US2058990A - Intake muffler - Google Patents

Description

()ct. Z7, 1936. w. E. JOHNSON INTAKE MUFFLER Filed Feb. l, 1956 llllil IIIn in um 1 m .nww @h/Wn to r HJ. O @Bmw vm A F M Patented Oct. 27, 1936 UNITED STATES INTAKE MUFFLER Wilfrid E. Johnson, Schenectady, N.

Y., assignor to General Electric Company, a corporation of New York Application February 1, 1936, Serial No. 61,947 6 Claims. (Cl. 181-47) My invention relates to intake mufflers for refrigerant compressors or other machines in which successive quantities of an elastic fluid are supplied to the machine.

In refrigerant compressors of the reciprocating type, for example, successive quantities of gaseous refrigerant are supplied through a suitable intake valve mechanism to the compressor cylinder during the successive intake strokes of the piston. It is desirable in designing such a machine to provide some arrangement for minimizing or substantially preventing the transmission of sound waves through the entering fluid, caused by the operation of the compressor valve mechanism or the like, in order to minimize the noise of operation of the machine. This problem is especially important in machines designed for household use since particular care should be taken to make their operation as unobtrusive as possible from the standpoint of noise.

It is an object of my invention to provide an improved intake muilier for a refrigerant compressor or the like in which sound waves set up in the fluid supplied to the compressor are confined within a closed mufiling chamber. I accomplish this by providing an arrangement at the inlet of the mufiiing chamber restricting the effective area of the inlet for maintaining the velocity of the fluid flowing therethrough, during the normal operation of the machine, at a value greater than the acoustical velocity of the fluid. As a consequence the egress from the inlet of sound waves set up in the fluid by the operation of the compressor valve mechanism or the like is substantially prevented.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawing in which Fig. 1 is a side elevation, partly in section, of a refrigerating machine provided with an intake muffler embodying my invention, and Fig. 2 is an enlarged plan View partly in section, of the intake muiiler shown in Fig. 1.

Referring to the drawing, I have shown in Fig. 1 a compression type refrlgerating machine especially designed for household use, which includes a Scotch yoke type refrigerant compressor I mounted on the top of and driven by a vertical electric driving motor II. The compressor II) and driving motor II are mounted within a cylindrical hermetically sealed steel casing I3 on a series of vertical helical compression springs Il. Gaseous refrigerant, such as-dichlorodifiuoromethane (CClzFz) is supplied from the interior of the casing I3 to the compressor I0 through an intake muffler I5, embodying my invention. 'I'he gaseous refrigerant compressed in the compressor I0 is discharged therefrom through a discharge conduit I6 and flows therethrough to a discharge muffler I1. The compressed gaseous refrigerant then flows from the discharge muiiler I1 through a conduit I8 to an elongated refrigerant circulatory passage I9 of a sheet metal cylindrical natural draft air-cooled condenser 20. The condenser 20 surrounds the casing I 3 and is mounted on a series of radial heat conducting fins 2l interposed between the adjacent surfaces of the casing and condenser 20. Refrigerant vapor flowing through the refrigerant circulatory passage I9 is cooled by the transfer of heat therefrom to the surrounding air which flows upwardly over the surfaces of the condenser 20 and between the casing I3 and condenser 20 over the surfaces of the fins 2| due to natural draft. The refrigerant thus liquefied in the condenser 20 flows therefrom through a conduit 22 to a flow controlling iioat valve 23 from which it is supplied through a liquid line 24 to an evaporator 25.

The evaporator 25 is supported on the lower side of a removable heat insulated top wall I2 of a refrigerator cabinet and within a cooling compartment of the refrigerator, which the evaporator is adapted to cool. The liquid refrigerant within the evaporator 25 is vaporized by the absorption of heat from the compartment in which it is located and the vaporized refrigerant is collected in a longitudinal cylindrical header 26 above the level of the liquid refrigerant therein. The header 26 is normally maintained about half full of liquid refrigerant so that the remainder of the evaporator 25 is flooded with liquid refrigerant. The vaporized refrigerant thus collected in the header 26 passes therefrom through a conduit 21 to the interior of the casing I3. The vaporized refrigerant within thecasing I3 is again supplied to the compressor I0 through the intake muiiler I5 and the cycle described above is repeated and continued until the compartment in which the evaporator 25 is located is cooled to the kdesired temperature.

The intake muiller casing 28, which may conveniently be formed I includes a tubular metal driving motor Il Iand extend about the rear end of the compressor I3 thus forming a compacty arrangement of the parts of the compressor unit mounted within the hermetically sealed casing i3. The ends of the casing 23 are closed by cupshaped sheet metal caps!! and 30 which are brazed or otherwise hermetically sealed thereto. Holes 3| and 32 are formed in the flanged portions of the caps 29 and 39. respectively, and these holes register with similar holes formed in the end portions of the casing 23. Suitable bolts 33 and 3l passing through the holes 3l and 32 respectively, as well as the registering holes in the casing 2l secure the casing in position on top of the driving motor Il and also aid in holding the caps 23 and 30 in position within the ends of the casing 23. A ilanged outlet opening 33 is formed in the cap 29 and one end of a conduit 33 is brazed or otherwise hermetically sealed to the sides thereof. 'I'he conduit 33 conveys vaporized refrigerant from the interior of the fluid muiiling chamber 31 formed by the casing 33 to the inlet of the compressor I0. A hanged inlet opening 33 is formed in the cap 30 at the opposite end of the fluid muming chamber 31.

I have provided an arrangement restricting the enective cross-sectional area of the inlet opening for maintaining the velocity of the vaporized refrigerant or vaporized refrigerant flowing therethrough. during the normal operation of the compressor, at a value greater than the acoustical velocity of the vaporized refrigerant to thereby substantially prevent the egress from the inlet of sound waves set up in the vaporized refrigerant within the muiiling chamber 31 by the operation of the compressor valve mechanism and the like. As best shown in Fig. 2, this arrangement includes a tubular nozzle 33 which is mounted in the flanged inlet opening 33 and is brazed or otherwise hermetically secured to the walls thereof. The nozzle 33 is provided with a sharply flared inlet passage 40 which communicates with a relatively narrow restricted throat Il. 'I'he nozzle is also provided withan elongatedoutwardly flaring discharge passage 42 which communicates with the throat ll. Although vaporized refrigerant is drawn into the compressor lli in successive quantities upon each suction stroke of the compressor piston. the volume of the muming chamber 31 is made large as compared to the displacement of the compressor, so that the pulsations of pressure within the chamber 31 will be relatively small. In the machine illustrated the volume of the munling chamber 31 is approximately twelve times the displacement of the compressor. As a consequence, the vaporized refrigerant flowing through the nozzle 39 into the muming chamber 31 moves at a velocity which is relatively constant. The cross-sectional area of the throat 4I of the nozzle 39 is so proportioned with respect to the average flow of vaporized refrigerant required by the compressor that the velocity of flow of vaporized refrigerant through the throat Il will be equal to or greater than the acoustical velocity of the vaporized refrigerant. 'I'he acoustical velocity, or rate of travel of sound waves through any gas, may be expressed by the well known equation:

yP WIV d where v is the acoustical velocity of the gas in i machine because it has a low so that the throat 4| of the *made less restricted and hence the losses caused ft. per second. P is the absolute pressure of the gas in lb. per sq. ft.. d is the density in lb. mass per cu. ft., and 'y is the ratio of specific heats of the gas at constant pressure and volume, respectively. From an inspection of this equation, it will be apparent that the acoustical velocities for different gases may vary widely. Thus. the acoustical velocity for air at 50 deg. F. is approximately 1100 ft. per second. while that for sulphur dioxide is approximately 800 ft. per second and that for dichloroditluoromethane is approximately 500 ft. per second. Consequently, the dimensions of the throat 4I of the nozzle 39 must also be proportioned in view of the particular gas to be used in the machine. I prefer to use dichlorodiiluoromethane as the refrigerant for the acoustical velocity nozzle 39 may be thereby minimized. The discharge passage l! of the nozzle 39 diverges or 4flares gradually so that the velocity head of the vaporized refrigerant flowing through the nozzle may be reconverted to pressure head without substantial loss.

It will be seen that in such an arrangement as that described above that any sound waves set up in the vaporized refrigerant in the muiiiing chamber 31 by the operation of the valve mechanism of the compressor or the like will be confined within the mufiiing chamber 31 since they cannot pass through the throat 4I, as the vaporized refrigerant flowing therethrough is moving inwardly at a velocity equal to or greater than the velocity of the sound waves. Thus no sound waves can be transmitted from the vaporized refrigerant within the muiliing chamber 31 through the vaporized refrigerant within the casing I3 to the walls of the casing and the noise of operation of the machine is, consequently, minimized. It should also be noted' that no pulsations in :tlow of vaporized refrigerant through the nozzle 39 will result from any pulsations in pressure within the muiliing chamber 31, so long as the pressure within the hermetically sealed casing I3 is maintained at a substantially constant value. This arises from the fact that when the nozzle 39 is designed to accommodate the average ilow of vaporized refrigerant therethrough required by the compressor, then no matter what the reduction of pressure within the mufiiing chamber 31 no greater flow through the nozzle 39 than the predetermined average can be obtained. Thus, no matter how the pressure pulsates within the muiiiing chamber 31 no pulsations can occur outside the nozzle 39. In this respect, it is desirable to make the volume of the mufiling chamber comparatively large in order to prevent excessive pulsations in pressure therein and consequent loss in eiliciency.

While I have shown a particular embodiment of my invention in connection with a compression type reirigerating machine designed for household use, I do not desire my invention to be limited to the particular construction shown and described. and I intend in the appended claims to cover all modifications within the spirit and scope of my invention.

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

l. An intake mufiier for a refrigerant compressor or the like comprising a chamber having a relatively large volume as compared to the displacement oi' the compressor used therewith, said chamber having an inlet and an outlet, and means restricting the effective cross-sectional area of said inlet for maintaining the velocity of the fluid flowing therethrough during the normal operation of the compressor at a value greater than the acoustical velocity of the fluid to thereby substantially prevent the egress from said inlet of sound waves set up in the fluid by the operation of the compressor.

2. An intake muffler for a refrigerant compressor or the like comprising a chamber having a relatively large volume as compared to the displacement of the compressor used therewith, said` chamber having an inlet and an outlet, and means in said inlet including a nozzle having a throat of relatively restricted cross-sectional area for maintaining the velocity of the fluid flowing therethrough during the normal operation of the compressor at a value greater than the acoustical velocity of the fluid to thereby substantially prevent the egress from said inlet of sound waves set' up in the fluid by the operation of the compressor.

3. An intake muffler for a refrigerant compressor or the like comprising a chamber having a relatively large volume as compared to the displacement of the compressor used therewith, said chamber having an inlet and an outlet, and means including a nozzle located at said inlet for maintaining the velocity of the fluid owlng therethrough during the normal operation of the compressor at a value greater than the acoustical velocity of the fluid to thereby substantially prevent the egress from said inlet of sound waves set up in the fluid by the operation of the compressor, said nozzle having a throat of relatively restricted cross-sectional area and an elongated outwardly flaring discharge passage communieating with said throat.

4. An intake muiiler for a refrigerant compressor or the like comprising a tubular casing having a relatively large volume as compared to the displacement of the compressor used therewith, means including caps extending across the opposite ends of said casing and hermetically secured thereto for closing the same, one of said caps having an outlet opening formed therein and the other of said caps having an inlet opening formed therein, and means restricting the effective cross-sectional area of said inlet for maintaining the velocity of the fluid flowing therethrough during the normal operation of the compressor at a value greater than the acoustical velocity of the fluid to thereby substantially prevent the egress from said inlet of sound waves set up in the fluid by the operation of the compressor.

5. An intake muilier for a refrigerant compressor or the like comprising a tubular casing having a relatively large volume as compared to the displacement of the compressor used therewith, means including caps extending across the opposite ends of said casing and hermetically secured thereto for closing the same, one of said caps having an outlet opening formed therein and the other of said caps having an inlet opening formed therein, and means including a nozzle positioned in said inlet opening and having a throat of relatively restricted cross-sectional area for maintaining the velocity of the fluid flowing therethrough during the normal operation of the compressor at a value greater than the acoustical velocity of the fluid to thereby substantially prevent the egress from said inlet of sound waves set up in the fluid by the operation of the compressor.

6. An intake muilier for a refrigerant compressor or the like comprising a tubular casing having a relatively large volume as compared to the displacement of the compressor used therewith, means including cup-shaped sheet metal caps positioned in the ends of said casing and hermetically secured thereto for closing the same, one of said caps having an outlet opening formed therein and the other of said caps having an inlet opening formed therein, means including a nozzle positioned in said inlet opening for maintaining the velocity of uld flowing therethrough during the normal operation of the compressor at a value greater than the acoustical velocity of the fluid to thereby substantially prevent the egress from said inlet of sound waves set up in the fluid by the operation of the compressor, said nozzle having a throat of relatively restricted cross-sectional area and an elongated outwardly flaring discharge passage communicating with said throat.

WILFRID E. JOHNSON.

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