JPH0681601A - Reaction and dynamic multistage turbine downhaul motor - Google Patents

Abstract

PURPOSE: To provide a multi-stage turbine for a multi-stage turbine motor for downhaul, which operates with a fluid shear force to a turbine blade edge only or a combination of the shear force and an impact force. CONSTITUTION: A turbine comprises an external casing 3 and an internal shaft 5 disposed in the casing and rotated with respect to the longitudinal axis. A plurality of turbine assemblies 9 are provided. Each turbine assembly includes a rim 15 and a plurality of turbine blades 13 secured to the rim. A stator 11 is positioned between adjacent turbine stages. Each stator has a wall portion and a diverter portion. The wall portion is perpendicular to the axis of a shaft and the diverter portion is at an angle less than 90 deg.. In a space between the wall portions, the turbine blade and the diverter portion form a seal for obstructing the flow passing the turbine assembly. The flow between the wall portions of the stator exerts a reaction force to the turbine blade. The flow passing the diverter portion exerts dynamic force to the turbine blade.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-stage turbine motor used as a downhole motor on a drill string, and more particularly to a reaction force (DRAG) or a shear force (SH-EAR STRESS) of a fluid flowing through a turbine, or a dynamic force. Or, it relates to a multi-stage turbine downhole motor driven in combination with an impulse.

[0002]

2. Description of the Related Art A conventional downhole motor used on a drill string converts the kinetic energy of the mass of fluid flowing on the surface of a turbine blade into a force for rotating a drill string, that is, a drill bit provided at the bottom of the drill string. There is. Turbines rely solely on dynamics or impulses. This type of conventional downhole motor has a relatively long length in order to generate a force for rotating the bit with a sufficient torque at an appropriate speed. However, since the downhole motor itself is long, it is difficult to move the drill string along the curve, and thus it is difficult to control the direction of the drill.

Another drawback of dynamic type downhole motors is that they occur at relatively high speeds, where maximum power and efficiency are faster than the operating range of many mechanical drill bits such as tricone bits. The reason for such characteristics is that the function of force and efficiency for the velocity of the fluid is proportional to the square of the velocity. This function is a parabola whose vertex lies between zero and the unloaded speed.

Yet another drawback of conventional downhole motors is that the turbine blades are inside with respect to the drill shaft. In order to drive the turbine, the fluid must flow through the internal structure of the drill string,
Therefore, the downhole motor bearings, seals, and other internal structures are damaged.

[0005]

DISCLOSURE OF THE INVENTION It is an object of the present invention to identify the shear force of a fluid at the blade edge of a turbine (SHEAR FORC).
E) is to provide a multi-stage turbine that operates either alone or in combination with the impulse of the fluid at the surface of the blade.

Another object of the present invention is to rotate the drill string and the drill bit provided at the tip thereof at a relatively low speed of 300-500 RPM to generate a strong torque, and to apply torque to the pipe itself of the drill string. It is to provide a downhole motor that does not generate.

Another object of the present invention is to provide a multi-stage turbine in which the rotor with turbine blades is outside the drill shaft, and thus the moving part is outside the drill shaft. Further, since the blade is attached to the external movable portion, the generated force is far from the shaft of the turbine, and the lever is used to increase the torque.

[0008]

SUMMARY OF THE INVENTION The present invention provides a multi-stage turbine for a downhole motor driven by a fluid flow. The turbine has a plurality of rims inside and a housing to which a shaft is fixed. The housing and rim rotate about the longitudinal axis. A plurality of turbine stages are fixed to the housing and rotate with it. Each turbine stage has a rim coaxial with the shaft and a plurality of turbine blades secured to each rim. A plurality of flow directing stators are positioned between the turbine stages. Each stator has a wall portion and a diverter portion, the wall portion is perpendicular to the axis of the shaft, and the diverter portion forms an angle of 90 degrees or less with respect to the axis of the shaft. The at least three turbine blades and the diverter portion form a seal that blocks flow from the passageway between them such that the flow through the turbine stages is perpendicular to the axis of the shaft in the space between adjacent walls. The diverter section is positioned relative to the wall to divert flow from the turbine stage to an adjacent turbine stage.

Turbine blades are positioned between adjacent stators, and the flow between the wall walls of adjacent stators strikes the edges of the turbine blades and causes the turbine blades to generate a DRAG FORCS. Then, the flow between the adjacent diverter portions collides with the surface of the turbine blade to generate a dynamic force on the turbine blade. Therefore, the turbine blades rotate with a combination of reaction and dynamic forces.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a multi-stage turbine having a plurality of single stages, each stage operating on the principle of shear stress of fluid flowing through a stage passage or space with respect to an edge of a turbine blade, and independently. Or, in combination with the impulse force against the surface of the blade, a reaction force is generated. Fluid volume is not a factor of reaction or shear at the edges of turbine blades. The power generated by the reaction force is a function of the relative speed and the reaction surface, which is the edge of the turbine blade, not the surface of the blade itself. The use of reaction force (DRAG FORCE) produces stronger torque than conventional turbines of the same size. Therefore, the motor according to the present invention can generate a sufficient torque with a small number of stages, so that the length can be shortened as compared with the conventional turbine motor.

FIG. 1 is an elevation view of a downhole motor having an outer case 3 and an inner shaft 5. The motor further has a bearing assembly and a turbine assembly 9 having multiple stages, each stage having a stator and rotor assembly.
Have. Each stator assembly has a plurality of flow directing stators 11, and each rotor assembly has a plurality of turbine blades 13 fixed to a rotor rim 15.

A plurality of turbine rotors 13 are preloaded and have nuts 28 located at the ends of the downhole motor.
It is fixed integrally by 29. A drill bit (not shown) is connected to the nut 28. These nuts also secure the bearing assembly 7. Bearing assemblies are other types of bearings such as tapered journal bearings or ball bearings. If desired, a nut that secures the assembly may be used in the middle of the motor. Block 31 separates bearing assembly 7 and turbine assembly 9 and provides a seal therebetween. Block 31 is also used to house a pressure compensator for the lubrication system when bearing lubrication is required.

In FIGS. 1, 1a and 1b, arrow F1
The fluid flowing as indicated by -F7 flows through the downhole motor as shown. The flow flows axially in the center of the shaft 5 in F1-F3 and flows in the slots 33 in the shaft 5 in F3-F4. In F4-F5, the flow flows through the turbine assembly 9 and rotates the turbine blades 13 and the outer case 3. The end piece 28 is threaded into the outer case 3 and clamped against the blade 13. Therefore, the blade 13 rotates together with the outer case 3. At F5-F6, fluid exits turbine assembly 9 through another slot 35, similar to slot 33, into shaft 5, and then exits the downhole motor. As shown, the turbine assembly is mounted on the outside of the shaft 5, so the moving part is outside the drill shaft.

FIG. 2 is a diagram showing a spiral flow through the turbine assembly 9. The turbine assembly 9 is attached to the shaft 5. The turbine assembly 9
Includes a plurality of stators 11 fixed to the shaft 5 and directing flow, with a plurality of turbine blades 13 fixed to corresponding rotor rims 15 positioned for rotation between adjacent stators 11 (see FIG. 1). ). The seal is formed between the flow guiding portions 19b and 19a and the turbine blade 13. Because the flow F is circular in the flow passages or spaces formed between the adjacent stators 11, and the flow diverters 17a and 17b in the adjacent turbine stages between the next adjacent stators 11.
And 19a or 19b through a flow path or space.
Then, as shown, the flow flows in a flat circular shape through almost the entire 360 ° and then spirally drops to the next tabine stage in a diagonal direction. The reaction force and impact force supplied to the turbine blade due to the flow through the turbine depend on the shapes of the turbine blade 13 and the stator 11, which will be described later in detail.

The turbine of this embodiment is driven by shear or reaction forces in combination with the dynamic or impulse forces of the fluid flowing through the turbine. The reaction force is generated by the flow of fluid against the ends of the turbine blades. Dynamic forces flow through the rotor blades at the inlet and outlet of each turbine stage and are thus generated by impingement of the flow against the surface surfaces of the turbine blades.

The total force F _T acting on the rotor is F _T = Fdr + Fdy (1) where Fdr is shear force or reaction force, and Fdy is impulse force or dynamic force.

The reaction force is expressed as follows. _{Fdr = γ · λdr · a dr} · u (C-u) 2 / 2g ··· (2) where, gamma is the specific weight of the fluid (Kgf / m ^2). λ
dr is a reaction coefficient (dimensionless) from the geometrical shape of the rotor blade and the flow path. C is the average velocity (m / sec) of the flow through the reaction flow path. u is the circumferential velocity (m / sec) of the rotor. a _dr is a reaction area (m ² ) on which the impulse pressure acts.

The dynamic force can be calculated with reference to FIG. 3a, which shows a portion of the rotor blade as seen from the side of the axis of rotation. In the figure, u is the tangential speed of the rotor (m /
sec), W ₁ is the relative velocity of the flow (m / sec), β ₁
Is the angle (degrees) of W _{1 in} the direction u, C ₁ is the absolute velocity of the vector of u and W ₁ , α ₁ is C in the direction of u
, W _x1 is the component of W _{1 in} the direction of movement u.

The subscript "1" corresponds to the flow inlet at all changes in direction through the blade assembly.

The subscript "2" is used to indicate the value which is consistent with the flow at the exit of all changes in the direction of the hydrodynamic impulse.

Referring to FIG. 3b, the configuration of the triangular relationship of velocity at the inlet and outlet of the flow at all impulses or changes in direction to deduce or obtain the equation for the dynamic force is shown.

According to Newton's second law, Fdy = ρQ (W _x1 -W _x2 ) (3) where W _x1 and W _x2 are relative velocity components in the direction of movement. ρ is a mass ratio and is γ / g. And

W _x1 = C ₁ cos α ₁ -u W _x2 = Cm ₂ ÷ tan β ₂ = Cm ₁ ÷ tan β ₂ = C ₁ sin α ₁ ÷ tan β ₂

Fdy = mρQ [(C ₁ cos α ₁ −u) + C ₁ sin α ₁ / tan β ₂ ] (4) Note that m is the number of changes in direction or impulse in each stage.

It can be seen from FIGS. 4 to 6 that the blade 13 is fixed to the rotor rim 15. Only four blades are shown, but the remaining blades are located around the entire rim 15. When the rotor assemblies are shown in FIG. 1, the rim 15 has the same width as the turbine blade 13 and the spacer 15 ′ is arranged adjacent to the rim 15. Alternatively, since the spacer 15 ′ is an essential part, the rim 15 is attached to the blade 13
Made wider. FIG. 6 is a front view taken on the plane 6-6 of FIG. 5 showing the placement of the blade 13 with respect to the rim 15 and the center of the rim 15. However, the blade 13 has a cross section of V
Other cross-sections that are V-shaped are curved V, V having different left and right lengths, V having a combination thereof, and the like.

FIG. 7 is a perspective view of the stator 11 that guides the flow. The stator 11 changes the flow with the wall portion 25 17a
And 17b and 19a and 19b. As shown in FIG. 2, the flow redirecting portions 17a and 19a use adjacent turbine blades 13 to form a seal. However, the seal is necessary for the turbine blades to rotate, and the seal substantially stops the flow of fluid of the main proper flow through the turbine assembly described below. Further, the stator 11 comprises a hub 21 having a fixing groove 23 for fitting the key 6 when the stator is mounted on the shaft 5. The stator assembly also includes a wall portion 25 that is integral with the flow directing portion. Referring to FIG. 4, the space 27 is formed between the wall 25 and the spacer 15 '. Space 27 is made very small because the flow of fluid through the space is negligible, but the spacers are sufficient to allow rotation of rotor 13 with respect to stator 11.

FIG. 8 shows another embodiment of the stator 11 with a hub 21 having a reduced diameter portion 21a. The length or angle of the reduced portion depends on the particular flow, but is generally less than 90 °. The effect of the reduced hub radius is to remove the impulse on blade 13c to allow it to flow below blade 13c and to quickly equalize the flow on both sides of blade 13d. If desired, the sharp corners between surfaces 17a and 17b and 19a19b may be rotated to smooth the flow and reduce turbulence.

FIG. 9 is a partial representation of the fluid flow through the two blade assemblers 13 in the first embodiment of the turbine of the present invention. Arrow F indicates flow, and arrows D and I indicate reaction force and dynamic force on turbine blade 13. Starting from the right, the flow F produces a reaction force D on the ends of the turbine blades 13. When the flow reaches the surface 17b, the flow turns downward as shown, hitting the blade 13a and the blade 1
Supply the dynamic force I to 3a. The flow then flows through the diverter 19 of the flow in adjacent stages of the turbine blades.
Continuing to flow through a and 19b, the dynamic force I is again supplied to the blade 13a. The reaction force is then supplied to the end of the blade 13 and the flow continues to the left.

FIG. 10 is a partial representation of the fluid flow according to the second embodiment of the turbine of the present invention with the three impulse forces generated at each stage. Arrow F shows the flow, and arrows D and I
Represents the reaction force and dynamic force on the turbine blade 13. Starting from the right, the flow F produces a reaction force D on one end of the turbine blade 13. In the embodiment of FIG. 8, the turbine blades are arranged so that the reaction forces are at both ends of the blade. The flow is on the surface 17 as shown.
When it reaches b, it changes to the downward direction and hits the blade 13a, and supplies the dynamic force I to the blade 13a. The flow then continues to flow through the flow diverters 19a and 19b in adjacent stages of the turbine blade 13 and again the dynamic force is provided to the blade 13a.

In the embodiment of FIG. 10, there are three changes in direction since three impulses are generated in all stages. In the equation (3), the variable “m” is 3 in this case. Figure 1
1-15 is a figure which shows the 3rd Example of the turbine of this invention. In FIG. 11, the stator 111 that guides the flow includes diverters 117 a, 117 b, 119 a and 119 b and a wall portion 125. The turbine blade stage 113 is shown in FIG.
Is the same as that of the embodiment of FIGS.

FIG. 12 is a perspective view of the stator 111 which guides the flow. The stator 111 has a fixing groove 123 and a wall portion 12.
It comprises a hub 121 having five. The wall portion 125 has a plurality of flow directing stators and a plurality of portions 125a-125k (not shown in FIG. 12) shown in FIG. 13 that are outlets of the turbine blade stages. FIG. 13 shows 13-1 of FIG.
FIG. 14 is a front view with three surfaces, and FIG. 14 is a side view from the 14-14 surface of FIG. Corresponding to FIGS. 11-15, the surfaces of diverter 117 and wall portion 125 are represented by the letters AG.

The flow through the turbine in the embodiment of FIGS. 11-15 is represented by arrow F in FIG. This flow is the outer half 113a of the turbine blade 113.
Causes an impulse on. The inner half 113b of the turbine blade 113 has no significant force to act,
The diverter wall section 12 to form the essential seal
Acts corresponding to 5a, 125e and 125i. The seal is ensured by the flow indicated by arrow F through the space between the turbine blades and wall sections 125a, 125e and 125i. The impulse on the turbine blade 113a is the same impulse as described above with respect to the embodiment of FIGS. However, as shown, there is no substantial reaction force on the turbine blades in this example. Wall portion 1 where centrifugal force due to flow is separated from the end of the turbine blade
There is a substantial lack of reaction as it moves the fluid outwards against 25c, 125k and 125g. "M"
Is increased to provide the maximum dynamic force, this embodiment is limited to dynamic forces.

FIG. 16 is a diagram showing a fourth embodiment of the turbine of the present invention. In this embodiment, blades 213 are staggered on the outer rotor rim (not shown). The sealing wall member uses one end of the blade 213 to form a seal, and the other end of the blade 213 forms a seal using the stator 211. The flow is in one direction around the annular space and is almost 360 ° at the point of flow through the outlet in the next stage. The undulating flow of stream F causes a reaction force D on the tip or edge of blade 213, as well as an impulse force I on the surface of the blade. The reaction force and the dynamic force can be calculated by the above four equations. However,
The flow is not very clear and the equation must be achieved with experimentally detected coefficients.

Instead of blades, flat or curved housings can be used, to eliminate swirl and turbulence,
And attached to the rotor rim to enhance the impulse on the inclined surface to cause the desired number of smooth changes in direction along the annular flow path.

17a to 17d show a fifth embodiment of the turbine of the present invention. In this embodiment, the turbine is essentially a pure reaction (reaction) turbine that is simple and versatile yet has high torque and relatively high efficiency. Additional turbine blades may optionally be added to generate additional forces, reaction forces or dynamic forces, which alter the performance of the turbine.

Referring to FIGS. 17a-17d, arrow F
The flow indicated by flows through the turbine with the intermediate seal 315 at the next diagonal inlet position. The turbine has blades 313 that contact the seal 315. The seal 317a and the diagonal diverter
ter) diverts the flow through the opening 317 in the wall of the stator 311. The flow path is cylindrical and covers approximately 360 ° and is coaxial and parallel to the cylindrical space covered by the rotor and its blades. In other words, the flow is cylindrical and intermediate the ends of the blades and the inner hub, as shown in Figure 17c.

The blade length, thickness, tilt angle, and blade spacing are variable. All these variables are
Reaction coefficient (drag coefficient) λdr, and thus the final reaction force,
Affects speed and efficiency.

The reaction for this embodiment of the invention is:
It is usually superior to that in other embodiments of the invention.

In the fifth embodiment, since the flow through the flow path is cylindrical and parallel to the rotor and blades, the blades are directed in the direction of flow so as to generate an impulse except when changing stages. Do not deviate from or cross this. The change of direction of flow from one stage to the next is made by the seal and the stator, so that the friction loss and also the head loss are small.

The following is a description of the operation including the operation of the intermediate seal according to the present invention. Figures 18a and 18b schematically show a cross section of the flow path with seven direction changes and consider one stage of a turbine with recoil and dynamics as shown in these figures. The rotor is shown divided into two parts. One is a seal part of a step-changing part, and the other is a supplemental part for supporting the rotor.

The balance equation for each of these parts is as follows:

[Equation 1] Where P ₁ and P ₇ are pressures at the inlet and outlet of the stage, Ap
Is the area where the blade pressure acts.

[Equation 2]

The total force acting on the rotor is as follows. F _T = ΣF _seal + ΣF _comp = − (P ₁ −P ₇ ) Ap + (P ₁ −P ₇ ) Ap + Fdr
+ Fdy F _T = Fdr + Fdy Therefore, the forces due to the pressure acting on the cross section cancel each other out.

Although the present invention has been described with reference to turbines, the principles of the present invention may also be used with pumps, blowers, or compressors. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. It is therefore to be understood that the embodiments described herein are illustrative in all respects and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description. . Also, all modifications within the meaning and range equivalent to the scope of the claims are to be included in the present invention.

[0044]

As described above, according to the present invention,
A multi-stage turbine can be provided that operates using the shear force of the fluid at the blade edge of the turbine alone or in combination with the impulse of the fluid at the surface of the blade, comparing the drill string and the drill bit at its tip. It is possible to provide a downhole motor that rotates at an extremely low speed to generate a strong torque and does not generate a torque on the pipe itself of the drill string. There is also a rotor with turbine blades on the outside of the drill shaft, so
It is possible to provide a multi-stage turbine with moving parts outside the drill shaft. Further, since the blade is attached to the external movable portion, the generated force is far from the shaft of the turbine, and the lever is used to increase the torque.

[Brief description of drawings]

FIG. 1 is a sectional view of a downhole motor according to the present invention.

1a is an enlarged view of a portion of FIG. 1. FIG.

1b is a cross-sectional view taken along the line 1b-1b of FIGS. 1 and 1a.

FIG. 2 is a perspective view of the flow of a turbine according to the present invention.

FIG. 3a is a diagram analyzing the flow and force of a turbine according to the present invention.

FIG. 3b is a diagram analyzing the flow and force of a turbine according to the present invention.

FIG. 4 is a partial cross-sectional view of the turbine of the first embodiment of the turbine according to the present invention.

FIG. 5 is a perspective view of a rotor stage according to the present invention.

6 is a front view of the rotor stage of FIG.

FIG. 7 is a perspective view of the stator of the turbine of the first embodiment of the turbine according to the present invention.

FIG. 8 is another perspective view of the stator according to the present invention.

FIG. 9 is a partial layout view showing a fluid flow of the first embodiment of the turbine according to the present invention.

FIG. 10 is a partial layout view showing a fluid flow of the second embodiment of the turbine according to the present invention.

FIG. 11 is a partial sectional view of a turbine of a second embodiment of the turbine according to the present invention.

FIG. 12 is a perspective view of a stator of a turbine of a second embodiment of the turbine according to the present invention.

13 is a front view of the rotor stage of FIG.

FIG. 14 is a bottom view of the rotor stage of FIG.

FIG. 15 is a partial layout view showing a fluid flow of the third embodiment of the turbine according to the present invention.

FIG. 16 is a partial arrangement showing a fluid flow of the fourth embodiment of the turbine according to the present invention.

FIG. 17a is a partial cross-sectional view of a turbine of a fifth embodiment of the turbine according to the present invention.

17b is a partial cross-sectional view of FIG. 17a taken along line 17a-17a ′.

FIG. 17c is a partial cross-sectional view taken along line 17b-17b ′ of FIG. 17B.

FIG. 17d is a perspective view of a rotor according to a fifth embodiment of the present invention.

FIG. 18a is a partial layout view showing an intermediate seal for a recoil and dynamic embodiment of the present invention.

FIG. 18b is a partial layout view showing an intermediate seal for a recoil and dynamic embodiment of the present invention.

[Explanation of symbols]

 3; outer case 5; inner shaft 7; bearing assembly 9; turbine assembly 11; stator 13; turbine blade 15; rotor rims 17a, 17b, 19a, 19b; diverter 21; hub 23; fixing grooves 28, 29; nuts 33, 35 ; Slot

Claims (11)

[Claims] 1. A turbine for driving a downhole motor driven by a flow of a passing fluid, comprising: (a) a housing; (b) a shaft located in the housing and rotating about a longitudinal axis; (c) A rotor having a plurality of turbine stages, each turbine stage including rim means coaxial with the shaft and a plurality of turbine blades secured to the rim means, the turbine stages mounted on the shaft for rotation therewith. An assembly, (d) each said stator means being located between adjacent turbine stages, each said stator means having wall means and diverter means, said wall means being perpendicular to the axis of said shaft and The diverter means makes an angle of less than 90 ° with respect to the axis of the shaft and the turbine is in the space between adjacent wall means. At least one turbine blade and said at least one turbine blade such that flow through a stage is perpendicular to the axis of said shaft and said diverter means is positioned with respect to said wall means to divert flow from a turbine stage to an adjacent turbine stage; The diverter means constitutes a seal which prevents flow between them.
A stator assembly having a plurality of flow-oriented stator means. 2. The turbine blades are adjacent to each other such that the flow between the wall means of adjacent stator means contacts the edges of the turbine blades, thereby imparting a reaction force to the turbine blades and causing the turbine to rotate. The turbine of claim 1 located between mating stator means. 3. The turbine blades have adjacent stator means such that the flow between adjacent diverter means impinges upon the surface of the turbine blades, thereby imparting a dynamic force to the turbine blades and causing the turbine to rotate. The turbine of claim 1 located in between. 4. The turbine blades wherein the flow between the wall means of adjacent stator means contacts the edges of the turbine blades thereby imparting a reaction force to the turbine blades and the flow through adjacent diverter means is further Located between adjacent stator means such that they impinge on the surface of the turbine blades thereby imparting a dynamic force to the turbine blades, the turbine blades being rotated by a combination of the applied reaction and dynamic forces. The turbine according to Item 1. 5. A turbine according to claim 1, 2 or 4 wherein each said wall means is flat in a single plane perpendicular to the axis of said shaft. 6. The turbine of claim 1, 2 or 4 wherein the turbine blades are mounted to the rim such that flow through a turbine stage contacts at least one side edge of the turbine blades. . 7. The turbine of claim 6, wherein the turbine blades are mounted on the rim such that flow through a turbine stage contacts both side edges of the turbine blades. 8. The turbine of claim 1, 2 or 4 wherein the turbine blades are mounted to the rim such that flow through a turbine stage contacts the leading edge of the turbine blades. 9. Each of said wall means comprises: (a) a plurality perpendicular to the axis of said shaft, wherein at least one said flat first portion is not coplanar with at least another said flat first portion. A flat first portion, and (b) a plurality of flat second portions located between the flat first portions and interconnecting the flat first portions with each other. The turbine according to item 1. 10. A central seal in which, if a seal is formed, the other side edge of the at least one turbine blade forms a seal of the stator means and the side edge of at least two of the turbine blades. A turbine according to claim 1, 2 or 4 further comprising means. 11. The turbine of claim 1, wherein the at least one turbine blade forming a seal with the diverter means is at least three turbine blades.