Radial turbine

Abstract

A radial turbine includes a housing, a rotor mounted on a shaft, an inlet channel for supplying a defined working medium, and an outlet channel. The rotor includes working cavities, with a generally spiral shape, which conduct the defined working medium from the inlet channel to the outlet channel, located near the center of the rotor. The working cavities have a generally rectangular cross-section, with a width (W), parallel to an axis of rotation of the rotor, and a height (H), parallel to a radius of the rotor. The width (W) is greater than the height (H), and the height (H) is not greater than six times a thickness of a boundary layer of the defined working medium.

Claims

1. A radial turbine comprising: a housing; a rotor mounted within the housing on a shaft; an inlet channel for supplying a defined working medium generally tangentially in respect to a circumference of the rotor; an outlet channel located near a centre of the rotor; the rotor comprising working cavities having a spiral shape starting tangentially to a circumference of the rotor, for conducting the defined working medium from the inlet channel to the outlet channel; each of the working cavities having a rectangular cross-section, which has a width, oriented parallel to an axis of rotation of the rotor, and a height, oriented generally parallel to a radius of the rotor; each of the working cavities having a wider wall with a boundary layer of the defined working medium developed on an internal surface of said wider wall; wherein said width is greater than said height of the rectangular cross-section, and said height is not greater than six times a thickness of said boundary layer.

2. The radial turbine according to claim 1, wherein the working medium is steam.

3. The radial turbine according to claim 1, wherein the rotor is formed by at least two discs inserted within said housing on said shaft oppositely to each other.

4. The radial turbine as claimed in claim 3, wherein the working cavities in a first disc of the at least two discs constitute spaces allowing insertion therein of a second disc of the at least two discs, the second disc being arranged opposite to the first disc, such that when the first disc is assembled with the second disc, their working cavities form the working cavities having a spiral shape, through which the working medium passes on its way from the inlet channel to the outlet channel, such that the working medium travels around the shaft at least 180 degrees before it reaches the outlet channel.

5. The radial turbine according to claim 1, wherein each of the working cavities has an end portion for directing the outflowing working medium opposite to a direction of rotation of the rotor.

6. The radial turbine according to claim 1, wherein said height is from 0.4 mm to 4 mm.

7. The radial turbine according to claim 1, wherein said width is at least 10 times larger than said height.

8. The radial turbine according to claim 1, wherein the rotor has a conical portion for mounting on the shaft, for directing the outflowing working medium to the outlet channel.

9. The radial turbine according to claim 1, wherein the height of each of the working cavities is equal to four times the thickness of said boundary layer.

10. The radial turbine according to claim 1, wherein the height of each of the working cavities is equal to two times the thickness of said boundary layer.

11. The radial turbine according to claim 1, wherein the spiral shape of each of the working cavities corresponds to a shape of a golden spiral.

12. The radial turbine according to claim 1, wherein the shaft is a hollow shaft comprising holes, wherein the holes are connected to ends of each of the working cavities, so that the hollow shaft constitutes the outlet channel.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The present invention is shown by means of exemplary embodiments on a drawing, in which:

(2) FIG. 1 shows a radial turbine assembly;

(3) FIG. 2 is an exploded view of the radial turbine assembly of FIG. 1;

(4) FIG. 3 shows a housing part;

(5) FIG. 4 shows a rotor discs mounted on the shaft

(6) FIG. 5 is an exploded view of the rotor of FIG. 4;

(7) FIG. 6 shows cross sections of the rotor assembly of the first embodiment;

(8) FIG. 7 shows enlarged view of a portion of the coupled discs 6a and 6b according to the first embodiment;

(9) FIG. 8 shows cross sections of the rotor assembly of the second embodiment;

(10) FIG. 9 shows enlarged view of a portion of the coupled discs 6a and 6b according to the second embodiment;

(11) FIG. 10 shows another embodiment of the turbine;

(12) FIG. 11 shows a shaft of the rotor according to another embodiment.

MODES FOR CARRYING OUT THE INVENTION

(13) FIG. 1 shows a radial turbine assembly in isometric view.

(14) As shown in FIG. 2, the turbine comprises two halves of a housing 1, which joined together constitute working space for the rotor 3. The working medium enters the turbine through the inlet channel 2 and leaves the turbine through the exhaust chamber 13 and the outlet channel 4. In this particular embodiment, each half of the housing 1 has its own outlet channel 4, as shown on the FIG. 2, and these outlet channels 4 are connected externally with a manifold 14.

(15) FIG. 3 shows housing part 1b, constituting with the other housing part la the housing 1 of the turbine. The housing part 1b is substantially a mirror image of part 1a, as presented in the FIG. 2. The housing part 1b comprises the inlet channel 2, which directs the incoming working medium substantially tangentially to the circumference of the rotor 3 disc. The flow of the working medium after its entrance through the inlet channel 2 is constrained within the housing by spiral extrusion, named here as directing channel 12. It favours gradual entering of the working medium into the cavities around substantially half of the rotors 3 perimeter. The outlet channel 4, situated in this embodiment perpendicular to the rotation axis of the rotor 3 relatively close to the shaft 5, allows for the exit of the working medium. The working medium, after travelling through the working cavities, enters the half spherical chamber 13, and then exits through the outlet channel 4. The spaces between the sides of the rotor 3 and the housing parts 1a and 1b comprise adequate sealing, preventing the working fluid from bypassing the working cavities 9 of the rotor 3 on its way from inlet channel 2 to outlet channel 4.

(16) FIG. 4 illustrates the rotor assembly, presenting two coaxial disc pairs joined together and mounted on the shaft 5.

(17) FIG. 5 shows the rotor assembly in an exploded view. The rotor comprises, in this particular embodiment, two pairs of discs, each pair having disc 6a and disc 6b. Discs 6a have cavities 8a with walls 7a and discs 6b have cavities 8b with walls 7b. These cavities 8a, 8b are of spiral shape, starting substantially tangentially to the perimeter of the discs. They may as well start angled about 9 in respect to the tangent of the rotors perimeter, e.g. for shortening the distance of the travel of the working medium. Discs 6a have an opening in the centre, to allow the travel of the working medium to the outlet channel 4. Discs 6a and 6b can be made of metal, preferably aluminium, and connected together to form one disc with very narrow slits. Two of such discs joint together on the shaft 5 create a rotor of the turbine. All four parts of the rotor disc are connected durably and symmetrically by means of the glue and screws in such a way, that the proper balance of the fast rotating rotor disc is preserved.

(18) FIG. 6 illustrates cross-sections of the rotor assembly of the first embodiment. The disc 6a is inserted into disc 6b, so that the working cavity 9 is created between the walls 7a and 7b. The working cavity 9, according to this invention, is of generally spiral shape and of generally rectangular cross-section with the width dimension W and height dimension H, such that it has a form of a slit. By width W it is meant, here and further in the description, a dimension of the top and the bottom sides of the rectangle constituting the cross-section profile of the working cavity, said top and bottom sides being arranged substantially parallel to the axis of the rotation of the rotor 3. The height H is oriented generally parallel to the radius of the rotor.

(19) The width dimension W is greater than the height dimension H. The height H of the slit is not greater than six times the thickness of a boundary layer of the working medium developed on the internal surface of the wider wall of the cavity 9, i.e. on the surfaces defining the width of the cavity 9. Therefore, the thickness of the core layer is not greater than the sum of the thicknesses of the boundary layers formed on the top and bottom sides of the rectangle profile constituting the cross-section. Such height of the slit is considered optimal, as the effects of viscosity are of high significance. For larger heights the effects of viscosity play smaller role and such embodiments are considered as not optimal. However, it is possible for the slit to have lower height, for example four times the thickness of the boundary layer (so that the core layer has a thickness equal to the total thickness of the boundary layers) or two times the thickness of the boundary layer (so that substantially no core layer is formed). The height H of the cavity 9 is therefore adapted to the parameters of the turbine operation under normal operation conditions, i.e. within a specific range of temperatures and pressures for which the turbine is designed to operate, and the type of the working medium for which the turbine is designed, i.e. a working medium defined for the turbine. The boundary layer thickness, , is the distance across a boundary layer from the wall to a point where the flow velocity has essentially reached the free stream velocity, u.sub.0. This distance is defined normal to the wall.

(20) The boundary layer will have, depending on the medium used and its parameters, a thickness from about 0.2 to about 0.7 mm. Therefore, the height H of the slit 9 is preferably from about 0.4 mm to about 4 mm. More preferably, the height H of the slit 9 is from 0.5 mm to 1.5 mm.

(21) This allows the working fluid to come into contact mainly with the top and bottom surfaces of the working cavity. The turbine uses the effects of adhesion and viscosity. This, in connection with the passing of the working fluid about from 180 to 270 of the discs circumference, assures high efficiency of the energy translation from the working medium to the shaft of the rotor. The mounting of discs 6b to the shaft 5 is of conical shape. This allows for directing the outflowing medium to the outlet channels 4 and favours more laminar flow of the working medium.

(22) FIG. 7 is an enlarged view of the cross-section of the first embodiment of the invention. It shows the working cavity 9, constituted by the walls 7a and 7b.

(23) Preferably, the profile of the working cavity 9 is of dimensions 18 mm0.8 mm, but may as well be of height measuring from 0.5 mm to 1.5 mm, and width of greater dimension than said height to the extent matching the demands, e.g. for specific output power. The profile may also have variable dimensions throughout subsequent sections, while maintaining the width-height ratio as stated above. In different possible embodiment, the working cavity may be created using only one disc with cavities, for example with said cavities cut in the disc material using a common CNC machine. In such embodiment, the fourth wall of the cavity cross-section profile would be formed by stacking either a smooth disc without cavities or another disc with cavities on the other side.

(24) FIG. 8 shows another embodiment of the invention. In this embodiment, the working cavity 9 has an end portion 10 for directing the outflowing working medium opposite to the direction of the rotor 3 rotation. It can be achieved for instance by increasing the curvature of the working cavity shape in the area near the half of the disc radius, so that it forms a half of the circle, starting tangentially to the initial curvature of the working cavity 9 near the half of the disc radius and ending substantially tangentially to the opening in the disc, allowing for the exit of the working medium in a manner as stated above.

(25) FIG. 9 is a closer view of the cross-section of the second embodiment, as described in the previous paragraph.

(26) FIG. 10 shows another embodiment of the turbine. The rotor 3 is mounted on a hollow shaft 15 comprising holes 16. The enlarged view E shows the end of working cavity 9, connected to the hole 16 so that the working medium can pass to the passage inside the hollow shaft 15. As a result, said hollow shaft 15 constitutes the outlet channel 4 for a working medium, which entered through the inlet. The enlarged view D shows the initial portion of working cavity 9. Preferably, in the initial portion, the height of working cavity 9 is about five times larger than its minimum height throughout the rotor 3. Similarly, the ending portion of the cavity working 9, as shown in the enlarged view E, widens before the connection to the hole 16, to provide expansion of the working medium. This widening, ending portion can be of up to 30% of the total length of the working cavity 9.

(27) The stream of working medium can be directed at an angle to the tangent of rotors 3 circumference, the angle being preferably up to 30 degrees, more preferably up to 15 degrees.

(28) The spiral shape of working cavities 9 can preferably resemble a golden spiral (e.g. Fibonacci spiral).

(29) FIG. 11 shows a shaft 15 of the rotor according to the embodiment, as described in previous paragraph.