US3050240A

US3050240A - Centrifugal contaminant extractor

Info

Publication number: US3050240A
Application number: US724717A
Authority: US
Inventors: Rex C Darnell
Original assignee: DYNAMIC FILTERS Inc
Current assignee: DYNAMIC FILTERS Inc
Priority date: 1958-03-28
Filing date: 1958-03-28
Publication date: 1962-08-21
Anticipated expiration: 1979-08-21
Also published as: GB886314A

Description

1962 R. c. DARNELL 3,050,240

CENTRIFUGAL CONTAMINANT EXTRACTOR Filed March 28, 1958 2 SheetsSheet 1 INVENTOR- Fax 6', ,Udrfie/Z Aug. 21, 1962 R. c. DARNELL 3,050,240

CENTRIF'UGAL CONTAMINANT EXTRACTOR Filed March 28, 1958 2 Sheets-Sheet 2 Fex 6'. ,Ddrzre/Z United States Patent Oflfice Patented Aug. 21, 1962 3,050,240 CENUGAL CONTAMINANT EXTRACTGR Rex C. Darnell, Dexter, Mic-11., assignor to Dynamic Filters, Inc, Detroit, Mich, a corporation of Michigan Filed Mar. 28, 1958, Ser. No. 724,717 1 Claim. (Cl. 233-31) This invention relates to contaminant extracting or filtering devices for liquids and more particularly to a contaminant extracting device having a rotating element imparting a centrifugal force to the liquid to be cleaned in order to purge it of any contaminant particles contained therein.

Fundamentally, the present invention comprises a centrifuge having means for the continuous flow of fluid therethrough, and is designed for use in liquid flow systems in which it is desired to extract a high percentage of contaminants from the liquid. The operation of the device of the present invention may be understood by reference to the phenomena of decantation and eieutration which deal with the law of falling bodies in liquids. It is known that under the influence of gravitational force (one G), a particle of a given surface area, volume and density will fall in a fluid of a given viscosity and specific gravity at a certain rate. It is also known that as the number of units of gravitational force (the G value) influencing the body increases, the rate of fall of the body through the liquid will increase. Thus, as liquid is flowed through the device of the present invention it is continuously subjected to extreme gravitational forces in order to accomplish a rapid separation of contaminating particles or bodies, such as sand, dirt, lint or globular ice particles, from the liquid. By the time a given quantity of liquid has completed its course of travel through the device of the present invention it will have been purged of substantially all contaminating particles down to ten microns in size and a percentage of the contaminating particles between ten and two microns in size. The device operates to retain these contaminants in special repositories within the rotating centrifuge assembly, while the cleaned liquid flows out of the device.

By way of example, the device of the present invention is highly suited for the removal of contaminants from aviation fuel after it has left the airplane tank and is about to enter the engines fuel system. The fuel injection nozzles of gas turbine engines are subject to becoming plugged from contaminants contained in the fuel under certain operating conditions and other control mechanisms are subject to malfunctioning from undesired foreign bodies in the fuel. Furthermore, the precision parts of high pressure fuel pumps require protection from the contaminants frequently found in unfiltered fuel. Therefore, modern aircraft design requires that fuel flowing to the aircraft fuel system from the fuel tank be purged of a high percentage of its contaminating particles. The efficient and reliable performance of this function constitutes a primary object of the present invention.

An additional object of the present invention is to provide a contaminant extracting device which may advantageously be used in aircraft operating in tropical climates and at high altitudes where fuel is subject to vaporizing and where inadequate static pressure exists to adequately feed a high pressure fuel pump. The use of line retention type filters having filtering media produces a resistance to fluid flow even when the filters are clean. This resistance, and consequent pressure drop, becomes increasingly greater as the filtering media become covered with contaminants, which process further aggravates inadequate pressure problems. The device of the present invention not only eliminates the drop in line pressure encountered with the static line type filter, but in fact provides an increase in pressure in order to avoid fuel pump cavitation.

In order to meet the problem of fuel pump cavitation some conventional aircraft filtering devices have incorporated by-pass valves which in response to low pressure permit unfiltered fuel to flow directly downstream to the engine fuel system. Serious damage can be done to vital parts under such circumstances, not only by dirt but by ice, which is frequently found in aviation fuel. It is therefore another object of the present invention to eliminate the need for a by-pass valve and assure continuous removal of the dirt, ice or other contaminants which might injure an aircraft fuel system.

It is an additional object of the present invention to provide a contaminant extracting device in which the aboveanentioned pressure increase boost may be varied by changing an inexpensive component of the device.

It is a further object of the present invention to provide a contaminant extracting device of the above character in which the contaminants are retained and stored within the rotating centrifuge assembly in a manner preventing remix-ture with the cleaned fuel flowing out of the device.

It is another object of the present invention to provide a contaminant extracting device in which the effectiveness of the contaminant storage means is independent of the position or attitude of the device and whereby the device may be completely inverted or placed in any position without danger of the contaminants emptying back into the fluid flow passages.

An additional object of the present invention is toprovide a device of the above character incorporating means to prevent shifting of retained contaminant and thus avoid any imbalance in the operation of the machine.

A further object of the present invention is to provide a device of the above character which may be easily and readily disassembled for cleaning and which incorporates means to prevent the exposure of relatively movable sealing surfaces during disassembly for maintenance so that such surfaces do not pick up dirt or contaminant as the device is being cleaned.

Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is an end elevational view of a contaminant extracting device embodying the principles of the present invention;

FIG. 2 is an enlarged sectional view of the structure illustrated in FIG. 1 taken along the line 22 thereof, the rotatable centrifuge being taken along the line 2'--2' of FIG. 3; and

FIG. 3 is a reduced sectional view of the structure illustrated in FIG. 2 taken along the line 3-3 thereof.

Referring now to the drawings:

FIG. 2 illustrates a stationary housing 11 having an interiorly threaded inlet port 13 through which contaminated fuel is admitted to the device from an aircraft fuel tank or other source of liquid to be cleaned. Rotatably supported in the center of the housing 11 is a drive shaft 15 having splined outer and inner ends 17 and 19, respectively. The left-hand side of the housing 11, as viewed in FIG. 2, is provided with an apertured flange 21 by which the entire device may be supportingly bolted to an engine framework or other supporting body. A pilot shoulder 23 is located radially inwardly from the flange 21 in order to accurately align the splined end 17 of the shaft 15 with its driving member. The right-hand side of the housing 11 is provided with an annular flange 25 coaxial with the axis of the shaft 15 and within which the annular extremity 27 of a generally cup shaped, stationary housing cover member 29 registers. Three identical bolts 30 serve to hold the housing cover 29 to the housing 11. The housing cover 29 is provided with an annular outer wall 31 and a generally circular end wall 33 having a hub 35 formed on the inside surface thereof. The hub 35 is provided with a bore 37 within which one end of a supporting spindle 39 is fixedly mounted. The housing 11 and its cover member 29 coperate to form an enclosure within which a centrifuge assembly, generally indicated at 41, is rotatably supported on the spindle 39 through a sleeve bearing 43.

The centrifuge assembly 41 is provided at its center with a drive member 45, having a sleeve portion 47 journalled on the bearing 43 and abutting a thrust washer 50. One end of the drive member 45 is splined at 49 to matingly engage the splined inner end 19 of the drive shaft thereby rotatably connecting the hub to the drive shaft 15. A main 'body 51 of the centrifuge includes a central hub portion 53 fixedly engaging the drive member 45, an annular outer wall 55, and a generally circular side wall 57 having a central tapered opening 59 through which the drive member 45 extends. Additionally, the hub portion 53 is provided with four circumferentially spaced, axially extending, radial ribs 61a, 61b, 61c and 61d, which integrally connect the hub 53 to the side wall 57.

Fuel or other liquid to be cleaned is admitted to the centrifuge assembly 41 from the inlet port 13 first through a series of holes 63 formed in an annular seal member 65 and then through an annular channel defined at its inner boundary by the drive member 45 and at its outer boundary by the annular seal member 65 and a second seal member 67. The seal member 67 is provided with a tapered end 69 adapted to matingly register within the tapered hole 59 of the centrifuge body side wall 57. Fluid flowing through this annular channel is thus directed into the interior of the centrifuge body 51 between the ribs 61 which, upon rotation of the centrifuge, operate as impellers, causing the incoming liquid to rotate with the centrifuge.

The end of the centrifuge assembly opposite from the side wall 57 is closed by a centrifuge cover member 71 which is generally annular in shape and engages the end wall 55 of the centrifuge body at its outer periphery 73. Three identical screws 72 secure the cover member 71 in position. The inner diameter of the cover member 71 is disposed in closely spaced relationship to the outer periphery 75 of the centrifuge hub 53 which has a groove 77 formed therein positioning an O-ring 79 in sealing engagement between the hub 53 and the cover member 71. An annular shoulder 81 extends inwardly from the centrifuge cover 71 around the hub 53 and is provided with six circumferentially spaced radial vanes 82 extending inwardly therefrom to the side wall 57 of the centrifuge body 51. The vanes 82 serve a contaminant distribution function which will be hereinafter described. Disposed within the centrifuge body and sleeved into the annular shoulder 81 is a first annular sleeve 83 having rows of spaced louvers 85 disposed between each of the contaminant storage vanes 82. The louvers 85 are formed by cutting and bending up sections of the sleeve 83 to form slots or openings 87 which are partially covered by the louvers 85, The louvers extend out of the plane of sleeve 83 at a 45 angle to the axis of rotation of the centrifuge and extend generally in the directionof travel of the liquid. The openings 87 serve to admit contaminant particles to a contaminant repository formed between the seleeve 83 and an annular shell 89 which is in pressed fit relationship with the centrifuge body Slat a shoulder 91 formed on the side wall 57 and which slidably registers on the radially outward sides of the vanes 82. At the outer end of the annular channel or space formed between the louvered sleeve 83 and the centrifuge hub 53 are a plurality of radially arranged ports 93 formed in the end cover shoulder 81 which serve to conduct liquid radially outwardly to a second annular channel or space bounded atits inner diameter by the shell 89 and at its outer diameter by a second louvered sleeve 95. The

sleeve 95 also is provided with rows of louvers 97 which extend at a 45 angle to the axis of rotation and which extend generally in the direction of the liquid flow. Located radially outwardly from the louvered sleeve 95 is the annular outer wall 55 of the centrifuge body 51 which has a plurality of identical circumferentially spaced and radially inwardly extending vanes 99 disposed between adjacent rows of louvers 97. The vanes 99 serve an identical contaminant retaining function as the vanes 82, which function will be hereinafter described. The side wall 57 of the centrifuge body 51 is provided with a series of annularly arranged exit holes 101 communicating with the outer annular channel formed between the shell 89 and the outer louvered sleeve 95 in order to permit the flow of liquid out of the centrifuge body to an outlet port 103 formed in the body member 11.

A variety of sealing elements are used throughout the device to prevent fluid leakage. An O-ring 104 is held against the flange 25 of the housing 11 by a lip 106 formed on the annular extremity 27 of the housing cover 29. Additionally, an O-ring is secured in a peripheral groove 107 formed in the right-hand end of the spindle 39 as viewed in FIG. 2 in order to prevent leakage past the spindle 39. The drive shaft 15 is also provided with a peripheral groove 109 retaining an O-ring 111 to prevent leakage of fluid therepast into the interior of the drive member 45. In order to prevent fluid entering the centrifuge assembly 41 from leaking into the interior of the housing cover 29 in substantial quantities, a face seal is provided between the seal member 65 and 67 at 113. The seal member 67 is driven by the centrifuge body 51 and rotates therevw'th, while the seal 65 remains stationary. The mating surfaces of said seals are microscopically flat in order to assure that no leakage will occur therebetween. A helical spring 115 engages an annular shoulder 117 formed peripherally on the seal 65 in order to urge the seal 65 against the seal 67 and maintain the sealing action therebetween. An annular seal housing 119 surrounds the spring 115 and is provided with an inwardly extending annular flange 120 which is abuttinigly engaged by an O-ring 121 thereby preventing leakage between the seal housing shell 119 and the seal member 65. The opposite end of the seal housing 119' is provided with a plurality of spaced ears 123 which are adapted to engage an annular shoulder 125 formed on the periphery of the seal 67 in order to retain seals 65 and 67 in sealing engagement upon 'disassembly of the device for field servicing and contaminant removal. When the centrifuge assembly 41 is disconnected from the drive shaft 15 the .tapered end 69 of the seal 67 dis engages from the tapered opening 59 of the centrifuge end wall 57 and the seal 67 is held against the ears 123 at its should 125 by operation of the spring 115. The mating surfaces of the seal 65 and 67 are thus not exposed to any contaminant or dirt with which they might otherwise come in contact.

In order to prevent leakage of entering fluid out of the housing 11 around the drive shaft 15 a seal assembly 127 is provided around the drive shaft 15. The seal assembly 127 includes a face seal between an annular face 128 of a rotatable seal element 131 and a carbon static seal 129 held by a sleeve 132 spacedly surrounding the drive shaft 15. The seal element 131 is keyed to the drive shaft 15 by a pin 135 which is held in place by a retaining ring 137, and thus the seal 131 rotates with the drive shaft 15. An O-ring 133 is held between the seal 131 and the drive shaft 15 to prevent the flow of fluid between said members. A generally annular seal housing 134, in press fit relation with the housing 11, surrounds the sleeve 132 and holds an O-ring against the outer periphery of the sleeve 132, thereby preventing fluid leakage radiallyoutwardly thereof. The seal housing 134 is also provided with an abutment shoulder 136 against which a spring 141 seats while engaging an annular shoulder 142.

75 formed on the inner end of the sleeve 132 order to urge the static seal 129 into engagement with the seal element 131.

A generally annular drive shaft thrust member 138 disposed radially outwardly of the seal element 131 is held in press fit relationship with the housing 11 and is arranged to abut an annular radial shoulder 143 formed on the seal element 131 in order to limit outward axial movement of the drive shaft 15 when the centrifuge is subjected to high internal pressures or when the device is disassembled. As will be seen in FIG. 2, the end of the seal 65 adjacent the opening 63 is so positioned as to abut the seal element 131 and limit axial movement of the drive shaft 15 in the opposite direction (toward seal 65). Thus upon disassembly of the machine the ears 123 of the seal housing 119 limit movement of the seal 67 and also position seal 65 as described above. The seal 131 then abuts the seal 65 under the influence of the spring 141. The seals 129 and 131 are thereby pressed into sealing engagement between the spring 141 and the seal 65. Thus, the ears 123 serve to hold the seals 129 and 131, as well as the seals 65 and 67, in sealing engagement upon removal of the centrifuge assembly 41 and assures that the finely finished mating surfaces of these seals do not collect dirt or other foreign matter which might impair the finish and thus cause leakage.

In the operation of the device of the present invention contaminated liquid is admitted through the inlet port 13, generally under pressure. In aircraft usage the fuel is drawn into port 13 by a fuel pump located upstream from the centrifuge. From the inlet port 13 the fuel flows along the annular channel within the seal members 65 and 67 to the interior of the centrifuge assembly 41. The centrifuge assembly includes the body 51, the cover 71, the drive member 45 and all parts enclosed therein. The entire centrifuge assembly 41 is driven through the drive shaft 15 at a high rotational speed of, for example, 6500 r.p.m. which is sufficient to produce a G value of 938 at the diameter of the first louvered sleeve 83. The rotation of the centrifuge assembly 41, which includes ribs 61, causes the incoming liquid to rotate with the centrifuge and imparts to it this high gravitational force. Contaminant contained in the incoming liquid is thrown radially outwardly against the louvered sleeve 83 and the contaminant particles pass through the slots or openings 87 and impinge against the shell 89. In view of the fact that the hub 53 and the louvered sleeve 83 produce an annular chamber of relatively large size compared to the inlet annulus formed between the seal member 67 and the drive member 45, the axial flow of liquid across the louvered sleeve 83 is sufiiciently slow to afford time for a high degree of contaminant separation. Test data indicates that particle sizes down to microns are extracted from contaminated fuel during this first centrifuging stage.

It will be noted that the first contaminant repository formed between the louvered sleeve 83 and the shell 89 is radially divided into a series of separate compartments by the vanes 82, which serve to space the stored contaminants relatively evenly around the centrifuge. In the absence of the ribs 82 it might be possible for the contaminants to slide to the bottom of the repository when the centrifuge is at a state of rest and the concentrated mass in one location would give rise to a prohibitive state of unbalance when the centrifuge was again rotated.

The louvered sleeve 83 also serves an important function when the centrifuge is restarted after being stopped. So long as the centrifuge is rotating contaminants will be thrown against the shell 89 and held there by operation by centrifugal force. However when the centrifuge is brought to a state of rest some provision must be made to prevent stored contaminant from falling back into the fluid passageway for remixing with cleaned fuel. The louvers 85 are designed to substantially overlap the openings 87 in a manner preventing re-entry of the contaminant into the fluid passageway yet permitting the proper entrance of the contaminant into the repository. The louver construction is such that an angled surface is pre- 5 sented to the incoming contaminant assuring the continued movement of the contaminant into the storage cavity.

When the liquid reaches the end of the first louvered sleeve 83 it passes on through the ports 93 radially outwardly into a second annular passageway bounded by the second louvered sleeve 95 and the shell 89, following the course indicated by the arrows in FIG. 2. The fluid then flows axially dong this annular passageway in the opposite direction from the flow of fluid in the first passage. The second louvered sleeve 95 functions in identical manner to the first louvered sleeve 83 with contaminant being admitted to the repository formed between the louvered sleeve 95 and the annular outer wall 55 of the centrifuge body 5-1. The ribs 99 located in this repository perform the same function as the ribs 82 in separating and locating stored contaminant in order to prevent possible unbalance through an accumulation of contaminant in one location. In traveling axially along the second louvered sleeve 95 the liquid is subjected to gravitational forces of approximately 1800 Gs because of the greater radial distance from the of rotation. This high gravitational force is sufiicient to purge fine constituents of contaminants in the region of two to ten microns from the liquid.

The fluid having been purged of all but a few percentage points of contaminant particles passes through a plurality of oircumferentially spaced exit holes 101 in the side Wall 57 of the centrifuge body 51 which communicate with the outlet port 103. The exit holes 101 are disposed radially outwardly of the annular inlet passage formed between the drive member 45 and seal 67. This difference in radii produces a substantially G value increase. The increased G value in the radius of the exit holes 1111 compared with that in the inlet chamber mentioned above is such that a strong pumping action develops, producing a pressure increase between the inlet port 13 and the outlet port 103 of the device. In aircraft usage this pressure increase assures an adequate supply of fuel to a high pressure fuel pump located downstream from the centrifuge, and eliminates the problem of fuel pump cavitation.

When a centrifuge device of the present invention is made for installation in a particular aircraft in which a known amount of pressure increase is desired, a pressure regulating plate 139 may be secured over the exit holes 101 in order to predeterminedly increase the diameter at which the outgoing fuel is released from the unit, thus increasing the G value of the outgoing fuel and consequently increasing the fluid pressure obtained for any given rotational speed. The pressure regulating plate 139 is generally annular in shape and may be secured in position by the screws 72. The pressure regulating plate 139 illustrated in FIG. 2 of the drawings draws the outgoing fuel radially outwardly from the exit holes 101 in order to increase the pressure boost which would be obtained in its absence. However, it will be appreciated that the pressure regulating plate 139 could be provided to effectively reduce the pressure increase by directing the fluid radially inwardly before releasing it from the centrifuge assembly 41.

When the dirt repository chambers have become filled the device should be disassembled and cleaned for further use.- This is accomplished by removing the screws 30 and pulling the housing cover 29 oif of the housing 11. The centrifuge assembly 41 is then pulled off of the splined end 19 of the drive shaft 15- and further removed from the spindle 39. In order to facilitate removal of the centrifuge body 51 from the centrifuge cover 71, the three screws 72 are each provided with a lock ring 74 secured thereto adjacent the inside surface of the centrifuge body side wall 57. The purpose of the lock rings 7 4 is to act as a shoulder on the screws 72 contacting the side wall 57 of the centrifuge body 51 when the screw is loosened. Turning of the screws 72 in loosening tends to push the centrifuge cover 71 away from the body 51, breaking the close fitting sealing relationship adjacent the periphery 73- of the centrifuge side Wall 55 and further breaking contact of the louvered sleeves 83 and 95 and the shell 89 with their mating surfaces. This feature eliminates the use of screw drivers and other such prying devices in parting all the surfaces which when compacted with dirt can become quite tight. Elimination of prying devices guards against the marring of fine finishes in close fitting relationships.

The centrifuge cover having been removed by the alternative loosening of the three screws 72, the dirt repositories are bared and may easily be cleaned by immersion in cleaning fluid of light viscosity' The entire de vice may then be reassembled by the reverse of the above described procedure.

While it will be apparent that the preferred embodiments herein demonstrated are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change Without departing from the proper scope and fair meaning of the subjoined claim.

What is claimed is:

A device for extracting contaminants from liquid including a stationary housing, a drive shaft rotatably supported in said housing, a centrifuge assembly rotatably connected to and adapted to be driven by said drive shaft, said centrifuge assembly including a central hub, a body member integrally joined to said hub and provided with a annular channel around said hub, contaminant storage means disposed radially outwardly of said hub operable to retain contaminants centrifuged from liquid flowing housing having a flat face sealingly engaging the fiat face of said first seal member, means limiting movement of said first seal away from said housing, means urging said second seal against said first seal member in a direction away from said housing whereby the sealing engagement of said seal members will be maintained upon disassembly of said centrifuge assembly from said housing.

References Cited in the file of this patent UNITED STATES PATENTS 1,417,064 Holmgren May 23, 1922 1,619,652 Carter Mar. 1, 192.7 2,450,737 Rundquist Oct. 5, 1948 2,540,474 Cox Feb. 6, 1951 2,691,944 Grosskopf Oct. 19, 1954 FOREIGN PATENTS 13,464 Great Britain June 16, 1898 703,182 France Feb. 2, 1931