AXIAL FLOW TURBINE TYPE ROTOR MACHINE FOR ELASTIC FLUID OPERATION

Abstract: An axial flow turbine machine intended for elastic fluid operation comprises a rotor (11) with two or more sections (26, 27) each carrying an array of radially directed drive blades (24; 64), and a stator (10) having a number of fluid inlet nozzles (12) and one or more sections (15) each carrying a circumferential array of guide vanes (14; 54) for directing motive fluid onto the drive blades (24; 64), wherein a flow path (30; 60) is formed between every two adjacent drive blades (24; 64) in each rotor section (26, 27) and a flow path (29; 59) is formed between every two adjacent guide vanes (14; 54) in each stator section (15), and a widened section (F, E) is provided between the entrance section (A, C) and the exit section (B, D) of each one of the rotor section flow paths (30; 60) and the stator section flow paths (29; 59), such that the radial distance between the inner flow path defining surface (28) and the outer flow path defining surface (18) is larger in the widened section (F, E) than in the exit section (B, D).

Description: Δxi_aJ flow turbine type rotor machine for el stic fluid operation. The invention relates to an axial flow turbine type rotor machine which is intended for elastic fluid operation and which comprises a rotor having one or more axially spaced sections each comprising a circumferential array of radially extending drive blades, and a stator having two or more axially spaced sections each comprising a circumferential array of radially extending guide vanes, wherein each one of the stator sections is located on opposite sides of the rotor sections, a flow path is formed between every two adjacent drive blades in each rotor section, and between every two adjacent guide vanes in each stator section, each one of the flow paths has a certain length and extends between an entrance region and an exit region. Turbine type machines of this type, for instance gas turbines of the above referred type have in general a limited efficiency due to flow losses in the flow paths of the rotor and the stator. Big gas turbine motors, having a power output of some thousand kilowatts, often reach a maximum efficiency of above 90 %. Mid size gas turbines motors, however, having a power output up to a few hundred kilowatts, reach a maximum efficiency of no more than 85 %. This is considered to be too low efficiency for making gas turbines in this size range interesting for certain application. It is the main object of the invention to accomplish an axial flow turbine type rotor machine for elastic fluid operation, wherein the flow losses through the rotor and stator flow paths are substantially reduced and the efficiency of the turbine is substantially increased. Characteristic features as well as further advantages of the invention will appear from the following detailed description of preferred embodiments of the invention and from the accompanying drawings . On the drawings : Fig. 1 shows a longitudinal section through a turbine machine according to the invention. Fig. 2 shows schematically a spread-out view of a number of drive blades of one rotor section and a number of guide vanes of one stator section of the turbine machine in Fig. 1. Fig. 3 shows, on a larger scale, a detail view of one guide vane and one drive blade of a turbine machine according to one embodiment of the invention. Fig. 4 shows a detail view of a drive blade / guide vane arrangement in a turbine machine according to another embodiment of the invention. Fig. 5 shows a spread-out view of the drive blade / guide vane arrangement shown in Fig . 4. Fig. 6 shows a drive blade / guide vane arrangement according to still another embodiment of the invention. The turbine machine examples described below in detail are suitable mainly as a gas turbine motors. Looking first at the example shown Fig. 1, the turbine machine comprises a stator housing 10 and a rotor 11. The stator housing 10 is of a mainly cylindrical shape and provided at its one end with a number of gas inlet nozzles 12 communicating with a gas inlet 16 and a funnel shaped outlet diffusor 13 at its opposite end. The stator housing 10 is also provided with a number of guide vanes 14 which are arranged in an annular section 15 and forming a circumferential array. The guide vanes 14 are mounted on an inner ring structure 17 and are supported by their outer ends against a mainly cylindrical surface 18 of the stator housing 10. The ring structure 17 is received in a peripheral space 19 in the rotor 11 and is arranged to sealingly co-operate with a cylindrical waist portion 20 on the rotor 11. The rotor 11 comprises an forward part 22 and a rear part 23 and is journalled relative to the stator housing 10 by two bearings which, however, are not illustrated. The rotor 11 comprises two axially spaced operating sections 26, 27 each carrying a circumferential array of drive blades 24. These two sections 26, 27 are separated by the stator section 15. An inner surface 28 formed by the rotor sections 26,27 as well as the stator ring 17 tapers slowly towards the outlet diffusor 13 so as to make the gas flow expand as it passes through the turbine. Between two adjacent guide vanes 14 in each array there is formed a stator flow path 29 having an entrance region A with a distance S A between adjacent guide vanes 14 and an exit region B with a distance S B between the guide vanes 14. See Fig. 2. Both distances S A and S B are measured transversely to the flow path 29. As clearly illustrated in Fig. 2, the distance S A is considerably bigger than distance S B which means that the area of the flow path 29 generally decreases from the entrance region A to the exit region B . In a similar way, two adjacent drive blades 24 in each array define a rotor flow path 30 in which the width S c at the entrance region C is larger than the width S D at the exit region D, which means that each rotor flow path 30 has a decreasing area towards the exit region D. As illustrated in Fig. 3, the rotor flow path 30 comprises a radially widened region F located between the entrance region C and the exit region D. In the described example, this widened region F is formed by a concave portion 31 in the inner surface 28. In this widened region F the radial extent R F of the drive blade 24 is larger than the radial extent R D of the drive blade 24 in the exit region D. This means that the cross sectional area of the flow path 29 is kept up in size close to the exit region D, which results in a lower gas velocity upstream of the exit region D and, hence, lower flow losses in the flow path 30. A similar arrangement is provided in each stator flow path 29 where a concave portion 32 is located in the ring structure 17 between the entrance region A and the exit region B and forms a widened region E. The radial extent of the guide vane 14 is larger in the widened region E than in the exit region B. It should be observed that the ring structure 17 is received in the waist portion 20 of the rotor 11. In Fig. 3, it is clearly shown that the concave portion 31 in the rotor 11 forms a radially widened region F in which the radial extent R F of the drive blade 24 is larger than the radial extent R D in the exit region D. The radial extent R c in the entrance region C is even smaller than the radial extent R D in the exit region D. The arrangement of radially widened regions E and F in the stator flow paths 29 and rotor flow paths 30, respectively, are effective in keeping down the fluid flow velocity through the flow paths 29,30 and, thereby, the flow losses. The radial extent of the drive blades 24 and the guide vanes 14 should be at least 5% larger in the widened regions E, F than in the exit regions B, D of the flow paths 29, 30 for obtaining a positive effect. In order to get a significant increase of the turbine efficiency, though, the difference in radial extent should be considerably larger than that. However, the percentage of increase of the drive blade / guide vane radial extent in the widened regions depends on the relationship between the radial extent and the length of the respective drive blade or guide vane, such that a drive blade or guide vane having a short length but a large radial extent must be combined with a relatively smaller concave portion so as to avoid too large and abrupt area changes of the flow paths . Employment of radially widened flow path regions according to the invention is particularly beneficial at turbines having drive blades and guide vanes with a small radial extent and a considerable length. In such turbines the radial extent of the drive blades and guide vanes in the widened regions may be 10-20% larger than the radial extent thereof in the exit regions . According to the invention, the radially widened regions of the flow paths through the rotor sections as well as the stator sections shall extend over at least 60%, preferably 80% of the flow path length, such that the fluid flow velocity is kept down during the main part of the flow path length. A low flow velocity gives low internal flow losses. At the very end of the flow paths, there is a reduction in cross sectional area which results in a rapid acceleration of the fluid flow. In order to further reduce the internal flow losses and increase the efficiency of the turbine machine, the embodiment of the invention shown in Figs. 4, 5 and 6 comprises a drive blade / guide vane arrangement where not only radially widened regions are employed between the flow path entrance regions and exit regions but also overlapping between the stator sections and the rotor sections is an essential part of the flow loss reduction. In the embodiment of the invention illustrated in Figs. 4 and 5, there are shown two stator sections with arrays of guide vanes 54, and one rotor section with an array of drive blades 64. Between two adjacent guide vanes 54 there is a fluid flow path 59 which has an entrance region A and an exit region B, and between adjacent drive blades 64 there are flow paths 60 each having an entrance region C and an exit region D. Between the entrance region A and exit region B of each stator flow path 54 there is a radially widened region E, and between the entrance region C and the exit region D of each rotor flow path 60 there is a radially widened region F. As in the previously described example, the distances between adjacent guide vanes 54 are characterized by a relatively large distance S A in the entrance region A and a relatively small distance S B in the exit region B. The distance between the guide vanes 54 decreases successively along the flow path 59, but due to an increased radial extent of the guide vanes 54 in the widened region E the cross sectional area of the flow path is kept up in size to a point close to the exit region B. Accordingly, each guide vane 54 has radial extent R E in the widened region E which is larger than the radial extent R B in the exit region B. In a similar way, the distance between adjacent drive blades 64 decreases successively from a large distance S c in the entrance region C to a small distance S D in the exit region D. The radial distance R F in the widened region F, however, is larger than the radial distance R D in the exit region D, which means that the cross sectional area of the flow path 60 is kept up in size in the flow direction to a point close to the exit region D. This means in turn that the flow velocity is kept low during the main part of the flow path 60 and is accelerated over a very short distance in the exit region D. As described above in connection with the previous embodiment of the invention, the inner boundary of the flow paths through the stator end the rotor sections is defined by an inner surface 28. This inner surface 28 is formed by CO a σ TJ rt CO t μ- rt rt 01 > CD rt φ Φ 1£> 0 l-T CO f- O a t ti Ω Φ tr Ω Ω - li 0) ti rt ) 0 ) Ω Ω Ω φ rr ? rt rt 0 ) Hi O rt μ- μ- o tr ft μ- H- TJ 0J ti tr ti 0 ) μ- li 0 TJ a j 0 H- TJ Ω Φ μ- μ- H O O 3 0 Φ a co φ φ CO a a μ- 0 ) a rt ti ti PJ φ Hi IP id a Ω CD O TJ rr CΛ Hi ti t Ω IP rt ti i H- 0 CD O CO CD rt 0 Φ Φ Φ μ» ti 0 Ml H . μ- s; a a rt li in CD rt a Hi 3 Hi O P. P, O μ- φ CO rt o li s a P< co rt Ω σ> tr 0 o CO μ- TJ TJ rt μ- O rt 0 U1 Φ 3 ti 0 0 tr a CQ μ- Hi 0 rr Φ rt Φ ϋ ti μ- IP Φ O Ω s; ^ * i O tr Ω rt rt D rt rt H a 0 Φ H- < 1 rt μ- μ- Hi tr CO tr a a 01 ω Φ ft μ- 0 O Φ Φ φ Φ < • ti O a a 3 ) ti ISJ 01 Φ H- ti ^ Hi a CD CO ζj" rt • σi H- X a 0 φ> 0 O C - a CO rt - rt ti rr in σi ^ H to a H- TJ Hi 0 tr 3 Φ t to μ- Φ I Φ 3 0 1— ' H rt Φ ^ 3 H- ti 0 a- TJ 0 O O φ O 0 ) rt Ξ CD Φ 0J a Hi Hi a Hi a O J H- φ Φ t P. rt P. C i 0 P. Ω TJ ) rt rt rt rt ti a H- rt o P. CO rt a ^ tr o tr Hi rr = > i H- H μ- tr Φ Φ Hi Φ ^ 0 ) 0 ) C Φ O rt 3 rt 0 Ω CD Ω ^ a H- ID. tr CO iQ p. ft CO rt Φ rt 0 Φ φ C li tr rt tr H- H- Ω a Φ μ- μ- Φ J Φ K) φ CQ 0 o P, μ- TJ P. < rt CD 0) a 3 0 a 0J Φ φ μ- O CD Ω TJ TJ Hi Φ a ti a t rt Ω - J rr li CD Φ rt rr < 0) 0 ti ^ H- rt ti CD 0 ) Φ PJ rt 3 0 ft co tr σi a 0 ) a a O TJ a 1— ' Φ Φ ω Hi O Φ α rt ti ti Φ > 0J CO Hi CO Φ μ- H- H- O 0 CO O ti CO CO 0 Hi Ω 0) a Hi s: rt in a 0 Φ Φ l-h 0 0 a ^ j^ CT\ rt Ω CO ii a Ω Φ rt TJ Φ J^ μ- 0 rt 3 Ω O H tr 0 ) i CD ti μ- 01 j cu a Φ rt CD H 0 ) O φ P, < <! O tr rt Φ a rt CD a Ω φ φ c 0 ) IT Φ 0 CO rr X H ti p. rt Φ 0 ) Ω o a rt ^ TJ Hi μ- Φ O X rt rt ti <! 0 ) 0 0 ) <! Hi ti rt μ- Φ rr rt ti Ω φ μ- Φ O X 0 tr rt Φ a t Φ H- μ- a a a O to 3 P- Φ a CD iQ portion 58 and a concave portion 59, whereof the convex portion 58 is partly formed by the neck portion 55. It also appears from Fig. 4 that in this embodiment of the invention the outer surface 18 which defines the flow paths 29, 30 is substantially cylindrical in shape, which means that all variations in the cross sectional areas of the flow paths are accomplished by the convex and concave portions on stator and rotor section parts of the inner surface 28. In Fig. 6 there is illustrated an alternative design of the inner and outer flow path defining surfaces 18, 28. Instead of locating all of the convex and concave portions on the inner surface 28, the outer surface 18 of this alternative is formed with convex and concave portions which are located opposite the convex and concave portions 58,57,68,69 on the inner surface 28. By this arrangement there is obtained further possibilities to give the flow paths optimum shapes in order to improve the fluid flow characteristics through the turbine. Still an alternative design would be to have cylindrical inner surface 18 and locating all of the convex and concave portions 58,57,68,69 on the outer surface 18.

Claims: Cl a i ms . 1. Axial flow turbine type rotor machine for elastic fluid operation, including a rotor (11) having one or more axially spaced sections (26,27) each comprising a circumferential array of radially extending drive blades (24,-64), a stator (10) having two or more axially spaced sections (15) each comprising a circumferential array of radially extending guide vanes (14; 54), each one of said stator sections (15) is located on opposite sides of said one or more rotor sections (26,27) , a rotor section flow path (30; 60) is formed between every two adjacent drive blades (24) m each rotor section (26,27), said rotor flow path (30;60) has a certain length (H) , a rotor section entrance region (C) and a rotor section exit region (D) , a stator section flow path (29 ;59) is formed between every two adjacent guide vanes (14,-54) m each stator section (15), said stator flow path (29;59) has a certain length (G) , a stator section entrance region (A) and a stator section exit region (B) , c h a r a c t e r i z e d m that m each rotor section flow path (30; 60) said rotor section entrance region (C) has a larger cross sectional area than said rotor section exit region (D) , and m each stator section flow path (29; 59) said stator section entrance region (A) has a larger cross sectional area than said stator section exit region (B) , each rotor section flow path (30; 60) has a substantially constant cross sectional area downstream from said rotor section entrance region (C) over at least 75% of said rotor section flow path length (H) , and each stator section flow path (29; 59) has a substantially constant cross sectional area downstream from said stator section entrance region (A) over at least 75% of said stator section flow path length (G) . 2. Turbine machine according to claim 1, wherein said constant cross sectional area of each stator section flow path (29; 59) extends over at least 60% of said stator section flow path length (G) , and said constant cross sectional area of each rotor section flow path (30; 60) extends over at least 60% of said rotor section flow path length (H) . 3. Turbine machine according to claim 2, wherein said constant cross sectional area of each stator section flow path (29; 59) extends over at least 80% of said stator section flow path length (G) , and said constant cross sectional area of each rotor section flow path (30; 60) extends over at least 80% of said rotor section flow path length (H) . 4. Turbine machine according to claim 1, wherein said drive blades (24; 64) and said guide vanes (14; 54) extend radially between a substantially rotation symmetric inner surface (28) and a substantially rotation symmetric outer surface (18) , each one of said rotor section flow paths (30; 60) has a radially widened region (F) located between said entrance region (C) and said exit region (D) , each one of said drive blades (24; 64) has a radial extent (R F ) in said widened region (F) that is larger than the radial extent (R D ) of said drive blade (24;64)in said exit region (D) , and each one of said stator section flow paths (29; 59) has a radially widened region (E) located between said entrance region (A) and said exit region (B) , each one of said guide vanes (14; 54) has a radial extent (R E ) in said widened region (E) that is larger than the radial extent (R B ) of said guide vane (14; 54) in said exit region (B) . 5. Turbine machine according to claim 4, wherein said inner surface (28) is formed partly by said rotor sections (26,27) and partly by said stator sections (15), said trailing part (62) of each drive blade (64) in each one of said rotor sections (26,27) extends beyond, in the fluid flow direction, that part of said inner surface (28) which is formed by the respective rotor section (26,27), said part of said inner surface (28) formed by each stator section (15) extends beyond said guide vanes (54) in the direction opposite the fluid flow direction, thereby forming an annular stator section neck portion (55) on the respective stator section (15) , wherein said trailing part (62) of each drive blade (64) on one of said rotor sections (26,27) extends over said stator section neck portion (55) of a following stator section (15) in the fluid flow direction, said trailing part (52) of each guide vane (54) in each one of said stator sections (15) extends axially beyond, in the fluid flow direction, that part of said inner surface (28) formed by the respective stator section (15) , said part of said inner surface (18) formed by each rotor section (26,27) extends beyond said drive blades (64) in the direction opposite said fluid flow direction, thereby forming an annular neck portion (65) on the respective rotor section (26,27), whereby said trailing parts (52) of said guide vanes (54) on one of said stator sections (15) extend over said rotor section neck portion (65) of a following rotor section (26,27) in the fluid flow direction. 6. Turbine machine according to claim 5, wherein said exit region (D) of each one of said rotor flow paths (60) is formed by said trailing parts (62) of two adjacent drive blades (64) , and said exit region (B) of each one of said stator flow paths (59) is formed by said trailing parts (52) of two adjacent guide vanes (54) . 7. Turbine machine according to claim 5, wherein on each rotor section (26,27) said inner surface (28) comprises a convex portion (68) followed in the fluid flow direction by a concave portion (69) , said convex portion (68) extends beyond said drive blades (64) in a direction opposite the fluid flow direction, thereby forming said rotor section neck portion (65) . 8. Turbine machine according to claim 5, wherein on each stator section (15) said inner surface (28) has a convex portion (58) followed in the fluid flow direction by a concave portion (57), said convex portion (58) extends beyond said guide vanes (54) in the direction opposite the fluid flow direction, thereby forming said stator section neck portion (55) . 9. Turbine machine according to anyone of claims 4 - 8, wherein said outer surface (18) is formed with two or more annular rotor flow regions each axially coinciding with one of said rotor sections (26,27), and each one of said rotor flow regions comprises a convex portion (88) followed in the fluid flow direction by a concave portion (89) . 10. Turbine machine according to anyone of claims 4 - 9, wherein said outer surface (18) is formed with one or more annular stator flow regions each coinciding with one of said stator section (15) , and each one of said stator flow regions comprises a convex portion (86) followed in the fluid flow direction by a concave portion (87) . 11. Turbine machine according to anyone of claims 1 - 10, wherein each drive blade (24; 64) has a maximum radial extent (R F ) which is equal to or smaller than the length (H) of each drive blade (24; 64) in the fluid flow direction. 12. Turbine machine according to anyone of claims 1 - 10, wherein each guide vane (14; 54) has a maximum radial extent (R E ) which is equal to or smaller than the length (G) of each guide vane (14; 54) in the fluid flow direction.

Inventors: JACOBSSON ROLF ALEXIS, JACOBSSON, ROLF, ALEXIS
Applicants: ATLAS COPCO TOOLS AB, JACOBSSON ROLF ALEXIS, JACOBSSON, ROLF, ALEXIS
Application year: 2000
Main classification: F01D5
IPC codes: F01D5, F01D9