CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a National Stage Patent Application of PCT International Patent Application No. PCT/KR2013/003264 filed on Apr. 18, 2013 under 35 U.S.C. §371, which claims priority to Korean Patent Application No. 10-2012-0049631 filed on May 10, 2012, which are all hereby incorporated by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to a reaction turbine, and more particularly, to a reaction turbine that generates a rotational force using a repulsive force when a working fluid, such as steam, gas, or compressed air, is injected. 
         [0003]    In general, a steam turbine is one of motor techniques that convert thermal energy of steam into a mechanical work. The steam turbine jets and expands high-temperature and high-pressure steam generated in a boiler from nozzles or fixed wings, makes a high-speed steam flow collide with rotating turbine wings and rotates a turbine shaft by an impulse or rebound action. Thus, the steam turbine is configured of nozzles that convert the thermal energy of the steam into velocity energy and turbine wings that convert the velocity energy into a mechanical work. Examples of the steam turbine include an impulse turbine that drives the turbine wings using only an impulsive force and a rebound turbine or a reaction turbine that is driven by a rebound force. 
         [0004]    Korean Patent Registration No. 10-1052253 discloses a reaction turbine, wherein two or more injection rotation portions within a housing communicate with each other and are disposed along a radial direction in a multi-stage manner and rotate by reaction of an injection action of a fluid injected through an injection flow path of each injection rotation portion. However, when the capacity of the turbine is changed, it is difficult to share each component, such as the injection rotation portion. 
         [0005]    The present invention provides a reaction turbine in which components can be shared so that a turbine having various capacities can be manufactured and the performance of the turbine can be enhanced by minimizing pressure loss that may occur when a working fluid flows. 
         [0006]    According to an aspect of the present invention, there is provided a reaction turbine including: a housing in which a housing inlet and a housing outlet are formed and a housing flow path that communicates the housing inlet and the housing outlet so that a high-pressure working fluid introduced into the housing inlet is capable of moving in a direction of the housing outlet; a rotation shaft that passes through the housing and is rotatably coupled to the housing; and a rotor that is integrally coupled to the rotation shaft within the housing flow path and rotates the rotation shaft as the working fluid introduced from a center side of the rotor in an axial direction is injected toward an outer circumference side of the rotor, wherein the rotor may include first and second rotor plates that are coupled to each other in the axial direction, and first and second flow paths may be formed on surfaces of the first and second rotor plates that face each other, respectively, and a combination of the first and second flow paths may constitute an inner flow path on which the working fluid is guided. 
         [0007]    According to another aspect of the present invention, there is provided a reaction turbine including: a housing in which a housing inlet and a housing outlet are formed and a housing flow path that communicates the housing inlet and the housing outlet so that a high-pressure working fluid introduced into the housing inlet is capable of moving in a direction of the housing outlet; a rotation shaft that passes through the housing and is rotatably coupled to the housing; and a rotor that is integrally coupled to the rotation shaft within the housing flow path and rotates the rotation shaft as the working fluid introduced from a center side of the rotor in an axial direction is injected toward an outer circumference side of the rotor, wherein the rotor may include first and second rotor plates that are coupled to each other in the axial direction, and an inner flow path on which the working fluid is guided, may be formed on a surface of the second rotor plate toward the first rotor plate, and the first rotor plate may be formed to cover an entire surface of the inner flow path. 
         [0008]    According to still another aspect of the present invention, there is provided a reaction turbine including: a housing in which a housing inlet and a housing outlet are formed and a housing flow path that communicates the housing inlet and the housing outlet so that a high-pressure working fluid introduced into the housing inlet is capable of moving in a direction of the housing outlet; a rotation shaft that passes through the housing and is rotatably coupled to the housing; and a rotor assembly that includes a plurality of rotors, which are stacked and disposed in a multi-stage manner along an axial direction within the housing flow path that are integrally coupled to the rotation shaft, and that rotate the rotation shaft as the working fluid introduced from a center of each of the plurality of rotors in the axial direction is injected toward an outer circumference side of each rotor, wherein the plurality of rotors may be integrally formed when two rotor plates are coupled to each other in the axial direction, and first and second flow paths of which cross sections are symmetrical with respect to each other, may be formed on surfaces of the rotor plates that face each other, and a combination of the first and second flow paths may constitute one inner flow path. 
         [0009]    In a reaction turbine according to the present invention, first and second rotor plates are coupled together to form an integrated rotor, and an inner flow path including a combination of first and second flow paths, which are formed on the surfaces of the first and second rotor plates that face each other, respectively, thereby enabling easier manufacturing into a form desired by a designer by eliminating the limitation of a cross-sectional shape of the inner flow path. In addition, a cross section of each of the first and second flow paths can be formed into a semicircular shape thus yielding a circular shape for the inner flow path, which is formed by combining the first and second flow paths, thereby effectively enhancing the performance of a turbine by minimizing pressure loss of a working fluid that passes through the inner flow path. 
         [0010]    In addition, in the reaction turbine according to the present invention, when a rotor includes first and second rotor plates and an inner flow path is formed only on one rotor plate, a forming work and time of the inner flow path can be reduced. Also, the cross section of the inner flow path is formed into a semicircular shape so that pressure loss of the working fluid can be reduced. 
         [0011]    Also, the cross section of each of the first and second flow paths formed on the first and second rotor plates is formed into a semicircular shape, and the first and second flow paths each have an involute curve shape so that a change in flow paths of the working fluid is more gentle and pressure loss that occurs due to the change in flow paths can be minimized and thus the performance of the turbine can be enhanced. 
         [0012]    Furthermore, since a plurality of rotors are stacked in a multi-stage manner along an axial direction, the number of rotors can be increased or decreased according to the capacity of the turbine so that the turbine having various capacities can be manufactured, components can be shared and thus manufacturing costs can be reduced. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a cross-sectional view of a reaction turbine according to a first embodiment of the present invention; 
           [0014]      FIG. 2  is an enlarged view of a portion A of  FIG. 1 ; 
           [0015]      FIG. 3  is a plan view of a first rotor plate illustrated in  FIG. 1 ; 
           [0016]      FIG. 4  is a cross-sectional view taken along a line B-B of  FIG. 2 ; 
           [0017]      FIG. 5  is a cross-sectional view of a part of first and second rotor plates according to a second embodiment of the present invention; 
           [0018]      FIG. 6  is a cross-sectional view taken along a line C-C of  FIG. 5 ; 
           [0019]      FIG. 7  is a cross-sectional view of a part of first and second rotor plates according to a third embodiment of the present invention; 
           [0020]      FIG. 8  is a cross-sectional view taken along a line D-D of  FIG. 7 ; 
           [0021]      FIG. 9  is a plan view of a first rotor plate according to a fourth embodiment of the present invention; and 
           [0022]      FIG. 10  is a cross-sectional view taken along a line E-E of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Hereinafter, a reaction turbine according to the present invention will be described in detail with reference to embodiments illustrated in the accompanying drawings. 
         [0024]      FIG. 1  is a cross-sectional view of a reaction turbine  1  according to a first embodiment of the present invention. 
         [0025]    The reaction turbine  1  according to the present invention generates a rotational force using a working fluid including high-pressure steam or gas, or compressed air. The working fluid includes high-pressure steam or gas, or compressed air. Hereinafter, in the present embodiment, a case where the working fluid is steam, will be described. 
         [0026]    In the reaction turbine  1 , a rotation shaft  20  is rotatably coupled to a housing  10 , and at least one or more rotors  200  are stacked on the rotation shaft  20  along an axial direction. 
         [0027]    The housing  10  includes an inlet housing  15  in which a housing inlet  10   a  is formed so that high-pressure steam that is the working fluid may be introduced into the inlet housing  15 , an outlet housing  16  that is disposed at the other side of the inlet housing  15  and is spaced apart from the inlet housing  15  by a predetermined distance and has a housing outlet  10   b  through which expanded low-pressure steam is discharged in the air or is recirculated, and intermediate housings  11 ,  12 ,  13 , and  14  that are disposed between the inlet housing  15  and the outlet housing  16  and form a housing flow path  10   c  on which the rotors  200  can rotate. At least one or more housing inlets  10   a  may be provided, and in the present embodiment, one housing inlet  10   a  is formed. At least one or more housing outlets  10   b  may be provided, and in the present embodiment, one housing outlet  10   b  is formed. The number of intermediate housings  11 ,  12 ,  13 , and  14  that corresponds to the number of rotors  200  may be provided. In the present embodiment, four rotors  200  that will be described later are provided. Thus, four intermediate housings  11 ,  12 ,  13 , and  14  are provided along the axial direction. 
         [0028]    Separation plates  30  are respectively provided at both sides of four intermediate housings  11 ,  12 ,  13 , and  14  so as to form the housing flow path  10   c  together with the intermediate housings  11 ,  12 ,  13 , and  14 . The separation plates  30  each have a disc shape, and through holes are formed in the middle of the separation plates  30  so that a first rotor plate  211  that will be described later can be rotatably inserted into the separation plates  30  through the through holes. A sealing member  40  for preventing leakage of steam is inserted between the separation plate  30  and the first rotor plate  211 . The sealing member  40  will be described in detail later. The sealing member  40  has a ring shape and is coupled to the separation plate  30  in the axial direction. The sealing member  40  is inserted into an inner circumferential surface of the separation plate  30  in the axial direction and then is fixedly installed using a fastening member, such as a bolt. The sealing member  40  is a Labyrinth seal having a shape in which a contact surface between the sealing member  40  and the first rotor plate  211  is minimized so that rotation of the first rotor plate  211  that will be described later can be easily performed. 
         [0029]    A bearing module through which the rotation shaft  20  that have passed through the housing  10  passes, is installed in the inlet housing  15  and the outlet housing  16 , respectively, and a bearing  21  that supports the rotation shaft  20  is disposed in the bearing module. Also, a mechanical seal  22  is disposed so as to prevent the working fluid in the inlet housing  15  and the outlet housing  16  from leaking toward the bearing module. Also, a sealing member  24  having a Labyrinth seal structure in which the sealing member  24  is installed between the mechanical seal  22  and the bearing  21  and prevents the working fluid that leaks from the mechanical seal  22  from being introducing into the bearing  21 , is disposed in the bearing module. 
         [0030]    The rotor  200  is integrally coupled to the rotation shaft  20  and rotates the rotation shaft  20  as the steam introduced from a center side of the rotor  200  in the axial direction is injected toward an outer circumference side of the rotor  200 . The capacity of the turbine may be changed according to the number of rotors  200  coupled to the rotation shaft  20 . That is, when the capacity of the turbine is small, the number of rotors  200  may be decreased, and when the capacity of the turbine is large, the number of rotors  200  may be increased. 
         [0031]    A plurality of rotors  200  are stacked and disposed in a multi-stage manner along the axial direction within the housing flow path  10   c , and the steam injected from a rotor in the previous stage toward the outer circumference of each of the rotors  200  is introduced into a center of a rear rotor through the housing flow path  10   c . In the present embodiment, the rotor  200  includes four, i.e., first-stage, second-stage, third-stage, and four-stage rotors  210 ,  220 ,  230 , and  240 . The four, i.e., first-stage, second-stage, third-stage, and four-stage rotors  210 ,  220 ,  230 , and  240  are disposed along the axial direction. 
         [0032]    First and second rotors  211  and  212  of each of the first-stage, second-stage, third-stage, and four-stage rotors  210 ,  220 ,  230 , and  240  are coupled together in the axial direction to form an integrated rotor. Hereinafter, configurations of the four, i.e., first-stage, second-stage, third-stage, and four-stage rotors  210 ,  220 ,  230 , and  240  in which they each include first and second rotor plates  211  and  212 , are similar. Thus, the first rotor plate  211  and the second rotor plate  212  of the first-stage rotor  210  will be described. 
         [0033]      FIG. 2  is an enlarged view of a portion A of  FIG. 1 .  FIG. 3  is a plan view of a first rotor plate illustrated in  FIG. 1 .  FIG. 4  is a cross-sectional view taken along a line B-B of  FIG. 2 . 
         [0034]    Referring to  FIGS. 2 through 4 , the first rotor plate  211  has a disc shape, and a first boss portion  211   b  is formed in the center of the first rotor plate  211  and protrudes toward the housing inlet  10   a  and constitutes a rotor introduction portion  201  into which the steam that is the working fluid is introduced, together with a second boss portion  212   b  that will be described later. A first flow path  211   a  is formed at a rear surface of the first rotor plate  211 , i.e., at a surface that faces the second rotor plate  212 . Since the shape of the first flow path  211   a  corresponds to the shape of a second flow path  212   a  that will be described later, the second flow path  212   a  will be described with reference to  FIG. 3 . 
         [0035]    A first nozzle portion  211   c  having a smaller cross-sectional area than that of a discharge side of the first flow path  211   a  is formed at the discharge side of the first flow path  211   a . That is, referring to  FIG. 2 , the first nozzle portion  211   c  is formed as a groove having a smaller radius than that of the first flow path  211   a  and thus increases flow velocity of the discharged fluid. The first nozzle portion  211   c  is limited to having the shape of the groove formed in the first rotor plate  211 . However, embodiments of the present invention are not limited thereto, and additional nozzles each having a small radius part may be installed in the first nozzle portion  211   c.    
         [0036]    The first rotor plate  211  may be manufactured using a casting method, and the first flow path  211   a  may be formed when a casting work is performed and may be finished using a ball end mill. Of course, embodiments of the present invention are not limited thereto, and the first flow path  211   a  may be manufactured in any one of methods, whereby a groove may be formed in a surface from the first rotor plate  211  to the second rotor plate  212 . Also, in the present embodiment, the first rotor plate  211  is finished using the ball end mill. However, embodiments of the present invention are not limited thereto, and the first rotor plate  211  may not be finished or may be finished using a different method. When the first nozzle portion  211   c  is finished, a ball end mill having a smaller diameter than that of the ball end mill used to form the first flow path  211   a  is used. 
         [0037]    The second rotor plate  212  has a disc shape, and the second boss portion  212   b  is formed on an inner circumferential surface of the second rotor plate  212  so that the rotation shaft  20  can be coupled to the second rotor plate  212 . A shaft insertion hole  212   d  into which the rotation shaft  20  is inserted, is formed in the second boss portion  212   b , and a key hole  212   e  into which a key of the rotation shaft  20  is inserted, is formed in an inner circumferential surface of the shaft insertion hole  212   d . An outer circumferential surface of the second boss portion  212   b  and an inner circumferential surface of the first boss portion  211   b  constitute the rotor introduction portion  201 . A second flow path  212   a  is formed on the entire surface from the second rotor plate  212  to the first rotor plate  211 . Referring to  FIG. 3 , the second flow path  212   a  is formed to guide the working fluid introduced from the rotor introduction portion  201  outwards. That is, the second flow path  212   a  extends from an outer circumferential surface of the rotor introduction portion  201  and is formed to be close to a circumferential direction from the outer circumferential surface of the second rotor plate  212 . 
         [0038]    A second nozzle portion  212   c  having a smaller cross-sectional area than that of a discharge side of the second flow path  212   a  is formed at the discharge side of the second flow path  212   a . That is, the second nozzle portion  212   c  is formed as a groove having a smaller radius than that of the second flow path  212   a  and increases flow velocity of the discharged fluid. The second nozzle portion  212   c  is limited to having the shape of the groove formed in the second rotor plate  212 . However, embodiments of the present invention are not limited thereto, and of course, additional nozzles each having a small radius part may be installed in the second nozzle portion  212   c.    
         [0039]    The second rotor plate  212  may be manufactured using a casting method, like in the first rotor plate  211 . The second flow path  212   a  may be formed when a casting work is performed and may be finished using a ball end mill. Of course, embodiments of the present invention are not limited thereto, and the second flow path  212   a  may be manufactured in any one of methods, whereby a groove may be formed in a surface from the second rotor plate  212  to the first rotor plate  211 . Also, in the present embodiment, the second rotor plate  212  is finished using the ball end mill. However, embodiments of the present invention are not limited thereto, and the second rotor plate  212  may not be finished or may be finished using a different method. When the second nozzle portion  212   c  is finished, a ball end mill having a smaller diameter than that of the ball end mill used to form the second flow path  212   a  is used. 
         [0040]    When the first rotor plate  211  and the second rotor plate  212  are coupled to each other in the axial direction, the first flow path  211   a  and the second flow path  212   a  are symmetrical with respect to each other based on a surface on which the first and second rotor plates  211  and  212  are coupled together, and constitute one inner flow path  202 . That is, the first flow path  211   a  and the second flow path  212   a  have cross sections that are symmetrical with respect to each other based on the surface on which the first and second rotor plates  211  and  212  are coupled together. In the present embodiment, a cross section of each of the first flow path  211   a  and the second flow path  212   a  is formed into a semicircular shape. As the cross section of each of the first flow path  211   a  and the second flow path  212   a  is formed into the semicircular shape, when the first and second flow paths  211   a  and  212   b  are combined with each other, the inner flow path  202  has a circular cross section. However, embodiments of the present invention are not limited thereto, and the cross-sectional shape of the inner flow path  202  is a circular shape, wherein the cross sections of the first and second flow paths  211   a  and  212   a  may not be symmetrical with respect to each other. Also, the cross sections of the first and second flow paths  211   a  and  212   a  are symmetrical with respect to each other and constitute an arc shape (not the semicircular shape) or have rounded edges so that pressure loss of the working fluid can be reduced. 
         [0041]    The rotor  210  having the above configuration includes first and second rotor plates  211  and  212 , and the first and second flow paths  211   a  and  212   a  formed in the first and second rotor plates  211  and  212  are combined with each other and constitute one inner flow path  202 . Thus, the cross-sectional shape of the inner flow path  202  may be a circular shape so that the pressure loss of the working fluid is minimized and performance of the turbine can be enhanced. 
         [0042]    An operation of the reaction turbine having the above configuration according to an embodiment of the present invention will be described as below. 
         [0043]    When high-pressure steam generated in a boiler is supplied to the housing inlet  10   a  of the housing  10  through a pipe, the steam is introduced into the rotor introduction portion  201  of the first-stage rotor  210  in the axial direction. The steam introduced into the rotor introduction portion  201  in the axial direction is distributed into a plurality of inner flow paths  202 . The distributed steam passes through the plurality of inner flow paths  202 , is moved toward an outer circumference side of the first-stage rotor  210 , and is injected toward the housing flow path  10   c  at high velocity along a circumferential direction of the rotor  200 . 
         [0044]    The steam injected toward the outer circumference side of the first-stage rotor  210  is introduced into the center of the second-stage rotor  220  disposed in the rear of the first-stage rotor  210 , and the steam introduced into the second-stage rotor  220  passes through the inner flow paths  202  and is injected toward the outer circumference side of the second-stage rotor  220 . The steam injected toward the outer circumference side of the second-stage rotor  220  is introduced into the center of the third-stage rotor  230 , passes through the inner flow paths  202  and then is injected toward an outer circumference side of the third-stage rotor  230 . The steam injected toward the outer circumference side of the third-stage rotor  230  is introduced into the center of the fourth-stage rotor  240 , passes through the inner flow paths  202  and then is injected toward an outer circumference side of the fourth-stage rotor  240 . The steam injected toward the outer circumference side of the fourth-stage rotor  240  is discharged to an outer portion of the housing  10  through the housing outlet  10   b . The steam discharged to the outer portion of the housing  10  is discharged in the air or is recovered by a steam condenser (not shown) and then is circulated in the boiler. This operation is repeatedly performed. 
         [0045]    The first-stage, second-stage, third-stage, and fourth-stage rotors  210 ,  220 ,  230 , and  240  rotate by a reaction generated when the high-pressure steam is injected in the circumferential direction. A rotational force generated in this case is transferred to the rotation shaft  20  to which the first-stage, second-stage, third-stage, and fourth-stage rotors  210 ,  220 ,  230 , and  240  are coupled. When the rotation shaft  20  rotates together with the first-stage, second-stage, third-stage, and fourth-stage rotors  210 ,  220 ,  230 , and  240 , the rotational force is transferred to the outside. 
         [0046]    In the reaction turbine having the above-described configuration, cross sections of the inner flow paths  202  through which the steam passes, have circular shapes. Thus, the pressure loss of the working fluid that passes through the inner flow paths  202  is reduced so that performance of the turbine can be enhanced. 
         [0047]      FIG. 5  is a cross-sectional view of a part of first and second rotor plates according to a second embodiment of the present invention.  FIG. 6  is a cross-sectional view taken along a line C-C of  FIG. 5 . 
         [0048]    A rotor  310  according to the second embodiment of the present invention includes first and second rotor plates  311  and  312 . The rotor  310  according to the second embodiment of the present invention is different from the rotor  200  according to the first embodiment in that inner flow paths  302  are formed only on a surface of a second rotor plate  312  toward a first rotor plate  311 , and the difference will be described in detail. 
         [0049]    The first rotor plate  311  has a disc shape, and a first boss portion  311   a  is formed in the center of the first rotor plate  311 , protrudes toward the housing inlet  10   a  and constitutes a rotor introduction portion  201  into which steam that is the working fluid is introduced, together with a second boss portion  312   a  that will be described later. 
         [0050]    The second rotor plate  312  has a disc shape, and the second boss portion  312   a  is formed on an inner circumferential surface of the second rotor plate  312  so that a rotation shaft  20  can be coupled to the second rotor plate  312 . An outer circumferential surface of the second boss portion  312   a  and an inner circumferential surface of the first boss portion  311   a  constitute a rotor introduction portion  201 . The inner flow paths  302  are formed on a front surface of the second rotor plate  312  toward the first rotor plate  311 . The inner flow paths  302  may have various cross-sectional shapes. Thus, in the present embodiment, the inner flow paths  302  have rectangular cross-sectional shapes. The inner flow paths  302  are formed in such a way that the surface toward the first rotor plate  311  is formed to be opened, and the inner flow paths  302  are covered by the first rotor plate  311 . The second rotor plate  312  is manufactured using a casting method, and the inner flow paths  302  are formed when a casting work is performed. Of course, embodiments of the present invention are not limited thereto, and the inner flow paths  302  may be manufactured in any one of methods, whereby a groove may be formed in a surface from the second rotor plate  312  to the first rotor plate  311 . Also, in the present embodiment, the inner flow paths  302  are not separately finished. However, embodiments of the present invention are not limited thereto, and the inner flow paths  302  may be finished so that their edges may be rounded so that the pressure loss of the working fluid can be reduced. 
         [0051]    A nozzle portion  303  having a smaller cross-sectional area than that of the inner flow path  302  is formed at a discharge side of the inner flow path  302 . 
         [0052]    The rotor  410  having the above configuration includes the second rotor plate  312  in which the inner flow paths  302  are formed, and the first rotor plate  311  that covers the inner flow paths  302 . As the rotor  310  includes first and second rotor plates  311  and  312 , the inner flow paths  302  may be formed in various shapes. The inner flow paths  302  are formed only on the second rotor plate  312  so that a structure of the rotor  310  is simplified and a forming work and time can be reduced. 
         [0053]      FIG. 7  is a cross-sectional view of a part of first and second rotor plates according to a third embodiment of the present invention.  FIG. 8  is a cross-sectional view taken along a line D-D of  FIG. 7 . 
         [0054]    A rotor  410  according to the third embodiment of the present invention includes first and second rotor plates  411  and  412 . The rotor  410  according to the third embodiment of the present invention is different from that rotor  310  according to the second embodiment of the present invention in that inner flow paths  402  are formed only on a surface of the second rotor plate  412  toward the first rotor plate  411 , wherein cross-sectional shapes of the inner flow paths  402  are semicircular shapes. The difference will be described in detail. 
         [0055]    The first rotor plate  411  has a disc shape, and a first boss portion  411   a  is formed in the middle of the first rotor plate  411  and protrudes toward a housing inlet  10   a . The first boss portion  411   a  constitutes a rotor introduction portion  201  into which steam that is a working fluid is introduced, together with a second boss portion  312   a  that will be described later. 
         [0056]    The second rotor plate  412  has a disc shape, and a second boss portion  412   a  is formed on an inner circumferential surface of the second rotor plate  412  so that a rotation shaft  20  can be coupled to the second rotor plate  412 . An outer circumferential surface of the second boss portion  412   a  and an inner circumferential surface of the first boss portion  411   a  constitute the rotor introduction portion  201 . The inner flow paths  402  are formed on a front surface of the second rotor plate  412  toward the first rotor plate  411 . Cross sections of the inner flow paths  402  may have various shapes. Thus, in the present embodiment, the inner flow paths  402  have semicircular cross sections. The second rotor plate  412  may be manufactured using a casting method, and the inner flow paths  402  may be formed when a casting work is performed and may be finished using a ball end mill. Of course, embodiments of the present invention are not limited thereto, and the inner flow paths  402  may be manufactured in any one of methods, whereby a groove is formed in a surface from the second rotor plate  412  to the first rotor plate. Also, in the present embodiment, the inner flow paths  402  may be finished using the ball end mill. However, embodiments of the present invention are not limited thereto, and the inner flow paths  402  may not be finished and may also be finished using a different method. 
         [0057]    A nozzle portion  403  having a smaller cross-sectional area than that of the inner flow path  402  is formed at a discharge side of the inner flow path  402 . The cross-sectional shape of the nozzle portion  403  may be a semicircular shape, and the nozzle portion  403  may be finished using a ball end mill having a smaller diameter than that of the ball end mill used to finish the inner flow path  402 . 
         [0058]    The rotor  410  having the above configuration includes the second rotor plate  412  in which the inner flow paths  402  are formed, and the first rotor plate  411  that covers the inner flow paths  402 . As the rotor  410  includes the first and second rotor plates  411  and  412 , the inner flow paths  402  may be formed in various shapes, and the inner flow paths  402  are formed only on the second rotor plate  412  so that a structure of the rotor  410  is simplified and a forming work and time can be reduced. Also, as the cross section of the inner flow path  402  is formed into a semicircular shape, pressure loss of a working fluid can be reduced. 
         [0059]      FIG. 9  is a plan view of a first rotor plate according to a fourth embodiment of the present invention.  FIG. 10  is a cross-sectional view taken along a line E-E of  FIG. 9 . 
         [0060]    A rotor according to the fourth embodiment of the present invention includes first and second rotor plates  511  and  512 . First and second flow paths  510  and  502  are formed on surfaces of the first and second rotor plates  511  and  512  that face each other, and the first and second flow paths  510  and  502  are combined with each other and constitute one inner flow path  520  that guides the working fluid. The rotor according to the fourth embodiment of the present invention is different from the above embodiments in that at least a part of the first and second flow paths  510  and  502  has an involute curve shape. The difference will be described in detail. Hereinafter, shapes of the first and second flow paths  510  and  502  formed on the surfaces of the first and second rotor plates  511  and  512  that face each other, are similar, and thus, the second rotor plate  512  will be described. 
         [0061]    As the second flow path  502  formed at the second rotor plate  512  has an involute curve shape, a change in directions of flow paths is gentle so that a pressure drop of steam caused by the change in the directions of flow paths can be reduced. An outer circumferential surface of the second flow path  502  is connected to an outer circumferential surface  501   a  of a circle that constitutes the rotor introduction portion  501  so as to constitute at least one arc shape. A radius r 2  of an arc  505  is greater than an inner diameter r 1  of the rotor introduction portion  501 . Also, a radius of a basic circle of an involute curve that constitutes the second flow path  502  is set to be smaller than the inner diameter r 1  of the rotor introduction portion  501 . 
         [0062]    A nozzle portion  503  having a smaller cross-sectional area than that of a discharge portion  502   b  of the second flow path  502  is installed at the discharge portion  502   b  of the second flow path  502 . The nozzle portion  503  is disposed in an extension line of the second flow path  502 , and the second flow path  502  and the nozzle portion  503  are placed in the same involute curve. Velocity energy and pressure energy of steam discharged by the nozzle portion  503  increase so that the steam can be injected at high velocity. However, embodiments of the present invention are not limited thereto, and additional nozzles each having a small radius may also be installed at the discharge portion  502   b  of the second flow path  502  using a fastening member. 
         [0063]    The second flow path  502  and the first flow path  510  have cross sections that are symmetrical with respect to each other based on a surface on which the first and second rotor plates  511  and  512  are coupled together. 
         [0064]    In the present embodiment, referring to  FIG. 10 , cross-sectional shapes of the first flow path  510  and the second flow path  502  are semicircular shapes. As the cross-sectional shapes of the first flow path  510  and the second flow path  502  are semicircular shapes, when the first and second flow paths  510  and  502  are combined with each other, the inner flow path  520  has a circular cross section. However, embodiments of the present invention are not limited thereto, and the cross-sectional shape of the inner flow path  520  is a circular shape, wherein the cross sections of the first and second flow paths  510  and  502  are symmetrical with respect to each other. Also, the cross sections of the first and second flow paths  510  and  502  are symmetrical with respect to each other and constitute an arc shape (not the semicircular shape), or edges of the first and second flow paths  510  and  502  may be formed to be rounded so that the pressure loss of the working fluid can be reduced. 
         [0065]    In the reaction turbine having the above configuration, each of the first and second flow paths  510  and  502  through which steam passes, has an involute curve shape. Thus, a change in flow paths of the steam that is guided from the center to an outer circumferential side of the turbine and is injected in a circumferential direction, is gentle so that the pressure loss can be reduced and performance of the turbine can be enhanced. 
         [0066]    While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. 
         [0067]    By using the present invention, a reaction turbine in which components can be shared so that a turbine having various capacities can be manufactured and pressure loss that occurs when a working fluid flows, is minimized so that performance of the turbine can be enhanced, can be manufactured.
A reaction turbine, according to the present invention, includes first and second rotor plates, which are coupled together to form an integrated rotor, and an inner flow path including a combination of first and second flow paths, which are formed on the surfaces of the first and second rotor plates that face each other, respectively, thereby enabling easier manufacturing into a form desired by a designer by eliminating the limitation of a cross-sectional shape of the inner flow path. In addition, a cross section of each of the first and second flow paths can be formed into a semicircular shape thus yielding a circular shape for the inner flow path, which is formed by combining the first and second flow paths, thereby effectively enhancing the performance of a turbine by minimizing pressure loss of a working fluid that passes through the inner flow path.