US2435236A - Superacoustic compressor - Google Patents

Description

Feb- 3, 1943- A. H. REDDING SUPERCOUSTIC COIPRESSOR Filed Nov. 23, 1943 matan WWW ou MN INVENTOR Hnnow H. Renovar F1 ATTORNEY Patented Feb. 3, 1948 SUPERACOUSTIC COMPRESSOR Arnold H. Redding, Swarthmore, Pa., aaaignor to Westinghouse Electric Corporation, East Pittsbui-gh, Pa., a corporation of Pennsylvania Application November 23, 1943, Serial No. 511,487

3 Claims. (Cl. 23o-120) This invention relates to gas compressors and it has for an object to provide an improved device of the character set forth.

In the design of kinetic machines the practice generally is t0 avoid superacoustlc flow velocities because of the losses associated with compression shock waves, which usually are added to all losses associated with subacoustic flow velocity. thereby causing a general decrease in the elliciency of the apparatus. This is especially true in the case of an expander or nozzle where the desired result is to convert pressure energy into velocity energy. However, a compression shock occurring normal to the path of flow of the medium traveling at superacoustc velocity is a good way oi converting the velocity energy into pressure energy. which is the function of a compressor.

It is, accordingly, a further object oi the invention to provide an improved compressor in which the medium to be compressed is subjected to a compression shock normal to its path of flow while traveling at superacoustic velocity relative to the moving compressor blades, between which the shock occurs.

By my invention I have provided a compressor, which by a single stage may achieve a compression ratio normally obtained with a plurality of stages in a conventional axial flow compressor.

In general. the moving blades of the present compressor have small camber and sharp inlet and outlet edges. The medium being compressed is supplied to the moving blades by guide vanes at such a direction and velocity relative to the moving blades that the medium is traveling at super-acoustic velocity with respect to the inlet edges of the moving blades, thus there is a superacoustic velocity field at the inlet side of the moving blades. The medium traveling at superacoustlc velocity is suddenly subjected to a normal compression shock front and reduced to a subacoustic velocity at the throat of the passage between adjacent moving blades. 'I'his sudden reduction in velocity provides an immediate pressure increase in the medium at or immediately following the throat region of the blades and the medium, then traveling at subacoustic velocity, gradually undergoes a further velocitypressure conversion in the remaining portion of the blade passage, which is preferably designed to function as a ditluser.

While the theoretically perfect moving blades of the compressor would have no camber and no thickness, I have shown one blade shape, which is approximately diamond-shaped in section from root to tip, providing sharp inlet and outlet edges,

2 and which provides a throat between adjacent blades substantially parallel to the path of the medium entering the blades. This blade shape also provides a. diiluser portion from the throat to the outlet of the blade passages which tends to further eilect compression oi the medium.

These and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part ol this application. in which:

Fig. 1 is a sectional view of one-hall' of a compressor made in accordance with the present inventlon;

Fig. 2 is a fragmentary developed plan view of the guide vane and moving blade, and straightening vane structure of the compressor shown in Fig. 1: and,

Fig. 3 is a vector diagram illustrating the velocity relations oi the guide vanes. blades and straightening vanes.

The compressor, indicated generally at Ill, comprises an outer tubular casing structure Il having a central core structure, generally indicated at I2, which deiines with the casing il an annular now passage i3 through which the medium to be compressed flows. The left or inlet end Il of the casing structure together with a. rounded nose portion lli oi' the central core structure defines an annular inlet to the compressor which is of gradually diminishing ow area. The sur faces of the inlet are smoothly curved to keep turbulence of the medium to be compressed at a minimum.

A plurality of circumferentially-spaced guide vanes IB extend across the inlet of the passage and are connected at their inner ends to the nose portion I5 and at their outer ends to the casing structure II, and serve to support the nose portion axially of the compressor.

I'he guide vanes I6 are preferably of airfoil section to minimize turbulence and are shaped to direct the gaseous medium at the proper angle to the plane of rotation of moving blades il of the compressor.

The core structure l2 also includes a drive shaft IB mounted in suitable bearings (not shown) carried by the casing structure and driven by any suitable means at a speed sumcient to provide a relative velocity between the medium and the inlet edges of the rotor blades II which is superacoustic. The drive shaft Il carries a rotor disc I9. on which the moving blades Il are fixed. l

While the optimum rotor blade would be flat and of no thickness. this o! course is not possible. Further, the inlet and outlet edges o: the rotor blades should be sharp and have a minimum camber to keep turbulence of the medium as low as possible. The rotor blades i1 shown in the drawing have been found eective and are approximately diamond-shaped in section from root to tip so that the leading edge 2l of each blade forms with the apical portion 22 of the preceding blade a slightly restricted throat in the blade passage in which the compression shock occurs. Referring to Fig. 2, this throat is substantially parallel to the path of iiow between the blades I1 and is represented approximately by the area lying between the broken linu 2l connecting the upper and lower ends of the leading edge 2i of a moving blade with the upper and lower ends, respectively, of the apex 22 oi' the preceding blade. From this throat, the adjacent surfaces of each blade diverge slightly to provide a diffuser passage between pairs of blades.

Rearwardly of the rotor blades, an annular passage 24 serves to direct the medium away from the blades l1 and is defined by an inner ring structure 25 supported from the casing structure i I by means of straightening varies 2l. One or more rows of these vanes may be provided for straightenlng the flow of the medium to bring it axially of the compressor.

The vanes 2B, in addition to straightening the flow of the medium, also tend to eii'ect a velocity to pressure conversion of the medium to further increase the pressure of the medium.

In Fig. 3, the vector diagram represents the velocity of the medium and compressor blades to illustrate the velocity to pressure conversion occurring when the medium is subjected to a compression shock while traveling ata superacoustic velocity relative to the moving blades l1. The vector 2l represents the velocity o! the air entering the guide vanes I8. The medium is turned and accelerated by the guide vanes, resulting in a velocity, represented by the vector 29, on leaving the guide vanes. Thus. the medium on entering the moving blades, the velocity of which is represented by vector 2l, has a velocity relative to the moving blades represented by the vector I2, this relative velocity being of superacoustic value. When the compression shock occurs between the moving blades. an immediate velocity to pressure conversion takes place, resulting in a lowered velocity, as represented by the vector I3, and an attendant increase in pressure.

While further compression may occur in the diffuser portion of the blade passage, after the medium has been subjected to shock at the throat region, the vector 2J is assumed to represent also the velocity of the medium leaving and relative to the moving blades. The velocity oi the medium with respect to the casing, on leaving the blades i1, is represented by the. vector 24, which is the resultant of vectors 32 and 2l. As the medium passes between the straightening vanes 2l, the medium is turned so that a further velocity to pressure conversion takes place and the medium again ows substantially axially of the compressor, as indicated by vector ll.

'I'he term "sharp" in the specification. when applied to the edges ot the blades or vanes reiers to the ratio of the radius of curvature of such edges to a reference dimension of the e width, for example, the width of the throat area, indicated at 2l in Fig. 2, said ratio preferably being in the nature of one per cent and in any event not over live per cent.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof. and it is desired, therefore. that only such limitations shall be placed thereupon as are speciiically set forth in the appended claims.

What is claimed is:

l. A compressor comprising a casing structure, a compressor rotor journaled axially in said casing structure and dening therewith an annular flow passage, blading carried by said rotor and extending across said annular flow passage, guide vanes carried by said casing structure and extending across said iiow passage forward of said rotor blades and arranged to direct the gaseous medium to be compressed at a proper angle to said rotor blades, said rotor blades being substantially diamond-shape in section from root to tip and leaving sharp inlet and outlet edges and intermediate apical portions, said blades being arranged so that the inlet edge of each blade together with an apical portion of the adjacent leading blade defines a restricted throat ln the passage between the blades, said throat `being substantially aligned with the direction of flow of the gaseous medium flowing through the blade passage for eil'ecting a normal compression shock to gaseous medium entering said throat at superacoustic velocity relative to the moving blades and thereby provide an immediate reduction in the velocity of said medium and an immediate increase in the pressure thereof.

2. A compressor comprising a casing structure having an annular air-iiow passage, a compressor rotor journaled axially in said casing structure, blading carried by said rotor and extending across said annular flow passage, means extending across said flow passage forward of said rotor blades for directing the gaseous medium, to be compressed, at a proper angie to said rotor blades, said blades having sharp inl'et and outlet edges and being so constructed and arranged as to provide a normal compression shock to the gaseous medium entering the blades to provide an immediate reduction in the velocity of said medium relative to said rotor blades and thereby eect an immediate increase in the pressure of said medium.

3. A compressor comprising a casingstructure. a compressor rotor iournaled axially in said casing structure and deilning therewith an annular now passage, blading carried by said rotor and extending across said annular iiow passage. guide venes carried by said casing structure and extending across said ow passage forward of said rotor blades and arranged to direct the gaseous medium to be compressed at a proper angle to said rotor blades. said rotor blades being substantially diamond-shape in section from root to tip providing sharp inlet and outlet edges and immediate apical portions, said blades being arranged so that the inlet edge of each blade together with an apical portion of the adjacent leading blade deiines a restricted throat in the passage between the blades. said throat being substantially aligned with the direction of flow of the gaseous medium owing through the blade passage i'or eilecting a normal compression shock to gaseous medium entering said throat at a superacoustic velocity relative to the moving blades and thereby provide an immediate reduction in 5 6 the velocity ot said medium and an immediate UNITED STATES PATENTS increase in the pressure thereof. and straightenumh" ing varies carried by said casing and extending N 408,864 voglsng lungo 1839 errors Said flow Passage rearward 0f Wd um 1 463 no wonnen "mn-.nn '24' im blades for directing the gaseous medium leaving 5 lmm Mmdka""""` Ay, 9' 1935 said moving blades substantially axially o! the 2:13419 Renew, 1?" Nav' 1' 1938 ,compressor 2,224,519 Mamme Dec. 1o: 194e ,ARNOLD E REDDmG- 1,552,637 Mothers] Sept. 8, 1925 REFERENCES crrnn 1 N ber FOREIGN PATENTS um Coun Date The following references are or record in the 501Mo: reet Britain Feb. s. man le 0f this Damit? 590.196 France June 13. 1925 Certiiicate of Correction Patent No. 2,435,236. February 43, 1948.

ARNOLD H. REDDING It is hereby certied that error appears in the rinted specification of the above numbered patent requiring correction as follows: lumn 4, line 23, for the iword leaving read having; and that the said Letters Patent should be read with this orection therein that the same may conform to the record of the case in the Patent signed mi sealed this zoiii diy of April, A. n. 194s.

[mtl

THOMAS F. MURPHY,

Aniatmtammeonef of Patata.

5 6 the velocity ot said medium and an immediate UNITED STATES PATENTS increase in the pressure thereof. and straightenumh" ing varies carried by said casing and extending N 408,864 voglsng lungo 1839 errors Said flow Passage rearward 0f Wd um 1 463 no wonnen "mn-.nn '24' im blades for directing the gaseous medium leaving 5 lmm Mmdka""""` Ay, 9' 1935 said moving blades substantially axially o! the 2:13419 Renew, 1?" Nav' 1' 1938 ,compressor 2,224,519 Mamme Dec. 1o: 194e ,ARNOLD E REDDmG- 1,552,637 Mothers] Sept. 8, 1925 REFERENCES crrnn 1 N ber FOREIGN PATENTS um Coun Date The following references are or record in the 501Mo: reet Britain Feb. s. man le 0f this Damit? 590.196 France June 13. 1925 Certiiicate of Correction Patent No. 2,435,236. February 43, 1948.

ARNOLD H. REDDING It is hereby certied that error appears in the rinted specification of the above numbered patent requiring correction as follows: lumn 4, line 23, for the iword leaving read having; and that the said Letters Patent should be read with this orection therein that the same may conform to the record of the case in the Patent signed mi sealed this zoiii diy of April, A. n. 194s.

[mtl

THOMAS F. MURPHY,

Aniatmtammeonef of Patata.

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