US3608395A

US3608395A - Drum rotor

Info

Publication number: US3608395A
Application number: US737731A
Authority: US
Inventors: Gunnar Walter Brandt
Original assignee: Studsvik Energiteknik AB
Current assignee: Studsvik Energiteknik AB
Priority date: 1967-06-28
Filing date: 1968-06-17
Publication date: 1971-09-28
Anticipated expiration: 1988-09-28
Also published as: SE320936B; NL6808692A; FR1573386A

Abstract

DRUM ROTOR HAVING A ROTATION-SYMMETRICAL, PREFERABLY CYLINDRICAL MANTLE AND AT LEAST ONE END WALL ATTACHED THERETO AND BEING ADAPTED TO BE ROTATED ABOUT ITS AXIS. THE MATERIAL IN THE END WALL HAS A RATIO BETWEEN DENSITY AND MODULE OF ELASTICITY WHICH IS SO MUCH HIGHER THAN THE CORRESPONDING RATIO FOR THE MANTLE THAT THE ELONGATIONS IN THE MANTLE AND THE END WALL IN THE JUNCTURE THEREBETWEEN DUE TO THE CENTRIFUGAL FORCE ARE ESSENTIALLY EQUAL.

Description

Sept. 28, 1971 G. w. BRANDT DRUM ROTOR Filed June 17, 1968 United States Patent 3,608,395 DRUM ROTOR Gunnar Walter Brandt, Nykoping, Sweden, assignor to Aktiebolaget Atomenergi, Stockholm, Sweden Filed June 17, 1968, Ser. No. 737,731 Claims priority, applic9atio1 Sweden, June 28, 1967,

Int. Cl. F16f 15/30; B04b 7/00 US. Cl. 74-572 4 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a drum rotor for use for instance in centrifugation at a high speed of rotation.

In conventional designs of drum rotors adapted for a high speed of rotation consisting of a cylindrical mantle and end walls attached thereto the structure, during the rotation of the drum, is subjected to forces in radial direction tending to stretch material in mantle and end walls. By experience and calculations it can be shown that the elongation in the mantle is greater than the elongation at the outer edge of the end walls. From this reason unacceptable additional strain arises at the juncture between mantle and end walls, and this additional strain causes fiexural stress at the ends of the mantle. Thus, the material of the drum may be subjected to too high a strain with regard to its strength, besides which great difliculties arise in connection with the attachment of the end walls to the mantle.

The present invention has for a purpose to eliminate the problems indicated above in drum rotors. The drum rotor according to the present invention has a rotation-symmetrical, preferably cylindrical mantle and at least one end wall attached thereto. The drum rotor is characterized in that the material in the end wall has a ratio between density and module of elasticity which is so much higher than the corresponding ratio for the mantle that the elongations in the mantle and the end wall in the juncture therebetween due to the centrifugal force are essentially equal.

The drum rotor is suitably made of a fibre-reinforced plastic, the material of the end wall having a smaller portion of reinforcing fibres than the material of the mantle. Alternatively, reinforcing fibres may be used in the end wall which have a lower module of elasticity than those of the mantle.

In a particularly preferred embodiment of the drum rotor of the invention the portion of reinforcing fibres oriented in the direction of the main stress is lower in the material of the end wall than in that of the mantle. It is also possible to use a plastic in the material of the end wall having a greater density than plastic in the material of the mantle.

The invention will now be described by an exemplifying embodiment with reference to the appended drawing that diagrammatically shows a centrifuge in section.

The centrifuge shown in the drawing is adapted for the separation of gases having different molecular weights. The centrifuge includes a drum rotor having a cylindrical mantle 3 and an end wall 1, 2 attached to each end of said mantle. An inlet tube for the gas mixture to be cenice trifuged is connected to the end Wall 1, and said inlet tube 5 is connected to the end wall 11 by means of a flange 6 in a manner not shown in detail, for instance by a weld or by screws. The end wall 1 is provided with a central opening, through which connection with the interior of the drum rotor is maintained through the inlet tube 5.

At a distance inside the end wall 1 and parallel thereto a partition wall 15 is arranged which is provided with a series of inner apertures 16 and a series of outer apertures 17, which apertures are suitably arranged along concentric circles.

At the opposite end of the centrifuge a

coupling assembly

8, 9 is arranged on the end wall 2, the rotatable coupling half 8 of which is attached to the end wall 2 by means of a flange 7. The fixed coupling half 9 supports a side outlet tube 11. Inside the end wall 2 and parallel thereto a partition wall 19 is arranged, which, as is the case with the partition wall 15, is provided with inner apertures 20 and outer apertures 21, said apertures also being suitably arranged along concentric circles. On the lower surface of the partition wall 19 and outside the inner apertures 20 a collecting cap 23 is arranged which at the bottom end is connected to an outlet tube 12 provided at its inner end with a flange 25 for the connection to the collecting cap 23. The interior of said cap 23 is connected to the interior of the outlet tube 12 through a central opening 26. The outlet tube 12 extends through the

coupling assembly

8, 9 and is rotatable relative the coupling half 9 and also gastightly sealed thereagainst. The inlet tube 5 and the outlet tube .12 are journalled in bearings not shown to allow the rotation of the rotor and thus act as pivots.

The function of the above described centrifuge is briefly the following. The drum rotor of the centrifuge is brought into rotation with a desired speed and the gas mixture to be separated is continuously supplied from above through the inlet tube 5. In view of the centrifugal force the heavy fraction of the gas mixture will be thrown outwardly towards the walls of the mantle 3 and flows downwardly through apertures 17 as shown with arrows in the drawing and further downwardly through the apertures 21 in the lower partition wall 19. The heavy fraction then enters the space between the

coupling assembly

8, 9 and the outlet tube 12 and is discharged through the side outlet tube 11. The light fraction remains in the central parts of the centrifuge and flows downwardly through the apertures 16 in the upper partition wall 15 and further downwardly through the apertures 20 in the lower partition wall 19 and into the collecting cap 23, from which the light frac tion leaves the centrifuge through the outlet tube 12.

In the following it is assumed that the rotor works with a gas having a low pressure, for instance mm. Hg, in view of which the centrifugal forces acting on the gas are negligible as compared to the centrifugal forces acting on the mantle in view of the fact that the mass of the gas is much lower than that of the mantle.

Now assume that the mantle 3 and the end walls 1, 2 are made of the same material, viz. glass fibre-reinforced plastic. In the following Table I certain data for the material of the drum rotor are given.

l Unsaturated chlorinated polyester, styrene modified Soredur G 10 1n cured form.

The mantle is assumed to have a diameter of 20 cm. and a length of 100 cm. If the drum rotor is brought to rotate with a speed of 650 revolutions per second it is possible to calculate from the data of Table I that the radial elongation of the mantle is about 0.7 mm., whereas the radial elongation of the end walls is merely 0.16 mm. Due to this difference in radial elongation undesirable stress arises in the juncture between mantle and end Walls.

While using the same material in the mantle the end walls are now made of another material and in Table II below the corresponding data as those of Table I are given for this material.

2 Polyvinylidene bromide in crystalline form.

It is possible from the data given in Table H to calculate that in this case the end walls will be subjected to a radial elongation of about 0.7 mm., i.e. the same elongation as that to which the mantle is subjected.

It will be easily understood by those skilled in the art ,what extraordinary advantages are obtained when mantle and end walls are subjected to an equal radial elongation when rotated. Firstly, the material in the juncture between mantle and end walls is not subjected to additional stress difficult to calculate, and, secondly, the joining of the end walls and mantle need not cause any problems because the requirements as to the strength of the joint will not be high.

It is easily understood that the desired ratio between density and module of elasticity in the material in the end walls can be obtained in many ways. The density of the material of the end walls can be increased by selecting a plastic material and/or a reinforcing material having a high density. The module of elasticity can be lowered by lowering the portion of reinforcing fibres in the material 'of the end walls. Moreover, the module of elasticity can be essentially reduced by orienting the reinforcing fibres in the end walls essentially in another direction than the radial direction which is a direction of the main stress.

As a principle, any material may be used in the drum rotor of the invention provided that the material fulfils the requirements as to strength with regard to rotational speed, dimensions etc. However, thermosetting resins in combination with glass fibre reinforcement are particularly suitable.

The mantle may also be reinforced with another fibre material than glass fibres, for instance with graphite fibres, the ratio between module of elasticity and density of which is essentially higher than the corresponding ratio for glass fibres, thereby causing a corresponding smaller elongation in the mantle. It has surprisingly been found that it is possible to produce graphite fibres having a very high strength, the graphite fibres being polycrystalline and consisting of small graphite crystallites, the graphite planes of which are mainly orientedparallel to the fibre axis. The control of this orientation is essential to obtain a high strength. Further examples of reinforcing materials having a high ratio between module 'of elasticity and density are found among several groups of materials, for instance single crystals, so-called whiskers, polycrystalline materials, such as Al O ZrO and composite materials, such as B 0 and SiC deposited on metal threads. The high .-strength of whiskers, that can consist of ceramic whiskers,

such as A1 0 and metal whiskers, for instance Cr, Cu, is supposed to depend on the fact that they have a high degree of crystalline perfection with few or no dislocations and that they are free from surface damages. For a cold-drawn metal thread having a small diameter the strength is explained by the very strong-deformation and by a certain grain orientation.

It is also possible to use completely different materials in mantle and end walls, for instance lightweight metal in the mantle and glass fibre-reinforced plastic in the end walls. I w

The above considerations regarding the ratio between density and module of elasticity of the material of the end walls 1, 2 are, of course, applicable also on the

partition walls

15, 19. The problems in connection with said partition walls at the juncture between the mantle and these walls are exactly the same as for the end walls as regards the elongation during the rotation.

What is claimed is:

1. Drum rotor having a rotation-symmetrical, preferably cylindrical mantle made from a fibre-reinforced plastic and at least one end wall of fibre reinforced plastic attached thereto and being adapted to be rotated about its axis, the improvement wherein the material in the end wall has a ratio between density and module of elasticity which by means of a difference in its reinforcing fibres in relation to the fibres in the mantle is so much higher than the corresponding ratio for the material in the mantle that the elongations in the mantle and the end wall in the juncture therebetween due to the centrifugal force are essentially equal.

, 2. Drum rotor according to claim 1 made of fibre-reinforced plastic, characterized in that the material of the endwall has a smaller proportion of reinforcing fibres than the material of the mantle.

. 3. Drum rotor according to claim 1 made of fibre-reinforced plastic, characterized in that the material of the end wall has reinforcing fibres having a lower module of elasticity than those of the mantle.

4. Drum rotor according to claim 1, made of fibrereinforced plastic, characterized in that the proportion of reinforcing fibres oriented in the direction of the main stress is lower in the material of the end wall than in the material of the mantle.

3/ 1958 Netherlands 233-27 FRED C. MATTERN, JR., Primary Examiner F. D. SHOEMAKER, Assistant Examiner U.S. C1.X.R.