EP2527600A1 - Turbo machine - Google Patents

Abstract

The turbomachine has stationary component and rotating component e.g. rotor (12) between which clearance (g1) is formed. The clearance has two values in stationary and steady-state operations of machine, respectively. The clearance has a value which traverses a curve having extreme value on account of different time variation of rotational speed and thermal expansion of components during transient operating phase between both operations. A self-adjusting device (20) has non-linear compensation mechanism that reduces or compensates extreme value during transient operating phase.

Description

TECHNICAL AREA

The present invention relates to the field of turbomachinery such as gas turbines, steam turbines, aircraft engines, stationary compressors or turbochargers. It relates to a turbomachine according to the preamble of claim 1.

STATE OF THE ART

The minimization of the games, in particular the radial play between stationary and rotating parts of a turbomachine during operation is crucial for minimizing flow losses and thus for maximizing the efficiency of such machines. For illustration shows Fig. 1 an example of a turbomachine 10 in the form of a compressor arrangement with a on a (about an axis 13) rotating shaft 12 seated blade 14 and By minimizing the radial clearance C _b and C _v between the tip of the blade 14 and the opposite housing 11 and the tip of the vane 15 and the opposite shaft 12, the flow losses can be reduced.

Due to the relative movement, e.g. between the blade tip of the blade 14 and the housing 11, it is not possible to set the radial clearance to zero. Contact between the two parts during operation may damage or even completely destroy the parts.

• ● die Herstellungstoleranzen der einzelnen Bauteile;
• ● die Zusammenbautoleranzen;
• ● die Ausdehnung der Schaufeln während des Betriebs aufgrund thermischer Effekte und Zentrifugalkräfte;
• ● die Deformation von Welle und Gehäuse im stationären Betrieb (z.B. in Form der sogenannten "Ovalisierung") und
• ● zeitabhängige Deformationen und relativen Bewegungen aller Bauteile während des transienten Maschinenbetriebs (betriebliche Übergangsphase der Maschine), wie zum Beispiel dem Aufstarten oder dem Abschalten der Maschine.

Basically, the radial plays during operation (so-called "hot games") are determined by a number of factors that must be taken into account in the construction of such a machine, if the assembly games (so-called "cold games", when the cold machine is at a standstill):

• ● the manufacturing tolerances of the individual components;
• ● the assembly tolerances;
• ● the expansion of the blades during operation due to thermal effects and centrifugal forces;
• ● the deformation of shaft and housing in stationary operation (eg in the form of so-called "ovalization") and
• ● Time-dependent deformations and relative movements of all components during transient machine operation (operational transition phase of the machine), such as the startup or shutdown of the machine.

In particular, the time-dependent deformations and relative movements of the main components during the transient operation are of importance for the determination of the cold-game and the resulting hot-game. The goal is to determine the cold clearance in such a way that during stationary operation the resulting hot clearance is minimal. Due to the different Time constants in the mechanical and thermal deformation of the blades, housing parts, and shafts during the warm-up or cool down of the machine will not necessarily cause the minimum hot clearance in hot steady state operation where minimum clearance is desirable. In general, the smallest possible play (so-called "pinch point") will occur during a transient operating phase, especially considering that the machine is also subject to rapid load changes or can be started when significant components of a previous operating period are still hot , In such a case, it is necessary to increase cold clearance to such an extent that hard contact between stationary and rotating parts during transient operation is avoided, which consequently leads, under steady state conditions, to a hot clearance which is greater than he wishes.

Known measures for minimizing the flow losses caused by remaining hot games include, for example, the introduction of shrouds at the tips of the blades and vanes. To minimize flow through the annular gap between shroud and housing or rotor, one or more ribs are often circumferentially provided on the rotating member, while the surface of the stationary member may be planar or stepped to form a total of a labyrinth-like seal , In addition, so-called honeycombs (honeycomb material) can be placed on the surface of the stationary part to allow the ribs to be cut during transient operating conditions so as to avoid hard contact. The resulting rotating part configuration and honeycomb cut resembles a stepped labyrinth seal and helps reduce flow losses over a configuration without honeycomb. Other known measures to minimize the hot-games are to apply so-called blade or brush seals to the stationary part, which can compensate for changes in play during operational transients to some extent. Finally, a combination of eg abrading elements and abradable coatings on the opposite side can be used to mitigate the negative effect of circumferentially occurring game variations, which may be caused, for example, by the ovalization of structural parts or some eccentricity of the shaft within the housing.

While all previously mentioned solutions are purely passive in nature, allowing for minimization of hot clearance without any active adaptation of the geometry during operation, there are also a number of known active measures for game reduction.

For example, a system is known where the entire rotor is displaced in the axial direction when the machine has reached its steady-state operating condition. In cooperation with a conical flow channel, this makes it possible to actively minimize the radial clearance in the hot turbine, whereby a combination with the passive measures described above is fundamentally possible. However, since the whole rotor has to be moved, there are enlargements of radial play on the compressor side. Therefore, this measure is only advantageous as long as the reduction of losses in the turbine outweigh the additional losses on the compressor side.

Instead of shifting the shaft, other solutions suggest either controlling the radial thermal expansion of the blades in each stage of the turbine, or employing a spring system which allows additional radial movement of the heat shields above a predetermined limit temperature.

The use of adjusting means is known for the linear adjustment of the game or of resilient mounting means. The latter is used for example in EP 1 467 066 A2 described. With these technical solutions However, it is not possible to compensate for an extreme value in the game in an operational transition phase of the machine.

The document US 2009/0226327 A1 describes a diaphragm made of a so-called. Memory alloy, which is installed in the rotor disk. Depending on the local temperatures, this orifice controls the amount of coolant flow into the turbine blade. By reducing the coolant flow, the blade thermally expands, thereby reducing the radial gap between the blade tip and the opposing stationary component. Increasing the coolant flow reduces the blade length and thus increases the radial gap.

The publication in GB 2 354 290 describes a valve made of a memory alloy installed in the cooling passage of a gas turbine blade. The valve regulates the consumption of coolant depending on the temperature of the component. Control of the radial clearance for blades and vanes is not described in this document.

The publication US 7,686,569 describes a system for the axial movement of a blade ring, which is caused by a pressure difference applied to the blade ring, the thermal expansion or contraction of a connection or by a piston. A memory alloy can also induce the necessary movement.

In principle, different passive, semi-active or active systems, as well as combinations thereof, may be considered for controlling the games between rotating and stationary components. The games C _b or C _v , which describe the relative distance between a rotating and a stationary component ( Fig. 1 ) vary during transient operating conditions due to the different and time-dependent thermal and mechanical deformations of the components. The actual time course depends on many factors, such as the volume of the components, the Contact with hot or cold media and the thermal properties of the alloys used.

Due to these temporally different deformations must be in accordance with Fig. 2 (a) the "hot" game C _b (with blades) or C _v (with vanes) in addition to a safety game C _s also a transient proportion g _{t, min} contained. This transient component must be taken into account in the definition of games in the cold state, C _{β, o, min} and C _{β, o, max} .

Fig. 2 Figure 2 (a) shows an example of the change over time t of the game between rotating and stationary hot parts for stationary operating phases (st) and transient operating phases (tr), where - as already mentioned - C _{s represents} a safety game, g _{a is} a tolerance band due to the manufacturing and assembly tolerances of the components, g _{t, min} and g _{t, max represent} the minimum and maximum differences between the steady-state clearance and the minimum clearance, C _{β, min} and C _{β, max} the mean minimum and maximum games for the nominal ("hot") operating conditions, and C _{β, o, min} and C _{β, o, max represent} the corresponding minimum and maximum games at standstill ("cold" operating condition) for "b" or blade or "v" or vane, see Fig. 1 ).

Fig. 2 (b) and (c) show possible variations in the rotational speed Ω of the shaft 12, the temperature T of the working fluid (hot gas) and the metal temperature T _m over time t, where Ω _n and T _n respectively represent the nominal rotational speed and nominal hot gas temperature in the engine. The metal temperature T _mn denotes the nominal temperature of the shaft and / or another mechanical component during stationary operation of the machine. t _Ωn and t _Tn are the times at which the stationary values Ω _n and T _{n are} reached.

Fig. 3 shows the cross section through a rotating member (in the example, a blade 14), which with a foot 16 in a corresponding receptacle in the rotor (shaft 12) is fixed, at standstill of the machine ( Fig. 3 (a) ) and under nominal steady-state operating conditions ( Fig. 3 (b) ). The foot 16 shown is representative of any foot geometry, such as a fir tree foot, a dovetail foot or a hammerhead foot. He engages with fingers 18 in corresponding lateral grooves 17 in the recording, for example in the rotor.

The centrifugal force brings one or more of the fingers 18 of the foot 16 into contact with the rotor 12 (FIG. Fig. 3 (b) ). At low rotational speed, a spring element 19 prevented the foot 16 from rattling in the receptacle at slow rotational speeds. At nominal rotational speed and after reaching the thermal equilibrium of all components of the machine, games C _b or C _{v are made} Fig. 1 reached. In this case, the designation g _{a again} stands for the tolerance band from production and assembly tolerances and is shown here by way of example between finger 18 and the rotor receptacle when the machine is at a standstill.

When starting the machine, the thermal expansion of the blading is typically much faster than that of the housing parts or the rotor shaft, which have a higher thermal inertia than the blades due to their larger mass. This means that the heating and thus the thermal expansion of the shaft or other structural parts continues even after the working fluid has already reached the nominal operating temperature T _n (time t _Tn in _FIG Fig. 2 (c) ). This circumstance leads to the occurrence of a so-called "pinch point", ie a point in time during the warm-up phase at which the radial clearance reaches its minimum value (see Fig. 2 (a) ). For this reason, for the nominal stationary operating condition, the resulting minimum clearance C _{b, min} (or C _{v, min} ) must include a safety clearance C _s and a minimum transient contribution to the gap, g _{t, min} . This must be determined analytically when designing the machine and depends on the thermal boundary conditions, dimensions and material properties of the rotating and stationary components. The transient contributions to the gap, g _{t, min} and g _{t, max} , prevent the Blade blade tips on the stationary housing or stationary heat shields or on the rotor or the rotor heat shields.

Under the nominal steady state operating condition, when all rotating and stationary parts have reached their maximum thermal and mechanical deformations, the transient contribution to the "pinch-point" gap (g _t ) is an essential part of the game in the "hot" steady state, C _{b, min} (or c _{v, min} ).

PRESENTATION OF THE INVENTION

It is now an object of the invention to provide a turbomachine of the type mentioned, in which the game between rotating and stationary parts for the different operating conditions is optimized in a simple manner.

The object is solved by the entirety of the features of claim 1. The invention is based on operating at an elevated operating temperature turbomachine with stationary and rotating components between which a game is provided to avoid a frictional contact, which assumes a second value at standstill of the machine and a second value in stationary operation of the machine, and in a transient phase of operation between standstill and stationary operation due to different time profiles of the rotational speed and the thermal expansion of different components undergoes a curve having an extreme value. It is characterized in that compensating means are provided with a non-linear compensation mechanism for reducing or compensating for the extreme value in the transient operating phase.

The problem underlying the application of the occurrence of an extreme value in the game in an operational transition phase of the machine is solved by the fact that the compensating means provided are not at the beginning or end of the transition have their maximum deflection, but in the transition area itself, and where the extreme value of the game occurs. For this purpose, a non-linear compensation mechanism is used in the compensating means, which is superimposed, for example, by two counter-rotating movements.

An embodiment of the turbomachine according to the invention is characterized in that the compensating means comprise a self-adjusting device which increases or decreases the clearance in dependence on external parameters.

In particular, the self-adjusting device changes its shape to increase or decrease the game.

Another embodiment is characterized in that the Selbstjustiervorrichtung has a predetermined height, and that the Selbstjustiervorrichtung to increase or decrease the game changes its height.

A further embodiment of the invention is characterized in that the self-adjusting device increases or decreases the game as a function of its temperature.

In particular, the self-adjusting device has a hysteresis in its temperature behavior.

According to a further embodiment, the self-adjusting device contains a bimetal.

It is also conceivable that the self-adjusting device contains a shape memory alloy.

Yet another embodiment of the invention is characterized in that the rotating components are moving blades, and that the play to be influenced is between the tips of the moving blades and the opposite stationary housing.

Another embodiment is characterized in that the stationary components are vanes, and that the game to be influenced between the tips of the vanes and the opposite rotor consists.

Another embodiment is characterized in that the blades each sit with a blade root in a receptacle in the rotor and supported by supporting means against attacking centrifugal forces on the rotor, and that the Selbstjustiervorrichtung between the support means and the rotor is arranged.

Another embodiment is characterized in that the self-adjusting device changes its height in the radial direction in a temperature-controlled manner between a first value and a second value, and that the difference of the two values corresponds to the extreme value of the curve of the game.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

in einer stark vereinfachten Schnittdarstellung das mechanische Spiel zwischen rotierenden und stationären Teilen in einer Turbomaschine der üblichen Art nach dem Stand der Technik;

Fig. 2

in mehreren Teilfiguren die zeitliche Abhängigkeit des Spiels bei einer Turbomaschine bei Durchlaufen eines transienten Startvorgangs bis zum Erreichen eines stationären Betriebszustands (Fig. 2(a)) sowie die zugehörige zeitliche Abhängigkeit der Rotationsgeschwindigkeit (Fig. 2(b)) und der Heissgas- und Metalltemperatur (Fig. 2(c));

Fig. 3

in einer stark vereinfachten Schnittdarstellung die Verankerung eines rotierenden Teils (Laufschaufel) im Rotor bei Stillstand (Fig. 3(a) und unter nominalen stationären Betriebsbedingungen (Fig. 3(b);

Fig. 4

in einer stark vereinfachten Schnittdarstellung ein selbstjustierendes System zur Steuerung des Spiels bei einer Verankerung gemäss Fig. 3 gemäss einem Ausführungsbeispiel der Erfindung;

Fig. 5

ein Beispiel für die thermo-mechanische Hysterese eines selbstjustierenden Systems gemäss der Erfindung;

Fig. 6

in einer stark vereinfachten Schnittdarstellung ein selbstjustierendes System gemäss Fig. 4 bei nominaler Rotationsgeschwindigkeit und

Fig. 7

die zeitliche Abhängigkeit des Spiels bei einer Turbomaschine mit einem selbstjustierenden System gemäss Fig. 4 und 6.

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. Show it:

Fig. 1

in a highly simplified sectional view, the mechanical play between rotating and stationary parts in a turbo machine of the usual type according to the prior art;

Fig. 2

in several subfigures the temporal dependence of the game in a turbomachine when passing through a transient Startup until steady-state operation is achieved ( Fig. 2 (a) ) as well as the associated temporal dependence of the rotational speed ( Fig. 2 (b) ) and the hot gas and metal temperature ( Fig. 2 (c) );

Fig. 3

in a simplified sectional view, the anchoring of a rotating part (moving blade) in the rotor at standstill ( Fig. 3 (a) and under nominal steady-state operating conditions ( Fig. 3 (b) ;

Fig. 4

in a highly simplified sectional view of a self-adjusting system for controlling the game in an anchoring according to Fig. 3 according to an embodiment of the invention;

Fig. 5

an example of the thermo-mechanical hysteresis of a self-adjusting system according to the invention;

Fig. 6

in a greatly simplified sectional view of a self-adjusting system according to Fig. 4 at nominal rotational speed and

Fig. 7

the time dependence of the game in a turbomachine with a self-adjusting system according Fig. 4 and 6 ,

WAYS FOR CARRYING OUT THE INVENTION

The present invention relates to the use of a Selbstjustiervorrichtung comprising a bimetal element and / or shape memory alloy element and / or an element made of another material, which in an elastic, super-elastic or pseudo-elastic Altered above a limit of temperature, pressure or mechanical stress of its form, which is actively or passively activated, and which is arranged in a turbomachine to minimize the games during operation and under various operating conditions. The Selbstjustiervorrichtung can be housed in a structural unit of a turbine, a compressor blade, a stator or rotor heat shield, a guide vane or other rotating or stationary components that are mounted on the rotor or on the housing.

1. a. durch einen äusseren 2-Wege-Effekt bewirkt, der durch eine einwirkende äussere Kraft wie zum Beispiel die Zentrifugalkraft initiiert wird und/oder
2. b. durch einen internen 2-Wege-Effekt bewirkt, wie bei einer Formgedächtnislegierung, bei der keine externe Kraft benötigt wird, um die gewünschte Deformation des Systems zu aktivieren.

As an example of the use of the invention, the attachment of a blade to the rotor of a turbine will be described below by way of example. Fig. 4 shows a Selbstjustiervorrichtung 20, which is arranged between the finger 18 of a blade root 16 and the associated groove 17 in the rotor 12. The deformations of the self-aligning device 20 can be characterized as

1. a. caused by an external 2-way effect, which is initiated by an acting external force such as the centrifugal force and / or
2. b. by an internal 2-way effect, as in a shape memory alloy, where no external force is needed to activate the desired deformation of the system.

The shape of the Selbstjustiervorrichtung 20 can be largely arbitrary and generally depends on the available space. Decisive in the form is the height, as in Fig. 4 is shown. In the example shown there, the height of the self-aligning device 20 under the condition of machine standstill corresponds to the minimum difference g _{t, min} (the transient gap contribution) that would be present without the use of the self-aligning device 20. During start-up of the machine, the centrifugal forces acting on the blade are transmitted via the finger 18 through the self-aligning device 20 to the groove 17 in the rotor 12. These forces increase with increasing rotational speed. The elastic properties of the self-aligning device 20 at the height g _t prevent the device from being pushed flat. As a result, the game at the blade tip remains the same Bucket length greater than without the Selbstjustiervorrichtung 20. However, a certain flattening of the Selbstjustiervorrichtung 20 due to the mechanical stress can be accepted.

With increasing power, from idle to full load, the temperature in the engine increases. In terms of rotational speed, this warm-up process requires significantly more time ( Fig. 2 (b), (c) ) and the various parts of the machine reach the stationary temperature T _n at different times. Typically, the warmest "slowest" component is the rotor. With increasing temperature of the blade root 16 and the rotor 12, the temperature of the self-aligning device 20 also increases due to the heat conduction at the contact surfaces and convective heat transfer due to any hot gas flow around the blade root 16.

The material of the self-aligning device 20 is conditioned so that its mechanical properties change as a function of its temperature T in accordance with a hysteresis behavior, as shown in FIG Fig. 5 is shown. At standstill and ambient temperature, the Selbstjustiervorrichtung 20 is deformed out of its flat state maximum by an expansion ε _t with εt = σ _t / E, which corresponds to the transient gap contribution g _t ( Fig. 4 ). As the temperature T increases, the self-aligning device 20 changes its rigidity in accordance with the trained hysteresis and becomes Fig. 6 completely flat when the predetermined temperature T _{n is} reached. During engine shutdown, the thermo-mechanical properties of self-aligning device 20 follow the upper curve of pre-programmed hysteresis (see arrows in FIG Fig. 5 ).

It is when the self-aligning device 20 is given the correct height (g _t ) and brought to the required elastic or super-elastic or pseudo-elastic behavior and thermal hysteresis that suits the centrifugal load and the warming and cooling of the adjacent components possible to minimize the occurrence of a transient "pinch-point" game or even completely avoided. As a result, the game in the stationary hot state takes its smallest possible minimum value, taking into account the minimum required safety game. Ideally, the length of the blade in the case without Selbstjustiervorrichtung 20 can be increased by the amount g _t , so that the minimum resulting game C _{β, o, min is} equal to C _s (see Fig. 2 (a) and Fig. 7 ).

Fig. 7 shows (compared to Fig. 2 (a) ) The time variation of the game at the top of a blade with built-in Selbstjustiervorrichtung 20 (curves a). The curve C _β (t) _{min red} demonstrates the possibility of reducing the play in the cold built state and in the warm state by eliminating the game g _{t, min} .

Given that the same principles can be applied to the radial movement of the stator heat shield over a blade tip, the machine designer has great freedom to set and control the games during transient and steady state operating conditions.

Further, considering that it is also possible to influence the cooling air and leakage air flows through the rotor and around the rotor and stator parts, it is also possible to actively control the behavior of the self-adjusting device 20.

Various shape memory alloys, bimetals, and / or other materials having comparable performance have been considered within the scope of the present disclosure. Their manufacture and their incorporation into a component have not been discussed in detail since they are known to those skilled in the art of shape memory alloys and bimetals. Thus, for example, a NiTi-based shape memory alloy could be considered in the area of the hot blade root whose allowable working temperature reaches up to 200 ° C when cooling with secondary air is available in a gas turbine. Ternary high-temperature NiTiX alloys and others containing Hafnium Hf, Palladium Pd and / or Platinum Pt as element X extend the working temperature range up to 800 ° C and more. Of course, in the context of the invention, other materials / alloys may be used, provided they have the desired and required properties.

LIST OF REFERENCE NUMBERS

10

turbomachinery

11

casing

12

Shaft (rotor)

13

axis

14

blade

15

vane

16

Foot (blade foot)

17

groove

18

finger

19

spring element

20

Selbstjustiervorrichtung

C

game

C _b

Blade clearance

C _s

margin of safety

C _v

Leitschaufelspiel

C _{β, o, max}

Maximum game (cold)

C _{β, o, min}

Minimal game (cold)

C _{β, max}

Maximum game (hot)

C _{β, min}

Minimal game (hot)

_Cβ (t) _min

Curve for minimal gameplay

C _β (t) _max

Curve for maximum play history

C _β (t) _{min red}

Curve for minimal gameplay with Selbstjustiervorrichtung 20

g _a

tolerance band

g _t

transient split contribution

g _{t, max}

Maximum difference (transient split contribution)

g _{t, min}

Minimum difference (transient split contribution)

Ω

rotation speed

Ω _n

Rotational speed (nominal)

st

stationary operating phase

tr

transient operating phase

T _n

Hot gas temperature (nominal)

T _mn

Metal temperature (nominal)

t

Time

T

temperature

ε

strain

σ

tension

e

modulus of elasticity

Claims (12)

Turbomachine (10) which operates at elevated operating temperature, with stationary and rotating components (11, 15 and 12, 14), between which a game (C) is provided to avoid rubbing contact, the machine at a standstill value (C _{β, omin} ; C _{β, omax} ) and in stationary operation (st) of the machine takes a second value (C _{β, min} ; C _{β, max} ), and that in a transient operating phase (tr) between standstill and stationary operation (st) undergoes a curve having an extreme value ("pinch-point", g _t ) due to different temporal courses of the rotational speed and the thermal expansion of different components, characterized in that compensating means (20) with a non-linear compensation mechanism for dismantling resp Equalization of the extreme value in the transient operating phase (tr) can be provided. Turbomachine according to Claim 1, characterized in that the compensating means comprise a self-adjusting device (20) which increases or reduces the clearance (C) in dependence on external parameters. Turbomachine according to claim 2, characterized in that the Selbstjustiervorrichtung (20) to increase or decrease the game (C) changes its shape. Turbomachine according to claim 3, characterized in that the Selbstjustiervorrichtung (20) has a predetermined height, and that the Selbstjustiervorrichtung (20) for increasing or decreasing the game (C) changes its height. Turbomachine according to one of claims 2-4, characterized in that the Selbstjustiervorrichtung (20) increases the game (C) in dependence on their temperature or reduced. Turbomachine according to claim 5, characterized in that the Selbstjustiervorrichtung (20) has a hysteresis in its temperature behavior. Turbomachine according to claim 5 or 6, characterized in that the Selbstjustiervorrichtung (20) includes a bimetal. Turbomachine according to claim 5 or 6, characterized in that the Selbstjustiervorrichtung (20) includes a shape memory alloy. A turbomachine according to any one of claims 1-8, characterized in that the rotating components are moving blades (14), and that the play (C _b ) to be influenced is between the tips of the moving blades (14) and the opposite stationary housing (11). A turbomachine according to any one of claims 1-8, characterized in that the stationary components are vanes (15) and that the play (C _v ) to be influenced is between the tips of the vanes (15) and the opposed rotor (12). Turbomachine according to claim 9, characterized in that the rotor blades (14) each sit with a blade root (16) in a receptacle in the rotor (12) and are supported by supporting means (18) against attacking centrifugal forces on the rotor (17), and in that Selbstjustiervorrichtung (20) between the support means (18) and the rotor (12, 17) is arranged. Turbomachine according to claim 11, characterized in that the self-adjusting device (20) temperature-controlled their height in the radial direction between a first value and a second value, and that the difference of the two values corresponds to the extreme value (g _t ) of the curve of the game (C).

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