HYDRAULIC TURBINE

Abstract: Hydraulic turbine, in particular for small power plants, with a substantially axial water flow therethrough and comprising a stator (5, 11) having guide vanes (5) and a turbine wheel (6, 13) of the propeller type, followed by a discharge part (3a, 3b). The guide vanes (5) are adapted to give the water flow a significant rotational component about the turbine wheel axis, and between the stator (5, 11) and the turbine wheel (6, 13) there is provided a convergent intermediate part (2, 7) of such long length that the water flow fulfills at least three complete rotations from the stator to the turbine wheel. The main use assumably is for utilizing hydraulic power in small rivers and brooks having a relatively small amount of water and a low water head, without being dependent upon dam building and other large constructional plants. Another possible employment of this hydraulic turbine is as a pressure reduction means in water works, at the same time as useful electric energy is produced.

Description: Hydraulic Turbine. This invention relates to various aspects of hydraulic turbins with associated equipment, in particular for small power plants. These may be small power plants for power out- puts up to some hundred kilowatts, either aiming at supplying electric power to a- local consumer on a separate network, or the power plant may be connected to a larger public co¬ ordinated supply network or the like. The invention is particularly well suited for the utili- zation of hydraulic power in small rivers and brooks having a relatively small amount of water and a- low water head. Moreover, the aim is solutions which make the utilization of small rivers and brooks independent of the building of dams and other large constructional plants. As examples of practical uses may be mentioned small power plants for farms, including greenhouse operations, small indust¬ ry such as sawmills, small family house and cottage areas, mobile auxiliary power units, possibly for military prepared¬ ness purposes,, charging stations for vehicles and simple stan- dard units for power supply in development countries. In the light of this the invention primarily has for an object to make it possible to satisfy small local needs for electrical energy in the vicinity of small rivers and brooks, with a hydraulic turbine and an associated generator in a unit which may be readily assembled and which is reliable in operation without expert supervision, while producing for these purposes the cheapest possible energy for the subscribers or consumers. A main aspect of this invention relates to the actual turbine structure which may constitute the core of a hydraulic power unit for producing electrical energy, preferably in the form of alternating current, for the above and other practical vises. In this aspect the invention takes as a basis known designs of a hydraulic turbine which has a substantially axial water flow therethrough and comprises a stator having guide vanes and a turbine wheel of the propeller type, followed by a discharge part. According to the "invention surprising improvements inter alia- in the efficiency, have been obtained in such a hydraulic turbine the novel and specific features consist therein the guide vanes are designe ' to give the water flow a signi¬ ficant rotational component about the turbine wheel axis, and that between the stator and the turbine wheel there is provi¬ ded a converging intermediate part of such long length that the water flow fulfills at least- three complete rotations from the stator to the .turbine wheel. The converging intermediate part in which the water flow is brought to rotate under its axial movement, is converging in that sense that- the flew cross-sectional area as seen in the axial direction, is decreasing in the direction from the stator towards the turbine wheel. In order to impart a certain degree of rotational move¬ ment to the input water flow as mentioned above, it is impor¬ tant according to the invention that each guide vane has a suitable and advantageous shape. Thus, according to a pre¬ ferred feature of the invention each guide vane has a substan¬ tially axial portion at its input end, with a following curved portion which continues in an output portion forming a signi¬ ficant angle with the turbine wheel axis. In this connection it is, moreover, practical to design each guide vane with a streamlined cross-section having a thickness which is demini- shing towards the output end. ' Finally, " a simple ' and. inexpen¬ sive design is obtained thereby that the guide varies of the stator are fixed. The features stated above are in contrast to conventional turbine designs in which in the first place the guide vanes or gates are usually located close to the turbine wheel and in which in the second place the guide vanes are normally adjust¬ able in the angular position or the like, in order to control the .power output of the turbine- This control mechanism in¬ volves rather complicated and expensive mechanical structures which are avoided with the present invention. With the solution stated here there is in principle pro¬ vided a hydraulic turbine having three velocity increasing steps, since in addition to the velocity increase in the con¬ verging intermediate part the turbine also gives the input water flow a first velocity increase in front of the guide vane.s of the stator, by providing in front, of" the stator an inlet cone- directed against the flow and tapering hub ' member for the stator. - As a consequence cf the above design of the stator and the guide vanes, there will also take place a velocity increase v/hen the water passes between the vanes. Thus, before the water flow reaches the stator, there exists a substantially laminary rectilinear water flow, whereas - in the following converging intermediate part there is estab¬ lished a homogenious helical rotating water flow which is also substantially laminary. This water flow . -fulfills a number of complete rotations along the whole length of the intermediate part, namely three , or more rotations. This number of rota¬ tions is not accurately determined, but. assumably 5-6 rota¬ tions will be optimal in certain configurations, i.e. relative .dimensions as - regards the diameter of the stator and the tur¬ bine wheel,, respectively, as well " as the length and shape of the intermediate part. This pattern of movement of the water flow in the intermediate part leads " o a very intense concen¬ tration of the effect of the ' water on the vanes or blades of the turbine wheel and inter alia results in ' an increased num- ■ her of revolutions per minute of the turbine wheel. Test runs of power units based upon this invention have shown that the efficiency is about 94 %, which is very high when considering that common -small turbines as a rule have an " efficiency in the range 20 - 60 %-. The rate " of rotation may for example be 1500 revolutions per .minute. Among the other aspects of this invention reference shall here be made to the solution that about the turbine wheel there is provided a replaceable constriction member dimensioned according to the outer diameter of the turbine wheel blades. In a specific embodiment according to the invention such con- striction members may be easily dismounted and mounted, respectively, for adapting the individual turbine units to the amount of water, the water head, the power and so on depending upon the conditions at each installation or plant site. In this embodiment it is an advantage to design the discharge part immediately downstream of the..turbine wheel, in a special way based upon a drum shape. The various aspects of this- invention as well as additional specific features and advantages thereof, shall be explained more closely in the following description with reference to the .drawings, in which: Figure 1 shows a vertical axial .section through an embodiment of a turbine according to the invention, • Figure 2 shows in detail a cross-section of a preferred form of guide vane in a turbine shown in Figure 1, Figure 3 shows a section through another embodiment accor¬ ding to the invention, and Figure 4 shows the turbine of Figure 3 with a portion of the structure dismantled. The main components of the turbine design as shown in Figure 1, are an inlet ' tube 1 in the form; of a flange end of standard type, a stator- comprising a hub member 11 and guide vanes 5, a following intermediate part with an outer casing 2 which converges in the direction towards a turbine wheel 6 the hub 13 of which is mounted on a through-axle 4. Further follow an inne . r expansion' tube in the form of a bend 3a and " an outer expansion tube 3b for discharging ' water which has passed through the turbine. - It is presumed that the axle 4 is prolonged to the left in Figure 1, to an electric generator which is not shown, preferably an alternating current generator. A regulating system for a complete power unit consisting of the turbine shown and an electric generator may be built up by .means. of per se known components. Centrally in the inlet tube 1 there is arranged a so- called inlet cone 8 which tapers in a direction against-the flow direction from a larger diameter substantially equal to the diameter cf the stator hub ' 11. With this shape the inlet cone 8 -results in a decreasing flow 1 cross-sectional .area in the inlet tube 1 towards the stator 5,11. Thereby the incoming water will get an increasing velocity through . the inlet tube 1 towards the stator- . A specific feature of the structure described here, is the intermediate part with the outer casing 2 and an inner conical member 7 which together define a flow passage having an annular cross-section and a significant lengt between the stator 5, 11 and the turbine wheel 6. When seen in axial direction the flow cross-sectional area here continues to decrease so that there will be a third velocity increase steD. OMPI after the first step in the inlet tube 1 and the second step in the stator 5, 11. In addition to this axial velocity in¬ crease, however, the guide vanes 5 are shaped so as to .give the ater, flow a rotational ' -component which is maintained and amplified through the intermediate part. This is indicated with the broken arrows S in the flow passage of the inter¬ mediate part. Thus, " the water flow will here follow a helix .with a decreasing diameter ' and possibly also a decreasing pitch in the direction towards the turbine wheel 6. The exact path will depend ' pon the various relative dimensions. The intermediate part is converging in the sense that said axial flow cross-sectional " area- is decreasing when the diameter of the outer casing 2 is being reduced in a direction towards the .turbine wheel 6 to a higher degree than the - corresponding reduction of the. diameter of the inner member 7. • It -is obvious, however, that other relationships between the diameter variation of these members may be thought of, without departing from the principles of axial 'velocity increase and water rotation. In this regard it is considered to be of sub- stantial importance that the water will have the opportunity to fulfill a number of complete rotations or revolutions about the common through-axis during the passage- through the intermediate part. It has been found that the number " of- ro¬ tations should be at least 3, but this does not represent any sharp limit, and in accordance with the relative dimensions, depending upon inter alia the .amount of water and the pressure head, the optimal number- of rotations may be about 5-6. Also a higher number of rotations, for example 8 rotations, may be found to be advantageous in certain designs. The signifi- cant distance between the guide vanes 5 and the turbine wheel 6 in any case represents a particular design principle which has not previously been used in hydraulic turbines. At this point it is suitable to refer to Figure 2 which shows a cross-section of a guide vane 5 with the direction of the common axis through the turbine shown as the vertical dot-dash line. This line corresponds -to the general water in-flow direction, from the inlet tube 1. • From the cross- section shown it appears that the guide- vane 5 is streamlined with a diminishing thickness from the- input end outp'ut -end. Moreover, it is seen that-the input end has a portion which runs .substantially axially (in parallel to the dot-dash line) and thereafter is curved and continues in a portion at the output end . which forms a significant angle to the axial direction. -This .shape is suitable for obtaining the above mentioned specific rotational component in the inter¬ mediate part following after the tator in the turbine of Figure 1. It is also important that the arrangement of guide varies 5 shown in the stator 11 -involves a notably diminishing, flow cross-sectional area between the guide vaπas in a direction from the input end of the stator to the * output end thereof. This is due to the above explained curvature of each guide vane 5. -Thus, at the " input end these vanes have -a relatively large spacing and will have an effective spacing which is relatively much reduced at the output end. Another .particular f.eature of the stator guide vanes 5 is the fact that these are fixed, i.e. they are not adjustable or variable as to their angle, which is common practice in hydraulic turbines. This fixed position of the guide vanes 5 in the turbine of Figure 1 means that the same "will have a simple mechanicle structure, which reduces -the -manufacturing costs and the maintenance operations. As mentioned in the introductory .part of this description, the turbine v/heel is of the propeller ^ type and comprises vanes or blades 6 attached to a hub .13 which in turn is keyed to the axle 4. In the turbine design described here the turbine wheel will have a relatively high rotational velocity, which is favourable, inter alia when a simple and inexpensive generator design is desired. After the turbine v/heel follows in the flew direction an outlet cone 9 which from a diameter corresponding approximately to. the diameter of the turbine wheel hub 13, tapers towards a bearing sleeve 16 the opposite' end of which is anchored outside the turbine housing or more particularly, on the tube bend 3a- Adjacent the outlet cone 9 the bearing sleeve 16 is provided with a water lubricated bearing 15. Another water lubricated bearing 14 is provided in th.e stator hub- 11 so that the- stator structure its.elf constitutes a support for this bearing. Finally, at the very left side of Figure 1 there are shown roller bearings 18 which serve to take up the axial load o.n the axle 4. These roller bearings 18 are seated in a bearing housing 17 which also comprises a chamber having a V-ring 19 on the axle 4 for the purpose of preventing moisture from reaching the roller bearings 18, From the chamber with the V-ring 19 there is provided a drain pipe 21. For the water lubrication of the bearing 15 water shall enter radially into the gap between the turbine wheel hub 13 and the outlet cone 9 and after having flown between ' the' bearing surfaces, the water may be discharged into the. main water flow through drain holes 22 at the -narrow end of the outlet cone 9. The water supply for lubricating the bearing 14 takes place through axial holes from the tip portion of the inlet cone 8. This water then proceeds ' through the bearing 14 and from there- into the inner cavity in the inlet cone 8 and finally from there out through a- drain pipe 24. The inner member 7 of the intermediate part is attached to the stator hub ' 11 and extends to the turbine wheel hub 13 while enclosing the axle 4. For supporting this inner member there are provided rods 12 which preferably have such a shape and orientation that the water flow in the intermediate part will be impeded to the least possible degree. The inner expansion tube or bend 3a contributes -to the high efficiency which is obtained by the turbine shown here. In contrast to " conventional designs the tube bend 3a has an expanding cross-section so that the flow cross-sectional area at the junction to the outer expansion tube 3b is several times larger than the -cross-sectional ' area immediately after the turbine wheel 6. Assumably, the wall portion pf the tube bend 3a -which has the smallest radius of curvature, leads to a specific reduced pressure region which gives an amplified suction effect at the outlet from the actual turbine. This effect continues in the outer' expansion tube 3b which- also has an expanding cross-section in a direction downwardly. The shape of the outlet cone 9 also contributes to the total effect of the discharge part of the turbine, consisting of the tube bend 3a and the outer expansion tube 3b. In the embodiment of Figures 3 and 4 the central or main * ZJfζj~ OMPI_ WIPO ^ coπiponents similar to those in Figure 1, are also found, in the form of an inlet tube 31b which here expands and leads the water towards guide vanes 35, an inlet- cone 38 projecting against the flow from these " vanes into' the inlet tube 31b. The cross-section of a guide vane is shown particularly at 35a. Further follows ' an intermediate part or outer casing 32 which together with an inner conical member- 37, gives the water the previously described particular movement • in its direction towards a turbine wheel having blades.36 and a hub 41. What is specific to the embodiment ^ of Figures 3 and 4 in the first place is the annular member 40 - here designated constriction member -- " which may be replaced and brought to mate ith the outer diameter of the turbine wheel blades 36. Thus, it is a 'necessary prerequisite that the turbine wheel and the constriction member are replaced at the same time so that these components may be adapted to each other- For the purpose of obtaining a simple assembly and dis¬ assembly, respectively, in connection with this replacement, the outlet member 33 has the shape of a drum based upon known principles, but here provided with an axial opening -43 adapted to be closed v/ith a rear member 42 which inter alia- comprises bearings for the' turbine wheel axle "34. As an. inner limitation of the flow space in the outlet member 33 there is provided a sleeve member 39 projecting inwardly -from the rear member 42 and tapering in the direction towards the turbine wheel hub 41 and carrying,respectively forming bearings for the turbine wheel axle 34. From the outlet member 33 the -water may flow out through a discharge passage 33a which is joined to a discharge or draught tube 33b. The relative dimensions of the actual turbine with its guide vanes, intermediate part and turbine wheel in Figures 3 and 4, are somewhat different from what is seen in Figure 1, but there is still provided for a significant rotational com¬ ponent in the water flow between the stator guide vanes 35 and the turbine wheel 36. ' The outlet member 33 showri in Figures 3 and 4 assumably under many conditions will result in a more favourable flow path for the water flow when the water leaves. OMPI the turbine wheel, than the expanding discharge bend which is shown in Figure 1. As it should appear from Figure 4, the dismantling of the rear member 32 with the urbine wheel axle 34 and the turbine wheel 36, ' take . s place by retraction axially to the left in the figure, subsequent to loosening of bolts which fix the rear member 42 to the opening 43. The constriction member ' 40 may for.example be-kept in place by means -of screws or bolts (not shown) inserted from the outside through the turbine housing and into the constriction member. When.these bolts have been screwed out, the constriction member 40 may be pulled axially to the left through the opening 43 the dia¬ meter of' which ' must of course be dimensioned in view of this. Finally, in Figures 3 and .4 there is shown a valve housing 31a with a valve " element 30 in front of the inlet tube 31b. These are conventional valve structural parts which do not need any closer explanation here. As mentioned in the introduction to this description, power plants based upon the hydraulic ' turbine according to the present invention, may primarily aim at the supply of ener¬ gy to public electric supply networks (coordinated networks1, for example, to ' local electricity supplies and from .there, de¬ pending upon the local -consumption, possibly to the coordinated public network, when there is produced surplus power which it is desired to deliver for sale. Another and very interesting use of the -hydraulic turbine described here, is ' in connection with water works in which the pressure head is so large that according to common practice there will be installed pressure reduction valves. This may be of interest when the water pressure is higher than 2 7 - 10 kg/cm . It has been previously proposed to take ad¬ vantage of such excess pressure in public and other water supply 'systems, for producing electric power. However, this idea has not been put into practical use, since suitable tur- bine units have not been available. The hydraulic turbine according to the present invention is very well suited for such a use and will make possible an effective utilization of hydraulic power in many water works in which there are today installed .pressure reduction valves. It is obvious that practical designs of hydraulic tur¬ bines based upon the principles according to this invention, may be modified in various ways in relation to what is here described " and illustrated in- the drawings. Thus, for example, the turbine may also be-designed with a vertical axle if this is most advantageous for example in consideration of the directions of water input and discharge. Moreover, the tur¬ bine housing may " apparently be shaped in various ways, ' since for example, it is not necessary to have a strictly recti- linear tapering intermediate part 2 as described above. The converging intermediate part may also follow other curves than the rectilinear shape shown.

Claims: CLAIMS: 1. Hydraulic turbine, in particular for small power plants, with, a substantially axial water flow therethrough and com¬ prising a stator having guide vanes (5, 35) and a turbine wheel (6,36) of the propeller type followed by a discharge part .(3a- 3b, 33a, 33b) , c h a r a c ' t e-r i z e d i n that the guide vanes (5, 35) are adapted to give the water flow a significant rotational component about the turbine wheel axis (4, 34) and that between the -stator (5, 35) and the turbine wheel (6, 36) there is provided a convergent intermediate part (2', 7, 32, 37) of such long length that the water flow : fulfills at least three complete rotations -from the stator to the turbine wheel. 2. Hydraulic turbine according to- claim . 1, c h a r a c t e ¬ r i z e d i n that the diameter of the inner member (7, 37) along a substantial portion o ' f its length is of the order of about equal to the half of the outer diameter of the flow cross- section in the intermediate, part (2, 32) . 3. Hydraulic turbine according to claims 1 or 2, c h a r ' a c t e r i z e d i n that each guide vane (5, 35) has a substantially axial portion at its input end, .with a following curved portion which continues in an Output,end portion which forms a significant angle to the turbine wheel axis (4, 34) , and that each guide vane (5, 35) has a streamlined cross-section with a diminishing thickness towards the output end. 4. Hydraulic turbine according to claims 1, 2 or 3, c h a r a c t e r i z e d i n that- the stator (5, 11) con¬ stitutes a support for a bearing (14) for journalling of. one end of an axle (4) for the turbine wheel " (6, 13) . 5. Hydraulic turbine according to claims 1, 2, 3 or 4 , c h a r a c t e r i z e d i n that in front of the stator .(5, 11, 35) there is provided an inlet cone (8, 3S) directed against, the flow and tapering " from a hub member (11) for the stator. 6. Hydraulic turbine according to any one of claims 1-5, c h a r a c t e r-i z e d i n that the inner (7) and outer member. (2)" of the intermediate part are mutually trussed by means of substantially radial rods (12) the cross-section of r^£A which preferably has such a shape and orientation that the •water flow- is impeded to the least, possible degree. 7. Hydraulic turbine according-to any one of claims 1-6, c h a r a c t e r i z e d i n that the ' discharge part ' imme- diately downstream of the turbine wheel comprises a tube bend (3a)having an expanding cross-section, preferably followed by an outer expansion tube(3b.) . &. Hydraulic turbineaccording to claim 7, c h a r a c t e r i z e d i n that from the turbine wheel hub (13) there extends a tapering outlet cone (9) into the expanding tube bend (3a) - 9. Hydraulic turbine according to claim 8 " , c h a r a c e r i z e d i n -that the outlet cone (9) forms the free end of a beating sleeve (16) the other end of which is attached to the tube bend (3a) , and that the bearing -sleeve (16) adjacent the outlet cone (9) carries a bearing (15) for journalling the turbine wheel axle (4). 10. Hydraulic turbine according to any one of claims 1-9, c h a r a c t e r i z e d i n that at least one of the bearings . (14 , 15) for the turbine wheel axle (4) is water lubricated. 11. Hydraulic turbine according to any one of " the .preceding claims, " c h a r a c t e r i z e d i n that around the tur- bine wheel (36, 41) there is provided a replaceable constriction member (40) mating with the outer diameter of the turbine wheel blades (36) .• 12. Hydraulic turbine according to any one of claims 1-6 and 10, c h a r a c t e r i z e d i n that the discharge part (33) is of the drum type and has an axial opening (43) -adapted to be closed with a rear member (42) which comprises bearings for t-he turbine "wheel axle (34) . 13. ' Hydraulic turbine according to claim 12, c h a r a c t e r i z e d i n that from the rear member (42) into the discharge part (33) there ' projects a bearing sleeve (39) towards the turbine wheel (36 " , 41) with such tapering shape that the sleeve constitutes ' a portion of the inner limitation of ' the flow passage in- the discharge part (33) . 14. The use of a hydraulic turbine according to any one of the preceding claims, as a pressure reduction means in

Inventors: BERNTSEN JAN KRISTIAN, SVENSSON SVEN
Applicants: BERNTSEN JAN KRISTIAN, SVENSSON SVEN
Application year: 1982
Main classification: F03B3
IPC codes: F03B3