EP0428705B1

EP0428705B1 - Centrifugal separator

Info

Publication number: EP0428705B1
Application number: EP19900909818
Authority: EP
Inventors: Per-Olof Andersson; Bengt Lahti; Otto Hellekant
Original assignee: Alfa Laval Separation AB
Current assignee: Alfa Laval Separation AB
Priority date: 1989-06-13
Filing date: 1990-05-31
Publication date: 1993-04-28
Anticipated expiration: 2010-05-31
Also published as: SE463903B; WO1990015667A1; ES2041179T3; SE8902127L; SE8902127D0; JPH04500333A; EP0428705A1

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

The present invention relates to centrifugal separators having rotors arranged rotatably in a gas containing space or chamber and on the outside are provided with a number of cavities, which cavities are open to the chamber during operation of the rotor.
Centrifugal separators of this kind generate a sound, which in many cases exceeds an acceptable sound level. In particular, this is the case in centrifugal separators whose rotate at a relatively high number of revolutions.
WO 86/06006 discloses a centrifugal separator 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 provide a rotor which generates substantially less sound than hitherto known rotors, even at a relatively high operational number of revolutions.
The solution according to the invention is based upon the understanding 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 generated by the gas which, during operation of the rotor, is passed by the openings of the cavities facing the chamber.
In order to achieve a reduction of the sound level 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 to and in front of the one of the cavities seen in the rotational direction of rotor. The irregularities are so designed that the creation of wave movements in the cavities at the resonance frequency of the cavities is disturbed.
In this way, 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 uniformly 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, preferably in the form of a fin, 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 can easily be made during manufacture, when turning the outside of the rotor.
In an alternative embodiment, the irregularity consists of a recess or recesses, each arranged on the outside of the rotor in front of a cavity or cavities.
In the following, the invention will be described with reference to the accompanying drawings, in which

Fig 1 shows, partly in side view and partly in section, a part of a centrifugal separator,
Fig 2 schematically shows an axial section through a part 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 surrounded 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 illustrated 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 at the resonance frequency of the cavities. Preferably, these projections are arranged near to and in front of each opening seen in the rotational direction of the rotor, and in the example shown, the projections 6 consists of fins extending from one opening to an adjacent opening. The longitudinal direction of these fins coincides with the rotational 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 in the embodiment shown in figure 1, this rotor has a number of cavities 5 in the form of openings arranged equally distributed around the rotor on its outside. Radially inside the openings 5, the rotor has a connection 7 extending around the rotational axis of the rotor and connecting the different openings to each other. On the outside of the rotor, near to and in front to each opening 5, seen in the rotational direction, a projection 6 is arranged in the form 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 the said connection 7 is schematically marked.
By designing a centrifugal separator in the described manner, the flow pattern of the gas present in the chamber 4 is disturbed at the front edges of the cavities 5 as they pass through the gas.

Claims

Centrifugal separator with a rotor (1) arranged in a gas containing space (4) and which 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 are open to the chamber (4) during operation of the rotor, characterized in that the outside of the rotor has at least one irregularity (6) disturbing the generation of a tone near to and in front of a cavity, seen in the rotational direction of the rotor, the irregularity (6) being so designed that the creation of wave movements in the cavities (5) at the resonance frequency of the cavities is disturbed.
Centrifugal separator according to claim 1, characterized in that the cavities (5) are equally distributed around the rotor.
Centrifugal separator according to claim 1 or 2, characterized in that the outside of the rotor has one irregularity (6) in front of each cavity.
Centrifugal separator according to any of the preceding claims, characterized in that said irregularity consists of a projection (6) projecting radially outwards from the outside of the rotor.
Centrifugal separator according to claim 4, characterized in that said projection consists of a fin, the longitudinal direction of which coincides with the rotational direction of the rotor.
Centrifugal separator according to claim 4 or 5, characterized in that said projection extends in the rotational direction from one cavity to an adjacent cavity.
Centrifugal separator according to claim 1, 2 or 3, characterized in that said irregularity consists of one or more recesses.