Gas turbine

Abstract: A high efficiency coolant collection type gas turbine is obtained by forming coolant supply and collection flow paths for moving blades in a more outer peripheral side of a gas turbine rotor than a hub, supplying the coolant supplied from a shaft end into the moving blades through the supply flow path, collecting the coolant after cooling into a combustion chamber side, on the other hand, supplying air extracted from a compressor to cool moving blades of downstream side stage or a rotor outer wall through slits formed from a turbine rotor central portion to the hub, reducing rotor thermal stress and a pressure loss of the coolant flow paths and cooling a high stage side of a compressor rotor.

Description: The present invention relates to a gas turbine having moving blades cooled with a coolant and, more particularly, to a coolant collection type gas turbine provided with flow paths for cooling moving blades inside the gas turbine rotor and made so as to collect the coolant after cooling the moving blades. Moving blades of a gas turbine, usually, are cooled with air supplied through an interior of a rotor in order to protect them from a high temperature combustion gas flowing in a combustion gas path (hereunder referred to as a gas path). Usually, a part of compressed air for combustion is used as a source of the air and discharged into the gas path after cooling. In gas turbines the higher the combustion gas temperature, the higher the efficiency. However, since a thermal load increases by making the combustion gas temperature higher, a flow rate of a cooling air is inherently increased. Discharging the cooling air into the gas path not only decreases the temperature of combustion gas, but disturbs a flow in the gas path and decreases the output performance of the turbine. Further, a coolant flowing in a circulating flow path in the rotor has revolution energy proportional to 2 powers of the radius, however, discharging the coolant from the moving blades arranged on the outer periphery of the rotor causes a lot of pumping power loss, and the loss increases proportionally to a flow rate of the coolant. Therefore, an effective efficiency improvement can not be expected by only making the temperature of combustion gas higher. In order to improve further the performance, it is necessary to collect the air supplied for cooling the moving blades to solve the above-mentioned problems. Therefore, for example, in a gas turbine disclosed in JP A 54-13809, a method of forming a course of supplying and collecting a coolant with piping inside the rotor is proposed, and in a gas turbine disclosed in JP A 3-275946 a method of forming a course of supply and collection of a coolant by perforating the inside of the rotor is proposed. Further, in the gas turbine disclosed in JP A 7-189739, an axial collection flow path is formed at a stacking connecting portion of a turbine rotor, and it is made so that the air after cooling blades is collected in the combustion chamber through the collection flow path. For constructing a coolant collection type gas turbine, it is necessary to form inside a turbine rotor a supply flow path for supplying a coolant for moving blades and a collection flow path for collecting the coolant after cooling. However, since cooling the moving blades increases the temperature of the coolant used therefor, thermal stresses occur in the rotor components having both the supply flow path and the collection flow path because of difference in coolant temperature. In the gas turbine of 1500°C class combustion gas temperature, since the temperature of a coolant rises to about 200-250°C in the case of air cooling and to about 150-200°C in the case of vapor cooling, excessively large thermal stresses beyond an allowable value may occur depending on construction of a flow path. Therefore, in order to realize a coolant collecting gas turbine of high efficiency by making the combustion gas temperature higher, it is one large subject to form a coolant supply flow path and a coolant collection flow path inside the rotor so as to reduce thermal stresses. Further, in a coolant collecting gas turbine of air cooling type in which moving blades are cooled by using a part of compressed air for combustion and the air after cooling is collected in a combustor, it is necessary to rise a collection pressure to at least a discharge pressure of the compressor. Therefore, the coolant is pressurized by a boost compressor before being supplied. However, because of high temperature, increasing a flow rate of the coolant inherently increases compression power of the boost compressor, so that it influences greatly the efficiency of the whole gas turbine system. Therefore, in order to attain an expecting high efficiency, it is necessary to devise a flow path construction which is able to extremely reduce a pressure loss of the coolant flowing inside the rotor. Those points are not considered in any prior arts. JP 08 014064 relates to a gas turbine and its turbine stage device having two discs, the respective outer peripheral surfaces of which are filled with moving blades being arranged in a plurality of stages in an axial direction. A moving blade is cooled from the inside by a cooling medium. When the cooling medium after cooling is recovered, a spacer at the inside and in the two side wall parts of which cooling medium flow passages are formed is located between the discs. The cooling medium is fed on the two wall surfaces of the disc and is discharged from the side wall part cooling medium flow passage in such a manner to flow in the same direction as a radial direction. After cooling the moving blades the cooling medium is recovered through the inner cooling medium flow passage of the spacer. Such an arrangement allows to perform sufficient cooling of a moving blade without the occurrence of thermal deformation to a disc even when the temperature of working gas is increased. EP 0 965 726 A1, which is a document according to Art. 54(3) EPC, refers to a refrigerant recovery type gas turbine in which a rotor shaft comprises a plurality of discs each having a plurality of moving blades driven by combustion gas and arranged annularly on the peripheral portion and spacers arranged between the discs. The discs and spacers are arranged in such a way that gap portions are formed between rotor axis side regions of the discs facing the spacers and ajacent spacers. Into the gap portions is introduced a fluid heating an axis portion of the rotor shaft at a starting time. Further, the turbine rotor is provided with a steam supply flow path for supplying steam to the moving blades and a steam recovery flow path for recovering the steam. Further flow path for an air empressed by a combustor passes through the moving blades and a nozzle in an outer peripheral gas flow path of the turbine rotor to generate power. Thereby it is possible to control heat flow from and to the rotor members to reduce thermal stress applied on the rotor members and to improve the reliability of the rotor members at the time of starting. In the closed cooling gas turbine disclosed in JP A 7-189739 or JP A 9-13902, a supply flow path and a collection flow path for cooling blades are present mixedly inside a rotor, so that thermal stress occurs in construction components of the rotor because of the above-mentioned temperature elevation of coolant. Thermal stress is influenced by the structure of a rotor and a flow path, and the thermal stress also can be reduced by measures for thermal shielding. However, since the rotor is a rotary body rotating at a high speed, the structure thereof is limited much with respect to the strength. Although it is possible to form relatively easily a flow path at a stacking connecting portion, including the thermal shielding measures, the flow path construction has many problems such that branching and joining are necessary for forming communication flow paths between the flow path and blades at an outer periphery because many blades are connected, that stress is apt to increase upon perforation of the flow path because the disk has a thin thickness at the outer periphery side, further that large thermal stress occurs due to temperature difference between the side faces of the disc when counter flow is effected between coolant supply and coolant collection on the both side faces of the disc. Further, as a supply temperature of a coolant, about 250°C is effective in view of operation of the gas turbine system, and in this case, a collection temperature is 400-500°C. Thereby, the temperature of some portions goes beyond an allowable temperature of a turbine rotor material usually used, so that it is necessary to use a material of high heat resistance and high cost. An object of the present invention is to provide a coolant collection type gas turbine in which thermal stress in the rotor and pressure loss is reduced and the efficiency is high. In order to achieve the above objects, a gas turbine according to the present invention is characterized by comprising a compressor discharging compressed air, a combustor for mixing and burning fuel and the compressed air, a turbine which has nozzles arranged at an outer periphery side of a turbine rotor and moving blades with a coolant flow path and is connected to the compressor and driven by combustion gas supplied from the combustor, a first coolant flow path inside the turbine rotor, in which a coolant supplied from a downstream end thereof flow to the inside of a first moving blade positioned at the most upstream side, and a second coolant path inside the turbine rotor, in which a coolant extracted from the compressor and supplied through a connecting portion between the compressor and the turbine flows to the inside of downstream side moving blades having coolant paths. For example, it is characterized to have, inside the above-mentioned turbine rotor, a first coolant flow path in which a coolant supplied from a downstream end flows to be supplied into moving blades of the first stage positioned at the most upstream side and a second coolant flow path in which a coolant extracted from the above-mentioned compressor and having a lower pressure than the above-mentioned coolant flows to be supplied into second moving blades positioned at the most downstream side of moving blades having coolant paths through inside a portion connecting the compressor and the turbine. Further, for example, it is characterized to have a second coolant flow path in which a coolant having a higher temperature than the coolant flowing in the first coolant flow path flows. Even in a gas turbine provided with moving blades arranged under the conditions that temperature, etc. differs greatly from a front stage side and a rear stage side, it is possible to suppress thermal stress, reduce a pressure loss and effect a good cooling, by optimum supply or collection of different coolants. Further, it is characterized by comprising a compressor for discharging compressed air, a combustor for mixing and burning the compressed air and fuel, a turbine having a turbine rotor, nozzles arranged at an outer periphery side of the turbine rotor and moving blades with coolant flow path, connected to the compressor and driven by combustion gas supplied from the combustor, a course for supplying a coolant to the other end of the turbine rotor, a course supplying a coolant extracted from the compressor to a compressor side end of the turbine rotor through a portion connecting the compressor and the turbine, a first coolant flow path, inside the above-mentioned turbine rotor, allowing a coolant introduced from the other end of the turbine rotor to flow toward the above-mentioned compressor side end, and arranged so as to communicate with coolant flow paths formed in moving blades at the most upstream side, a coolant collection line supplying the coolant after cooling the above-mentioned moving blades at the most upstream side into the compressed air discharged from the compressor, a second coolant flow path, inside the above-mentioned turbine rotor, arranged inside the turbine rotor so as to allow the coolant introduced from a compressor side end into the turbine rotor to flow toward the other end side of the turbine rotor and communicate with coolant flow paths formed in moving blades of the second stage from the most downstream side, and a discharge path formed in the above-mentioned moving blades in the second stage from the most downstream side so as to discharge the coolant having supplied and raised in temperature into the above-mentioned combustion gas flow. Thereby, it is possible to suppress complication of flow path construction, reduce a flow rate of a high pressure coolant supplied into compressed air discharged from the compressor, suppress a pressure loss accompanied by supply and collection of the coolant to a small amount as a whole, and operate the gas turbine at a high efficiency. Further, it is characterized by comprising a compressor rotor having a plurality of discs axially arranged each having moving blades at the outer periphery side, a compressor having stationary vanes and the moving blades arranged at the outer periphery portion of the compressor rotor and discharging compressed air, a combustor mixing and burning the compressed air and fuel, and a turbine having moving blades and nozzles, connected to the compressor and driven by combustion gas supplied from the combustor, the above-mentioned discs having a gap portion between adjacent discs in a region including a central axis portion of the above-mentioned rotor, an annular connecting portion contacting with a disc adjacent to an outer periphery side of the region including the above-mentioned central axis portion of the rotor and an air extraction port for supplying a part of compressed air flowing in the compressor into the rotor, each formed therein, wherein a disc at a downstream side of the disc having the air extraction port formed therein has a compressor cooling flow path in which air extracted from the air extraction port flows in the contacting portion or in an outer peripheral portion of the contacting portion, a communication path communicating the above-mentioned cooling flow path and the above-mentioned gap portion, and a communication hole communicating each of said gap portions to the region including the central axis portion, each formed therein, and wherein a course supplying extracted air flowed in the above-mentioned compressor cooling flow path or the above-mentioned gap portion into the turbine is provided at the connecting portion between the compressor and the turbine, and a course leading, as a coolant, the extracted air flowed in the above-mentioned connecting portion to moving blades at the second stage form the most downstream side of the turbine, a course supplying a coolant to a downstream end of the turbine and a course leading, as a coolant, the above-mentioned coolant to moving blades at the most upstream side of the turbine each are provided inside the turbine rotor. Thereby, by effecting optimum supply or collection of different coolants, it is possible to suppress thermal stress to a small value and cool sufficiently while reducing a pressure loss. Further, it is possible to effectively cool a region the temperature of which becomes high such as a high pressure portion of a downstream side among blade rows of the compressor. Fig. 1 is a sectional view of an upper half of a coolant collection type gas turbine of an embodiment of the present invention; Fig. 2 is a view taken along a line X-X of Fig. 1; Fig. 3 is a view taken along a line Y-Y of Fig. 1; Fig. 4 is a vertical sectional view of a part of a gas turbine of another embodiment of the present invention; An embodiment of the present invention is explained hereunder in detail. Fig. 1 shows a sectional construction of an upper half of a closed air cooling type 4 stage gas turbine. In Fig. 1, the gas turbine comprises a casing 1, a compressor 2 arranged inside the casing 1 for compressing air and discharging compressed air, a combustor 3 for mixing compressed air and fuel and burning the mixture, a turbine 50 having nozzles 4, moving blades 5, a turbine rotor 6, etc., a bearing 8 and an exhaust duct 9. The moving blades 5 are supported on the outer periphery of the turbine rotor 6. Cooling flow paths 51 are formed inside the moving blades of the first to the third stage, and the shape of each cooling flow path 51 is different depending on thermal stress so as to be able to bear a thermal load of the combustion gas flowing in the gas path 91. The turbine rotor 6 comprises 4 discs 61a to 61d each moving blades planted thereon, 3 spacers 62a to 62c and a shaft 63, and they are connected at a hub by bolts. The turbine rotor 6 is connected to a rotor of compressor 2 through a distant piece 64. Central holes 65a to 65d are formed in the distant piece 64, discs 61a, 61b of the first stage and the second stage and the shaft 63, respectively. Discs of the third stage and the fourth stage each are solid. At the hub of the rotor, a plurality of supply main flow paths 66 each axially passing through the first to fourth discs and a plurality of collecting main flow paths 67 passing through the distant piece 64, the first stage disc 61a and a 1/2 stage spacer 62a (a spacer between the first stage disc and the second stage disc) are arranged in a peripheral direction. One end of each supply main flow path 66 communicates with the central hole 65 of the shaft at a downstream side through an inside cavity 68d at the downstream side of the fourth disc 61d and a supply slit 70c, and one end of each collecting main flow path 67 is opened in a wheel space 31a partitioned by seals 32a and 32b. Further, at the hub joining portion of the distant piece 64, the first and second discs 61a, 61b and a 2/3 stage spacer 62b, supply slits 70a and 70b are formed, and at both side joining portions of the 1/2 stage spacer 62a, collection slits 71a and 71b are formed. One end of the supply slit 70 and one end of the collection slit 71 communicate with the supply main flow paths 66 and the collecting main flow paths 67, respectively. The other ends of them communicate with the cooling flow path 51 for moving blades through cavities 69a to 69d at the outer side of the hub and a supply hole 72 and collection hole 73 at the outer peripheral portion of the disc. Further, at the hub joining portion of the 2/3 stage spacer and the third stage disc, a gas extraction system slit 74 radially extending and communicating an inner cavity 68a and an outer cavity 69e of the hub is formed. On the other hand, the rotor of the compressor 2 is composed of a plurality of discs 22 each having moving blades 21 planted on the outer periphery, and an air extraction port 23 is formed at a root of each moving blade of a specific stage selected from intermediate stages. Discs at a front stage side of the air extraction port 23 are solid and the discs at a rear stage side of the air extraction port 23 each have a central hole 28 formed therein which is a communication hole communicating gaps between the discs, and the air extraction port 23 is communicated with the central hole 28 through an outer cavity 24 of the hub, a plurality of slits 26 and an inner cavity 27. Further, the outer calvities 24 are communicated with each other at the outside of the hub by communication holes 25 which are communication flow paths. Fig. 2 shows a view viewed from X-X of Fig. 1, the supply main flow paths 66 and the collecting main flow paths 67 are alternately arranged in a midway between a plurality of bolt holes 75 arranged in a circumferential direction of the hub. The number of supply holes 72 and collection holes formed at the outer periphery of the disc is the same as the number of the moving blades. Fig. 3 shows a view viewed from Y-Y of Fig. 1, the gas extraction system slits 74 and the supply main flow paths 66 are alternately arranged in the peripheral direction. A coolant supplied from an end of shaft 63 of the turbine rotor upon stating of the gas turbine is introduced, as shown by an arrow 92a, into the supply main flow paths 66 formed in the hub so as to axially pass through the discs and spacers through the central hole 65d of the shaft 63, the cavity 68b at the rear side of the fourth stage disc and the slit 70c. A part of the coolant introduced in the supply main flow paths 66 is supplied into the second stage moving blades (as shown by an arrow 92b) through the slit 70, cavity 69d and supply holes 72 at the outer peripheral portion of the disc. The coolant after cooling the moving blades is introduced into the collecting main flow paths 67 (as shown by an arrow 92c) through the collection holes at the outer peripheral portion of the disc, the cavity 69c at the front side of the disc and the collection slit 71b, discharged into the wheel space 31a from the discharge port 76 of the distant piece hub, and then collected in the combustor side through collection holes 33 of an inner barrel. The collection coolant is supplied into the combustor together with air discharged from the compressor. A coolant remaining except for the coolant for the second stage moving blades is supplied into the coolant flow paths 51 of the first stage moving blades 5 (as shown by an arrow 92d) through the supply slit 70a at the front side of the first stage blade, cavity 69a and supply holes 72 at the outer peripheral portion of the firs stage disc. The coolant after cooling the moving blades is introduced into the collecting main flow path 67 (as shown by an arrow 92e) through the collection holes 73 at the rear side of the disc, cavity 69b and collect slit 71a of the joining portion of the hub, and in the similar manner to the cooling the second stage moving blade, is collected into the combustor side through the discharge hole 76 and wheel space 31a. That is, the coolant for the first stage moving blades flows so as to circulate around the outer side of the disc, and coolants of 2 systems of supply and collection systems pass through the hub. On the other hand, the coolant extracted from the air extraction port 23 of the compressor outer peripheral portion at an intermediate stage portion is distributed approximately evenly to cavities 24 downstream side of the outer side of the hub by the communication holes 25, and then the distributed coolants are joined in the central hole of the disc through the slit 26 and cavities 27 at the inner side of the hub. The joined coolant flows in the central portion of the turbine rotor through the central hole 65a of the distant piece (as shown by an arrow 93a). Inside the turbine rotor, the coolant is supplied in the cooling paths in the third stage moving blades through the central holes 65b, 65c of the disc, cavity 68a, gas extraction system slit 74 and cavity 69e of the hub outer periphery (as shown by an arrow 93b), cools the same moving blades and then is discharged into the gas path 91 (as shown by an arrow 93b). As mentioned above, by constructing, inside the rotor, a coolant supply system in which a coolant is supplied from the shaft end and an extraction coolant system in which a coolant is supplied from the compressor, the hub positioned at a midway of the radius of the rotor is made as an axial coolant path for moving blades, communication paths with the moving blade are formed in the radially outer side of the hub, the circumstances for the extraction coolant extracted from the compressor are formed in the radially inner side of the hub, and the shaft end supply flow path 68b and air extraction flow path 68a are partitioned by a solid disc 61d of the final stage, whereby 3 systems of supply, collection and air extraction can be formed simple without interconnecting. Further, the main flow paths for supply and collection of coolant for moving blades are formed in the hub portion joining the discs, shafts, etc., the supply main flow path is communicated with the supply port of the shaft end, and the collection main flow path is opened to the wheel space at the first stage side. Further, the supply slit and collection slit are formed at the joining portion of the hub so that the one ends thereof communicate with the supply and collection main flow paths, respectively. Further, the slits are formed which communicate with the central hole of the above-mentioned disc at the hub joining portion of the third stage disc having the third stage moving blades at the final stage side of moving blades provided with coolant flow paths. With this structure, the coolant supplied from the above-mentioned shaft end port is supplied into the moving blades before the third stage through the supply main flow path and supply slits, the coolant after cooling is collected into the combustor side through the collection slit and collecting main flow path. Further, compressed air having an intermediate temperature between above-mentioned supply coolant and collection coolant is extracted from the compressor, this air is supplied to the third stage moving blades through the central hole of the disc and the slit of a n-stage disc. Thereby, the hub positioned at a midway of the radius of the rotor is made into an axial coolant path for moving blades, communication paths with the moving blade are formed in the radially outer side of the hub, the circumstances of the extraction coolant from the compressor are formed in the radially inner side of the hub, and the shaft end supply flow path 68b and air extraction flow path 68a are partitioned by a solid disc 61d of the final stage, whereby 3 systems of supply, collection and air extraction can be formed simple without interconnecting, in addition to that, reduction of thermal stress at the time of steady and unsteady operation of the above-mentioned rotor, cooling of the compressor rotor, collection of the coolant, etc. become effective. Further, in the central hole of the rotor, although it is known that a lot of pressure loss occurs by eddy flows before entering the central hole, the pressure loss is small because a flow in the central hole is not included in the flow path structure for the coolant supplied from the shaft end, and boost compression power for the coolant can be suppressed to a minimum value. Further, the shaft end supply portion, the joining portion between the disc at the outer periphery of the outer side cavity 68 and the spacer, the fitting portion of the disc and moving blades, the sealing portion 32b of the wheel space 31a, etc. are considered as leak portions of flow lines at which leak may occur, however, leakage from the joining portions and fitting portions can be prevented by contact surface sealing, and additionally, the coolant leaked from the seal portion 32b can be used as sealing air for preventing combustion gas leakage from the gas path to the wheel space 31b, so that most of the coolant supplied from the shaft end can be effectively collected. Since the radial position of the discharge port 76 can be made to be 1/2 or less, a pumping power loss accompanied by discharging the coolant can be reduced to 1/4 or less. By causing the coolant extracted from the compressor to flow in parallel in the flow paths 24 to 28 formed in the side faces of the discs, and introducing the coolant into the central portion of the turbine rotor 6 through the distant piece 64, it is possible to uniformly cool discs of high stages of the compressor, additionally, the distant piece heated from the outer periphery by the collection coolant can be cooled from the inside. Therefore, it is possible to construct so as to raise a compressor discharge pressure without raising the heat resistance of rotor material so much. Further, when the temperature of extracted coolant is set to an intermediate temperature between the shaft end supply coolant and collection coolant, a low temperature portion around the shaft end supply main flow path 66 formed in the hub is heated, and a high temperature portion around the collecting main flow path 67 is cooled, whereby a function of damping high and low temperatures in the rotor temperature distribution is operated and thermal stress is reduced. Further, since the extracted coolant is unnecessary to collect or withdraw, boost compression power can be served and such an advantage can be attained that the size of the compressor can be small. Further, in the central hole of the discs, the above-mentioned pressure loss occurs by eddy flows before entering the central hole, the pressure loss depends greatly on a flow rate, however, since the flow rate of each flow path decreases by dividing the extracted coolant in a plurality of flow paths between the discs, a pressure loss accompanied thereby decreases and a sufficient supply pressure to the third stage moving blades can be secured. Since combustion gas of high temperature flows in the gas path at the same time as ignition when the gas turbine is started, the temperature of the outer peripheral side of the rotor rapidly rises in connection with the influence of a heat load from the gas path and a heat conduction area. Therefore, on the rotor central portion in which the temperature rises slowly, further larger stress than in the time of steady operation occurs, however, in the present embodiment, since the air extracted from the compressor flows in the rotor central portion at the same time as starting and the portion is uniformly heated, a great effect can be attained even for reducing unsteady thermal stress at the time of starting. Further, as for the coolant supplied from the shaft end, the flow rate, temperature, etc. can be controlled outside the apparatus, so that it is also possible to control unsteady thermal stress of the rotor to a minimum value by a supply delaying means, etc. The reason that a coolant for the first stage moving blades is supplied from the front side of the disc is for cooling the hub of the first stage disc and the front side thereof by flowing the coolant of low temperature to the hub and the front side, whereby a temperature of the distant piece 64 and a temperature of the hub become about an average temperature of the supply coolant and collection coolant, and the temperature rise can be suppressed to a low temperature as compared with the case where only a collection coolant flows in the hub by supplying the coolant from the rear side. However, by this influence, the temperature of the out side of the 1/2 stage spacer rises near to the temperature of the collection coolant, however, a temperature gradient in the axial direction is not formed, the outer periphery and the hub are cooled by seal air and supply coolant for cooling the first stage, respectively, and a centrifugal load of the spacer is smaller than the disc loaded by the centrifugal load of the moving blades, so that a problem due to the stress is less than in the disc. Further, by supplying a coolant into the cooling flow path 51 inside the moving blade from the front side, difference in temperature between the coolant and the combustion gas flowing in the gas path 91 is effectively formed for cooling, so that it is effective even for rising the cooling efficiency of moving blades. Next, considering the construction of the flow paths from the viewpoint of pressure loss, the flow path length of a course from the shaft end to the combustion chamber by bypassing the cooling flow paths for moving blades is formed to be extremely short, and the flow path is formed so as to bypass the central hole flow path the pressure loss of which is large. Therefore, the pressure loss of the course is small and the boost compression power of the coolant can be suppressed to a minimum. However, in the central hole 28 of the compressor discs, a swirling speed of eddies increases in the course in which the coolant flowed out of the slit 26 of the hub flows inwardly in the cavity 27, the swirling speed energy disappears in the course of axial flow in the central hole thereby to cause a pressure loss, however, in this embodiment, since the coolant flow is divided in many flow paths and a flow rate of the coolant in each divided flow paths is made small, a swirling component of the coolant flow attenuate by friction at the wall face when the coolant flows in the cavity 27. Therefore, the pressure loss in the central hole is small. Accordingly, in a high stage side, a sufficient supply pressure to the third stage moving blade can be secured irrespective of air extraction stage. Further, as a flow path construction in the case where air is not extracted as a coolant from the compressor, although it is considered that it is most effective to reduce the loss caused by collecting a total amount of a coolant for moving blades and discharging the collected coolant into the gas path, however, in this case, it is necessary to effect boost compression of the total amount of the coolant. On the contrary, in the present embodiment, since the coolant for the moving blades of the third stage is discharged into the gas path, the efficiency of the gas turbine decreases by that discharge, however, since boost compression power is unnecessary as to the same coolant, a loss due to the discharge can be compensated. With the construction of the present embodiment, excellent cooling can be effected while suppressing an amount of coolant necessary to compress to a small amount, and reducing the necessary power. As is noted from the coolant course for the first stage moving blades and the second stage moving blades, a region exposed to the collection coolant of high temperature in the turbine rotor is limited to a narrow region indicated by A which is radially outside of the hub and the front side of the second stage disc. However, about a half of a coolant-wet surface within the region is exposed to a supply coolant of low temperature, On the other hand, since the coolant extracted from the compressor flows in the region B from the compressor rotor to the central portion of the turbine rotor, members in the region B are exposed to atmosphere of the coolant of extracted air. A region C form the 2/3 stage spacer to the rear side of the third stage disc is exposed to a supply coolant and a coolant of extracted air, and the remaining region D in the rear side of the 3/4 stage spacer is exposed mainly to a supply coolant of low temperature. As an example, in the case where a coolant of 230°C is supplied from the shaft end and a compressed air of 370°C is extracted from the compressor, the temperature of a collection coolant after cooling moving blades is 450-500°C in the case of a gas turbine of 1500°C class. Thereby, an average temperature of the members in the region A exposed to the supply coolant and collection coolant is raised to 340-365°C which is an average of the supply coolant and the collection coolant, and the temperature of the members in the region D exposed to only the supply coolant is raised to 220°C which is close to the supply coolant temperature. On the other hand, the temperature of members in the region B in which the extracted air coolant flows rises to an temperature close to the extracted air coolant temperature 370°C, and the temperature of members in the region C rises to about 300°C of an average temperature of the extracted air coolant and the supply coolant. Further, since the distant piece is heated at the outer periphery by the collection coolant and at the inner periphery by the extracted air coolant, the distant piece is raised to 410-430°C of an average temperature of both coolants. That is, when a shaft end supply coolant of 230°C and a compressor extracted air of 370°C are used as a coolant for cooling the moving blades, it is possible to construct rotor inside coolant flow paths by which a rotor average temperature becomes about 430°C or less. Further, a temperature distribution of the hub in the axial direction changes so that the temperature in the regions A, C and D drops in the mentioned order, and a difference between high and low temperatures is small even if partial changes in each region are included, which is effective to make a minimum difference in radial elongation of the hub joining portion and reduce stress in the fitting portion. Therefore, although the maximum centrifugal stress due to high speed rotation occurs in the disc central portion, by making the temperature of the disc central portion higher than the radially outer side, the above-mentioned centrifugal stress is damped by thermal expansion. The temperature of the hub portion becomes about an intermediate temperature of the supply coolant and the collection coolant, as mentioned above, so that by making the temperature of air extracted from the compressor higher than the intermediate temperature, the rotor central portion is heated by the collection coolant and becomes higher in temperature than the hub. Therefore, an effect of reducing stress in that portion can be attained by selecting a suitable temperature of the extracted air coolant. In this case, since the temperature of an extracted air is decided by a position of stage of the air extraction port 23, an extraction stage at which an effect of reducing thermal stress is highest should be selected as for the construction of coolant flow paths formed inside the rotor. Further, in the present embodiment, the extraction course shown by an arrow 93c is formed in the front side of the third stage disc, however, it is also possible to form the course around the central hole and supply the coolant to the third stage moving blades from the rear side. The reason that the course is formed in the front side is for forming a cavity 68c through which a coolant does not flow between discs and reducing thermal stress caused on the side surfaces of central portion of the fourth disc 61d by difference in temperature between the shaft end supply coolant and the extracted air coolant. In the case where the difference in temperature between the shaft end supply coolant and the extracted air coolant can be made small in order to reduce thermal stress of the whole of the rotor, even if the extracted air course is formed in the rear side of the third stage disc, an effect equivalent to the above-mentioned can be attained. In the embodiment explained above, intervening of the spacers between the discs is for reducing stress by shortening the axial span of the disc hub and the outer peripheral rim, however, it is possible to omit the spaces when the stage span of the turbine can be shortened. Fig. 4 shows a sectional construction of a turbine rotor in which coolant flow paths are formed without intervening of spacers. The rotor 10 is composed of discs 11a to 11 d and a shaft 63, and connected to the compressor rotor at the first stage side through a distant piece. The discs from the first stage to the third stage each have a central hole 19, and the disc of the fourth stage is made solid. The discs have moving blades 5 planted on the outer periphery and, particularly, the moving blades of the first to third stages are cooled from the inside. In this case also, a supply main flow path 12 and collecting main flow path 13 of the hub can be formed in the same as the above-mentioned embodiment. However, since there is no spacer, supply slits 14a, 14b, a collection slit 15 and a compressor extracted air system slit 16 are formed between the hub joining portions of the disc 11 and, particularly, the collection slit 15 is used for collecting both coolants for the first stage moving blades and the second stage moving blades. With this flow path construction, a part of the coolant supplied from the shaft end into the supply main flow path 12 is supplied to the second stage moving blades through the supply slit 14b and an outer cavity 17c between discs, and the remaining coolant is supplied from the supply slit 17a to the first stage moving blades through the front side of the disc. After joining at the cavity 17b, the coolant is collected into the combustion chamber side through the collection slit 15 and the collection main flow path 13. On the other hand, the coolant extracted from the compressor is flowed into the central hole 19 of the turbine rotor through the distant piece, and supplied into the third stage moving blades through the cavity 18 at the inner side, the extracted air system slit 16 and the outer side cavity 17d. In this case also, an approximately similar effect to the above-mentioned embodiment can be attained as for reduction of steady and unsteady thermal stresses and a pressure loss, cooling of the compressor rotor, etc., additionally, there is an advantage that the rotor construction itself can be constructed simple by omitting the spacers. Further, it is also possible to make the third stage moving blades solid and the other moving blades hollow. A different point from Fig. 1 is that such a course is not taken that the coolant flowing in the central hole 65d is introduced into the supply main flow path 66 through the cavity 68b at the rear side of the fourth stage disc and slit 70c, but the course is taken in which a central hole is formed in the fourth stage disc and the coolant flowed in the central hole 65d is introduced into the supply main flow path 66 through the central hole of the fourth stage disc 61d, the cavity 68c formed between the third and fourth stage discs and the slit. As a concrete construction, the above-mentioned rotor is as follows. A flow path (a first coolant flow path) for a coolant supplied from the shaft end uses a central hole of the disc center as a first through course constructed so as to pass through the fourth stage disc at the axis. Further, a cavity and slit ( first communication course) are formed which are formed between the fourth stage disc and the adjacent third stage disc so that the coolant flowing in the above-mentioned central hole flows in the outer peripheral direction. The coolant flowing in the above-mentioned communication path is supplied into the supply main flow path 66 (second through course). The coolant flowing in the supply main course 66 is supplied into the coolant flow path in the first stage moving blades through the supply slit 70a (second communication course). A flow path (the above-mentioned second coolant flow path) for extracted air coolant from the compressor is constructed as follows, that is, the extracted air coolant supplied through the disc central holes 65b, 65c, etc.(third through course) made so as to pass through the discs of the above-mentioned rotor at the axis from the compressor side and flowing in the central holes 65b, 65c is supplied into an extracted air system slit 74 (third communication course) directed radially outward along the disc, and constructed so as to communicate with the flow paths in the third stage moving blades to be introduced into the moving blades. In this case also, steady and unsteady thermal stress can be damped and effective cooling can be achieved while reducing a pressure loss. As mentioned above, according to the present embodiment, supply and collection flow paths for coolant which are suitable to reduce thermal stresses and a pressure loss and cool the compressor rotor are formed inside the turbine rotor, and a coolant collection type gas turbine of high efficiency can be provided.

Claims: A gas turbine comprising: a compressor (2) discharging compressed air, a combustor (3) for mixing and burning fuel and the compressed air, and a turbine (50) having nozzles (4) arranged at an outer periphery side of a turbine rotor (6) and moving blades (5) with coolant flow paths (51), connected to the compressor (2) and driven by the combustion gas supplied from the combustor (3), wherein the turbine rotor (6) has inside: a first coolant flow path in which a first coolant is supplied from a downstream end of the turbine rotor (6) to first stage moving blades (5) positioned at a most upstream side with respect to a flow of the combustion gas, and a second coolant flow path in which a second coolant extracted from the compressor (2) is supplied to moving blades (5) with coolant paths on a downstream side through an inside of a connecting portion between the compressor (2) and the turbine (50), characterized in that the pressure of the second coolant flowing in the second coolant flow path is lower than that of the first coolant flowing in the first coolant flow path, or the temperature of the second coolant flowing in the second coolant flow path is higher than that of the first coolant flowing in the first coolant flow path. A gas turbine in accordance to claim 1, characterized by a course (12, 19) for supplying the coolant to the other end of the turbine rotor (6), and a course (14a, 17a) for supplying the second coolant into an upstream end of the turbine rotor (6), a coolant collecting course (13, 15) for supplying the coolant after cooling the moving blades (5) at the most upstream side into the compressed air discharged from the compressor (2), whereby the second coolant flow path is arranged so as to communicate with coolant flow paths constructed in moving blades (5) of the second stage from the downstream side, and discharge paths provided in the moving blades (5) of the second stage from the downstream side for discharging the second coolant supplied and elevated in temperature into the combustion gas flow (91). A gas turbine in accordance to claim 1, characterized in that the compressor (2) is further provided with a compressor rotor having a plurality of discs (22) axially arranged each having moving blades (21) at outer periphery, nozzles being arranged at the outer periphery side of the compressor rotor for discharging compressed air, wherein the discs (22) have a gap portion forming gaps (24, 27) between adjacent discs (22) in a region including an axis portion, an annular connecting portion at which adjacent discs (22) are in contact with each other at a radially outer side of the axis portion-including region, an extraction port (23) for supplying a part of compressed air flowing in the compressor (2) into an inside of the compressor rotor, a compressor cooling flow path formed in the connecting portion or in an outer side of the connecting portion in a disc downstream of the disc (22) having the extraction port formed therein, a communication flow path communicating the compressor cooling flow path and the gap portion, and communication holes (25, 28) communicating the axis portion-including region and the gaps (24, 27) of the gap portion, whereby the gas turbine further comprises a course provided at a connecting portion of the compressor (2) and the turbine (50) for supplying the extracted air flowing in the compressor cooling flow path or the gap portion into the turbine (50), a course formed inside the turbine rotor (6) for leading, as a coolant, the extracted air having flowed in the connecting portion into moving blades (5) of the second stage from the most downstream side, a course for supplying a coolant into a downstream end of the turbine (50), and a course formed inside the turbine rotor (6) for leading the coolant into the moving blades (5) at the most upstream side of the turbine (50). A gas turbine in accordance to claim 1, characterized in that the turbine rotor (6) having a plurality of discs (61a, 61b, 61c, 61 d) axially arranged; each disc (61 a, 61 b, 61 c, 61 d) having moving blades (21) at a periphery side thereof and a plurality of respective disc-fixing devices passed through and inserted therein in an annular shape, the second coolant is supplied into the moving blades (5) of the second stage from the most downstream side, wherein the first coolant flow path comprises a first through course formed so as to pass through an axis portion of the disc (61 d) provided with moving blades (5) at the most downstream side from an opposite end side of the turbine rotor (6) to the compressor (2), a first communication course (68c) formed between the disc (61d) at the most downstream side and a disc (61c) adjacent to the disc (61d) so that the first coolant flowing the first through course flows toward the outer periphery, a second through course (66) formed in a region between adjacent ones of the fixing devices so that the first coolant flowing in the first communication course (68c) flows passing through the discs (61c, 61d) toward the compressor side, and a second communication course (70a) formed so that the first coolant flowing in the second through course (66) communicates with coolant flow paths (51) inside the first stage moving blades (5), and wherein the second coolant flow path comprises a third through course (65b, 65c) formed so as to pass through the axis portion of the discs (61 a, 61 b) from the compressor side of the turbine rotor (6), and a third communication course (74) formed so that the second coolant flowing in the third through course (65b, 65c) flows along the disc in a radially outer direction and communicates with coolant flow paths (51) in the moving blades (5) of the second stage from the most downstream side.

Inventors: IKEGUCHI TAKASHI, KAWAIKE KAZUHIKO, MARUSHIMA SHINYA, MATSUMOTO MANABU, IKEGUCHI, TAKASHI, KAWAIKE, KAZUHIKO, MARUSHIMA, SHINYA, MATSUMOTO, MANABU
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1998
Main classification: F01D5
IPC codes: F01D25, F01D5