US2609140A

US2609140A - Radial compressor with auxiliary bladewheel

Info

Publication number: US2609140A
Application number: US27496A
Authority: US
Inventors: Jonker Frits
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1947-05-23
Filing date: 1948-05-17
Publication date: 1952-09-02
Anticipated expiration: 1969-09-02

Description

p 2, 1952 F. JQNKER 2,609,140

RADIAL COMPRESSOR WITH AUXILIARY BLADE WHEEL Filed May 17. 1948 2 Sl-IEETS-SHEET l Fig. 5

\nvenror Fr-H's Junk e:- a Mz MZ H Sept. 2, 1952 F. JONKER RADIAL COMPRESSOR WITH AUXILIARY BLADE WHEEL Filed may 17, 1948 2 SHEETS-SHEET 2 \nveni'or: Fr-H' Jar- Kerbz. l-us AH'ar-neu Patented Sept. 2, 1952 RADIAL COMPRESSOR WITH AUXILIARY BLADEWHEEL Frits J onker, Delft, Netherlands, assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application May 17, 1948, Serial No. 27,496 In the Netherlands May 23, 1947 This invention relates to radial compressors, such, for example, as are used in turbo-jet engines or in turbo-propeller installations for aeroplanes.

.A very important criterion for a jet engine is the thrust per unit of frontal area. In the case of a jet engine having a radial compressor of given dimensions the aim will, therefore, be to obtain a maximum output of the compressor, since the thrust supplied by the jet engine is directly proportional to the output of the compressor.

As is well known, the discharge pressure of a centrifugal compressor is largely determined by its circumferential velocity at the outlet. It'is generally believed that gas velocities within the compressors should not exceed a critical velocity, dependent upon the local acoustic velocity. All of the circumferential velocitiesused nowadays are of the order of 400 meters per second. 7

In the case of a compressor with a given outlet diameter and speed, the aim will be to obtain a maximum output by making the inlet opening of the compressor as large as possible. If, however, owing to this enlargement of the inlet opening and, hence, of the radius of this opening, the relative velocity of the inflowing air in relation to the tip (the point on the circumference) of the compressor blade in the compressor blade begins to approach a critical velocity, then as a result of a shock at the entrance to the compressor blades, not only does the efficiency of the compressor decrease considerably, but also the output shows a considerable decline. any theory regarding thecause of this shock; it may be due to too close an approach of the relative velocity of the blade to the inflowing air to the local velocity of sound and the so-called compressibility phenomena; however, other phenomena of air-flow may be involved.

Since it is impossible to reduce the angular velocity of the compressor without decreasing its discharge pressure, it will be obvious that the output of the compressor is limited by the extent to which the inlet opening can be enlarged without approaching too closely the critical velocity at the entrance to the compressor blades. With a compressor having a given discharge pressure and external (outlet) diameter, a value can be found for the diameter of the inlet opening and for the absolute inflow velocity at which the compressor attains a maximum output.

It is the principal object of the invention to raise this maximum output value of a radial I do not desire to be bound by 4 Claims. (Cl. 230119) (centrifugal) compressor by reducing the local relative velocity of the compressor blade to the infiowing air. 1

A further object is to provide an improved radial compressor having a plurality of radial compressor vanes wherein the local relative velocity of the compressor blade to the inflowing air is reduced by providing one or more auxiliary bladewheels in advance of the inlet and rotating in the same direction but at a lesser angular speed than the main compressor blades. Ancillary thereto, it is a specific object to provide a compressor of the type described wherein the auxiliary bladewheel or bladewheels is/are effective only to act on the circumferential portion of the inflowing air (away from the axis of rotation).

"Still another object is to provide an improved radial gas compressor wherein the gas is supplied to a radially inwardly disposed portion of a compressor blade by an auxiliary blade which is mechanically driven in common with the main compressor blading in the same direction but at a lower speed in a manner to reduce the entrance shock.

With these and other objects in view, which will become apparent from the following detailed description, reference is made to the accompanying drawings forming a part of this specification and showing certain illustrative embodiments of the invention, wherein:

Fig. 1 is a perspective view of a conventional radial compressor blade;

Fig. 2 is a vector fiow diagram for a conven tional radial compressor;

Fig. 3 is a longitudinal sectional view of a rotor according to the invention, provided with an auxiliary blade-wheel;

' Fig. 4 is a vector flow diagram for the rotor according to Fig. 3;

Fig. 5 is a schematic diagram showing, in longitudinal section, a comparison between the usual shape of-compressor and one according to the invention;

Figs. 6 and 8 are longitudinal sectional views illustrating two other embodiments;

Fig. 7 is a longitudinal sectional view showing a modified form of the invention, wherein the auxiliary bladewheel is driven through a bearing cage;

f Fig. 9 is a longitudinal sectional view of a mechanism which may be used to drive the auxiliary bladewheel;

Figs. 10, 11 and 12 are sectional views taken on lines l0|0, Hll and |2--|2, respectively, of Fig. 9; and

the blade at its circumferential inlet point I); W'

the absolute inlet velocity of the gas; and R the v inlet velocity in relation to the blade. cated above, the relative velocity R must be low AS indi enough to avoid shock. For a given angular speed of the rotor l, the maximum radial distance of the point b from the axis of shaft 2 and, hence, the maximum size of the inlet opening to the blades is limited by this requirement.

According to the present invention, however, it is possible to use a larger inlet opening by pre-- compressing an annular current of inflowing gas, moving forwardly in a direction generally parallel to the axis of rotation of the rotor, and simultaneously imparting to it a rotational motion about said axis in the same direction as and at an angular speed less than that of the rotor, and charging the precompressed and rotating gas into the blades of the rotor substantially without shock. The last step implies not only that the inlet velocity of the gas in relation to the blade is reduced below the critical velocity, but also that the entrance angle of the blades of the rotor be such as to take into account the altered direction of flow of the infiowing gas.

I am aware that others have, heretofore, sought to alter the direction of the inflowing gas by providing inclined nozzles or bafiies which, however, did not eifect precompression. When such baffles or blades have, in earlier constructions, been rotatably mounted, they were rotated at the same speed as the main rotor, and the same difficulty was encountered at the entrance to such baffles; the instant invention is distinguished therefrom in providing for a rotation of the air or'other gas at an angular velocity somewhat less than that of the main rotor. Finally, auxiliary, independently rotatable blades, such as used by Lincoln in U. S. Patent No. 2,400,240, sought to decrease the flow of air by preliminary rotation in the same direction; there the auxiliary blades effected little, if any, compression and did not charge the air into the main rotor blading without shock.

The method according to the invention may be carried out by the construction shown in Fig. 3, wherein a larger inlet opening may be used by arranging an auxiliary bladed rotor or impeller 4 in advance of the main compressor rotor I, carrying radial blades 3, and rotating the auxiliary impeller in the same direction as and at a smaller angular speed than the main rotor l. The blading in the auxiliary impeller is arranged to compress the advancing, annular stream of gas and to impart to it a rotational movement about the compressor shaft. The auxiliary bladewheel can be driven by any mechanical or pneumatic, e. g., air-flow, arrangement, either independently of or through the shaft driving themain compressor, as will be described hereafter. The blade entrance angle of the main rotor is designed to receive the gas discharged from the auxiliary blade without shock, this angle being different than in the conventional compressors without auxiliary bladewheels, as will be apparent to persons, fa-

miliar with blade design from a consideration of Fig. 4. In Fig. 4, it is assumed that the angular velocity of the auxiliary bladewheel is equal to half of the angular velocity of the main compressor (although I do not limit myself to this .relation). This figure shows the flow at the circumference of the compressor inlet; U, W and R have the same meaning as in Fig. 2, R1 being the relative velocity of the gas in relation to the blades of the auxiliary impeller 4, and R2 that with respect to the blades of the main compressor impeller l. R2 is greater than R1, but smaller than the resultant of W and U of Fig. 2. The diameter of the compressor inlet may be enlarged to such an extent that the value R2 begins to approach the limiting critical velocity, e. g.. the local velocity of sound which, moreover, may be some what greater in this case due to compression and heating of the gas in the auxiliary impeller. If the inlet diameter and the absolute inlet velocity are properly correlated, a very considerable increase in the maximum output of the compressor may thus be obtained.

The effect of increasing the inlet diameter is illustrated in Fig. 5, wherein the solid lines show the usual construction, while the dotted lines indicate the shape of the compressor made possible by applying the present invention.

It is also possible to have a multi-stage inlet; in that case the compressor is provided with several auxiliary impellers. For example, as shown in Fig. 6, I may provide two auxiliary impellers 5 and 6 in advance of the main impeller I; these may be rotated, for example, with angular velocities in the ratio of l:%: for the impellers l, 5 and 6, respectively. A still greater output could thereby be obtained. This multiplication of auxiliary impellers cannot, however, be carried on indefinitely because too large a compressor inlet would create unfavorable relations in the compressor and lower its efliciency.

The improvements resulting from this invention can, for instance, be turned to account by modifying the compressor of an existing jet engine with two-sided inflow to provide acne-sided inflow, retaining the same outlet diameter; by doing so, much more favorable conditions for design and assembly are obtained, while the air can be supplied to the compressor under much more favorable conditions. Besides, the thrust of an existing engine with a one-sided inlet could thereby be increased considerably; the other engine parts, however, will then have to be made heavier.

The auxiliary impeller may be driven by any mechanical or pneumatic means, either independently or through the main compressor shaft, as described hereafter.

As previously indicated, the danger of entrance shock is greatest at the circumferential part of the. inlet opening, e. g., the part between the solid and dotted lines in Fig. 5. It is, therefore, not necessary to have the auxiliary impeller act on all the the infiowing air, but only on the annular outermost portion. Such a construction is illustrated in Fig. 7, which further illustrates a simple driving arrangement for the auxiliary impeller. In this figure, la is the main rotor, secured to rotating shaft 2, the outer portions of the blades 3a being notched to receive auxiliary blades 4a. Annular partition 1 is fixed to the main rotor blades and the auxiliary blades 4a are connected to a separate annular partition 8 at their radially inner edges. Partition 8 is supported by radial spokes '9 connected to a bearing cage lil' of a ball or tapered roller race interposed between 'shaft 2 and stationary part ll, fixed toi the compressor housing; -In*tl 1e embodiment illustrated thecage has'an'a'nnular ring of: large ba11s"|2 rolling in rings |3'1a'rid- 4, fixed to the shaft 2 and to the stationary part I l, respectively. and an auxiliary ring of smaller-balls Hi to steady the cage. Balls and rollers are herein referred to generically as rolling antifriction elementsfi, As thel'shaft 2 andmain rotorilf'rotate, the page l0 rotates at a speed less" than that of the'shaft, thereby driving the auxiliary blades. To prevent slip, a considerable axial load must be placed on the bearing, and to reduce the need for such a heavy axial loading it is desirable to reduce the load on the auxiliary blades. This is effected by using auxiliary blades of short radial lengths, i. e., by having the partitions 1 and 8 as far away from the shaft axis as possible while avoiding shock at the entrance to the main blades just inside of the partition 1. The spokes 9 should have streamlined cross-sections and be disposed to offer the minimum resistance for the normal operating speed of the auxiliary rotor and normal air velocity.

It is, further, possible to assist the rotation of the auxiliary bladewheel in the embodiment according to Fig. 7 by disposing the air-foil spokes 9 to impart rotation to the wheel. Preferably, the spokes are given such a shape only near the shaft, where the danger of entrance shock is smallest, whilst the portions farther out, just inside the partition '1, are disposed to have almost no effect on the air.

A much more positive drive is effected by using gearing of any approved type. For example, I may use planetary gearing of the form shown in Figs. 9-12, which may be used to drive either a full-size auxiliary blade wheel of the type shown in Fig. 3, or a partial blade Wheel, of the type shown in Fig. 7. In these figures, l6 represents the compressor shaft; I! the hub of the auxiliary blade wheel; and I8 a stationary part, supported from the compressor casing. A plurality of pinions I9, e. g., ten to fifteen in number, are enclosed by an elongated, annular body 20, hereinafter called the pinion cage, and mesh with

rings

26 and 21. The pinion cage is supported by outer and inner rings of

ball bearings

29 and 30. Ring 26 is externally toothed and keyed on its inner face to the shaft I6, while ring 21 is toothed internally and keyed on its outer face to the part IS. The pinion cage engages the hub I! for driving the latter as the pinions and cage revolve between the relatively

rotating rings

26 and 21.

A strong and compact construction of such a mechanism can only be ensured if there is certainty that all of the pinions are equally loaded. According to the illustrated embodiment, this certainty is brought about by providing a bearing brass 2| for each pinion within niches in the pinion cage, the brasses forming bearings for the leading sides of the cylindrical shafts at the ends of the pinions l9. As the shaft i6 is rotated the pinions are driven in a counter-clockwise direction in Fig. 11, imparting a moment or torque to the brasses urging them in a counter-clockwise direction as viewed in Figs. 10 and 11 and toward the bottom of the drawing as viewed in Fig. 12. This moment is transmitted to the pinion cage through balls 35 in engagement with inclined faces on the bearings 2| and cage 20. The axial thrust on the balls 35 is counteracted by bodies 3|, which transmit the thrust via balls 36 to loose paratus.

ringsegments 23 supported by the-rim of. the pinion cage 20. It will benoted that the: seg-'- ments 23"havetheir ends-located opposite the balls 36 and shaped to'provide camming surfaces, whereby adjacent segments will be shifted apart (by-circumferential movement) when the body 3| and ball 36 are urged axially toward the segments. Conversely, movement of the segments against the ball 36 tends to shift the body 3| axially against the ball 35, thereby moving the bearing 2| against the pinion l9. In this manner even loading'on the pinions is assured.

Reference numbers

24 and 25 indicate-detachable rings enabling fraising'of the teeth; of rings l6 and I1. Ring 28 prevents bodies 3| from being flung outwardly by centrifugal force. Bevelled gear wheel 32 is adapted to engage a pinion connected to the starter and other auxiliary ap- Sealing members 33 and 34 prevent leakage of oil to the outside.

Entirely different mechanisms to ensure equal load on all pinions are, however, possible, the foregoing detailed disclosure being presented merely to show one practical way of carrying out the invention by the use of a positive gear drive.

Such a compact drive renders it possible to apply one single inlet opening in front of the compressor, as shown in Fig. 8, wherein I6 is the main compressor shaft, carrying main compressor blades 3 represents the auxiliary blades; and 31 and 33 represent portions of the casing, supporting stationary part I 8. Number 39 represents a shaft connected to the starter.

It is also possible to apply a one-sided compressor in a turbo-propeller unit in which the inlet opening is concentric with the propeller shaft, as shown in Fig. 13. The propeller 40 is carried by shaft 4|, driven by the main rotor 42, in advance of which the auxiliary blade wheel 43 is mounted. The propeller shaft is supported from the stationary casing 44 by supports 45 and bearing housing 46.

While I prefer to construct the auxiliary blade wheel in the nature of an axial-flow compressor, so as to admit the infiowing air into the main compressor blading more or less axially, as shown in Fig. 3, I may extend the auxiliary blades at their inner extremities in the manner shown in Fig. 7 to admit the air with some divergence.

I claim as my invention:

1. A radial compressor comprising a main rotor having radially extending blades, a gas inlet disposed concentric to the axis of rotation of said main rotor, an auxiliary bladed wheel arranged in said gas inlet and near said main rotor having impeller blades only at the circumferentially outer portion of the inlet to the main rotor, the blades of said auxiliary bladed wheel and of said main rotor being shaped to charge gas from the auxiliary wheel into the blades of the main rotor substantially without shock, said auxiliary bladed wheel having openings disposed radially inwardly from said outer portion permitting the flow of gas therethrough into said main rotor, and means for rotating said auxiliary bladed wheel in the same direction as and at a lower angular velocity than said main rotor. 2. In combination with the compressor according to claim 1, an annular partition at the radially inner extremity of the impeller blades of the auxiliary bladed wheel.

3. The radial compressor according to claim 2 wherein the partition is fixed to the auxiliary wheel and is rotatable therewith.

4. The radial compressor according to claim 2 7 wherein the partition is fixed to the blades of the main rotor and the blades of the-main rotor are matched radially outwardly from said partition to provide a space for the impeller. blades of the auxiliary bladed wheel. 1 I FRITS JONKER.

REFERENCES CITED The following references are of record in the file of this patent: v

V UNITED STATES PA'I'ENTS" Number V Name :Date

921,118 Kasley May ,11, 1909 Number Number I 10 347,766 579,780

8 Name Date Shelton Feb. 12, 1918 DeBolt June 8, 1943 Hornschuch May 23, 1944 Lincoln May 14,1946 Fawick Feb. 1, 1949 FOREIGN PATENTS Country Date Great Britain May '7, 1931 Great Britain Aug. 15, 1946