EP2609295B1 - Flow dividing device for a condensation steam turbine having a plurality of outlets - Google Patents

Description

The invention relates to a flow divider device for a condensing steam turbine having a plurality of outlets.

For example, one stage of a condensing steam turbine, consisting of a fixed stator and an impeller rotating about the machine axis, is designed as a Baumann stage in which an annular web is mounted, with which the blade channels are divided into an outer and an inner sub-channel. In this case, the steam mass flow is divided in the stage with flow divider into two partial streams, which are then guided via different expansion paths through the further blading to a condenser. The web is the vanes intersecting built into the vane grille, wherein the web has a circumferential leading edge.

Conventionally, the web is rigid, so that the inclination of the leading edge to the machine axis of the condensing steam turbine is always constant over time. As a rule, the angle of inclination is taken as the angle of flow of the steam flow with which the steam flow in the design operating state of the condensing steam turbine strikes the leading edge of the web. However, if the operating state of the condensing steam turbine deviates from the design mode, the velocity components of the steam flow may change such that the angle of flow of the steam flow is no longer equal to the angle of attack of the leading edge of the web. Any deviation of the angle of attack from the angle of attack in the design mode of operation results in a false flow of the web, which results in an increase of flow losses in the steam flow. This false flow of the web may, for example, cause, depending on the inside or outside Fehlanströmung that form a pressure side or a suction side on the inside or the outside of the web. On the suction side there is a risk that the flow separates, which in turn high flow losses of the steam flow are the result. These flow losses adversely affect the thermodynamic efficiency of the condensing steam turbine so that the condensing steam turbine is operable in operating conditions away from the design mode of operation only at lower efficiencies.

The object of the invention is to provide a flow divider device for a condensing steam turbine having a plurality of outlets, wherein the condensing steam turbine can be operated with a high thermal efficiency in operating states which do not correspond to the design operating state of the condensing steam turbine. According to the invention, this object is solved by the features of claim 1.

DE 3 025 041 A1 discloses a steam turbine with flow divider for efficiency improvement in operating conditions outside the design mode. The flow divider for a multi-outlet condensing steam turbine of the present invention includes a flow divider dividing the total steam flow into two steam streams each flowing through a condenser associated therewith, a stagnation point detecting means for locating the stagnation point formed at the flow divider leading edge when dividing the total steam flow, and a cooling medium dividing means the cooling medium supply to the capacitors is controlled in dependence on the localization of the stagnation point in such a way that the stagnation point is centrally located while avoiding flow separation at the stagnation point divider. If the stagnation point is located centrally on the flow divider, then the flow divider leading edge is flowed around substantially symmetrically, so that flow separation does not occur at the flow divider. If, on the other hand, the stagnation point on the flow divisor front edge changes its position to the outside or inside, the flow divider would be misdirected, as a result of which flow separation can occur at the flow divider.

The position of the stagnation point on the flow divider leading edge results from the current operating state of the condensation steam turbine and the ratio of the discharge pressures of the vapor streams. The Abströmdrücke are in turn given by the cooling medium supply to the capacitors. An increase in the cooling medium supply to the condenser causes an increase in the heat dissipation when condensing the respective vapor stream and thus an increase in the condenser capacity, whereby the condensation pressure is lowered as the Abströmdruck this vapor stream. In contrast, the back pressure of the vapor stream increases as the condensing temperature and thus the condensation pressure are increased by decreasing the cooling medium supply to the condenser. Thereby, in each of the capacitors by the corresponding cooling medium supply to each of the capacitors, the condensation temperature and thus the condensation pressure for each of the vapor streams can be adjusted. According to the ratio of the discharge pressures of the vapor streams, the total vapor mass flow at the flow divider is divided into corresponding partial mass flows, which according to the invention are set so that the dew point settles in the middle of the flow divider leading edge, whereby the flow separation at the flow divider is prevented.

The quality of the flow around the flow divider is to be determined by the localization of the stagnation point at the flow divider leading edge with the stagnation point detection device, which controls the outflow pressure ratio of the vapor streams with the corresponding coolant supply to the individual condensers depending on the flow quality, ie the position of the stagnation point at the flow divider leading edge is. This achieves according to the invention that the location of the stagnation point at the flow divider leading edge can be kept at the flow divider in the central position due to the localization and the matching cooling medium supply, so that the flow divider always avoids the flow divider at different operating states of the Kondensaticnsdampfturbine Flow separation is flowed around with little loss. As a result, the condensation steam turbine with the flow divider device according to the invention has a high thermal efficiency, even in operating states which are away from a design operating state, to which the aerodynamically effective contour of the flow divider is tuned.

The stagnation point detection device preferably has a differential pressure detection device with which the differential pressure in the region of the flow divider leading edge between the vapor streams at the flow divider can be measured and the differential pressure of the cooling medium distribution device is provided for controlling the cooling medium supply to the condensers. If the stagnation point is located centrally on the flow divider, then the flow around the flow divider is essentially symmetrical. As a result, in the region of the flow divider leading edge for the vapor streams at the flow divider, pressure levels which are essentially the same are obtained. If the stagnation point on the flow divider leading edge is displaced on one side, then on the side of the flow divider which faces the stagnation point, there is generally a higher pressure level than on the other side of the flow divider facing away from this side. Thus, the differential pressure in the region of the flow divider leading edge between the vapor streams at the flow divider is a measure of the mean of the stagnation point.

The differential pressure detection device preferably has, for each of the vapor streams, a pressure transducer for measuring the static pressure on the surface of the flow divider in the region of the flow divider leading edge and a differential pressure determination device with which the difference between the static pressures can be determined. As a result, the differential pressure-determining device supplies the differential pressure for the two sides of the flow divider, so that with the differential pressure determining device, the cooling medium supply to the capacitors in dependence of the differential pressure, which is determined by the differential pressure detection device controllable.

At least one of the pressure transducers is preferably arranged directly below the surface location of the flow divider, at which the static pressure is measured with the respective pressure transducer. Alternatively or additionally, it is preferred that at least one of the pressure transducers is remotely located from the surface location of the flow divider against which the static pressure to be measured is located and coupled to the surface location by a pressure transmitting channel in the flow divider. The pressure-transmitting channel may be, for example, a pressure measuring bore. Alternatively, it may also be preferable to provide a differential pressure measuring device instead of the pressure transducer and the differential pressure measuring device, which determines the static pressure to be measured at the respective surface locations of the flow divider.

The flow divider is preferably provided as a ring concentric with the machine axis of the condensing steam turbine, which is fixed to at least one Axialleitschaufel the Kondensationsdampfturbine, wherein the axial upstream of the Axialleitschaufelvorderkante projecting in the flow divisor leading edge, so that the surface locations of the flow divider, where the static pressures to be measured abutment, upstream of the Axialleitschaufelvorderkante are arranged. As a result, secondary flow influences of the axial guide vanes, such as corner vortices and boundary layers, are located downstream of the surface locations of the flow divider, so that the static pressures to be measured at these surface locations are substantially unaffected by the secondary flow influences of the axial guide vanes. As a result, the position of the stagnation point at the flow divider leading edge is an accurate measure of the flow divider flow, since the detection of the stagnation point position with the aid of the static pressure to be measured at the surface locations is not adversely affected by the secondary flow effects of the axial guide vanes.

Preferably, a predetermined cooling medium mass flow as the cooling medium supply to the capacitors is divided with the Kühlmediumaufteilungseinrichtung depending on the differential pressure. In this case, the predetermined cooling medium mass flow preferably corresponds to the maximum available cooling medium mass flow for the condensation steam turbine. As a result, the maximum available heat is always dissipated by the maximum available cooling medium mass flow for dissipating the heat of condensation from the capacitors, wherein the maximum available cooling medium mass flow is divided among the capacitors. Further, it is preferable that with the cooling medium dividing means, the cooling medium supplies to the condensers are controlled so that the back pressures of the individual vapor streams are such that the stagnation point is located at the flow divisor leading edge in the middle. The cooling medium distribution device is preferably fed back with the differential pressure detection device via the differential pressure that the back pressures of the individual vapor streams are set such that the absolute, detected by the differential pressure detection device differential pressure is minimal. As a result, it is achieved according to the invention that the position of the stagnation point is always centered on the flow divider, the absolute minimum pressure detected by the differential pressure detection device being essentially zero.

Figur 1

ein Schemadiagramm einer Kondensationsdampfturbine mit dem Ausführungsbeispiel der Strömungsteilereinrichtung,

Figur 2

einen Detailquerschnitt einer Vorderkante eines Strömungsteilers des Ausführungsbeispiels der Strömungsteilereinrichtung und

Figuren 3 bis 5

den Detailquerschnitt aus Figur 2 bei verschiedenen Strömungszuständen um die Vorderkante des Strömungsteilers.

In the following, a preferred embodiment of a flow divider device according to the invention will be explained with reference to the accompanying schematic drawings. Show it:

FIG. 1

1 is a schematic diagram of a condensation steam turbine with the exemplary embodiment of the flow divider device;

FIG. 2

a detail cross-section of a leading edge of a flow divider of the embodiment of the flow divider and

FIGS. 3 to 5

the detail cross section FIG. 2 at different flow conditions around the leading edge of the flow divider.

Like it out FIGS. 1 to 5 It can be seen that a condensation steam turbine 1 has an exhaust steam housing 2, in which a turbine rotor 3 is arranged. During operation of the condensation steam turbine 1, a total vapor mass flow that exits at an exhaust steam outlet 4 of the exhaust steam housing 2 flows through the exhaust steam housing 2.

In the exhaust steam housing 2, a flow divider 5 is arranged as an annular web, which is coaxially located around the turbine rotor 3 and divides the flow channel in the Abdampfgehäuse 2 in an inner region and an outer region. The flow divider 5 has a flow divider leading edge 6, wherein 7 a flow divider chord in the cross section of the flow divider 5 is shown in phantom. The inner region of the flow channel of the exhaust steam housing 2 is delimited by a flow divider inner side 8, whereas the outer region is delimited by a flow divider outer side 9, wherein both the flow divider inner side 8 and the flow divider outer side 9 adjoin the flow divider leading edge 6.

The flow divider 5 is held in the exhaust steam housing 2 by an inner vane 10 and an outer vane 11, the flow divider 5 with its flow divider inside 8 attached to the inner vane 10 and with its flow divider outer side 9 on the outer vane 11. Of the flow divider 5, the total vapor mass flow is divided into an inner vapor stream and an outer vapor stream, wherein at the Abdampfaustritt 4 for the inner vapor stream an inner exhaust steam line 12 and for the outer vapor stream an outer exhaust steam line 13 are provided. The inner vapor flow is through the inner exhaust steam line 12 to a first condenser 14 and the outer vapor stream is passed through the outer exhaust pipe 13 to a second condenser 15, wherein the inner vapor stream in the first condenser 14 and the outer vapor stream in the second condenser 15 is condensed. From the first condenser 14, the condensate condensed by the inner vapor flow is discharged in a first condensate line 16, whereas the condensate condensed by the outer vapor flow is removed by a second condensate line 17 from the second condenser 15.

In the area of the flow divider front edge 6, an inner pressure sensor 18 is installed in the flow divider 5 on the flow divider inside 8 and an outer pressure sensor 19 is installed on the flow divider outer side 9. With the pressure transducers 18, 19, the static pressure at the flow divider inside 8 with the inner pressure transducer 18 and the static pressure at the flow divider outer side 9 with the outer pressure transducer 19 are measured when flowing around the flow divider 5 immediately downstream of the flow divider leading edge 6. Further, in the flow divider 5, a pressure difference measuring device 20 is provided, with which the difference between the static pressures, which are measured by the pressure transducers 18, 19, is determined. The pressure difference is supplied in the form of an electrical signal with a differential pressure signal line 21 to a cooling water splitting device 22.

With the cooling water splitting device 22, a division of a total cooling water supply is accomplished, which is supplied through a total cooling water supply line 23 of the cooling water splitting device 22. The total cooling water supply is divided into a first cooling water supply and a second cooling water supply, wherein the first cooling water supply in a first cooling water supply line 24 to the first capacitor 14 and the second cooling water supply in a second cooling water supply line 25 to the second capacitor 15 is supplied. With the first cooling water supply in the first capacitor 14, the first vapor stream condensed to condensate, whereas in the second condenser 15 with the second cooling water supply in the second cooling water supply line 25, the second vapor stream is condensed to condensate. Of the capacitors 14, 15, the condensate is discharged in each case with a cooling water discharge line 26, 27.

The flow around the flow divider leading edge 6 is in FIGS. 3 to 5 illustrated with streamlines 28, 30, 31. The inflow has a stagnation point stream line 28, which forms a stagnation point 29 at the flow divider leading edge 6. In FIGS. 3 to 5 below, an inner streamline 30 and at the top an outer streamline 31 are shown, wherein the inner streamline 30 represents the inner vapor stream and the outer streamline 31 represents the outer vapor stream. In FIG. 3 is the stagnation point 29 on the flow divider 7, so that the stagnation point 29 is located symmetrically to the flow divider leading edge 6. As a result, the streamlines 30, 31 are formed symmetrically about the flow divider chord 7, whereby the flow around the flow divider 5 is symmetrical by the vapor streams. The values of the static pressures measured by the pressure transducers 18, 19 are thus approximately the same, so that with the differential pressure measuring device 20 the differential pressure is determined to be approximately zero, wherein a corresponding signal is fed from the pressure difference device 20 into the pressure difference signal line 21.

At the in FIG. 4 shown flow around the flow divider leading edge 6 of the stagnation point 29 is located above the flow divider chord 7, so that the flow around the flow divider leading edge 6 is asymmetrical. Thus, a separation region 32 is formed on the flow inside 8, associated with the flow losses and efficiency reduction of the steam turbine condensation. Analog is in FIG. 5 a flow around the flow divisor leading edge 6 is shown, in which the stagnation point 29 is arranged offset below the flow divider chord 7, so that at the flow divider outer side 9, a separation region 32 is formed.

At the in FIG. 4 As shown, the value of the static pressure measured by the outer pressure transducer 19 is greater than the value of the static pressure measured by the inner pressure transducer 18, so that a corresponding signal is fed from the differential pressure gauge 20 to the cooling water treatment device 22 via the differential pressure signal line 21. The same applies to the flow conditions in FIG. 5 wherein the value of the static pressure measured by the outer pressure transducer 19 is less than the value of the static pressure measured by the inner pressure transducer 18. The signal in the differential pressure signal line 21 is thus in accordance with the flow conditions FIG. 3 in about zero, in the flow conditions according to FIG. 4 for example, positive when the differential pressure is defined as the difference between the pressure at the outer pressure transducer 19 and the inner pressure transducer 18. Accordingly, according to the flow conditions FIG. 5 the differential pressure negative. Via the differential pressure signal line 21 of the cooling water splitting device 22, the differential pressure signal is provided, wherein the cooling water splitting device 22 is switched so that in the positive differential pressure signal, the cooling water supply through the first cooling water supply line 24 to the first condenser 14 and reduces while maintaining the total cooling water supply through the entire cooling water supply line 23, the cooling water supply the second cooling water supply pipe 25 is increased to the second condenser 15. The flow conditions change in the direction of the flow conditions that occur in FIG. 3 are shown, so that the stagnation point 29 migrates from the flow divider outer side 9 on the flow divider chord 7. This again the in FIG. 3 achieved symmetrical flow conditions around the flow divider 5, whereby the in FIG. 4 shown detachment area 32 has disappeared.

The in the flow conditions according to FIG. 5 present negative differential pressure signal in the differential pressure signal line 21 in the cooling water splitting device 22 causes the total cooling water supply in the total cooling water supply line 23 to be divided into corresponding cooling water supplies for the first cooling water supply line 24 for the first condenser 14 and for the second cooling water supply line 25 for the second condenser 15 such that the cooling water supply for the first condenser Increased 14 and the cooling water supply for the second capacitor 15 is lowered, so that the stagnation point 29 moves from the flow divider inside 8 on the flow divider 7. This dissolves in FIG. 5 shown Ablösegebiet 32 and the flow is again according to FIG. 3 homogeneous and even.

By deposited in the cooling water distribution device 22 control, which is coupled to the current location of the stagnation point 22 via the differential pressure signal, leads in FIGS. 4 and 5 shown inhomogeneous flow conditions back into the according FIG. 3 shown symmetrical flow conditions. In doing so, the in FIGS. 4 and 5 dissolved separation areas 32, whereby a reduction of flow losses in the steam flows is achieved. Thus, with the control logic stored in the cooling water splitter 22, maintaining the thermal efficiency of the condensing steam turbine 1 at a high level is maintained, although the operating conditions of the condensing steam turbine may vary and deviate from a design point of the condensing turbine.

Claims (10)

1. Flow dividing device for a condensation steam turbine having a plurality of outlets,
   having a flow divider (5) which divides the total steam flow into two steam flows (30, 31) which each flow through one condenser (14, 15) assigned to them,
   a stagnation point detection device (18-20) for locating the stagnation point (29) which forms on the leading edge (6) of the flow divider when dividing the total steam flow and a coolant dividing device (21, 22) by means of which the coolant supply (23) to the condensers (14, 15) is controlled as a function of the location of the stagnation point (29) such that
   the stagnation point (29) is located centrally, avoiding a flow separation (32) on the flow divider (5).
2. Flow dividing device according to Claim 1,
   wherein the stagnation point detection device (18-20) has a pressure differential detection device (20),
   by means of which it is possible to measure the pressure differential in the region of the leading edge (6) of the flow divider, between the steam flows (30, 31) at the flow divider (5), and the pressure differential of the coolant dividing device (21, 22) is prepared in order to control the coolant supply (24, 25) to the condensers (14, 15).
3. Flow dividing device according to Claim 2,
   wherein the pressure differential detection device (18-20) has in each case, for each of the steam flows (30, 31), a pressure sensor (18, 19) for measuring the static pressure at the surface of the flow divider (5) in the region of the leading edge (6) of the flow divider, and a pressure differential determining device (20),
   by means of which it is possible to determine the pressure differential between the static pressures.
4. Flow dividing device according to Claim 3,
   wherein at least one of the pressure sensors (18, 19) is arranged directly below that point on the surface of the flow divider (5) at which the static pressure can be measured using the respective pressure sensor (18, 19).
5. Flow dividing device according to Claim 3 or 4,
   wherein at least one of the pressure sensors (18, 19) is arranged at a distance from that point on the surface of the flow divider (5) at which the static pressure to be measured acts, and is coupled to the surface point by means of a pressure-transmitting duct in the flow divider (5).
6. Flow dividing device according to one of Claims 3 to 5, wherein the flow divider (5) is provided as a concentric ring which is secured to at least one axial guide vane (10, 11) of the condensation steam turbine (1),
   wherein in the region of the leading edge (6) of the flow divider this leading edge projects axially upstream from the leading edge of the axial guide vane, such that that point on the surface of the flow divider (5) at which the static pressures to be measured act are arranged upstream of the leading edge of the axial guide vane.
7. Flow dividing device according to one of Claims 2 to 6, wherein, by means of the coolant dividing device (21, 22), a predetermined coolant mass flow rate (23) is divided as the coolant supply (24, 25) to the condensers (14, 15) as a function of the pressure differential.
8. Flow dividing device according to Claim 7,
   wherein the predetermined coolant mass flow rate (23) corresponds to the maximum available coolant mass flow rate.
9. Flow dividing device according to one of Claims 2 to 8,
   wherein, by means of the coolant dividing device (21, 22), the coolant supplies (24, 25) to the condensers (14, 15) are controlled such that the back pressures of the individual steam flows (30, 31) are such that the stagnation point (29) is located centrally on the leading edge (6) of the flow divider.
10. Flow dividing device according to Claim 9,
    wherein the coolant dividing device (21, 22) is fed back to the pressure differential detection device (20) via the pressure differential such that the back pressures of the individual steam flows (30, 31) are set such that the absolute pressure differential detected by the pressure differential detection device (20) is minimal.

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