US2798657A - Compressor - Google Patents

Description

K. A. DARow July 9,1957

COMPRESSOR Filed Aug. so, 1954 [n Venter Ms Attorney.

United States lPatent COMPRESSOR Kenneth A. Darrow, Sprakers, N. Y., assignor to General Electric Company, a corporation of N ew -York Application August 30, 1954, Serial No. 452,935

2 Claims. (Cl. 230-114) This invention relates to compressors and more particularly to a method and apparatus for eliminating pulsation in such compressors.

A compressor in which pulsation is eliminated is desirable to provide an eicient machine. Pulsation is a serious problem in centrifugal or axial flow compressors because it reduces compressor performance greatly at low rates and makes continuous operation untenable. Such pulsation occurs when fluid flow becomes completely separated along the length of the flow passages in both the impeller and diffuser. The vibrations which are caused by such pulsation are suicient in a large compressor to destroy the machine.

Accordingly, it is an object of my invention to provide an improved compressor which has a long, useful operating range.

It is another object of the invention to provide an improved ycompressor in which high eticiencies are maintained at the low flow range near or below the normal pulsation point.

It is a further object of the invention to provide a novel method to extend the operating range in a cornpressor.

In carrying out my invention in one form, a constant fluid flow is maintained through the compressor diffuser by the addition of secondary air adjacent the impeller to supply air to the diffuser entrance.

These and various other objects, features and advantages of the invention will be better understood from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a sectional view of a centrifugal compressor which embodies my invention;

Fig. 2 is a bottom plan view taken along lines 2-2 of Fig. l; and

Fig. 3 is a `sectional view similar to Fig. l with the air inlets in an open position.

In Fig. 1 of the drawing, a centrifugal compressor is shown generally at which comprises a casing 11 to define a chamber 12 therein. An air inlet or aperture 13 is centrally disposed in the upper wall of casing 11. A centrifugal blower impeller 14 with a plurality of curved blades 15 thereon is mounted on a shaft 16 in axial alignment with inlet 13. Shaft 16 is connected to a suitable source of power, such as an electric motor (not shown). Impeller 14 is provided with a back wall 17 and a forward Wall 18 which extend laterally therefrom to form a diffuser 19 which may be of the vane or vaneless type. `A plurality of apertures 20 are located in wall 17 adjacent the free end of impeller 14 to admit secondary air near the impeller tip and the diifuser entrance. A member 21 with a pair of opposed apertures 22 near its periphery is mounted on the outside of wall 17 by means of an upstanding ange 23 thereon through which bolts 24 are secured. Member 21 is also provided with two pairs of opposed brackets 25 on its outer surface to retain a sliding closure member 26. As it is best shown in Fig. 2, member 26 is provided with a central aperture 27 through which shaft 16 extends. An aperture 28 is located at each of the opposite ends of member 26 for the admission of secondary air.

A control device 29 which operates member 26 comprises a casing 30 with a piston 31 therein to move a connecting rod 32. Rod 32 may be connected to member 26 by any suitable means, such as, for example, a bolt 33 and a nut 34. Piston 31 is connected to the opposite end of cylinder 30 by a spring 35. Movement of piston 31 within cylinder 30 is controlled by a Pitot tube 36 which is positioned in air inlet 13. Tube 36 comprises an inner tube 37 with an inlet 38 to measure the total pressure head and an outer tube 39 with an inlet 40 to measure the static pressure head. 'I'ube 37 is connected to the spring side of cylinder 30 while tube 39 is connected to the opposite side of piston 31.

In Fig. 3, centrifugal compressor 10 is shown with apertures 22 and 28 in alignment to admit secondary air through apertures 20. This secondary air is pumped by the injector action of the air which ows from the outlet of impeller 14 to diffuser 19 to provide a constant ow therethrough. The open position of apertures 22 and 28 is attained during separation of the fluid from the wall of the flow passage to prevent pulsation in compressor 10.

In the operation of compressor 10, centrifugal action of impeller blades 15 drives air from inlet 13 downwardly and outwardly towards the inner wall of casing 11. Member 26 closes apertures 22 until the fluid begins to separate from the wall of diffuser 19. A decrease in the total pressure head which is caused by a change in flow through inlet 13 is transmitted through tubes 37 and 39 to change the differential pressure in cylinder 30 to move piston 31 outwardly. Piston 31 controls member 26 through connecting rod 32 to change the area of apertures 22--28. Thus, a varying flow of secondary air in the necessary amount is admitted to the back of impeller 14 to provide an essentially constant diffuser How at a flow point where separation will not occur. Compressor 10 utilizes pumping action of the back of impeller 14 and ejector action of the air which leaves impeller 14 to furnish a secondary diffuser How. A reduction in the fluid ow through impeller 14 requires additional secondary air to provide a constant diifuser ow.

As will be apparent to those skilled in the art, the

f objects of my invention are attained by the use of a constant fluid flow through the diffuser which is provided by the addition of secondary air adjacent. the impeller.

While other modifications of this invention and variations of apparatus which may be employed within the scope of this invention have not been described the invention is intended to include all such as may be embraced within the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A compressor comprising a casing having an air inlet therein, an impeller within said casing arranged to receive air from said inlet, a diffuser adjacent the periphery of said impeller arranged to receive air from said impeller, secondary air apertures adjacent said impeller, adjustable closure means normally closing said apertures, said closure means comprising a member having at least one aperture therein enclosing said secondary air apertures, a second member normally closing the aperture of said first member, and means responsive to changes in air inlet pressure to adjust said adjustable closure means.

2. In a centrifugal compressor the combination comprising, a casing having an inlet therein, an impeller in said casing, a diffuser surrounding said impeller and arranged to receive air therefrom, said casing having an opening therein to admit air to the back of said impeller and near the impeller tip and the diffuser inlet, and means responsive to the change of air pressure in said Patented July 9, 1957 l inl'e'tv to adnit air through' said opening to said diuser tcrrn'aintair1- a' wnstant' ow'therein:

Refernces Cited the lepf this patent v,

UN'IIEDSTATES PTENTSi Y 5 1,089,665 Pagel .;g- 111311210;19.131'i Irwin Iuly 14, 1931 Browne( Feb: 1-5", 19441 Loss May 17, 1949 Klein et al. Nov. 24, 1953 Muhlberg Sept. 28, 1954

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