EP1832717A1 - Method for influencing the blade tip flow of an axial turbomachine and annular channel for the main axial flow through a turbomachine - Google Patents

Abstract

In the flow channel of a gas turbine or compressor there is a gap (35) between the tips (33) of the vanes (22) of a fan wheel (13,14) and a facing limit wall (25,27). At least one part-flow (49) is detached from the main flow (32) for return upstream of the separation point (49) into the main flow. A setting unit (51) adjusts the mass flow of the part-flow in the passage (41) back into the main flow in each feedback zone (43).

Description

The invention relates to a method for influencing the near-gap flow, wherein in each case a gap is provided between the tips of the blades of a blade ring and a boundary wall opposite the tips of a turbomachine, coupled from a mainstream flowing through the flow mainstream at least a partial flow and upstream of its removal position the main flow is fed again. Furthermore, the invention relates to an annular flow channel for a flowable in the axial direction of a main flow machine, which is concentrically disposed about an axially extending central axis and which is bounded by a circular cross-section boundary wall, wherein an axial wall portion of the boundary wall, which at least the tips of Flow channel radially profiled blades of a blade ring is in each case opposite gap formation, a plurality of distributed over the circumference return flow regions through each of which a main stream at a removal position auskoppelbarer partial flow at an upstream in relation to feed position in the main stream is traceable.

Gas turbines and their functions are well known. The sucked by a compressor of the gas turbine air is compressed in this and then mixed with fuel in a burner. The subsequently flowing into a combustion chamber mixture burns to a hot gas, which then flows through a turbine downstream of the turbine and meanwhile offset due to its relaxation, the rotor of the gas turbine in rotation. Due to the rotation of the rotor, in addition to the compressor, a rotor coupled to the rotor Powered generator that converts the provided mechanical energy into electrical energy.

Both the compressor and the turbine each consist of several successively connected blade stages, each comprising two successive wreaths of blades. A turbine stage is composed of a stator vane formed by non-rotating vanes and a rotor blade disposed downstream thereof, whereas a stage disposed in the compressor is composed of a rotor blade and a stator vane arranged downstream thereof; each viewed in the flow direction of the medium flowing through. In a single-shaft gas turbine all blades are permanently mounted on the common rotor.

The series-arranged, i. axially successive compressor stages promote due to the rotating rotor blades with the sucked air from the inlet of the compressor in the direction of the compressor outlet, wherein the air within each stage (or ring) undergoes an incremental pressure increase. The total pressure increase across the compressor is the sum of all incremental pressure rises across each stage (or all of the rings).

In a known manner, during operation of the gas turbine, in particular during operation of the compressor of the gas turbine, it may happen that a stall occurs on one or more airfoils within the compressor, where the flow of air in the main flow direction through part of a compressor stage ceases the energy transferred from the rotor to the air is insufficient to convey the air through the compressor stage and to produce the required pressure ratio of the compressor stage concerned. The pressure ratio is the pressure increase occurring over the relevant stage of the compressor, based on the inlet pressure of the respective stage. If the stall is not immediately counteracted, its progression may be cause all the air flow through the compressor to reverse direction, known as compressor pumps. This particularly critical operating condition endangers the blading and prevents sufficient supply of the combustion chamber with compressor air, so that a faulty operation of the gas turbine must be diagnosed.

This is from the EP 0 719 907 A1 in which the problem described is counteracted, a structured boundary wall facing the tips of the blades is known. Due to the structuring, a partial flow is coupled out of the main flow and then returned to the main flow upstream of the removal position. This structuring of the housing, the so-called "Casing Treatment", serves to positively influence the gap-near flow for the situations in which a risk of stalling an airfoil. By this measure occurs a stall - compared with a flow channel without casing treatment - delayed.

A similar device and a similar method are known from EP 1 286 022 A1 known.

In both known embodiments, however, it is disadvantageous that for all operating states of the gas turbine or the compressor influencing the near-gap flow takes place, although this is only useful for such an operating condition in which a stall or a compressor pumps threatens. When stationary operating condition usually no risk of stall in the compressor, so that the effect achieved by the casing treatment can then lead to losses in the main flow and thus reduced efficiency of the compressor or the gas turbine.

What is needed, therefore, is a method of affecting the near-gap flow and an annular flow channel that provides the advantages of the prior art and yet reduces, if not eliminates, the problems associated with the prior art Use of the casing treatment during steady-state operation are caused.

According to the invention, a method is provided for influencing the near-gap flow and a suitable annular flow channel for an axial flow-through turbomachine, wherein the mass flow of the decoupled partial flow is adjusted by means of an adjusting member. For this purpose, the device according to the invention in at least one of the return flow areas on an adjusting member for adjusting the mass flow of the decoupled partial flow. Thus, the essential difference with the already known solutions lies in the fact that the decoupling and the upstream recirculation of the substream, the so-called overflow, is carried out only in such an operating condition which is close to or close to the stability limit of the compressor, the respective compressor stage maximum pressure ratio of the blade ring is. Thus, an overflow is allowed only in the critical operating range. In the event that there is no risk of disruption in the form of a stall or compressor surge, virtually all the negative effects of the then unnecessary overflow can be avoided.

The compressor or the compressor stage or the blade ring is then operated in the stationary operating state, which allows a continuous, reliable and efficient delivery of the medium to be compressed in the downstream direction.

Further advantageous embodiments of the invention are specified in the subclaims.

The partial flow decoupled from the main flow is taken off in the region of the trailing edges of the blades of the blade ring. Preferably, the inlet opening for decoupling of the partial flow in the Rückströmbereich is completely or partially downstream of the trailing edge of the opposite Airfoil, since the partial flow driving the pressure of the main flow at this point is relatively constant. This leads to a particularly continuous partial flow, which has a particularly positive influence on the gap or wall-near flow.

In the known casing treatments, the partial flow was often taken upstream of the trailing edge, since the permanent withdrawal of the partial flow from the highest pressure level, i. downstream of the trailing edge, with permanent performance losses appeared unreasonable. Due to the now adjustable mass flow of the partial flow is also driven by a higher pressure mass flow, which only briefly flows at approaching risk of flow separation, justifiable. But it is also conceivable that the removal of the partial flow or the partial flows upstream of the trailing edge, as in the prior art, is provided.

In order to achieve a particularly efficient influencing of the gap-near flow, the partial wall flow taken from the boundary wall side is supplied to the main flow in the area of the leading edges of the blades of the blade ring. Preferably, the outflow opening of the partial flow is completely or partially directly upstream of the leading edge of the opposite airfoil. This results locally locally improved flow conditions in the area of the leading edges of the blades, as a result of which the pressure ratio to be overcome in this area, ie at the tips of the blades, is lowered slightly, so that a tearing off of the flow in the blade tip area can be effectively avoided.

Particularly advantageous is the method in which the mass flow of the partial flow is controlled or regulated. Thus, during operation of the turbomachine, the desired or required mass flow can be adjusted. Either all blades of the stage and / or the blade ring are operated in the optimum operating range without overflow, ie there is no partial flow, or, at elevated Likelihood of stall or compressor-pumping, it can be positively influenced the gap near flow by means of a flowing partial flow, with overflow so. Efficiency losses due to an operation in which a stall or compressor pumps is not expected, do not occur due to the then non-flowing partial flow.

In addition, the connection of the partial flow leads to a pulse in the flow of the airfoil, which also counteracts the impending stall.

In a development of the method, the adjustment or regulation of the mass flow of the partial flow takes place as a function of the actually occurring pressure ratio of the blade ring, which pressure ratio indicates the downstream edge pressure of the main flow with respect to the inflow edge side pressure. The regulation takes place in such a way that, if the actually occurring pressure ratio is below a predetermined limiting pressure ratio, the flow of a partial flow is prevented. Only when the actually occurring pressure ratio is above the limiting pressure ratio, a partial flow flows. The regulation may even be such that, as the distance between the actually occurring pressure ratio and the limiting pressure ratio decreases, the mass flow of the partial flow is increased linearly or not linearly. Usually, the limiting pressure ratio is as close to the maximum, based on the blades of the blade ring pressure ratio as possible or corresponds to this.

The state known as compressor pumps and stalls can be avoided in particular when the limit pressure ratio is always above the instantaneous operating pressure ratio.

The advantages directed to the method are correspondingly transferable to the device according to the invention.

It is particularly advantageous if each return flow region has an adjusting member, so that evenly over the circumference of the annular flow channel a uniform influencing of the gap and wall near flow can be set for each return flow region.

Advantageously, the return flow areas are each formed as a return flow channel which extends in the interior of the boundary wall in the axial direction. The arranged in the wall portion return channel then has an inflow opening for the partial flow, the axial position is partially or preferably completely downstream of the trailing edge of the opposite airfoil. The outflow opening of the return flow channel arranged in the wall section then lies in the region of the leading edge of the blade profile, that is to say partially or preferably completely upstream thereof.

If one or both openings are outside the axial region of the boundary wall swept by the tip of the airfoil, a partial flow that is continuous in size can be achieved for each return flow region formed in this way. If the openings were located in the axial section of the boundary wall on which the blades run past, then a strongly periodic pressure field on the input side and / or output side would adversely affect the mass flow of the partial flow due to the passing blades.

In a further development of the flow channel, the adjusting member or each adjustment member, which may be formed as a slide, throttle or valve, connected to a control or a control device for adjusting the mass flow to adjust these preferably depending on the respective blade ring outlet pressure. For this purpose, the flow channel has a measuring device, which, with respect to the blade, has downstream pressure of the main flow and which is connected to the adjusting member is in communication via the control or regulating device. By such a device, an adjustment of the mass flow of the recirculated partial flow is possible, which can be optimally adjusted for each occurring during operation load case, so that both the risk of stall or of compressor pumps can be reduced, or if this is not required , the blades can be operated in aerodynamically optimal flow conditions.

FIG 1

eine Gasturbine in einem Längsteilschnitt,

FIG 2

einen Ausschnitt aus einem Eingangsbereich des Verdichters der Gasturbine gemäß FIG 1 mit einer Verdichterstufe,

FIG 3

die Schnittansicht III des Ausschnitts gemäß FIG 2 mit einer unterhalb der Rückströmbereiche angeordneten Schaufel und

FIG 4

einen Ausschnitt gemäß FIG 2 mit einer alternativen Ausgestaltung eines im Rückströmbereich angeordneten Einstellorgans.

The foregoing and other features and advantages of the present invention will become more apparent from the following description of an embodiment. It shows:

FIG. 1

a gas turbine in a longitudinal section,

FIG. 2

1 a section from an input region of the compressor of the gas turbine according to FIG. 1 with a compressor stage,

FIG. 3

the sectional view III of the detail according to FIG. 2 with a blade arranged below the return flow regions and

FIG. 4

a section according to FIG 2 with an alternative embodiment of a arranged in the return flow adjustment.

1 shows a gas turbine 1 in a longitudinal partial section. It has inside a rotatably mounted about a rotation axis 2 rotor 3, which is also referred to as a turbine runner. Along the rotor 3 successive an intake 4, a compressor 5, a toroidal annular combustion chamber 6 with a plurality of rotationally symmetrical to each other arranged burners 7, a turbine unit 8 and an exhaust housing 9. The annular combustion chamber 6 forms a combustion chamber 17 which communicates with an annular hot gas channel 18. There are four The turbine unit 8 is connected in series with one another. Each turbine stage 10 is formed from two blade rings. Viewed in the flow direction of a hot gas 11 produced in the annular combustion chamber 6, follows in the hot gas channel 18 in each case one row of vanes 13 formed by a blade 15 row 14. The vanes 12 are attached to the stator, whereas the blades 15 a row 14 each by means of a turbine disk 19 on the rotor 3 are attached. On the rotor 3, a generator or a working machine (not shown) is coupled.

2 shows in a cross section the input-side section of the compressor 5. Between an outer boundary wall 25 and an inner boundary wall 27, a circular cross-section, the rotation axis 2 concentrically encompassing flow channel 29 is provided, through which sucked by the compressor 5 medium 30 in a main flow direction , which is indicated by the reference numeral 31, is pressed. The main flow direction 21 coincides with the axial direction. The arranged on the rotor 3 inner boundary wall 27 is formed by the platforms of the rotor mounted in a ring 13 arranged blades 15. Each blade 15 has an aerodynamically optimized profiled blade 22, the tips 33 each have a gap 35 forming the outer boundary wall 25 opposite. Referring to the main flow direction 31, upstream of the blade ring 13, there is shown a vane 12 of the vane ring 14 fixed to the outer shell side boundary wall 25. Instead of this guide vane 12 may be provided at this point also with respect to the axis of rotation 2 of the rotor 3 about the radial direction rotatable inlet guide vane.

In the flow channel 29, a vane 12 of the blade ring 14 is also shown downstream of the blade 15, which is also attached to the housing or on the outer boundary wall 25. These two blade rings 13, 14 form a compressor stage. Each vane 12 closes with its opposite end of the rotor 3 also with the boundary wall 27 a gap. On the boundary wall 27 and a casing treatment can be provided.

As casing treatment for influencing the flow near the gap, a plurality of return flow channels 41 distributed over the circumference are provided as return flow regions 43 in the outer boundary wall 25. Each return flow channel 41 has at an extraction position 45 an inflow opening for decoupling a partial flow 49 from the main flow 32. Each return flow channel 41 opens into an outflow opening located at a feed position 47, always in relation to the main flow direction 31, upstream of the inflow opening.

Through each return flow 41, a partial flow 49 can be flowed, which is in the flow channel 29 flowing main flow 32, such as air, coupled out and this upstream of the removal position 45 is traceable again.

According to the invention, in at least one of the return flow regions 43 or in at least one of the return flow channels 41, an adjusting member 51 is provided for adjusting the partial flow 49 flowing through the return flow region 43. The adjusting member 51 may be formed as a slide 52, throttle or valve (FIG 4) and are in communication with a control or regulating device, so that they can act on the adjusting member 51 to adjust the mass flow of the partial flow 49.

The removal position 45 for the disengageable partial flow 49 is axially seen in the wall portion of the boundary wall 25, which downstream of the trailing edge 53 of the opposing profiled airfoil 22, based on the flowing in the main flow direction 31 the annular flow channel 29 medium 30. Accordingly, under the wall section also to understand the immediately and slightly further downstream of the trailing edge 53 lying region of the boundary wall 25. The axial feed position 47 of the return flow region 43, ie, the mouth of the return flow channel 41, is located in the region of the leading edge 55 of the wall section opposite blades 22, preferably completely immediately upstream thereof. Consequently, this area is also to be understood as meaning the axial wall section of the boundary wall 25, which lies directly upstream of the leading edges 55 of the blade 22.

FIG. 3 shows, in abstracted form, a plan view (in the radial direction) of the tip 33 of a blade 15, in which the return flow regions 43 uniformly distributed over the circumference in the outer boundary wall 25 can be seen as return flow channels 41. The boundary wall 25 itself is hidden here.

In this case, the airfoil 22 is first of all flown against at its leading edge 55 by a medium 30 flowing in the main flow direction 31. The coinciding with the circumferential direction of rotation of the rotor 3 rotating blade 15 is indicated by the arrow U.

In order to adjust the partial flow 49 flowing back through the return flow channels 41 counter to the main flow direction 31, a common slide 52 is provided therein as an adjustment member 51 by means of which the minimum cross section of each return flow region 43 can be varied. The example comb-like slide 52 is displaceable in the circumferential direction U and each has a projecting into each return flow channel 41 tooth, which is also pushed out to set the minimum cross-section of this.

Alternatively or additionally, it is possible to partially or completely close the inlet side openings (and / or outlet side outlet openings) for the partial flow 49 to be coupled in order to adjust the mass flow of the partial flow 49 flowing through the return flow channel 41 as required.

In a further alternative embodiment according to FIG 4, instead of a slide 52 for each return flow channel 41, a valve 51 is provided as adjusting.

Threshold in a first operating state, a stall at the tips 33 of the blades 15 of the blade ring 13, the slider 52 is actuated such that a gap near flow positively influencing partial flow 49 through each return flow 43 and Rückströmkanal 41 sets.

In the event that the compressor 5 operates during a second operating state in the rated operation, with a stall or a compressor-pumping is to be expected in any way. A backflow partial flow 49 would cause flow losses in the main flow 32. By a suitable adjustment of the adjusting member 51, which is effected by a control or a control device, a backflow of a partial flow 49 is inventively avoided for this operating condition.

In order to distinguish between the two aforementioned operating conditions or to decide whether a backflow of the partial flow 49 is required or how large the required mass flow of the partial flow 49 is at the relevant point at which the casing treatment is provided, at least one downstream pressure of the main flow 32 detecting measuring device is provided, which is indirectly connected to the adjusting member 51 via a control or regulating device, so that they can cause the need-based adjustment. By adjusting a partial flow 49, the pressure difference in the flow channel 29 near the boundary wall 25 between the upstream and downstream regions on the blade tip 33 of a blade 15 can be slightly reduced, which advantageously prevents tearing of the main flow 32 in this area. The flow of the gap-near main flow 32 affecting partial flow 39 is only useful if an increased Risk of stall or compressor pumping exists.

Overall, the invention provides a flow channel 29 for a through-flow of a main flow 32 in the axial flow machine, wherein the flow channel 29 is concentrically disposed about an axially extending central axis 2 and which is bounded by a circular cross-section boundary wall 25, 27, wherein a axial wall portion of the boundary wall 25, 27, which approximately opposite the tips 33 of the flow channel 29 radially arranged profiled blades 22 of a blade ring 13, 14 in each case with gap formation. In the area of the wall section, return flow areas 41 are provided, through which a return flow 49, which can be removed from the main flow 32, is decoupled and can be supplied again upstream of the coupling-out position. In order to provide an adjustable return flow in the boundary wall 25, 27 for different operating states of the compressor 5, the return flow regions 41 are equipped with adjusting members 51. Furthermore, a method for influencing the gap-near flow is specified, whereby the risk of flow separation on the blade blades is significantly reduced.

Claims (19)

Method for influencing the fissure close flow,
wherein a gap (35) is provided in each case between the tips (33) of the blades (22) of a blade ring (13, 14) and a boundary wall (25, 27) of a turbomachine opposite the tips (33),
wherein at least one partial flow (49) is decoupled from a main flow (32) flowing through the turbomachine and returned to the main flow (32) upstream of its withdrawal position (45),
characterized in that
the mass flow of the partial flow (49) is adjusted by means of an adjusting member (51). Method according to claim 1,
in which the partial stream (49) is decoupled from the main stream (32) completely or partially downstream of the outflow edges (53) of the blades (22) of the blade ring (13, 14). Method according to claim 1 or 2,
in which the partial flow (49) is supplied wholly or partly upstream of the leading edges (55) of the blades (22) of the blade ring (13, 14) to the main flow (32). Method according to claim 1, 2 or 3,
in which the mass flow of the partial flow (49) is controlled or regulated. Method according to one of the preceding claims,
in which a pressure ratio of the blade ring (13, 14) is used for adjusting the mass flow of the partial flow (49), which pressure ratio indicates the downstream edge pressure of the main flow with respect to the inflow edge side pressure. Method according to one of claims 1 to 4,
in which the partial flow (49) flows only above the limiting pressure ratio,
wherein the limit pressure ratio approximately corresponds to the maximum, over the blades (12, 15) of the blade ring (13, 14) buildable pressure ratio. Method according to claim 6,
where the limit pressure ratio is above the steady-state operating pressure ratio. Ring-shaped flow channel (29) for a flow-through in the axial direction of a main flow (32) flow machine for carrying out the method according to one of claims 1 to 7,
which is arranged concentrically about an axial center axis (2) and which is delimited by a boundary wall (25, 27) of circular cross-section,
wherein an axial wall portion of the boundary wall (25, 27) facing at least the tips (33) of profiled airfoils (22) of a blade ring (13, 14) radiantly arranged in the flow channel (29) in each case under gap formation (35), several over the Circumferentially distributed return flow regions (43) through which in each case one the main flow (32) at a removal position (45) auskoppelbarer partial stream (49) at an upstream in feed position (47) in the main stream (32) is traceable
characterized in that
in at least one of the return flow areas (43) is provided an adjusting member (51) for adjusting the mass flow of the partial flow (49). Flow channel (29) according to claim 8,
in which each return flow region (43) has an adjusting member (51). Flow channel (29) according to one of claims 8 to 9, in which the removal position (45) of each return flow region (43) is provided in the region of an outflow edge (53) of the blade sections (22) opposite the wall section. Flow channel (29) according to claim 10,
in which, viewed axially, the removal position (45) of each return flow region (43) is provided downstream of the outflow edges (53) of the airfoils (22) opposite the wall section. Flow channel (29) according to one of claims 8 to 11, in which, seen axially, the feed position (47) of each return flow region (43) in the region of a leading edge (55) of the wall section opposite blade leaves (22) is provided. Flow channel (29) according to claim 12,
in which, viewed axially, the feed position (47) of each return flow region (43) is provided upstream of the leading edges (55) of the airfoils (22) opposite the wall section. Flow channel (29) according to one of claims 8 to 13, wherein the return flow region (43) is formed as a return flow channel (41). Flow channel (29) according to one of claims 8 to 14, wherein the adjusting member (51) is connected to a control or a control device for adjusting the mass flow. Flow channel (29) according to one of claims 8 to 15, wherein the adjusting member (51) is designed as a slide, throttle or valve. Flow channel (29) according to one of claims 8 to 16, wherein at least one measuring device which detects the outlet-side pressure of the main flow (32) is provided on the blade ring (13, 14), which is connected to the adjusting member (51). Flow channel (29) according to claim 17,
in which on the blade ring (13, 14) at least one of the pressure ratio of the blade ring (13, 14) constituting sensing device is provided, which is in communication with the adjusting member (51). Compressor (5) with a flow channel (29) according to one of claims 8 to 18.

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