STEAM TURBINE AND METHOD FOR ADJUSTING THRUST FORCES THEREOF
A steam turbine having at least a HP blade cascade, an IP blade cascade and a plurality of dummy members that are attached to a common rotor shaft, is provided with, but not limited to, a detection unit that detects a steam flow into an IP chamber, a pressure reducing unit that reduces a pressure difference between both sides of a target dummy member of said plurality of the dummy members when the steam flow into the IP chamber stops, the target dummy member having one side communicating with a part of the IP chamber, and a control unit that controls the pressure reducing unit based on a detection result obtained by the detection unit.
The present invention relates to a steam turbine and a method of adjusting a thrust force of the steam turbine, particularly regarding a steam turbine and a method of adjusting a thrust force of the steam turbine which are capable of balancing of a thrust force acting on a rotor shaft of the steam turbine which includes at least a high-pressure (HP) blade cascade, an intermediate-pressure (IP) blade cascade and a plurality of dummy members that are attached to a common rotor shaft.
Since the rotor shaft is subjected to the thrust force acting thereon, the steam turbine is provided with a thrust bearing. With a limited load capacity of the bearing, it is necessary to design the steam turbine in consideration of a thrust balance so that the thrust force acting on the rotor shaft does not exceed the load capacity of the bearing under any operating condition.
Hence, the dummy members (dummy pistons) and the blade cascades are attached to the same rotor shaft, so as thrust forces in a counter-thrust direction are generated by the dummy members to balance the forces acting in an axial direction of the entire rotor shaft. In this manner, the thrust force acting on the rotor shaft is kept within the scope of the load capacity of the bearing under any operation condition.
In a conventional steam turbine 1 depicted in
Further, a HP blade cascade 2 to which the HP main steam is supplied, an IP blade cascade 4 to which the reheat steam 24 is supplied and a low-pressure (LP) blade cascade 6 to which the LP main steam 26 is supplied are attached to the rotor shaft 10 in this order. The IP blade cascade 4 and the LP blade cascade 6 have steam inlets that are open to one side, whereas the HP blade cascade 2 has a steam inlet is open to other side being opposite to the one side. Between the steam inlet of the HP blade cascade 2 and the steam inlet of the IP blade cascade 4, a high-pressure (HP) dummy member 12 is provided. On a steam outlet side of the HP blade cascade 2, an intermediate-pressure (IP) dummy member 14 and a low-pressure (LP) dummy member 16 are provided in this order. Further, a thrust balance conduit 30 is provided so as to communicate the outlet side of the IP dummy member 14 to a latter half of the IP blade cascade 4.
In the steam turbine 1 as described above, the HP main steam 22 from a boiler and the like (not shown) enters the HP blade cascade 2. And, the HP main steam 22 gives a rotary force to the rotor shaft 10 while the steam passes through the HP blade cascade 2. The steam that has done the work through the HP blade cascade 2 drops the pressure and the temperature gradually and is discharged out of the steam turbine 1 as a low-temperature reheat steam 28. The low-temperature reheat steam 28 discharged out of the steam turbine 1 is reheated by a reheat boiler (not shown) to be the reheat steam 24.
The IP reheat steam 24 that is reheated by the reheat boiler gives the rotary force to the rotor shaft 10 and gradually reduces the pressure and the temperature while the reheat steam 24 passes through the IP blade cascade 4. Further, the LP main steam 26 gives the rotary force to the rotor shaft 10 and gradually reduces the pressure and the temperature while the LP main steam 26 passes through the LP blade cascade 6.
Further, a part of the high-pressure (HP) main steam 22 passes by the high-pressure (HP) dummy member 12 and a part of the low-temperature reheat steam 28 that has passed through the HP blade cascade and has reduced the temperature and the pressure, passes by the intermediate-pressure (IP) dummy member 14 and the low-pressure (LP) dummy member 16.
Further, in
As shown in
Further, in the steam turbine, in order to prevent the thrust bearing from being damaged, the resultant thrust force needs to be brought into balance not only in a case where the steam turbine is operated under a normal operating condition but also in a case where either the HP main steam supply or the reheat steam supply is stopped.
First, attention is paid to a case where the flow of the HP main steam 22 through the steam turbine 1 as shown in
As shown in
In the next place, attention is paid to a case in which the flow of the reheat steam 24 and the LP main steam 26 through the steam turbine 1 as shown
As shown in
In such case, in an LP system (a low-pressure part of the steam turbine), the pressure difference between both sides of the LP blade cascade 6 and the pressure difference between both sides of the LP dummy member 16 become approximately 0, resulting in the thrust force acting on the rotor shaft being 0.
Further, in relation to the IP system (the intermediate-pressure part of the steam turbine), the pressure at the outlet of the IP dummy member 14 becomes a level of vacuum pressure and in response to the vacuum pressure level, the thrust force represented by the encircled numeral 2 as shown in
Further, in relation to a HP system (a high-pressure part of the steam turbine), the thrust force generated in the HP blade cascade 2 represented by the encircled numeral 3 is approximately the same as that of a normal operation condition, whereas the thrust force represented by the encircled numeral 2 generated in the HP dummy member 12 increases by an amount corresponding to the vacuum pressure level at the outlet of the HP dummy member 12. Thus, the thrust force acting in the direction of the HP dummy member (rightward in
Hereby, the increase of the thrust force generated in the IP system is greater than the increase of the thrust force generated in the HP system. Accordingly, the resultant thrust force generated in the whole steam turbine 1 increases in the leftward direction in
In a case where the flow of the reheat steam 24 is stopped, it may be considered that the HP dummy member 12 is upsized so that thrust force in the rightward direction increases and the resultant thrust force is balanced. However, the upsizing of the HP dummy member 12 spoils the balancing in the normal operation and thus, this approach is not appropriate.
Hence, in relation to each of
In addition, Patent Reference 1 discloses another technology; according to this technology, thrust forces acting on the steam turbine are evaluated based on the measured data such as bearing temperatures. Based on the results of the measurements, the thrust forces acting on the dummy members can be adjusted in an electronic control approach, and the resultant thrust force developed in the whole steam turbine is brought into balance.
REFERENCES Patent ReferencesPatent Reference 1: JP1996-189302
SUMMARY OF THE INVENTION Subjects to be SolvedIn the conventional technology as explained above in reference to
Further, in the technology as disclosed by Patent Reference 1 where the balancing of the thrust forces is performed by use of an electric control, there is a possibility that the reliability of the electric system may cause a problem.
In view of the above problems of the related art, it is an object of the present invention to provide a steam turbine and a method of adjusting a thrust force of the steam turbine acting on a rotor shaft of the turbine in an entire operating range of the steam turbine without upsizing a LP dummy member or without using an electric control of a complicated system.
Means to Solve the SubjectsTo solve the above issues, the present invention provides a steam turbine having at least a high-pressure (HP) blade cascade, an intermediate-pressure (IP) blade cascade and a plurality of dummy members that are attached to a common rotor shaft. The steam turbine may include, but is not limited to:
a detection unit that detects a steam flow into an intermediate-pressure (IP) chamber;
a pressure reducing unit that reduces a pressure difference between both sides of a target dummy member of said plurality of the dummy members when the steam flow into the IP chamber stops, the target dummy member having one side communicating with a part of the IP chamber; and
a control unit that controls the pressure reducing unit based on a detection result obtained by the detection unit.
In this manner, the thrust force generated at the IP dummy member when the steam flow into the IP chamber stops can be eliminated. Thus, it is no longer necessary to increase the diameter of the LP dummy member which was conventionally needed to balance the thrust force generated at the IP dummy member. As a result, the diameter of the LP dummy member can be reduced and the thrust forces acting on the rotor of the steam turbine can be balanced in the entire operation range of the steam turbine without using the electric control of the complicated system.
The above pressure reducing unit may include, but is not limited to, a first conduit that connects the both sides of the target dummy member and a first valve that is provided in the first conduit to adjust the pressure difference between the both sides of the target dummy member.
In this way, the thrust forces acting on the rotor shaft of the steam turbine can be balanced, with a simple configuration.
The above steam turbine may further include:
a third conduit that connects the one side of the pressure reducing unit to an outlet of the IP chamber; and
a third valve that is provided in the third conduit.
When the first valve opens while the steam flow into the IP chamber is not stopped, the control unit may control the third valve to open so as to generate the pressure difference between the both sides of the target dummy member.
In this way, even when the first valve is out of order, the thrust forces generated in the steam turbine can be balanced and, the reliability of the steam turbine can be enhanced.
The above pressure reducing unit may include, but is not limited to:
a second conduit that connects the part of the IP chamber and the one side of the target dummy member; and
a second valve that is provided in the second conduit to adjust the difference between the both sides of the target dummy member.
The second valve may be closed when the steam flow into the IP chamber stops.
In relation to the above, the second conduit is often provided even in the conventional steam turbines. Thus, in remodeling or modernizing the conventional existing steam turbine, the pressure reducing unit can be provided by simply fitting the second valve to the existing second conduit without newly installing a conduit to the steam turbine. Thus, the remodeling can be easily accomplished.
The above steam turbine may further include:
a bypass conduit that is provided to bypass the second valve; and
an orifice that is provided in the bypass conduit.
In this way, the thrust forces generated in the steam turbine can be easily balanced.
The above steam turbine may also include:
a third conduit that connects the one side of the pressure reducing unit to an outlet of the IP chamber; and
a third valve that is provided in the third conduit.
When the second valve closes while the steam flow into the IP chamber is not stopped, the control unit may control the third valve to open so as to generate the pressure difference between the both sides of the target dummy member.
To achieve the object of the present invention, the present invention provides a method of adjusting a thrust force of a steam turbine having at least a HP blade cascade, an IP blade cascade and a plurality of dummy members that are attached to a common rotor shaft. The method may include, but is not limited to, the step of reducing a pressure difference between both sides of a target dummy member of said plurality of the dummy members when the steam flow into the IP chamber stops, the target dummy member having one side communicating with a part of the IP chamber.
Further, in the above method, the pressure difference between the both sides of the target dummy member may be reducible by use of a first valve provided in a first conduit that connects the both sides of the target dummy member.
Further, in the above method, when the first valve opens while the steam flow into the IP chamber is not stopped, the pressure difference may be generated between the both sides of the target dummy member by opening a third valve which is provided in a third conduit that connects the one side of the target dummy member to an outlet of the IP chamber.
In the above method of adjusting the thrust force of the steam turbine, the pressure difference between the both sides of the target dummy member may be reducible by use of a second valve provided in a second conduit that connects the part of the IP chamber and the one side of the target dummy member.
In the above method of adjusting the thrust force of the steam turbine, when the second valve closes while the steam flow into the IP chamber is stopped, the pressure difference may be generated between the both sides of the target dummy member by opening a third valve which is provided in a third conduit that connects the one side of the target dummy member to an outlet of the IP chamber.
EFFECTS OF THE INVENTIONAccording to the present invention, the steam turbine and the method of adjusting the thrust force of the steam turbine can be provided which are operable to balance the thrust forces in the entire operation range of the steam turbine without upsizing the LP dummy member, as well as, without using the electric control of a complicated system.
A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. It is intended, however, that unless particularly specified, dimensions, materials, shape, its relative positions and the like shall be interpreted as illustrative only and not limitative of the scope of the present invention.
PREFERRED EMBODIMENTS First Preferred EmbodimentTo the rotor shaft 10, attached are a HP blade cascade 2 to which the HP main steam is supplied, an intermediate-pressure (IP) blade cascade 4 to which the reheat steam 24 is supplied and a low-pressure (LP) blade cascade 6 to which the LP main steam 26 is supplied in this order.
In the steam turbine, steam inlet sides of the IP blade cascade 4 and the LP blade cascade 6 are arranged such that the steam streams through the IP blade cascade 4 and the LP blade cascade 6 in the same direction, whereas a steam inlet side of the HP blade cascade 2 is arranged such that the steam streams through the HP blade cascade 2 in the opposite direction. Further, a HP dummy member 12 is provided between the steam inlet side of the HP blade cascade 2 and the steam inlet side of the IP blade cascade 4. On the steam outlet side of the HP blade cascade 2, an IP dummy member 14 and a LP dummy member 16 are provided in this order. Furthermore, a thrust balance conduit 30 is provided to communicate the steam outlet side of the IP dummy member 14 to a part of the IP blade cascade 4.
Differently from the conventional technology shown in
Further, a conduit 42 is provided to communicate the steam inlet side of the IP dummy member 14 to the steam outlet side thereof and a valve 43 is provided on the conduit 42. A conduit 44 is connected to the conduit 42 on a side closer to the steam outlet side of the IP dummy part than the valve 43 and in communication to the steam outlet side of the IP blade cascade 4. A valve 45 is provided on the conduit 44. A valve 41 is provided on the thrust balance conduit 30.
Further, a control unit 52 is provided. The control unit 52 reads a detected value detected by a pressure sensor 54 which is provided at the reheat steam inlet 25 and controls opening and closing of the valves 41, 43 and 45 based on the detected value. In the normal operating state where the reheat steam 24 is supplied to the steam turbine 1 and the pressure detected by the pressure sensor 54 is within a normal pressure range of the reheat steam 24, the control unit 52 controls the valve 41 to open and the valves 43 and 45 to close as shown in
In
As shown in
Next, a case where the supply of the HP main steam 22 is stopped in the steam turbine 1 shown in
In
Next, a case where the supply of the reheat steam 24 and the LP main steam 26 is stopped in the steam turbine 1 shown in
In
When the control unit 52 (not shown in
Further, in the case of
In addition, the diameter of the LP dummy member 16 is designed in advance so as to balance the thrust forces in a case where the valves 41 and 43 are opened in the state where the supply of the reheat steam and the LP main steam is stopped and, the diameter of the IP dummy member 14 is designed in advance so as to balance the thrust forces in the normal operating state and the state where the supply of the HP main steam is stopped. In this way, the thrust force is prevented from being generated at the IP dummy member 14 when the supply of the reheat steam and the LP main steam is stopped, and it becomes unnecessary to upsize the diameter of the LP dummy member 16, apart from the conventional technology in which the diameter upsizing was inevitable. Hence, the diameter of the LP dummy member 16 can be small and the steam leakage to the gland can be reduced. As a result, the performance of the steam turbine can be enhanced.
Next, the countermeasures against the possible abnormal-conditions that may be caused by providing the valves 41, 43 and 45 are explained.
First, abnormal conditions of the valve 43 are now explained.
In
In the event as described above, the pressure detected by a pressure sensor 56 provided in the thrust balance conduit 30 increases. When the detected pressure value exceeds a prescribed value, then the control unit 52 (not shown in
Once it is determined that the valve 43 or 41 is not working properly, the control unit 52 opens the valve 45.
When the control unit 52 opens the valve 45, the steam outlet side of the IP dummy member 14 communicates with the steam outlet side of the IP blade cascade 4 via the conduit 44. A part of the steam at the steam outlet side of the IP dummy member 14 streams to the steam outlet side of the IP blade cascade 4. This causes the pressure at the steam outlet side of the IP dummy member 14 to drop so that the pressure difference between both sides of the IP dummy member 14 is generated, thereby generating the thrust force at the IP dummy member 14. As a result, the resultant thrust force generated in the whole steam turbine 1 is balanced. In addition, it is necessary to design the conduits 44 and the valve 45 in advance so that the steam flow rate through the conduit 44 is almost the same as the steam flow rate through the valve 43 when the valve 45 is opened in a case when the valve 43 is abnormally opened.
As described above, even when the valve 43 is in the abnormal condition, the resultant thrust force can be kept balanced; thus, the reliability of the steam turbine 1 can be enhanced with additionally provided simple-components.
Next, the abnormal-conditions of the valve 41 are explained.
In
In the event as described above, the pressure detected by the pressure sensor 56 provided on the thrust balance conduit 30 increases. When the detected pressure exceeds a prescribed value, then the control unit 52 (not shown in
Once it is determined that the valve 43 or 41 is not working properly, the control unit 52 opens the valve 45.
When the control unit 52 opens the valve 45, the steam outlet side of the IP dummy member 14 communicates with the steam outlet side of the IP blade cascade 4 via the conduit 44. Then, a part of the steam at the steam outlet side of the IP dummy member 14 streams into the steam outlet side of the IP blade cascade 4. Thus, the pressure at the steam outlet side of the IP dummy member 14 drops so that the pressure difference between both sides of the IP dummy member 14 is generated. Accordingly, the thrust force is generated at the IP dummy member 14 so that the resultant thrust force generated in the whole steam turbine 1 is balanced.
As described above, even when the abnormal condition of the valve 41 happens, the resultant thrust force is kept balanced. Thus, the reliability of the steam turbine can be enhanced with additional simple-components.
Next, abnormal-conditions that may occur on the valve 41 in a case where the supply of the reheat steam and the LP main steam is stopped are explained.
As described already based on
In
In the event as described above, the pressure detected by the pressure sensor 56 provided on the thrust balance conduit 30 drops. When the detected pressure value is processed below a prescribed value, then the control unit 52 (not shown in
Once it is determined by the control unit 52 that the valve 43 is not working properly, the control unit 52 closes the valve 41.
With the valve 41 being closed, the pressure difference between both sides of the IP dummy member 14 becomes approximately 0 due to the steam leakage from the IP dummy member 14. Accordingly, the thrust force acting on the IP dummy member 14 becomes almost 0.
In this manner, the resultant thrust force is balanced as is the case with
Specifically, the resultant force is kept balanced, even when the abnormal condition regarding the valve 43 takes place.
Second Preferred EmbodimentThe disclosed technology of the present invention is also applicable to HP-IP steam turbines.
The HP-IP steam turbine 101 depicted in
Further, a high-pressure (HP) chamber blade cascade 102 to which the HP steam is supplied and an intermediate-pressure (IP) chamber blade cascade 104 to which the IP steam is supplied are attached to the rotor shaft such that steam inlets of the HP chamber blade cascade 102 and the IP chamber blade cascade 104 are disposed facing each other. Further, between the steam inlet of the HP chamber blade cascade 2 and the steam inlet the IP chamber blade cascade 104, a first dummy member 111 and a second dummy member 112 are provided. Further, a third dummy member 113 is provided at a steam outlet of the HP chamber blade cascade 102. Further, a balance conduit 121 is provided to communicate a location between the first dummy member 111 and the second dummy member 112 to both sides of the third dummy member 113. Furthermore, a balance conduit 122 is provided to communicate the steam outlet of the third dummy member 113 to the steam outlet of the IP chamber blade cascade 104. In addition, a valve 141 is provided on the balance conduit 121 between both sides of the third dummy member 113 and the downstream side of the third dummy member 113 and a valve 142 is provided on the balance conduit 122.
In relation to the HP-IP steam turbine as described above, the table in
As shown in
The same components in
In
In a manner similar to the second preferred embodiment, the resultant thrust force can be balanced, except when the IP system is closed. When the IP system is closed, the resultant thrust force can be balanced by adjusting the opening of the valve 142.
In the above event, when it is difficult to adjust the opening of the valve such as setting the opening of the valve 142 at a minimal level, it is recommendable to close the valve 42 and use the orifice 123. In relation to this event, it is necessary to set the size of the orifice in advance so that with the valve 142 being full-closed, the steam pressure at a back side of the third dummy member 113 is appropriate.
In other words, in a case where the IP system is closed, the valve 142 is closed and the steam streams through the orifice 124. Thus, the steam pressure at the back side of the third dummy member 113 is appropriately maintained. Hence, the resultant thrust force can be balanced.
INDUSTRIAL APPLICABILITYAccording to the present invention, it is possible to provide a steam turbine and a method of adjusting a thrust force of the steam turbine acting on a rotor shaft of the turbine in an entire operating range of the steam turbine without upsizing a LP dummy member or without using an electric control of a complicated system.
Claims
1. A steam turbine having at least a high-pressure blade cascade, an intermediate-pressure blade cascade and a plurality of dummy members that are attached to a common rotor shaft, the steam turbine comprising:
- a detection unit that detects a steam flow into an intermediate-pressure chamber;
- a pressure reducing unit that reduces a pressure difference between both sides of a target dummy member of said plurality of the dummy members when the steam flow into the intermediate-pressure chamber stops, the target dummy member having one side communicating with a part of the intermediate-pressure chamber; and
- a control unit that controls the pressure reducing unit based on a detection result obtained by the detection unit.
2. The steam turbine according to claim 1,
- wherein the pressure reducing unit comprises:
- a first conduit that connects the both sides of the target dummy member; and
- a first valve that is provided in the first conduit to adjust the pressure difference between the both sides of the target dummy member.
3. The steam turbine according to claim 2, further comprising:
- a third conduit that connects the one side of the pressure reducing unit to an outlet of the intermediate-pressure chamber; and
- a third valve that is provided in the third conduit,
- wherein, when the first valve opens while the steam flow into the intermediate-pressure chamber is not stopped, the control unit controls the third valve to open so as to generate the pressure difference between the both sides of the target dummy member.
4. The steam turbine according to claim 1,
- wherein the pressure reducing unit comprises:
- a second conduit that connects the part of the intermediate-pressure chamber and the one side of the target dummy member; and
- a second valve that is provided in the second conduit to adjust the difference between the both sides of the target dummy member,
- wherein the second valve is closed when the steam flow into the intermediate-pressure chamber stops.
5. The steam turbine according to claim 4, further comprising:
- a bypass conduit that is provided to bypass the second valve; and
- an orifice that is provided in the bypass conduit.
6. The steam turbine according to claim 4, further comprising:
- a third conduit that connects the one side of the pressure reducing unit to an outlet of the intermediate-pressure chamber; and
- a third valve that is provided in the third conduit,
- wherein, when the second valve closes while the steam flow into the intermediate-pressure chamber is not stopped, the control unit controls the third valve to open so as to generate the pressure difference between the both sides of the target dummy member.
7. A method of adjusting a thrust force of a steam turbine having at least a high-pressure blade cascade, an intermediate-pressure blade cascade and a plurality of dummy members that are attached to a common rotor shaft, the method comprising the step of:
- reducing a pressure difference between both sides of a target dummy member of said plurality of the dummy members when the steam flow into the intermediate-pressure chamber stops, the target dummy member having one side communicating with a part of the intermediate-pressure chamber.
8. The method of adjusting the thrust force of the steam turbine according to claim 7,
- wherein the pressure difference between the both sides of the target dummy member is reducible by use of a first valve provided in a first conduit that connects the both sides of the target dummy member.
9. The method of adjusting the thrust force of the steam turbine according to claim 8,
- wherein, when the first valve opens while the steam flow into the intermediate-pressure chamber is not stopped, the pressure difference is generated between the both sides of the target dummy member by opening a third valve which is provided in a third conduit that connects the one side of the target dummy member to an outlet of the intermediate-pressure chamber.
10. The method of adjusting the thrust force of the steam turbine according to claim 7,
- wherein the pressure difference between the both sides of the target dummy member is reducible by use of a second valve provided in a second conduit that connects the part of the intermediate-pressure chamber and the one side of the target dummy member.
11. The method of adjusting the thrust force of the steam turbine according to claim 10,
- wherein, when the second valve closes while the steam flow into the intermediate-pressure chamber is stopped, the pressure difference is generated between the both sides of the target dummy member by opening a third valve which is provided in a third conduit that connects the one side of the target dummy member to an outlet of the intermediate-pressure chamber.
Type: Application
Filed: Jun 29, 2011
Publication Date: Jan 26, 2012
Inventors: Takashi MARUYAMA (Tokyo), Asaharu MATSUO (Kobe-shi)
Application Number: 13/171,563
International Classification: F01K 13/02 (20060101);