US3762841A - Axial compressor - Google Patents

Abstract

An axial compressor which includes a housing formed of two end parts within which is rotatively mounted a rotor the axle of which is rotatively carried on bearings in the respective end parts. Radial openings are located in the rotor and wings are positioned in these openings which are adapted to be moved axially back and forth. This movement is caused by screwlike direction surfaces on the inner surface of each of the two end parts which surfaces are axially opposite each other. The direction surface on one end part lowering with a certain rising angle from a maximum point through 180* to a minimum point and from the minimum point rising with the same rising angle back to the maximum point so that the maximum and minimum points of the direction surfaces of one end part is situated at 180* from the corresponding points of the other end part. The screw-like direction surfaces are made oblique so their general line crosses the axle at an angle smaller than 90*. The axial ends of the rotor are formed as cones which are tapered axially outward from the middle of the rotor. The cone angle of the cone is twice as large as the inclination angle of the first-mentioned angle.

Description

Savikurki 1 3,762,841 1 Oct. 2, 1973 AXIAL COMPRESSOR Auvo Antti Savikurki, Nekala, Tampere, Finland 22 Filed: Feb. 26, 1971 21 Appl.No.:ll9,ll6

[76] Inventor:

4/1949 Great Britain 418/219 OUTLET OF LOW PRESSURE SIDE Primary Examiner-Carlt0n R. Croyle Assistant ExaminerJohn .l. Vrablik Attorney-Woodling, Krost, Granger & Rust [57] ABSTRACT An axial compressor which includes a housing formed of two end parts within which is rotatively mounted a rotor the axle of which is rotatively carried on hearings in the respective end parts. Radial openings are located in the rotor and wings are positioned in these openings which are adapted to be moved axially back and forth. This movement is caused by screwlike direction surfaces on the inner surface of each of the two end parts I which surfaces are axially opposite each other. The direction surface on one end part lowering with a certain .rising angle from a maximum point through 180 to a minimum point and from the minimum point rising with the same rising angle back to the maximum point so that the maximum and minimum points of the direction surfaces of one end part is situated at 180 from the corresponding points of the other end part. The screw-like direction surfaces are made oblique so their general line crosses the axle at an angle smaller than 90. The axial ends of the rotor are formed as cones which are tapered axially outward from the middle of the rotor. The cone angle of the cone is twice as large as the inclination angle of the first-mentioned angle.

2 Claims, 12 Drawing Figures /NLE T OF HIGH PRESSURE SIDE CONDENSER PATENTED W 2 I973 SHEET l 0F 5 lnvantor:

w w M? PATENIED U 2W5 3.762.841 SHEET 2 or s In ventor AM. A. 5mm

PATENTEU W 21975 SHEET 3 [IF 5 lnventor: Am A. Smwkw'u AXIAL COMPRESSOR This invention relates to an axial compressor, in which to a box formed by two end parts fastened against each other is mounted a rotor, the axle of which is pivotally attached with bearings to the end parts and to the radial openings going through them is adapted wings to move axially to and fro, the motion of which wings is directed by a screw-like direction surface made to both inner surfaces of the end parts, which surfaces are opposite to each other, the direction surface lowering with a certain rising angle from the maximum point (a) to a for example 180 angle distance to a minimum point rising from it with the same rising angle again to the maximum point so that the maximum and minimum points of the direction surfaces of one end part are situated at a 180 angle distance from the corresponding points of the other end part.

Such compressors or pumps of above-described type are known, in which the mentioned direction surfaces are situated in 90 angle to the axle of the cylindrical rotor so that the wing ends being in connection with the direction surfaces are also in 90 angle to the rotor axle. A noticeable disadvantage of this kind of pumps is however that due to the friction between the wing ends and the direction surfaces when the wings are wearing away and becoming shorter in the axial direction harmful leakages follow in the pressure forming conditions, which leakages impair the efficiency of the pump. Besides the lubrication of the wings is not efficient, for when the wing ends and the direction surfaces are in 90 angle to the rotor axle touching each other, the lubrication oil strives to flee to the outer sphere of the wings because of the centrifugal force so that the parts of them close to the rotor axle remain unlubricated.

The object of this invention is to eliminate disadvantages described above, which is accomplished with a compressor according to the invention being mainly characterized in that the screwlike direction surfaces are made oblique so that their general line cuts the axle of the rotor in an angle smaller than 90 and that the ends of the rotor are formed as cones, which are tapered outwards from the middle of the rotor, the cone angle of which cones is twice as large as the inclination angle of the adjacent direction surface.

An advantage of the compressor according to the invention is especially that as a result of the obliqueness of the direction surfaces and the trapezoidal form of the wings, leakages resulting from the wing ends that touch the direction surfaces and also from the wearing away of the outer surface of the wings have been eliminated, which again leads to a better efficiency of the compressor, being additionally influenced by the fact that a supporting hoop prevents the radial movement of the wings excluding this kind of a movement due to the wearing away of the wings. This is also retarded by the eflicient lubrication and cooling of the wings that is attained as a result of that the lubrication oil keeps well in the oblique direction surfaces so that the wing ends sliding along the direction surfaces receive an equal lubrication.

The invention is disclosed nearer in the following explanation with accompanying schematic drawings, where FIG. 1 is a section of a compressor according to the first adaptation of the invention parallel to the axle being made as single-phase,

FIG. 2 is a cross section of the FIG. 1 taken along the line II-II FIG. 3 shows one end of the rotor in a parallel perspective and a cut view of a supporting hoop fastened to the rotor,

FIGS. 4-6 are side and radial views of different rotor wings,

FIG. 7 is a similar section as FIG. 1 of the end parts of the compressor and of the box formed by them,

FIG. 8 is a partly cut view in a parallel perspective of one end part with its end chamber,

FIG. 9 shows suction and pressure chambers spread to the level in the radial direction,

FIG. 10 is a section of FIG. 3 taken along the line X-X,

FIG. 11 is a partly cut section parallel to the axle of the compressor according to the second adaptation of the invention being made as two-phased and FIG. 12 shows an end chamber of the low pressure side of the compressor by FIG. 11 being spread to the radial direction.

By FIGS. l-I0 to the single-phase compressor according to the first adaptation of the invention belongs two end parts 1 and 2 fastened against each other in their flanges forming the compressor body so that between them is shaped a box. To this is mounted a rotor 4 attached to the axle 3 that is fastened with bearings 5 to central holes in the end parts. The rotor 4 divides the box into two parts so that around the axle to the both end parts is formed the end chamber 5, 6, 7. Near to the outer sphere of the end parts 1, 2 is made a cylindrical annular groove 8 and the surfaces of the end parts between this and the axle 3 are formed as direction or line surfaces 9 being described later on.

As best illustrated in FIGS. l-'3 the rotor 4 consists of two truncated cones 10, 11 so that between these is an intermediary flange 12, from the end surfaces of which the cone surfaces continue with the same cone angle to the sphere of the axle 3 of the rotor. To the intermediary flange 12 is fastened a cylindrical supporting hoop 13 that when being in the rotor box is situated in the annular groove 8 of the end parts and rolling in it when the rotor is rotating. In the longitudinal direction through the rotor 4 goes radially eight narrow openings 14 spaced the same angle distance from each other in the shown case. Their depth is such that they extend as grooves 15 to the surface of the axle 3 at both sides of the rotor. In the point of the openings 14 to the inner surface of the supporting hoop 13 is made also axial grooves 16. To each groove 14 is adapted a wing 17 being shaped as a trapezoid separately shown in FIG. 4, the longer base of which is located in the bottom of the opening 14 and in the groove 15 on the axle and the shorter base in the groove 16 on the supporting hoop 13. In the shown case to the ends of both bases are made extension pieces in order to improve the direction. Besides to these extension pieces are made radial borings 17a so that the space between these borings and the wing ends is split in the axial direction. The length of the wings is such that their slanting ends 18 or sides with sliding tightness lean against the beforementioned direction or line surfaces of the opposite end parts 1 and 2. Spacings between the wing 17 and opening 14 and the grooves 15, 16 are such that the wing is able to move axially to and fro influenced by the direction or line surfaces 9 of the end parts described closer in the following, against which surfaces the slanting or properly bevelled or curved ends 18 of the wings lean. For the lubrication of the wings 17 is to the axle 3 of the rotor 4 made a central boring 19, from which lubrication material can go into the openings 14 through distribution channels 20.

In the following is referred to FIGS. 1, 2, 7 and 8 and especially to FIG. 7. As mentioned before between the annular groove 8 of both end parts 1, 2 and the axial boring inside the end chamber 6, 7 is formed a direction or line surface 9 of the wings 17 which surface is annular when seen in the direction of the rotor axle 3. This direction surface 9 is formed as an eccentric or screw surface so that it lowers from its maximum point marked by a dotted line a in FIGS. 2 and 8 with a certain rising angle a to a 180 angle distance or to the diametrically situating minimum point and rises from it with'the same rising angle a to its maximum point. Besides the direction surface 9 is made oblique so that the angle of inclination [3 between the line parallel to the axle 3 and the direction surface 9 is smaller than 90 in other words so that the general line of the surfaces-9 cuts the rotor axle in an angle smaller than 90. This angle of inclination, the half of the cone angle of the rotor 4 and the angle of obliqueness of the ends 18 of wings 17 must be equal. End parts 1, 2 and their direction surfaces 9 are otherways equal, but they are twisted l80 to each other, in other words the maximum point of the direction surface of one end part is in the minimum point of the direction surface of the other end part and vice versa. Then the surface of the rotor 4 is in the sliding contact with the direction surface 9 to the maximum point along the line a. As an example it can be mentioned that the angle between the normal of the direction surface 9 and the middle line of the rotor axle the so called critical rising angle can be 7075 most properly about 73, when the inner diameter of the direction surface is about 100 mm and the outer diameter about 300 mm.

By FIGS. 1, 2, 7 and 8 both end parts 1, 2 contain a suction channel 21 that gets opened as a suction opening 22 to the direction surface 9 in front of the maximum point a in regard to the rotation direction of the rotor on the lowering side, it is, on the suction side of the direction surface. This suction opening 22 is outstretched in the direction of the sphere becoming smaller towards the minimum point of the direction surface. Through both end parts 1, 2 leads also a removalchannel 23 that gets opened as a removal opening 24 to the direction surface 9. This opening is situated beside the maximum point a of the direction surface'at the opposite side to the suction opening 22, in

other words at the pressure side and at the end of this. The removal opening 24 is dimensioned short in the direction of the sphere.

When the rotor 4 is rotating the slanting ends 18 of the wings l7 lean with sliding tightness against the direction or line surfaces 9 of the opposite end parts 1, 2 and perform influenced by these a forced motion to and fro parallel to the rotor axle 3. Then between both conical surfaces, the direction surface 9 and. the inner surface of the supporting hoop 13 is formed spaces restricted always by two successive wings 17. The volume of these spaces is enlarged continuously on the suction side from the maximum point a to the minimum point, air penetrating to them through the outstretched suction opening 22 after which spaces become smaller during half a round accomplishing thus pressure on the pressure side so that air departs from the removal opening 24 being under pressure.

In FIG. 9 is shown the suction and pressure side 25, 26 in the radial direction spread to the level. In the FIG. 9 in the lower part of the suction side 25 begins a suction phase, whereat absorption happens through the suction opening 22 in the direction of arrows during half a round. After this begins a pressing phase at the pressure side 26 continuing to the removal opening 24. Because the compressor contains two suction or pressure sides or chambers, pressing of the total air amount happens at the same time at both pressure sides.

When the suction volume of the space between two successive wings 17 is in its largest before the minimum point of the direction surface 9, the air flown into the said space is under depression. This can be prevented by the nozzle device 27 shown in FIGS. 7 and 10, which device gets opened to the direction surface 9 in the point 28 before the pressing phase and through which device cooling oil or air can be sprayed into the space between Wings 17 when the suction volume of this space is in its largest. So the initial pressure before the pressing phase is got to excess, which improves remarkably the efficiency of the compressor. Same kind of a nozzle device may be adapted also after the minimum point of the direction surface 9 getting opened to the pressure side.

The above-described compressor according to the invention works as single-phased, for the cone angles of both truncated cones 10, 11 of the rotor 4 are equal and the before-described rising angles a and oblique planes 3 are respectively equal so that in both end chambers 6, 7 or at both pressure sides air is pressed from the same initial pressure to the same final pressure. However the compressor according to the second adaptation of the invention can work also as twophased so that in one end chamber air is pressed first to a lower pressure and is led then through e.g. an intermediary condenser to the other end chamber, where it is pressed to a higher pressure. The condenser may be any suitable type. It may be normal pressure proof piping or it can be formed by bending a tube into a spiral or other form in a flat plane in similar manner as in a car radiator so that the cooling surface is increased. This kind of a two-phased compressor is described closer in the following with reference to FIGS. 11 and 12'. In the adaptation by FIGS. 1 l and 12 are same parts marked with same reference numbers as in the referred figures of the description of the adaptation presented before. The compressor according to this adaptation differs from the one of the first adaptation only in regard to the structure of the rotor 4 and to the Wings 17 and the obliqueness of their direction surfaces 9 and to their radial extension.

By FIG. 1 l the height of the left-hand truncated cone 10 of the rotor 4 is larger than the height of the righthand truncated cone 11. This is attained so that the diameter of the axle journal 30 of the cone 10 is smaller than the diameter of the axle journal 3b of the cone 1], when the cone angles of both truncated cones are equal. Naturally the before-mentioned inclination angle B and the width of the direction surface 9 of the left-hand end part 1 corresponds to the cone angle and mantle surface of the truncated cone 10 and the inclination angle and the width of the direction surface 9 of the right-hand end part 2 corresponds to the cone angle and the mantle surface of the truncated cone 11. Be-

cause according to FIG. 5 the wings are shaped as a regular trapezoid, grooves made to the thicker axle journal 3b are deeper than the grooves 15 made to the other axle journal 3a. In this structure air is pressed first in the left-hand pressure chamber to a lower pressure and is then led to the right-hand pressure chamber to be pressed to a higher pressure. Because the direction or line surfaces 9 of the end parts 1, 2 of the compressors according to the invention being described above are situated in oblique positions, in other words the before-mentioned angle [3 between them and the line parallel to the axle 3 of the rotor 4 is smaller than 90, the wings 17 can have been shaped as a trapezoid. This is of very great importance in regard to the lasting time of the wings that is longer than before and to their lubrication. When the rotor 4 and wings 17 are rotating performing the axial motion to and fro, the friction caused by the rotation appears only between the oblique ends 18 of the wings l7 and the direction surfaces 9 of the end parts 1, 2. Due to the motion to and fro of the wings, friction is caused only between the flange surfaces of the wings and the openings 14 as well as between the shorter base of the wings and the groove 16 of the supporting hoop 13, because the wings push influenced by the centrifugal force against the bottoms of the grooves 16 on the supporting hoop. Thus the wings are wearing away substantially in their ends and in their shorten base sides. Then, however, a worn wing 17 moves in the radial direction outwards influenced fluenced by the centrifugal force and its length between the direction surfaces 9 and its tightness against them remains unchanged so that, however, the longer bases of the wings become directed in the openings 14 of the rotor 4 and in the grooves 15 on the axle. So according to the invention the spaciousness caused by the wearing away of the wings between their oblique ends 18 and the direction surfaces 9 of the end parts is eliminated, which improves the efficiency of the wings and lengthens the lasting time of them. Due to the obliqueness of the wing ends and of the direction surfaces lubrication oil greases smoothly the contact point between the wing ends and the direction surfaces, which still increases the lasting time of the wings. Same advantages are attained also in the case, where the wings are curved in the axial direction as is shown in FIG. 6.

The invention is not of course restricted to the adaptation examples described above, but may be varied in its details even remarkably in the limits of the patent claims. So for example the inclination angle B of the direction or line surfaces and the cone angle of the truncated cones of the rotor, which cones co-operate with the surfaces and thus also the obliqueness of the oblique wing ends may vary within large limits. According to the invention it is also possible that the inclination angles of the direction surfaces of the end parts and so that respective cone angles of the corresponding rotors are different. Further on such an adaptation is possible, where in the same direction surface there are more pairs of maximum and minimum points.

1 claim:

1. Axial air compressor having a rotor (4) fitted into a casing composed of two end blocks (1, 2) mounted to face one another, the rotor axle (3) of which air compressor is rotatably mounted to the center of the end blocks, trapezoidal-shaped wings (17) in radial slots (14) extending through the rotor and arranged to move reciprocatingly in the axial direction to form compression chambers in the casing, which movement is guided by a screw-shaped guiding surface (9) provided at both opposite inner surfaces of the end blocks (1, 2), which guiding surfaces decends by a given angle of climb from the maximum point (a) to 180 angular distance from the minimum point, at which the maximum and minimum points of the guiding surface (9) of one end block arelocated 180 angular distance from the corresponding points of the other end block, and the screw-shaped guiding surfaces (9) are made to slope in such a way that imaginary line extensions on said guiding surfaces intersect the axle (3) of the rotor (4) at angles (3,, [3 below and correspondingly that the ends of the rotor (4) are made into truncated cones (10, 11) converging outwards from the center of the rotor, and the cone angle of which is twice the sloping angle (3,, {3 of the adjacent guiding surface (9), and having an air suction opening (22) for air, oblong in the direction of the circumference and becoming smaller towards the minimum point of the guiding sur face, characterized in that an outlet opening (24) is provided which is situated at the maximum point (a) as a sufficiently narrow opening in the direction of the circumference, so that when the rotor (4) rotates, the sucked air is first compressed to a given pressure determined by the upwards sloping screw-shaped guiding surface, and thereafter leaves the outlet opening (24) under pressure, two chambers in the compressor at opposite ends of the rotor, the diameter of the rotor axle of the low pressure stage being smaller than that of the high pressure stage in order to produce the ratio between the two compression volumes, an intermediate condenser, the air compressed in one of the said chambers of said compressor is compressed to a given lower pressure and conducted through said intermediate condenser into the other of said chambers where it is compressed to a given higher pressure, so that the air leaves the last mentioned chamber under the said higher pressure.

2. Compressor according to claim 1, characterized in that nozzles (27) are positioned to open into the said guiding surfaces (9) close to their minimum points, through which nozzles air is conducted into the space between the wings (17) together with oil coolant, for the purpose of bringing the starting pressure before the compression stage to overpressure, and in this way improve the efficiency of the compressor.

i l 0' i i

Claims (2)

1. Axial air compressor having a rotor (4) fitted into a casing composed of two end blocks (1, 2) mounted to face one another, the rotor axle (3) of which air compressor is rotatably mounted to the center of the end blocks, trapezoidal-shaped wings (17) in radial slots (14) extending through the rotor and arranged to move reciprocatingly in the axial direction to form compression chambers in the casing, which movement is guided by a screwshaped guiding surface (9) provided at both opposite inner surfaces of the end blocks (1, 2), which guiding surfaces decends by a given angle of climb from the maximum point (a) to 180* angular distance from the minimum point, at which the maximum and minimum points of the guiding surface (9) of one end block are located 180* angular dIstance from the corresponding points of the other end block, and the screw-shaped guiding surfaces (9) are made to slope in such a way that imaginary line extensions on said guiding surfaces intersect the axle (3) of the rotor (4) at angles ( Beta 1, Beta 2) below 90*, and correspondingly that the ends of the rotor (4) are made into truncated cones (10, 11) converging outwards from the center of the rotor, and the cone angle of which is twice the sloping angle ( Beta 1, Beta 2) of the adjacent guiding surface (9), and having an air suction opening (22) for air, oblong in the direction of the circumference and becoming smaller towards the minimum point of the guiding surface, characterized in that an outlet opening (24) is provided which is situated at the maximum point (a) as a sufficiently narrow opening in the direction of the circumference, so that when the rotor (4) rotates, the sucked air is first compressed to a given pressure determined by the upwards sloping screw-shaped guiding surface, and thereafter leaves the outlet opening (24) under pressure, two chambers in the compressor at opposite ends of the rotor, the diameter of the rotor axle of the low pressure stage being smaller than that of the high pressure stage in order to produce the ratio between the two compression volumes, an intermediate condenser, the air compressed in one of the said chambers of said compressor is compressed to a given lower pressure and conducted through said intermediate condenser into the other of said chambers where it is compressed to a given higher pressure, so that the air leaves the last mentioned chamber under the said higher pressure.

2. Compressor according to claim 1, characterized in that nozzles (27) are positioned to open into the said guiding surfaces (9) close to their minimum points, through which nozzles air is conducted into the space between the wings (17) together with oil coolant, for the purpose of bringing the starting pressure before the compression stage to overpressure, and in this way improve the efficiency of the compressor.

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