DE102017114153A1 - Electromagnetic vibration exciter for vibrational excitation of the blades of a blade ring - Google Patents

Abstract

The present invention relates to an electromagnetic vibration exciter (1) for vibrational excitation of the blades (21) of a blade ring (2) having at least one iron core (10, 13, 14), which at least partially, preferably continuously, in the circumferential direction (U) over a circumferential angle (θ) is annular, wherein the iron core (10, 13, 14) is further arranged to be arranged in the circumferential direction (U) perpendicular to the blades (21), so that at least one top side (13a, 14a) of the iron ( 10, 13, 14) at least in sections, preferably continuously, a distance (d (θ)) in the height (Z) to the blades (21), and with at least one field coil (15) which is formed, electrically supplied to and to generate an electromagnetic field which extends at least in sections through the iron core (10, 13, 14), through the blades (21) and over the distance (d (θ)), the distance (d (θ) ü Has at least one change in the height (Z) over the circumferential angle (θ).

Description

The present invention relates to an electromagnetic vibration exciter for vibrational excitation of the blades of a blade ring according to claim 1.

In units such as gas turbines, steam turbines or aircraft engines blades are used to effect a power transmission between a rotating or rotatable shaft of the unit and a working medium. These blades of the aggregate can also be referred to together as a blade ring or blading. Depending on the o.g. Use case can be e.g. speak of turbine, stator or compressor blades.

In operation, the individual blades of the blading can be excited to vibrate. The excitation may be due to inhomogeneities in the flow with the working medium such. the air done. The resulting vibrations can have a negative effect on the service life of the blades, since long load periods can cause cracks, which can ultimately lead to a fatigue failure of the individual blades. Likewise, by a short-term overload with very high oscillation amplitudes a violent fracture of a single blade occur. Both types of fractures of at least one single blade can typically result in the failure of the entire aggregate.

In order to avoid such fractures, the blades of a blading can be designed to be correspondingly robust, so that they meet the o.g. Be able to withstand vibrations permanently and even under short-term heavy loads. For this purpose, it is necessary for the design of the blades of the blading to know the vibration behavior of the blades under flow excitation as accurately as possible.

For designing the vibrational behavior of e.g. Turbine blading is carried out in addition to numerical simulations and experimental experiments. These are used primarily for the validation of the developed calculation programs. In other words, under certain boundary conditions, the result of the numerical simulation is compared with the measurement results of an experimental experiment under the same boundary conditions and the numerical simulation program is adjusted accordingly so that the simulation results correspond as well as possible to the measurement results. It can then be assumed that the real conditions of the application can be simulated with sufficient accuracy by means of the numerical simulation program, so that by means of the numerical simulation program it is possible to design a blading which can withstand the real conditions.

For this purpose, the blading is usually displaced in the experimental attempt by a force excitation in a possible defined vibration state. The comparison with the results of a numerical simulation program can be done so easily by performing a simulation with the same force excitation.

As an experimental experiment, an experimental experiment under real flow in a centrifugal bunker or on a real aggregate is unfavorable for this, since such an experimental experiment can be associated with high costs and high uncertainties and critical operating conditions can often not be considered.

Therefore, concepts for excitation of rotating blading by means of experimental experiments are generally aimed at generating an excitation force profile which has only certain excitation frequencies EO _i contains to generate the above-defined state of excitation of the blading. The excitation force profile of a blading is in many cases periodic over its circumference. It can thus be described by a Fourier series, which describes the spatial force curve over the circumference of the blade ring. This spatial force curve consists of a sum of harmonic terms with an excitation frequency EO _i and a phase phi _i .

A widely used variant for exciting a rotatable blading is to mount housing-mounted permanent magnets beneath the blades of the blading, which attract each blade as it passes the permanent magnet. In this case, one or more permanent magnets can be arranged over the circumference. The rotating blading is then energized during operation by force pulses generated by the permanent magnets when a blade of the blading passes through a permanent magnet. In this case, act on each blade per revolution as many power pulses as individual permanent magnets are arranged. The fundamentalharmonic excitation frequency EO ₁ thus corresponds to the number of magnets, if they are arranged equidistantly.

In order to clarify the problem, an example of a blade ring should be considered, which with a force curve of the excitation frequency EO ₁ = 4 is stimulated accordingly. 1 Figure 4 shows the normalized course of the idealized excitation force experienced by a single blade of blading during one revolution over four permanent magnets. The individual impulses are in the first approximation as Rectangular signals over the circumference angle θ modeled. 2 shows this signal in the frequency domain.

In addition to the non-interfering constant term EO ₀ = 0, the desired excitation frequency EO ₁ = 4 is clearly contained. Only slightly weaker, however, is the first harmonic EO ₂ = 8, which forms a fault term. All higher harmonics EO ₃ etc. decrease only slowly in their amplitude. This form of excitation thus has the disadvantage that the harmonics EO ₂ etc. stimulate the blades to vibrate, which is the vibration shape of the desired excitation frequency to be examined EO ₁ = 4 can disturb.

Also in the 2 to recognize that much of the energy provided in the higher excitation frequencies EO ₂ etc., which no longer excite the desired excitation frequency EO ₁ is available. This means that strong permanent magnets must be used, and the stronger the less permanent magnets are used. However, the use of less strong permanent magnets places a great load on the individual blades. The actual excitation force curve does not provide an ideal rectangular function as in FIG 1 Nevertheless, the fundamental problem also remains with a real course of the excitation force, even if the amplitudes of the harmonics EO ₂ etc. compared to the fundamental harmonic excitation frequency EO ₁ lose weight.

The excitation of the rotating blade ring can be done by electromagnets instead of permanent magnets. For non-magnetic blade materials, the excitation in the rotating system can also be done with magnets. The explained basic problem of the jerky excitation and the resulting unwanted excitation frequencies EO ₂ etc. is usually present in these variants.

In conjunction with the use of electromagnets, the jerk-like excitation can be completely avoided by using a non-rotating blade ring. In this variant, a bucket is always above the same electromagnet. However, the use of a non-rotating test stand has the disadvantage that dynamic effects such as "spin softening" and "stress stiffening" can not be generated or only with great effort. Likewise, damping structures such as sub-platform dampers and Shroud coupling can not be used in a realistic manner due to the lack of centripetal acceleration. Therefore, in particular for the design of blade rings with damping structures, the previously described test stands with rotating blades as test carriers are to be preferred.

A disadvantage of the test stands with rotating blades or with rotating blade ring, however, that may result in an unwanted heating of the blades for the excitation with individual (permanent or electric) magnet. This is caused by eddy currents, which inevitably arise in the blades when moving through a spatially changing magnetic field. These eddy currents can lead to melting of the blade tips. These eddy currents are stronger, the more unsteady the magnetic field in the room is. The fact that the blades are exposed by the individual magnets to a magnetic field with large gradients, therefore leads to strong eddy currents.

In addition to the excitation concepts described above, there are also excitation concepts based on fluid forces generated by air or oil jets. In such test stands, however, the excitation forces acting on the individual blades, can not be set as accurate and reproducible as in a magnetic excitation, which is why this excitation concept is usually preferred.

The DE 43 34 799 A1 relates to a device for testing blades of a turbomachine, in particular a turbine, with a motor-driven, rotatably mounted shaft train, on which a wheel disc is arranged rotationally fixed, on which the blades are releasably anchored. All blades are heated. Furthermore, an electromagnetic shaking device is provided with which the blades can be impressed on the rotating shaft train vibrations.

An object of the present invention is to provide an electromagnetic vibration exciter for vibrational excitation of the blades of a blade ring of the type described above, so that the described harmonics EO ₂ etc. eliminated in the excitation force profile or at least can be reduced so that the excitation of the blading can be possible only with desired frequencies. At least an alternative to known such electromagnetic vibration exciters should be created.

The object is achieved by an electromagnetic vibration exciter for vibrational excitation of the blades of a blade ring with the features of the claim 1 solved. Advantageous developments are described in the subclaims.

Thus, the present invention relates to an electromagnetic vibration exciter for vibrational excitation of the blades of a blade ring with at least one iron core, which at least in sections, preferably continuously, in the circumferential direction over a circumferential angle θ is annular. As a result, in principle, as will be explained in detail below, discontinuities of the magnetic field can be avoided or at least reduced with respect to an arrangement of individual magnets in order to avoid or at least reduce the heating of the blades caused by the individual magnets.

The iron core is further configured to be arranged in the circumferential direction perpendicular to the blades, so that at least one upper side of the iron circle at least in sections, preferably continuously, has a distance in the height to the blades. This distance can also be referred to as an air gap, as is customary in magnetic circuits. The upper side of the iron circle is understood to mean the side which points towards the distance or the air gap.

The electromagnetic vibration exciter also has at least one field coil which is designed to be supplied with electricity and to generate an electromagnetic field which extends at least in sections through the iron core, through the blades and over the distance. The field coil may preferably consist of several turns of enamelled copper wire whose ends can be led to the outside and connected to a voltage source. The field coil can be operated by means of the voltage source with DC voltage or with AC voltage. In other words, by means of the electric field coil, a magnetic circuit can be closed by the iron core via the air gap in the blades and from there via the air gap at another point back into the iron core. The distance or the air gap points over the circumferential angle θ at least one change in height.

The present invention is based on the finding that the attraction of an electromagnet in addition to the parameters of the field coil such as diameter, number of turns and coil current also depends significantly on the distance of the structure to be attracted, here the blades, from the iron core. It applies to the attraction of a simple electromagnet: $$F=\frac{{\mathrm{<figure-callout\; id="2"\; label="U\; m"\; filenames="DE102017114153A1\_0008.png"\; state="\{\{state\}\}">U\; </figure-callout>}}_m^{}}{2{\mathrm{\mu }}_0\mathrm{<figure-callout\; id="2"\; label="A\; R\; m"\; filenames="DE102017114153A1\_0008.png"\; state="\{\{state\}\}">A\; </figure-callout>}{R}_m^{}{}_2^{}}$$

Here is U _m the magnetic tension, μ ₀ the magnetic field constant, A the cross-sectional area of the magnetic circuit, ie here the surface of the iron core, and R _m the magnetic resistance of the magnetic circuit. The magnetic tension U _m can be generated by the field coil, which in turn is instrumental in generating the magnetic attraction F can contribute.

angegeben werden. d bezeichnet dabei den Abstand der anzuziehenden Struktur, d.h. der Schaufeln, vom Eisenkern.The magnetic resistance of the magnetic circuit R _m can, ignoring the magnetic resistance R _m of the iron core, as $$R_m=\frac{2d}{{\mathrm{\mu }}_{0}A}$$

be specified. d denotes the distance of the structure to be attracted, ie the blades, from the iron core.

Combining these two equations with each other, it becomes clear that the magnetic attraction F , which acts between the surface of the iron core and the blades, inversely proportional to the square of the distance, ie to the air gap, is: $$F\alpha \frac{1}{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="DE102017114153A1\_0008.png"\; state="\{\{state\}\}">d</figure-callout>}}^2}$$

In the case of the above-described experimental experiments or their electromagnetic vibration exciters, it has hitherto been known that these have individual magnets arranged in the circumferential direction and spaced from one another. An iron core, which at least in sections, preferably continuously, in the circumferential direction over a circumferential angle θ is annular, is not known.

Furthermore, the individual magnets are so far arranged at identical distances from the blades, so that, viewed in the circumferential direction, a constant air gap results over the entire extension of the blades or of the electromagnetic vibration exciter. In contrast, the distance or the air gap according to the invention over the circumferential angle θ at least one change in height. As a result, the generation of the magnetic attraction force in dependence on the circumferential angle θ be influenced so that the explained harmonics EO ₂ etc. in the excitation force profile can be eliminated or at least reduced. As a result, the excitation of the blades of the blade ring possible only with the desired fundamental harmonic excitation frequency EO ₁ respectively.

In other words, according to the invention, an angle-dependent distance d ( θ ) or air gap d ( θ ), which compared to the previously known constant distance h ₀ , the here an arbitrarily selectable zero distance h ₀ can be with the Height h ( θ ) of the iron core is related as follows: $$d\left(\theta \right)=H_0-H\left(\theta \right)$$

angeregt werden, so ist erfindungsgemäß der über den Umfangswinkel ϑ veränderliche Verlauf der Höhe h(ϑ) des Eisenkerns und damit des Abstands d(ϑ) bzw. Luftspalts d(ϑ) gegenüber den Schaufeln zu $$h\left(\vartheta \right)=h_0-\frac{\alpha }{\sqrt{F_0+F_1\text{ sin}\left(E{O}_1\vartheta \right)}}$$

auszulegen. Hierbei ist α eine Konstante, welche die übrigen Einflussparameter der allerersten Gleichung, siehe weiter oben, berücksichtigt.Consider a sinusoidal magnetic attraction as an example of a steady harmonic magnetic attraction $$F_{}$$$${}_1=\widehat{F}sin\left(\mathrm{<figure-callout\; id="1"\; label="e\; O"\; filenames="DE102017114153A1\_0007.png"\; state="\{\{state\}\}">e\; </figure-callout>}{O}_{}{}_1\theta \right)$$

are excited, so according to the invention over the circumferential angle θ variable course of height h ( θ ) of the iron core and thus the distance d ( θ ) or air gap d ( θ ) towards the blades $$H\left(\theta \right)=H_0-\frac{\mathrm{<figure-callout\; id="0"\; label="\alpha \; F"\; filenames="DE102017114153A1\_0007.png"\; state="\{\{state\}\}">\alpha \; </figure-callout>}}{\sqrt{F_{}}}$$

interpreted. Here is α a constant which takes into account the other influencing parameters of the very first equation, see above.

Preferably, instead of exciting the blades with only one frequency, it is also possible to simultaneously excite multiple frequencies of interest. For this purpose, only the course of the height h ( θ ) for a force curve formed as a combination of sine terms of several frequencies. The course of the height h ( θ ) can also be designed for other, arbitrary excitation forms, which need not be sinusoidal or cosinusoidal.

According to one aspect of the present invention, the distance is over the circumferential angle θ a plurality of changes in height. As a result, the freedom of design to vary the magnetic attraction over the distance can be further increased.

According to a further aspect of the present invention, the change or the changes in height in the circumferential direction is at least in sections, preferably continuously, continuous. In this way, a harmonic excitation can be made possible, which can come as close as possible to the defined test excitations which have to be experimentally simulated. Furthermore, the eddy currents described above, which can result from discontinuities, can be avoided.

According to another aspect of the present invention, the distance is over the circumferential angle θ at least in sections, preferably continuously, on a harmonious course in height. As a result, a harmonious excitation of the magnetic attraction can be ensured, which may be advantageous for the reasons already described above.

According to another aspect of the present invention, the distance corresponds to the circumferential angle θ at least in sections, preferably continuously, in height a course of a Fourier transformable function. In this way, all Fourier transformable functions can be used, which can significantly increase the design latitude for implementing the knowledge described above.

According to a further aspect of the present invention, the change or the changes in the height in the circumferential direction is at least partially, preferably continuously, discontinuous. As a result, alternative suggestions can be created in comparison to steady progressions. For example, can be readjusted as suggestions, as they can occur in reality by the wake of the vanes of an aircraft engine.

In another aspect of the present invention, the iron core is U -shaped, so that from the iron core, an upwardly open interior is formed, wherein the field coil is disposed within the interior. This allows a compact electromagnetic vibration exciter, which can be arranged and operated in a corresponding test stand perpendicular to the blades or to the blade tips. The magnetic circuit can pass from the field coil through the one leg of the U-profile and the overlying distance or air gap in the blades and from there on the other distance and the other leg of the U-profile back to the field coil.

According to another aspect of the present invention, the iron core has a base ring with a radially inner leg and a radially outer leg, wherein the two legs define the interior radially on both sides, and the iron core has an inner profile ring, which on the radially inner leg of the base ring is arranged, and an outer profile ring, which is arranged on the radially outer leg of the base ring, wherein the top of the inner profile ring and or or the top of the outer profile ring forms the top of the iron core or form. In this way, the electromagnetic vibration exciter according to the invention can be realized in that an always the same base ring is used as a basic element, which is U-shaped and receives the field coil in its interior, as previously described. This primitive can then vary depending on Use case be adapted by appropriately trained profile rings to the desired excitation form.

Thus, the two profile rings can each have a profile which, by changing its height and thus the distance over the circumferential angle θ can produce the desired magnetic attraction. As a result, the basic element can be adapted and used repeatedly for different excitation processes once or by exchanging the profile rings. In other words, for each excitation frequency or combination of excitation frequencies, a new set of profile rings can be provided, by the use of which the base ring can be adapted.

According to a further aspect of the present invention, the inner profile ring and / or the outer profile ring is arranged interchangeably on the base ring. As a result, as already mentioned above, a flexible adaptation of the base ring as a basic element to various applications can take place in that only the profile rings have to be exchanged. This may include the manufacture and storage of one-piece iron cores with different pitches over the circumferential angle θ avoid, whereby the cost of using the present invention can be significantly reduced.

According to another aspect of the present invention, the tops of the profile rings are over the circumferential angle θ at least in sections, preferably continuously, the same or a different course. If, which is to be preferred, the same course of the distances for the two profile rings selected, then these courses or the suggestions thereby caused are in phase with each other. However, if a further possibility for using the present invention is to use profile rings with the same but circumferentially offset profiles of the height, excitation with different force amplitudes of the two profile rings can take place. Alternatively, different gradients of heights can be combined with each other, which can create more design options.

According to a further aspect of the present invention, the iron core is annularly closed in the circumferential direction except for a passage of the electrical connections of the field coil and the profile rings in the circumferential direction are closed continuously annular. In this way, carried out in the lower region of the base ring, the magnetic flux does not pass directly into the distance, carrying out the electrical connections of the field coil to arrange them within the U-shaped profile of the base ring and still be able to supply electricity. At the same time, the iron core in the region of the two profile rings, which border directly on the distance to the blades, can be made continuously closed in the circumferential direction in order to achieve a continuous and uninterrupted magnetic flux between the iron core and the blades. As a result, strong gradients, which result from discontinuities of the magnetic field and can lead to heating of the blades, can be avoided or at least reduced.

According to a further aspect of the present invention, the profile rings are positively held, preferably in each case by a plug connection, and / or non-positively, preferably in each case by at least one pair of centering pins on the legs of the base ring. In this way, a simple but still secure hold can be made possible, which can be repealed at the same time non-destructive, if the profile rings are to be replaced, as described above.

According to a further aspect of the present invention, the profile rings are positioned in the radial direction and / or in the circumferential direction defined on the legs of the base ring, preferably in each case by at least one pair of centering pins. As a result, on the one hand can be carried out a positioning in the radial direction to align the two profile rings relative to the axis of the vertical direction of the electromagnetic vibration exciter. In other words, a radial centering of the two profile rings can be achieved thereby. On the other hand, an orientation of the two profile rings in the circumferential direction against each other, in order to realize a desired phase offset or to avoid a phase shift.

According to a further aspect of the present invention, the inner profile ring and / or the outer profile ring comprises a high permeability ferromagnetic material, preferably consisting of a high permeability ferromagnetic material. As a result, the magnetic field can be conducted or guided as effectively as possible.

• 1 ein Diagramm der magnetischen Kraft über den Umfangswinkel bei einer permanentmagnetischen Anregung gemäß des Standes der Technik;
• 2 ein Diagramm der Kraftamplitude über der Frequenz des Diagramms der 1;
• 3 eine perspektivische schematische Darstellung eines Schaufelkranzes;
• 4 eine perspektivische schematische Darstellung eines erfindungsgemäßen elektromagnetischen Schwingungsanregers;
• 5 einen schematischen Querschnitt des erfindungsgemäßen elektromagnetischen Schwingungsanregers;
• 6 eine schematische Draufsicht auf einen Basisring des erfindungsgemäßen elektromagnetischen Schwingungsanregers;
• 7 ein Diagramm der magnetischen Anziehungskraft über den Umfangswinkel für ein erstes Profil des Eisenkerns des erfindungsgemäßen elektromagnetischen Schwingungsanregers;
• 8 ein Diagramm der magnetischen Anziehungskraft über den Umfangswinkel für ein zweites Profil des Eisenkerns des erfindungsgemäßen elektromagnetischen Schwingungsanregers;
• 9 ein Diagramm der magnetischen Anziehungskraft über den Umfangswinkel für ein drittes Profil des Eisenkerns des erfindungsgemäßen elektromagnetischen Schwingungsanregers;
• 10 ein Diagramm der magnetischen Anziehungskraft über den Umfangswinkel für ein viertes Profil des Eisenkerns des erfindungsgemäßen elektromagnetischen Schwingungsanregers;
• 11 ein Diagramm der magnetischen Anziehungskraft über den Umfangswinkel für ein fünftes Profil des Eisenkerns des erfindungsgemäßen elektromagnetischen Schwingungsanregers; und
• 12 ein Diagramm der magnetischen Anziehungskraft über den Umfangswinkel für ein sechstes Profil des Eisenkerns des erfindungsgemäßen elektromagnetischen Schwingungsanregers.

Several embodiments and further advantages of the invention will be explained below in connection with the following figures. It shows:

• 1 a diagram of the magnetic force over the circumferential angle in a permanent magnet excitation according to the prior art;
• 2 a graph of force amplitude over the frequency of the graph of the 1 ;
• 3 a perspective schematic representation of a blade ring;
• 4 a perspective schematic representation of an electromagnetic vibration exciter according to the invention;
• 5 a schematic cross section of the electromagnetic vibration exciter according to the invention;
• 6 a schematic plan view of a base ring of the electromagnetic vibration exciter according to the invention;
• 7 a diagram of the magnetic attraction over the circumferential angle for a first profile of the iron core of the electromagnetic vibration exciter according to the invention;
• 8th a diagram of the magnetic attraction over the circumferential angle for a second profile of the iron core of the electromagnetic vibration exciter according to the invention;
• 9 a diagram of the magnetic attraction over the circumferential angle for a third profile of the iron core of the electromagnetic vibration exciter according to the invention;
• 10 a diagram of the magnetic attraction over the circumferential angle for a fourth profile of the iron core of the electromagnetic vibration exciter according to the invention;
• 11 a diagram of the magnetic attraction over the circumferential angle for a fifth profile of the iron core of the electromagnetic vibration exciter according to the invention; and
• 12 a diagram of the magnetic attraction over the circumferential angle for a sixth profile of the iron core of the electromagnetic vibration exciter according to the invention.

1 shows a diagram of the magnetic force over the circumferential angle θ in a permanent magnet excitation according to the prior art. 2 shows a graph of the force amplitude over the frequency of the graph of the 1 , These figures or their diagrams were already explained at the beginning, so that this should not be repeated here.

3 shows a perspective schematic representation of a blade ring 2 , which can also be referred to as blading. Such a blade ring 2 can be used in units such as gas turbines, steam turbines or aircraft engines to effect a power transmission between a rotating or rotatable shaft of the unit and a working medium. The scoop wreath 2 is rotationally symmetric to the axis of the vertical direction Z , which also as height Z can be designated. In the radial direction r which are perpendicular from the axis of the vertical direction Z extends, the blade ring points 2 in the middle a blade body 20 on, with the shovel wreath 2 can be attached to the unit. Radially outward extends a plurality of identically constructed and aligned blades 21 which are in contact with the working medium during operation. These are in the circumferential direction U , which are perpendicular to the radial direction r is oriented, evenly distributed and evenly spaced from each other. In the circumferential direction U the circumferential angle extends θ around the axis of the vertical direction Z ,

4 shows a perspective schematic representation of an electromagnetic vibration exciter according to the invention 1 , 5 shows a schematic cross section of the electromagnetic vibration exciter according to the invention 1 , 6 shows a schematic plan view of a base ring 10 the electromagnetic vibration exciter according to the invention 1 ,

The electromagnetic vibration exciter 1 has a base ring 10 on, which is U-shaped open at the top. The base ring 10 forms a radially inner leg 10a and a radially outer leg 10b from which each project vertically upwards and radially between an interior space 10c of the base ring 10 form. Inside the interior 10c is a field coil 15 arranged from several turns of copper wire, see 5 , whose electrical connections (not shown) via a passage 12 led to the outside and there with a power supply (not shown) can be connected as a voltage source.

On the inner thigh 10a of the base ring 10 is an inner profile ring 13 arranged, which the first leg 10a in height Z extended to the top. A corresponding outer profile ring 14 is on the outer thigh 10b arranged. The base ring 10 , the inner profile ring 13 and the outer profile ring 14 together form the iron core 10 . 13 . 14 of the electromagnetic vibration exciter 1 and are therefore formed of a high permeability ferromagnetic material. The two profile rings 13 . 14 close each with a top 13a . 14a from the top down, which together the top 13a . 14a of the iron core 10 . 13 . 14 in height Z form. The two profile rings 13 . 14 are in the circumferential direction U annularly closed formed during the base ring 10 through the implementation 12 is interrupted.

Above the tops 13a . 14a of the iron core 10 . 13 . 14 are the shovels 21 of the scoop wreath 2 arranged, see 5 so the topsides 13a . 14a of the iron core 10 . 13 . 14 in the circumferential direction U perpendicular to the blades 21 are arranged. Between the tops 13a . 14a of the iron core 10 . 13 . 14 and the blades 21 or whose undersides there is a distance d ( θ ), which also serves as an air gap d ( θ ). The magnetic field lines passing through the field coil 15 generated during operation, thus flow from the base ring 10 for example, its inner thigh 10a in the inner profile ring 13 , above its top 13a into the air gap d ( θ ) exit. From there, the magnetic field lines enter the blades 21 and flow radially outward through the blades 21 through to above the outer profile ring 14 into the air gap d ( θ ) exit. About this air gap d ( θ ) the magnetic field lines pass over the top 14a of the outer profile ring 14 in these and from there into the base ring 10 again, so that close the magnetic field lines.

According to the invention, on the one hand, the two profile rings 13 . 14 closed annularly, giving a magnetic attraction F in the circumferential direction U unbroken on the blades 21 can work. This can cause gradients and the resulting heating of the blades 21 be avoided.

According to the invention, on the other hand, the two profile rings 13 . 14 with one over the circumference U or over the circumferential angle θ varying height h ( θ ) of their top 13a . 14a formed so that the distance d ( θ ) or air gap d ( θ ), see 5 , This is also in the 4 to recognize by the perspective view, so there is a minimum 16 the height h ( θ ) and a maximum 17 the height h ( θ ) Marked are. Through this change in the height h ( θ ) over the circumferential angle θ can the distance d ( θ ) or the air gap d ( θ ) over the circumferential angle θ be varied accordingly, resulting in an influence of the magnetic attraction F ( θ ) over the circumferential angle θ results. By this way of generating the magnetic attraction F ( θ ) can be a much more pronounced oscillation of the fundamental harmonic excitation frequency EO ₁ . d .H. a stronger amplitude of the fundamental harmonic excitation frequency EO ₁ , are excited as the interfering harmonics EO ₂ ,

Here are the profile rings 13 . 14 detachably designed to allow different courses of height h ( θ ) on the same base ring 10 to be able to realize. The profile rings 13 . 14 can do this from the top of the base ring 10 put on and taken off again upwards. Both for mounting and for alignment in the radial direction r and in the circumferential direction U has each profile ring 13 . 14 on its underside a pair of diametrically opposed recesses in the form of two holes (not shown), in each of which a centering pin can be received (not shown). The base ring 10 has at its top the corresponding four recesses 11 as holes 11 in which the centering pins (not shown) can be accommodated.

The 7 to 12 each show a diagram of the magnetic attraction F ( θ ) over the circumferential angle θ for a first to sixth profile of the iron core 10 . 13 . 14 the electromagnetic vibration exciter according to the invention 1 , Through various harmonic processes, continuous magnetic forces of attraction F ( θ ), which, for example, may have a sinusoidal course, cf. 7 , The 8th shows, for example, a Fourier series in the form of the superposition of several harmonic functions with different frequencies. However, discontinuous discontinuous courses are also possible in order to consider such magnetic excitations, cf. 9 and 11 , For example, the shows 9 discrete expressions that follow a harmonic function. The 10 shows the course resulting from a random surface profile. The 11 shows a single sawtooth as a gradient. Furthermore, the shows 12 two phase-shifted functions of the profile rings 13 . 14 ,

In this way, different magnetic excitations with comparatively large amplitudes of the desired fundamental harmonic excitation frequency can be used according to the invention EO ₁ on the blades 21 a shovel wreath 2 exercise the resulting measurement results, for example, with the results of a simulation program for the design of blades 21 to compare and thereby improve the simulation program.

In other words, it is possible by the present invention, a well-defined, continuous excitation force profile F ( θ ) on a blading 2 impress. This is currently not possible with existing excitation concepts. The above-explained disadvantage of existing excitation concepts of the occurrence of higher-harmonic, disturbing excitation frequencies EO ₂ etc. can be avoided with the present invention significantly better than previously known. This makes it possible for the first time, the excitation force profile F ( θ ) to know and control as precisely as possible in experimental experiments. It can in particular validate the Calculation programs to simulate the dynamic behavior of blading 2 be improved.

The resulting magnetic field is at a choice of a corresponding course of the tops 13a . 14a the profile rings 13 . 14 over the circumference U steady and does not have strong gradients. This also causes the above-mentioned very strong heating of the blades 21 avoided by the excitation with individual magnets.

The present invention can be used in addition to university research in industrial design process, for example, the turbine manufacturer. By means of the possibility of validating the calculation programs better with the present invention, real executed blading can be achieved 2 be designed to be safer and more time-efficient in the future. The higher accuracy in the design process can lead to better properties of the blades 21 lead, which ultimately increases the efficiency of the turbine or the engine.

LIST OF REFERENCE NUMBERS

α

constant

A

Cross sectional area of the magnetic circuit or surface of the iron core 10, 13, 14 of the inner profile ring 13 or the outer profile ring 15th

d (θ)

Distance of the inner profile ring 13 and / or the outer profile ring 15 from the blade 21 in the height Z over the circumferential angle θ; air gap

F (θ)

magnetic attraction over distance d (θ) over the circumferential angle θ

h (θ)

variable thickness or height of the iron core 10, 13 14 of the inner profile ring 13 and / or the outer profile ring 15 in the height Z over the circumferential angle θ

h ₀

Zero distance in height Z; Height Z of the smallest minimum 16

μ ₀

magnetic field constant

r

radial direction to the vertical direction Z

R _m

magnetic resistance of the iron core 10, 13, 14

θ

Circumferential angle about vertical direction Z

U

Circumferential direction perpendicular to the radial direction r

U _m

magnetic tension

Z

vertical direction; height

EO _i

i-th excitation frequency

EO ₀

constant term of the excitation frequencies

EO ₁

first or fundamentalharmonic excitation frequency

EO ₂

second excitation frequency or first harmonic wave

EO ₃

third excitation frequency or second harmonic wave

1

electromagnetic vibration exciter

10

Base ring of the iron core

10a

radially inner leg of the base ring 10th

10b

radially outer leg of the base ring 10th

10c

Interior of the base ring 10

11

Connector receptacle; Recesses or holes for centering pins

12

Feedthrough for electrical connections of the field coil 16

13

inner profile ring of iron core

13a

Top of the inner profile ring 13th

14

outer profile ring of iron core

14a

Top of the outer profile ring 14th

15

field coil

16

Minimum height h (θ) or maximum of distance d (θ)

17

Maximum of the height h (θ) or minimum of the distance d (θ)

2

Blade ring; blading

20

blade body

21

shovel

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4334799 A1 [0017]

Claims (14)

Electromagnetic vibration exciter (1) for vibrational excitation of the blades (21) of a blade ring (2), with at least one iron core (10, 13, 14), which is of annular design over at least sections, preferably continuously, in the circumferential direction (U) over a circumferential angle (θ), wherein the iron core (10, 13, 14) is further arranged to be arranged in the circumferential direction (U) perpendicular to the blades (21), so that at least one top side (13a, 14a) of the iron circuit (10, 13, 14) at least Sectionally, preferably continuously, a distance (d (θ)) in the height (Z) to the blades (21), and with at least one field coil (15), which is designed to be electrically supplied and to generate an electromagnetic field, which at least partially through the iron core (10, 13, 14), through the blades (21) and over the distance (d (θ)), wherein the distance (d (θ)) over the circumferential angle (θ) at least one change in the height (Z). Electromagnetic vibration exciter (1) according to Claim 1 , characterized in that the distance (d (θ)) over the circumferential angle (θ) has a plurality of changes in the height (Z). Electromagnetic vibration exciter (1) according to Claim 1 or 2 , characterized in that the change (s) in the height (Z) in the circumferential direction (U) at least in sections, preferably continuously, is / are continuous. Electromagnetic vibration exciter (1) according to one of the preceding claims, characterized in that the distance (d (θ)) over the circumferential angle (θ) at least in sections, preferably continuously, a harmonic curve in the height (Z). Electromagnetic vibration exciter (1) according to one of the preceding claims, characterized in that the distance (d (θ)) over the circumferential angle (θ) at least in sections, preferably continuously, in the height (Z) corresponds to a curve of a Fourier transformable function. Electromagnetic vibration exciter (1) according to one of the preceding claims, characterized in that the change (s) in the height (Z) in the circumferential direction (U) at least in sections, preferably continuously, is / are sudden. Electromagnetic vibration exciter (1) according to one of the preceding claims, characterized in that the iron core (10, 13, 14) is U-shaped, so that of the iron core (10, 13, 14) an upwardly open interior (10c) is formed, wherein the field coil (15) within the interior (10 c) is arranged. Electromagnetic vibration exciter (1) according to Claim 7 , characterized in that the iron core (10, 13, 14) has a base ring (10) with a radially inner leg (10a) and a radially outer leg (10b), wherein the two legs (10a, 10b) the inner space (10c ) radially on both sides, and that the iron core (10, 13, 14) an inner profile ring (13) which on the radially inner leg (10a) of the base ring (10) is arranged, and an outer profile ring (14), which is arranged on the radially outer limb (10b) of the base ring (10), wherein the upper side (13a) of the inner profile ring (13) and / or the upper side (14a) the outer profile ring (14) the upper side (13a, 14a) of Iron core (10 13, 14) forms / form. Electromagnetic vibration exciter (1) according to Claim 8 , characterized in that the inner profile ring (13) and / or the outer profile ring (14) is arranged interchangeably on the base ring (10) / are. Electromagnetic vibration exciter (1) according to Claim 8 or 9 , Characterized in that the top faces (13a, 14a) of the profile rings (13, 14) over the circumferential angle (θ) at least in sections, preferably continuously, the same or a different course have. Electromagnetic vibration exciter (1) according to one of Claims 8 to 10 , characterized in that the iron core (10, 13, 14) in the circumferential direction (U) except for a passage (12) of the electrical connections of the field coil (15) is annularly closed, and that the profile rings (13, 14) in the Circumferential direction (U) are closed continuously annular. Electromagnetic vibration exciter (1) according to one of Claims 8 to 11 , characterized in that the profile rings (13, 14) positively, preferably each by a plug connection, and / or non-positively, preferably by at least one pair of centering pins on the legs (10a, 10b) of the base ring (10) are held. Electromagnetic vibration exciter (1) according to one of Claims 8 to 12 , characterized in that the profile rings (13, 14) in the radial direction (r) and / or in the circumferential direction (U) defined on the legs (10a, 10b) of the base ring (10), preferably each by at least one pair of centering pins are positioned. Electromagnetic vibration exciter (1) according to one of Claims 8 to 13 , characterized in that the inner profiled ring (13) and / or the outer profiled ring (14) comprises / have a high permeability ferromagnetic material, preferably consisting of a high permeability ferromagnetic material.

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