Inertial filter

Abstract: This invention relates to an inertial filter (1) which utilises differential fluid velocity of a fluid flowing through fluid passageways (9) to remove particulate matter entrained in said fluid. The filter (11) has a plurality of baffle plates (2) located within a housing (3). Each baffle plate (2) has a medial deflector plate (4) from which extends a pair of lateral deflector plates (5). The plates have flanges (7,8) and adjacent plates are cooperable in use to form a fluid passageway (9) through the filter. The orientation and configuration of the flanges and plates form at least two areas where fluid flowing between the plates is alternately speeded up and slowed down. As the fluid flows centrifugal force flings particulate matter entrained in this fluid outwardly where it collects on the plates, flows operatively downwardly along the plates, is collected in a channel towards the operative bottom of the filter and is removed.

Description: THIS INVENTION relates to an inertial filter primarily for use in extracting matter from fluids. Inertial filters which make use of the inertia of particulate matter in a fluid passing through the filter to separate the particulate matter from the fluid are well known. These types of filters have a series of generally arcuate baffle plates arranged within a housing such that the longitudinal edges of the plates overlap defining a fluid passageway having at least two opposite directed bends per pair of baffle plates. As a fluid passes through the fluid passageway and negotiates the bends, the fluid velocity at the outer margin of the bend is greater than the fluid velocity at the inner margin of the bend. This difference in velocity coupled with the change in direction of the fluid urges particulate matter in the fluid towards the outer margin of the bend. When the fluid negotiates an oppositely directed bend, the fluid velocity is reduced and the particulate matter is precipitated out and collected, usually in channels towards the bottom edge of the housing, for removal. DE-C-358,014 discloses an inertial filter which is comprised of a plurality of baffle plates within a housing, each baffle plate having, when viewed in transverse cross-section, a medial deflector plate and a pair of lateral deflector plates projecting from a central rachis. The medial deflector plate has a single flange orientated outwardly and downstream, and the medial deflector plate and flange co-operate with the lateral deflector plates of adjacent baffle plates to form a fluid passageway through the filter. In many cases the velocity of fluid at the inner margin of the bend is not sufficiently low to enable small particles like water or fat droplets to precipitate out. This reduces the efficiency of the filter. It is an object of this invention to provide an inertial filter which at least partly alleviates the above disadvantage. In accordance with this invention there is provided an inertial filter comprising a plurality of baffle plates within a housing, wherein each baffle plate has, when viewed in cross-section in the same plane as the intended fluid flow through the filter, a medial deflector plate and a pair of lateral deflector plates projecting from a central rachis, the medial deflector plate having a pair of outwardly orientated flanges extending therefrom and each lateral deflector plate having an inwardly orientated flange extending therefrom, the medial deflector plate flanges co-operating with the lateral deflector plate flanges of adjacent baffle plates to form through the filter a fluid passageway arranged to create at least two areas of differential fluid velocity, each around a respective pair of a medial deflector plate flange and an opposing lateral deflector plate flange, which utilise inertia of particulate matter entrained in fluid flowing through the filter to remove said particulate matter from the fluid. Preferably each lateral deflector plate is angled at approximately 135° relative to the medial deflector plate. Preferably, the flanges are at right angles to the longitudinal filter axis. Advantageously, each baffle plate can consist of a pair of sub plates affixed to each other, each sub plate forming one half of the width of the medial deflector plate and one lateral deflector plate, the sub plates of each baffle plate being mirror images of each other in cross-section. Desirably, the lower margins of the baffle plates, or alternatively of one of a pair of sub plates, co-operate with the housing to form a gutter for collection and removal of particulate matter. In accordance with further aspects of this invention, there is provided a baffle plate for use in an inertial filter as described above or a sub plate for use in constructing baffle plates as described above. A preferred embodiment of the invention will be described below by way of example only, and with reference to the accompanying drawing which is a part sectional isometric view of an inertial filter according to the invention. Referring to the the drawing, an inertial filter (1) consists of a plurality of generally vertically orientated baffle plates (2) within a housing (3). Each baffle plate (2), when viewed in transverse cross-section, has a medial deflector plate (4) and a pair of lateral deflector plates (5) projecting from a central rachis (6). Each medial deflector plate (4) has a pair of operatively outwardly orientated flanges (7) extending therefrom and each lateral deflector plate (5) has an operatively inwardly orientated flange (8) extending therefrom. The lateral deflector plate flanges (8) in a filter (1) are positioned such that they are opposite the rachis (6) of an adjacent baffle plate (2). In this way a fluid passageway (9) is formed between adjacent baffle plates (2). In the embodiment illustrated the lateral deflector plates (5) are disposed at an angle of 90° to each other and at an angle of 135° to the medial deflector plate (4). The flanges (7 & 8) are at right angles to the longitudinal axis of the filter (1). Each baffle plate (2) consists of a pair of identical but mirror imaged sub plates (11) affixed to each other at the medial deflector plate (4). In the assembled filter the baffle plates (2) are substantially vertically orientated and the sub plates are vertically staggered so that a continuous channel is formed at the operatively upper and lower ends of the filter. The housing (3) is formed from a number of channel sections (12) affixed to each other with the flanges (13) of the channels facing inwardly. The baffle plates (2) are located within the channels and are affixed thereto. In the embodiment illustrated the channel sections (12) and baffle plates are manufactured from aluminium although it will be appreciated that any suitable metal sheets can be used. The elements are spot welded to each other. In use, air or any other fluid is drawn through the fluid passageways it is forced to negotiate a bend formed by the flange (8) of a lateral deflector plate and the side of an adjacent lateral deflector plate. In negotiating this bend air towards the outer periphery of the radius of the bend speeds up while air towards the centre slow down. This differential causes particulate matter entrained in the fluid to be flung outwardly. Once the first bend has been negotiated the fluid passageway turns in the opposite direction. This reduces the velocity of the fluid which had previously been increased and particulate matter entrained in the fluid precipitates out or collects on the walls of the deflector plates to run down and collect in the gutter at the outermost end of the filter. It is envisaged that the cross sectional profile and arrangement of the baffle plates will render the inertial filter more efficient at removing particulate matter from a fluid than most conventional inertial filters. In addition the filter is bi-directional In particular the filter may be manufactured from any suitable sheet material and it may be adapted for either vertical or horizontal operation.

Claims: An inertial filter (1) comprising a plurality of baffle plates (2) within a housing (3), wherein each baffle plate (2) has, when viewed in cross-section in the same plane as the intended fluid flow through the filter, a medial deflector plate (4) and a pair of lateral deflector plates (5) projecting from a central rachis (6), the medial deflector plate (4) having a pair of outwardly orientated flanges (7) extending therefrom and each lateral deflector plate (5) having an inwardly orientated flange (8) extending therefrom, the medial deflector plate flanges (7) co-operating with the lateral deflector plate flanges (8) of adjacent baffle plates (2) to form through the filter a fluid passageway (9) arranged to create at least two areas of differential fluid velocity, each around a respective pair of a medial deflector plate flange (7) and an opposing lateral deflector plate flange (8), which utilise inertia of particulate matter entrained in fluid flowing through the filter to remove said particulate matter from the fluid. An inertial filter as claimed in claim 1, wherein each lateral deflector plate (5) is angled at approximately 135° relative to the medial deflector plate (4). An inertial filter as claimed in claim 1 or 2, wherein the flanges (7,8) are at right angles to the longitudinal filter axis. An inertial filter as claimed in any one of the preceding claims, wherein each baffle plate (2) consists of a pair of sub plates (11) affixed to each other, each sub plate (11) forming one half of the width of the medial deflector plate (4) and one lateral deflector plate (5), the sub plates of each baffle plate (2) being mirror images of each other in transverse cross-section. An inertial filter as claimed in claim 4, wherein the lower margins of a pair of sub plates (11) co-operate with the housing to form a gutter for collection and removal of particulate matter. An inertial filter as claimed in any one of claims 1 to 3, wherein the lower margins of the baffle plates co-operate with the housing to form a gutter for collection and removal of particulate matter. Baffle plates (2) for constructing an inertial filter, the baffle plates having, when viewed in cross-section in the same plane as the intended fluid flow around the baffle plates, a medial deflector plate (4) and a pair of lateral deflector plates (5) projecting from a central rachis (6), the medial deflector plate (4) having a pair of outwardly orientated flanges (7) extending therefrom and each lateral deflector plate (5) having an inwardly orientated flange (8) extending therefrom, the baffle plates being shaped such that an arrangement of the baffle plates with the medial deflector plate (4) of one baffle plate between the lateral deflector plates (5) of an adjacent baffle plate creates an inertial filter in which the medial deflector plate flanges (7) co-operate with the lateral deflector plate flanges (8) of adjacent baffle plates (2) to form through a filter a fluid passageway (9) arranged to create at least two areas of differential fluid velocity, each around a respective pair of a medial deflector plate flange (7) and an opposing lateral deflector plate flange (8), which utilise inertia of particulate matter entrained in fluid flowing through the filter to remove said particulate matter from the fluid. A sub plate (11) for constructing an inertial filter, the sub plate having, when viewed in cross-section in the same plane as the intended fluid flow around the sub plate, a medial deflector plate portion and a lateral deflector plate (5) projecting therefrom, the sub plate being shaped such that an assembly of two sub plates which are mirror images of each other with the medial plate deflector portions assembled together creates a baffle plate having, when viewed in cross-section in the same plane as the intended fluid flow around the baffle plate, a medial deflector plate (4) and a pair of lateral deflector plates (5) projecting from a central rachis (6), the medial deflector plate portions each having a flange (7) extending therefrom and each lateral deflector plate (5) having a flange (8) extending therefrom, the flanges (7,8) being arranged such that in said assembly of two sub plates the pair of medial deflector plate flanges (7) are orientated outwardly and the pair of lateral deflector plate flanges (8) are orientated inwardly, and the sub plate being shaped such that an arrangement of said baffle plates with the medial deflector plate (4) of one baffle plate between the lateral deflector plates (5) of an adjacent baffle plate creates an inertial filter in which the medial deflector plate flanges (7) co-operate with the lateral deflector plate flanges (8) of adjacent baffle plates (2) to form through a filter a fluid passageway (9) arranged to create at least two areas of differential fluid velocity, each around a respective pair of a medial deflector plate flange (7) and an opposing lateral deflector plate flange (8), which utilise inertia of particulate matter entrained in fluid flowing through the filter to remove said particulate matter from the fluid.

Inventors: DE WITT JAMES JOHN, OOSTHUIZEN PETRUS MARTHINUS, DE WITT, JAMES JOHN, OOSTHUIZEN, PETRUS MARTHINUS
Applicants: OOSTHUIZEN PETRUS MARTHINUS, WITT JAMES JOHN DE, DE WITT, JAMES JOHN, OOSTHUIZEN, PETRUS MARTHINUS
Application year: 1995
Main classification: B01D45
IPC codes: B01D45