CENTRIFUGAL SEPARATOR

Abstract: Centrifugal separator with a rotor (1), which is arranged in a gas containing chamber (4) and on its outside is provided with a number of cavities, which are located at a distance from each other and open to the chamber (4). In order to disturb the generation of sound waves in the cavities (5) of the resonance frequency of the cavities, an irregularity (6), preferably in the shape of a projection, is arranged nearby and in front of a cavity (5) seen in the rotational direction of the rotor.

Description: Centrifugal separator The present invention relates to centrifugal separators, more precisely to centrifugal separators, the rotors of which are arranged rotatably in a gas containing chamber and on the out¬ side are provided with a number of cavities, which cavities during operation of the rotor are open to the chamber. Centrifugal separators of this kind generate a sound, which in many cases exceeds the sound level, which can be accepted. In particular this is the case in centrifugal separators, the rotors of which during operation rotates at a relatively high number of revolutions. In WO 86/06006 a centrifugal separator is disclosed, which has a rotor of this kind. This rotor is arranged in a gas containing chamber and has a number of cavities in the form of openings on its outside, which openings are open to the chamber. It has shown to be very difficult to reduce the sound level during operation of such a centrifugal separator to an acceptable level. The sound of the centrifugal separator is generated inter alia as wave movements in the gas which is present in said openings. The object of the present invention is to accomplish a rotor, which generates essential less sound than hitherto known rotors even at relatively high operational number of revolutions. The solution according to the invention is based upon the under- standing that the wave movements in the gas present in the cavities often are responsible for a great deal of the sound generated by the rotor and that these wave movements are gene¬ rated by the gas, which is present in the chamber and during operation of the rotor is passed by the openings of the cavities towards the chamber. In order to achieve a reduction of the sound level of the sound generated by a rotor of the kind initially described, there is suggested according to the present invention that the outside of the rotor has at least one irregularity disturbing the generation of a tone near by and in front of the one of the cavities seen in the rotational direction of the rotor. The irregularities are so designed that the creation of wave movements in the cavities of the resonance frequency of the cavities is disturbed. Hereby, the gas flow at the opening of the cavity is disturbed in a way such that the sound level of the tone of the resonance frequency, which the gas flow generates in the cavity is reduced considerably or completely eliminated. The irregularity is preferably equally distributed around the rotor. Suitably, the outside of the rotor has one irregularity in front of each cavity. In a preferred embodiment of the invention the irregularity consists of a projection projecting radially outwards from the outside of the rotor in the shape of a finj the longitudinal direction of which essentially coincides with the rotational direction of the rotor. In this embodiment it is beneficial if the projections or fins extend in the rotational direction from one cavity to an adjacent cavity. If the projections consist of fins the irregularities easily can be made during manufacturing when turning the outside of the rotor. In an alternative embodiment the irregularity consists of a recess, which is arranged on the outside of the rotor in front of the cavities. In the following, the invention will be described with reference to the accompanying drawings, in which Fig 1 shows partly in a side view and partly in section a part of a centrifugal separator, Fig 2 schematically shows an axial section through a nart of a centrifugal separator according to the invention, and Fig 3 schematically shows a part of a radial section through a centrifugal separator according to the invention. The centrifugal separator shown in figure 1 has a rotor 1 , which is driven and supported by a vertical shaft 2. The rotor is sur- rounded by a stationary casing 3, which forms a gas containing chamber 4, in which the rotor rotates. A number of cavities 5 are arranged on the outside of the rotor, which are open to the chamber 4 and located at a distance from each other in the rotational direction of the rotor. In the shown embodiment these cavities consist of openings, which are equally distributed around the rotor. Through these openings a component separated in the rotor is thrown out intermittently. Between these openings, projections 6 are arranged to disturb the creation of wave movements in the cavities of the resonance frequency of the cavities. Preferably, these projections are arranged near by and in front of each opening seen in the rotational direction of the rotor, but in the shown example the projection 6 consists of fins extending from one opening to an adjacent opening. The longitudinal direction of these fins coincides with the rotatio¬ nal direction of the rotor. In figure 2 there is shown schematically an axial section through a rotor of a centrifugal separator, which is designed in accordance with the present invention. As the embodiment shown in figure 1, this rotor has a number of cavities 5 in the shape of openings arranged equally distributed around the rotor on its outside. Radially inside the openings 5 the rotor has a connec- tion 7 extending around the rotational axis of the rotor and connecting the different openings to each other. On the outside of the rotor near by and in front of each opening 5, seen in the rotational direction, a projection 6 is arranged in the shape of a fin as in the embodiment shown in figure 1. In figure 3 there is shown schematically a part of a radial section through the rotor shown in figure 2. This section extends through the openings 5 and is seen towards the fins 6. In this figure, the said connection 7 is schematically marked. By designing a" centrifugal separator in the described manner, the flow pattern at the front edge of the cavities is disturbed for the gas present in the chamber 4, which is passed by the cavities 5-

Claims: Claims 1. Centrifugal separator with a rotor (1), which is arranged in a gas containing space (4) and on its outside is provided with a number of cavities (5), which are located at a distance from each other in the rotational direction of the rotor and open to the chamber (4) during operation of the rotor, c h a r a c t e r i z e d i n that the outside of the rotor has at least one irregularity (6) disturbing the generation of a tone near by and in front of a cavityj seen in the rotational direction of the rotor, the irregularity (6) being so desi~ ιed that the creation of wave movements in the cavities (5) of the resonance frequency of the cavities is disturbed. 2. Centrifugal separator according to claim 1, c h a r a c ¬ t e r i z e d i n that the cavit ' .es (5) are equally distri¬ buted around the rotor. 3. Centrifugal separator according to claim 1 or 2 c h a - r a c t e r i z e d i n that the outside of the rotor has one irregularity (6) in front of each cavity. 4. Centrifugal separator according to any of the preceding claims, c h a r a c t e r i z e d i n that said irregula- rity consists of a projection (6) projecting radially outwards from the outside of the rotor. 5. Centrifugal separator according to claim 4j c h a r a c ¬ t e r i z e d i n that said projection consists of a fin, the longitudinal direction of which coincides with the rotational direction of the rotor. 6. Centrifugal separator according to claim 4 or 5, c h ¬ r a c t e r i z e d i n that said projection extends in the rotational direction from one cavity to an adjacent cavity. 7. Centrifugal separator according to claim 1, 2 or 3, c h a r a c t e r i z e d i n that said irregularity consists of a recess.

Inventors: ANDERSSON PER-OLOF, HELLEKANT OTTO, LAHTI BENGT, ANDERSSON, PER-OLOF, HELLEKANT, OTTO, LAHTI, BENGT
Applicants: ALFA LAVAL SEPARATION AB, ALFA-LAVAL SEPARATION AB
Application year: 1990
Main classification: B04B7
IPC codes: B04B1, B04B7, G10K11