retained in holding areas each and subjectable to hydraulic pressure in known manner to enable the rolling pressure required in each case to be applied to the blade elements 11 via the ball elements 33 and 34.

The holding areas 35 and 36 are here inserted into, and threadedly connected, preferably by means of grub screws, to adapter elements 37 and 38 which are firmly threadedly connected to the pliers-type bodies 17 and 18 and are at least approximately finger-shaped.

Each of the adapter elements 37 and 38 is changeable so that the rolling tool 14 provides for various engagement depths in the radial direction between the blade elements 11. Moreover, adapter elements 37 and 38 designed with respect to the transmittable pressure or rolling force, respectively, are connectable to the pliers-type bodies 17 and 18, with thinner adapter elements being insertable into narrower areas between the blade elements 11. Here, lower rolling or pressure forces, respectively, are applied to thinner blade elements 11 with more slender adapter elements 37 and 38, with the adapter elements 37 and 38 then having a certain elasticity and the maximum rolling force being limited by the elasticity of the adapter elements 37 and 38. Full solidification of the blade elements during compression rolling is avoidable by limiting the maximum rolling force, with excessive pressure loading during roller compression producing a tensile stress maximum in the center area of the blade elements 11 which promotes internal crack formation under vibratory loading. This, however, is undesirable as it affects the service life of the blade elements 11.

The rolling force imparted in each case to the rotor area during roller compression is variable at each location of a blade element 11 and also in the transition areas 12 and the remaining surface 13 of the base body 10 by controlling the hydraulic pressure applied to the rolling areas 21, 22 via a pressure control unit not further shown in the drawing, thereby enabling the rotor area 9 to be solidified to the desired extent by producing the optimum residual compressive stresses required at each location of the rotor area 9 and an improvement to be obtained with regard to the durability of the blades.

In order to facilitate, for example, CAD-CAM programming upstream of a roller compression process using the rolling tool 14 and subsequent implementation of the manufacturing programs on a multi-axes machining center by means of a post processor, an axis 39 of the carrier spindle 16 in the operating state connected to the tool carrier 15 passes between the rolling areas 21 and 22 through a contact point present at a distance between the rolling areas 21 and 22 equal to zero. Thus, the axis or the spindle carrier axis 29, respectively, and an axis through the contact point between the rolling areas 21 and 22 are congruent, thereby substantially facilitating programming.

In order to avoid damage to the blade elements 11 to be processed and to the rolling tool 14 proper, a distance between the rolling areas 21 and 22 is reducible via the drive unit 20 no further than to a defined limit value. Since the two ball elements 33 and 34 cannot be brought into contact with each other by respective turning or swivelling of the pliers-type bodies 17 and 18 and, thus, the adapter elements 37 and 38, damage to the rolling tool 14 is prevented in a simple manner.

The rolling tool 14 enables integrally bladed disks and rotors of jet engines to be roller-compressed at low cost. The rapid and easy exchange of the adapter elements 37 and 38 qualifies the rolling tool 14 with low setup times for use with rotor areas having different geometry, with different engagement depths between blade elements as well as different processing forces during the rolling process being representable on differently conceived components with high safety and process capability.

The pliers-type design of the rolling tool 14 enables blade elements or airfoils, respectively, of one-piece rotor areas to be processed from the tip to the fillet, with simultaneous roller compression of the pressure and suction sides of blade elements being provided to avoid distortion due to residual stress.

In addition, various individual tools enable the fillets or the transition areas, respectively, between the surface of the blade elements and the surface of the base body between the blade elements on the suction and pressure side to be processed to the desired extent. Moreover, the surface of the base body between the blade elements or the annulus, respectively, is roller-compressible by means of individual tools.

Basically, the rolling tool 14 can be integrated into any known machining center. In contrast to resolidification by shot peening, there is no need to procure expensive facilities. The rolling tool 14 enables resolidification to be performed, for example, in conventional milling centers. The milling centers are equipped with the rolling tool 14 and the one-piece rotor areas are processed using the rolling tool 14 in the area of their surfaces analogically to milling.

LIST OF REFERENCE NUMERALS

• 1 Jet engine
• 2 Bypass duct
• 3 Inlet area
• 4 Fan
• 5 Engine core
• 6 Compressor arrangement
• 7 Burner
• 8 Turbine arrangement
• 9 One-piece rotor area
• 10 Annular base body
• 11 Blade element
• 12 Transition area
• 13 Surface of the base body
• 14 Rolling tool
• 15 Tool carrier
• 16 Carrier spindle
• 17, 18 Pliers-type body
• 19 Rotating bearing
• 20 Driving unit
• 21, 22 Rolling area
• 23 Piston element
• 24 Cylinder element
• 25 End of pliers-type body 17
• 26 End of pliers-type body 18
• 27 Rotary axis
• 28, 29 Piston element
• 30, 31 Spring-action device
• 32 Resetting device
• 33, 34 Ball element
• 35, 36 Holding area
• 37, 38 Adapter element
• 39 Axis

Claims

1. Method for the production of a one-piece rotor area, preferably a rotor area of a jet engine, with the rotor area including an annular base body and several, circumferentially distributed blade elements extending essentially radially from the base body, with residual stresses being imparted to the blade elements in surface-near areas by way of roller compression using a rolling tool introduced between the blade elements, with one each area of a blade element being arranged between areas of the rolling tool during roller compression, and with longitudinal sides of the blade element being simultaneously roller-compressed, characterized in that the rolling tool is radially introduced between the blade elements and the surfaces of the blade elements are roller-compressed.

2. Method in accordance with claim 1, characterized in that the surfaces of the blade elements are roller-compressed by sequential radial traversing at least in certain areas.

3. Method in accordance with claim 1, characterized in that the surfaces of the blade elements are roller-compressed by sequential axial traversing at least in certain areas.

4. Method in accordance with claim 1, characterized in that the surfaces of the blade elements are roller-compressed by arbitrarily moving the rolling tool along the surfaces of the blade elements at least in certain areas.

5. Method in accordance with claim 1, characterized in that the transition areas between the surfaces of the blade elements and the surface of the base body between the blade elements are roller-compressed using a rolling tool.

6. Method in accordance with claim 1, characterized in that the surface of the base body between the blade elements is roller-compressed using a rolling tool.

7. Method in accordance with claim 1, characterized in that the surfaces of several blade elements axially arranged one behind the other are roller-compressed.

8. Method in accordance with claim 1, characterized in that a rolling force for setting a residual stress profile on the surfaces of the blade elements and/or the transition areas and/or the surface of the base body is variable between the blade elements.

9. One-piece rotor area with an annular base body and several blade elements distributed over the circumference of the base body and extending essentially radially from the base body, characterized in that at least the blade elements feature a roller-compressed surface.

10. One-piece rotor area in accordance with claim 9, characterized in that the transition areas between the surfaces of the blade elements and the surface of the base body between the blade elements feature a roller-compressed surface.

11. One-piece rotor area in accordance with claim 9, characterized in that the base body features a roller-compressed surface at least in the area between the blade elements.

12. One-piece rotor area in accordance with claim 9, characterized in that several blade elements axially arranged one behind the other on the base body are provided with a roller-compressed surface.