Abstract:
The gas-liquid separation device consists of two concentric pipes rotationally driven about their common longitudinal axis and between them defining first and second longitudinally extending channels. The mixture is passed into the first channels and the second channels collect and evacuate the liquid particles which have been separated from the gas in the first channel. The device may be mounted within a shaft of a turboengine and be used to de-oil the ventilating air of turboengine bearing cases. It may be combined with a mounting sleeve which also serves to distribute the lubricating oil of the bearings within the case.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for the purification of gases, in particular the removal of oil from air circulated through turboengine bearing cases. 
     2. Brief Description of the Prior Art 
     The entrainment of lubricating oil in air passing through turboengines occurs near labyrinth seals utilized to seal relatively moving elements of the turboengine due to pressure variations across the labyrinth seal structure. The oil entrained in the air presents problems regarding the operation of the turboengine, particularly the loss of bearing lubrication oil, the danger of fire should the entrained oil contact hot engine parts, and the danger of polluting cabin air circulation circuits. Even in the strongly turbulent state around the labyrinth seal structure, a mist of fine oil droplets in suspension is formed within the bearing case. Absent any effort to recover as much of this oil as possible, the amount of oil entrained in the air would be sufficient to rapidly deplete the lubricating oil reservoir, thereby limiting the operational radius of the aircraft or causing bearing failure. 
     Liquid separation equipment, commonly known as de-oilers, are presently used in jet turbine engines to recover as much as the entrained oil as possible. Typically, such equipment utilizes centrifugal forces to separate the oil from the air and comprises a rotor, driven by the engine shaft or otherwise, against which the gas-liquid mixture is directed. French Pat. No. 1,590,886 describes such a centrifugal separator in which a hollow rotor is provided with radial blades to centrifuge the liquid droplets from the air. A perforated sleeve located along the fins is provided with evacuation passages for removal of the recovered liquid. The purified gas is evacuated to the outside through a duct within an internal pipe. 
     Although the efficiency of such a device is well known, its bulk represents a substantial drawback to its efficient useage. The bulk of the device renders it difficult to place on the engine and to supply the requisite rotational force to the rotor. Although it can be mounted within the accessory support on the engine, large size conduits must be provided to limit the fluid load losses and to limit the heat leaks of the conduits passing through the main air flow. All of these factors result in an increase of the mass and complexity of the engine. The de-oiler also may be mounted against the engine shaft, but would increase the overall length of the device and necessitate an increase in the volume of the bearing sections. 
     Another centrifugal separation device is shown in French Pat. No. 2,033,022 wherein the oil-air mixture from the bearing cases is guided toward a central conduit fashioned within the engine shaft by forcing it to cross radial passages in such a manner that the denser oil particles are centrifugally separated. A second separation is carried out within the central passage where the particles, having acquired an eddying motion are collected along its inside wall. This device has been found to be less efficient than the previously described centrifugal separator. Furthermore, since it is integral with the shaft, it is much less amenable to installation, modification and servicing, and decreases the mechanical strength of the shaft structure. 
     SUMMARY OF THE INVENTION 
     The instant invention is directed toward an apparatus for separating liquid particles from a gas having an efficiency equal to that of the centrifugal separator of the prior art devices, but being much more compact to enable its mounting within a shaft of a turboengine. The apparatus comprises the first and second concentric hollow pipes which are rotationally driven about their common longitudinal axis. The second or outer concentric pipe defines an inlet allowing the gas-liquid mixture to pass into the first channels defined by the first and second pipes, and by longitudinally extending partition walls. A plurality of first orifices are defined by the partition walls to allow separated liquid to pass into a plurality of second channels. A plurality of second orifices are defined by the second pipe and communicate with the second channels to permit the withdrawal of the separated oil. The purified gas passes into the interior of the first pipe and is withdrawn therefrom. 
     The separated liquid is collected inside the second channels along the entire path of the gas-liquid mixture and may be evacuated therefrom by orifices arranged in a common, transverse plane. This eliminates the need for a bulky casing structure covering the separator assembly, as shown in French Pat. No. 1,502,216. 
     The apparatus according to the invention is particularly adaptable for de-oiling the ventilating air of turboengine bearing cases and may be easily mounted within the turboengine shaft near the bearings. A mounting sleeve which attaches the apparatus to the interior of the hollow shaft may define, in combination with the shaft interior, a plurality of chambers, one of which may collect the oil emanating from the apparatus and return it to the lubricating oil reservoir. Additional chambers may be formed between the mounting sleeve and the exterior of the second pipe of the apparatus such that lubricating oil may be supplied thereto and, in turn, passed along to the lubricating feed circuits of the turboengine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a transverse cross-section of the separation apparatus according to the invention. 
     FIG. 2 shows a longitudinal sectional view taken along line II--II in FIG. 1. 
     FIG. 3 is a longitudinal sectional view taken along lines III--III in FIG. 1. 
     FIG. 4 is a partial longitudinal sectional view showing the apparatus according to the invention installed in a low pressure shaft of a turboengine. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The apparatus according to the invention comprises a first, inner pipe 1 and a second, outer pipe 2 arranged concentrically with respect to each other so as to have a common longitudinal axis. Means (not shown) are provided to rotate the first and second pipes about their common longitudinal axis. Pipes 1 and 2 are closed near one end by cross wall 21 while, as shown in FIGS. 2 and 3, first pipe 1 projects beyond the extremity of pipe 2. The first and second pipes 1 and 2 are interconnected by partition means comprising pairs of longitudinal partition walls 3 and 4, best shown in FIG. 1. Each pair of the partition walls 3 and 4 define first channels 5 between them. Second channels 6 are defined by the second pipe 2 and adjacent partition walls. Longitudinal partition walls 3 and 4 may be oriented such that, in each pair, the walls are parallel to each other, as shown in FIG. 1. This arrangement thus defines second channels 6 as being generally triangular in cross-section. However, longitudinal partition walls 3 and 4 may be oriented differently without exceeding the scope of the invention. 
     First channels 5 are each provided with transverse baffles 7 which sequentially extend from first pipe 1 and second pipe 2 as best shown in FIG. 2. Each of these baffles 7 extend approximately to one-half the height of first channels 5. Baffle 7&#39;, located at one end of outer pipe 2, defines an inlet passage through which the gas-liquid mixture is directed. Each of the first channels 5 also communicate with the interior of inner pipe 1 through radial slots 9 in the wall of pipe 1. The purified air or other gas may be evacuated through the interior of inner pipe 1. 
     Each of the first channels 5 also communicate with an adjacent second channel 6 through first orifices 8 extending through longitudinal partition walls 3. First orifices 8 are located only in this partition wall such that, as the device is rotated in the direction of arrow F, shown in FIG. 1, the separated oil may pass through these first orifices in a direction opposite to that of the rotation. The ends of second channels 6 are sealed by transverse partitions 21 and 21&#39;, as best seen in FIG. 3. Each of these channels communicate with the exterior of the device through second orifices 10 which may be arranged in a common, transverse plane near the inlet end of outer pipe 2. 
     FIG. 4 shows the apparatus according to the invention installed in a low pressure shaft of a turboengine and used for de-oiling the air ventilating the turboengine bearing cases. The downstream end of the low pressure shaft 60 is rotationally supported by bearings with respect to a fixed bearing block connected to the casing of the turboengine (not shown). Low pressure shaft 60 may itself rotationally support a high pressure shaft through an intershaft bearing. This intershaft bearing structure, which is well-known in the prior art, typically consists of roller bearings distributed between an inner race formed integral with the low pressure shaft and an outer race which is formed integrally with the high pressure shaft journal. For the sake of clarity, these known components have been omitted from FIG. 4. 
     The de-oiler apparatus is mounted within the low pressure shaft 60 by means of cylindrical sleeve 30. Sleeve 30, which may also serve to distribute the bearing lubication oil, is joined to the shaft 60 by any known means which will prevent any relative rotation between them. Longitudinal ribs 30&#39; are provided on the interior of sleeve 30 to add additional stiffness to the structure. Sleeve 30 is provided with end walls 31 and 34 and two intermediate annular transverse walls 32 and 33. The inner peripheries of transverse walls 31, 32 and 33 bear against the outer periphery of pipe 2 in order to retain the device in position. The length of sleeve 30 exceeds that of pipe 2 such that end wall 34, with transverse wall 33 define an annular chamber 37. Additional chambers 35 and 36 are defined between transverse wall 31 and 32, and 32 and 33, respectively. Longitudinal openings 55 and 56 are circumferentially spaced through partitions 33 and 32, respectively, to provide communication between chambers 35, 36 and 37. 
     The exterior of sleeve 30, in conjunction with transverse annular walls 38, 39, 40, 41 and 42 formed on the interior of low pressure shaft 60 defines annular chambers 43, 44, 45 and 46. Radial holes 47, 49 and 51, provided through sleeve 30, provide communication between chambers 35 and 43; 36 and 44; and 37 and 46, respectively. Lubicating oil, which may be supplied by a nozzle, schematically indicated by arrow C is centrifuged in chamber 37 where it forms a pressurized liquid ring. The oil communicates with chambers 36 and 35 through longitudinal openings 55 and 56 and subsequently passes into chambers 43, 44 and 46 through radial openings 47, 49 and 51. From these chambers, the oil may be supplied to the lubicating oil feed circuit of the turboengine structure. Chamber 43 may communicate with the inner race of the intershaft roller bearing through radial passage 48, while chamber 44 may supply lubricating oil to the outer race of the intershaft bearing through radial passage 50. Similarly, chamber 46 may supply lubricating oil to the bearing which supports low pressure shaft 60 through radial passage 52. 
     Chamber 45, formed between transverse annular walls 40 and 41 communicates with the second channels 6 of the separating device via radial passages 53 which are aligned with second orifices 10 through the outer pipe 2. The oil collected in this chamber may be returned to the lubricating oil reservoir through radial passage 54. 
     As noted previously, the air in the bearing cases must be evacuated to the outside in order to maintain a blocking air flow through the labyrinth seals located between the fixed walls of the turboengine case and the rotor engine elements. The air is contaminated with oil droplets which must be removed before the air is evacuated. This oil-air mixture enters the inlet formed by transverse wall 7&#39; and enters the first channels 5. Due to the rotational movement of the device, a tangential velocity is imparted to the mixture. The constant cross-section of first channels 5 enhances the laminar flow thereby limiting the load loses. The oil-gas mixture follows a meridian trajectory and is sequentially subjected to a centrifugal and centripetal movement as it passes over baffles 7. The elements have different densities are separated and the inertia of the droplets causes them to be deposited along the partition walls. 
     The collected oil moves through first orifices 8 into second channels 6 and along the inside wall of pipe 2. The oil is evacuated through second orifices 10 and passes into chamber 45 through radial passages 53. 
     The purified air after passing the last baffle 7 is deflected into radial slots 9 toward the interior of first pipe 1 and may be withdrawn therefrom for further useage. 
     The foregoing is provided for illustrative purposes only and should not be construed as in any way limiting this invention, the scope of which is defined solely by the appended claims.