US2180259A - Suction mechanism - Google Patents

Description

Nov. 14, 193 9. B. SA\RG ENT SUCTION MECHANISM Filed Dec. 18, 19:57

5o ing communicates with said chamber.

. ing further is provided with an internal flange Patented Nov. 14, 1939 UNITED STATES 2,180,259 7 SUCTION amonamsn Richard B. Sargent, Philadelphia, la., assignor to The Bale Fire Pump 00., Inc., onshohock-- en, Pa... a corporation of Pennsylvania Application December 18,1937, Serial No. 180,654

SCIalms.

nisms may be employed, for example for priming centrifugal pumps, and are of particular utility in connection with fire fighting apparatus wherein the internal combustion motor of the fire engine iscommonly employed to drive the pump or pumps forming essential elements of the equipment.

A principal object of the present invention is to provide a device of the stated type that by reason of a novel design hereinafter described will exhibit in operation a performance in the pump priming function materially in advance of the prior commercially available devices of this character.

More specifically, an object of the invention is to provide a mechanism of the stated type that shall be capable of producing relatively high derees of vacuum. I

The invention further resides in certain novel structural details and arrangements of parts hereinafter described and illustrated in the attached drawing, in which: I

Figure 1 is a view in perspective of an ejector made in accordance with my invention and constituting an element of the suction mechanism; Fig. 2 is a longitudinal sectional view of the ejector;

Fig. 3 is a section on the line 3-3, Fig. 2;

Fig. 4 is a detached view in perspective of one of the ejector elements, and Fig. 5 is a line draw- 35 ing showing the suction mechanism as a whole.

With reference to the drawing, the ejector in a preferred embodiment comprises three principal elements consisting, respectively, of a cylindrical housing I, a nozzle 2, and a body member 3. The housing I is provided at one end with a threaded port 4 for connection with the exhaust manifold or exhaust pipe of an internal combustion engine. and is provided at its opposite end with an outwardly projecting annular flange 5 45 having tapped holes for reception of screws 6 which secure the-body member 3 to'the housing. Intermediate its ends the housing has in its inner wall an annular recess I, and a tapped port I formed in a boss 9 on the wall of the hous- The hous- I I which provides a solid abutment or seat for the nozzle 2. I

. The nozzle 2 is formed at its rear end, namely.

5; that end which in assembly abuts the flange l I,

PATENT: OFFICE with a cylindrical surface I2, and this surface, as shown in Fig. 4, neatly fits the bore of the housing I. From this end the body of the nozzle 2 tapers inwardly to a cylindrical extension I3 of relatively small external diameter. Ribs I4 extend outwardly at the base of the extension I3, and the outer surfaces of these-ribs fit neatly against the inner wall surface of the housing I, asshown in Figs. 2 and-3. These ribs, with the surface I2, form an extended bearing for the nozzle upon the housing and maintain the noz- "zle definitely in a concentric position within the housing bore. The bore of .the nozzle at the end adjoining the flange II is conical in form, as indicated at I5; and the inner end of this conical portion terminates in a cylindrical passage it which extends through the extension" I3 of th nozzle.

The body member 3 is formed at one end to neatly fit within the bore of thehousing I, and is provided intermediate its ends with an outwardly extending flange I I through which the bolts 6 pass. It will be noted thatin assembly the flange I! does not engage the flange 5 of the housing, so that when the bolts 6 are tightened, the inner end of the body member 3, which engages the end edges of the ribs f4, forces the nozzle 2 solidly against the abutment flange II. The three principal elements of the nozzle are thereby held securely in their relative positions directly with the nozzle passage l6, and as shown in Fig. 2, the passage l8 of the body member communicates at its rear or inner end with a conical terminal recess l9, which through the spaces between the ribs ll of the nozzle 2 is in direct communication with the annular chamber I. By reason 'of the neatly fitted contacting surfaces of the body member 3 and the housing I, and the similar close fit between the nozzle 2 and the housing, the bores of the nozzle 2 and of the body member 3 are held in accurate longitudinal alignment.

' The housing I, as previously set forth, is connected through the port 4 with the exhaust manifold of the internal combustion engine l0, see Fig. 5, which engine with the ejector above described, constitutes the suction mechanism. A suitable two-way valve is positioned in the connection be- REISSUED f APR 2 1940 tween-the exhaust manifold of the engine and the ejector and is operable to direct the exhaust gases of the engine directly to the ejector or directly'to the exhaust pipe of the engine, it being understood that the exhaust gases are passed to the ejector only during such time as it is desired to create suction at the ejector for pump priming or other suction purposes. Flow of the exhaust gases through the nozzle 2 and the body. member 3 evacuates the chamber 1 and tends to draw into that chamber, through the port 8, fluid from a source with which the said port is connected. When this device is employed for priming centrifugal pumps, the port 8 is connected with the eye of the pump in well known manner.

Design of an ejector adapated to operate at the relatively low gas pressures available in the exhaust of an internal combustion engine, and to. produce the required relatively high lifts, presented a problem of considerable complexity involving definite departure from the conventional design practice. It was necessary to consider not only the characteristics of the ejector per se atthe available pressures, but also the effect of the presence of the ejector in the exhaust line upon the operation of the engine which constitutes the source of the operating pressure when said engine is functioning as an exhaust gas compressor. The velocity of the gases discharged through the ejector nozzle is a function of the exhaust pressure, whereas the pressure developed in the exhaust is a function of engine operation,

the efliciency of which operation, when said engine is functioning as an exhaust gas compressor, being determined by the diameter and form of the nozzle passage of the nozzle. I have discovered that if the diameter of the nozzle'is too great, the exhaust pressure obtainable from the engine when said engine is functioning as an exhaust gas compressonis not suflicient to provide back pressure existing between the engine and the ejector will materially interfere with the operation 'of the engine, i. e., it will prevent the engine from operating smoothly and properly,

.and if too great will even cause the engine to stop. I have discovered that there is a direct relation between the diameter and shape of a nozzle inserted in the exhaust of an internal combustion engine and the exhaust pressure of that engine and that it is possible to design a nozzle which, within definable limits of size and shape, will be productive of the development of maximum attainable exhaust pressures by the engine when said engine is functioning as an exhaust gas compressor and, therefore, of maximum velocities of gas discharge through the nozzle. Velocity alone is not sufficient, on the other hand, to obtain high lift characteristics in the ejector, these characteristics being a. function of the relation of the nozzle to the other elements of the ejector and the form and relative dimensions of those elements. I have discovered that between definable limits there is a direct relation between the forms and relative dimensions of the nozzle and of the other elements of the ejector affording maximum lift characteristics in the ejector. I have found further that all of these relations are substantially constant. and that they may, therefore, be expressed in'terms of formulae permitting ready application of the principle involved to the production of ejectors for use with substantially any character of internal combustion engine and capable of affording, when used with any specific engine, performances heretofore considered unobtainable.

Referring again to the drawing, I have found that maximum velocity of nozzle discharge may be obtained by passing the exhaust gases of an internal. combustion engine through a nozzle passage of the cylindrical form shown where the diameter (DN) of the passage, in inches, is approximately 1/22 of the square root of the maximum brake horsepower of the said engine, and

the length of the passage (LN) is approximately three times its diameter. With a nozzle passage of this character and with the ejector connected to the exhaust of an internal combustion engine when said engine is functioning as an exhaust .With a nozzle passage of a diameter in inches of approximately l/22 of the square root of the maximum brake horsepower of the internal combustion engine, maximum velocity and pressure effects will be obtained at the ejector and the said engine will operate smoothly and efllciently as an exhaust gas compressor, 1. e., no excessive back pressure will be built up between the ejector and engine which would tend to affect adversely the normal operation of. the engine as an exhaust gas compressor and the nozzle passage is such that the exhaust gas does not pass too readily therethrough. I have found further that exceptionally good results may be obtained by variation of these dimensions in either direction between certain limits. Thus the diameter of the nozzle passage may vary .between M and of the square root of the maximum brake horsepower of the engine, and the length of the nozzle may vary between 1% times the diameter of the nozzle passage and five times said diameter. These dimensions. therefore, may be expressed in terms of the following formulae:

aximum brake um brake H. P. of engine I H. P. of engine DN= 15 to 30 understood that I refer only to the emciency of the engine to function as an exhaust gas compressor, i. e., I am not at all concerned with the efiiciency of the said engine to perform other work, such as driving a pump, propelling the vehicle, or the like, it being obvious that the ejector is connected to the engine only during such time as the said engine is exhaust gas pressure As previously set that to utilize the velocities thus afforded to obtain a maximum lift in the ejector, the elements of the ejector structure should bear, between certain limits, a definite relation to each other. Thus the passage l8 through the body member 3 should diverge forwardly from a point of maximum restriction adjoining the nozzle 2, and this angle of divergence should be approximately 2, and may vary between 1 and 3. The diameter of the throat of the passage l8, i. e., the diameter .(DB) at the point of maximum restriction, should for best results be approximately 1.5 times thediameter (DN) of the nozzle passage, and may vary between 1.3 times that diameter and 1.7 times the diameter; and the outside diameter (dN) of the outer end of the'nozzle 2 which lies in proximityto the throat of the passage 18 should be from a e" to plus the diameter (DN) of the nozzle passage. It was found. that the length (LB) of the passage l8 should for maximum results be approximately 7 times the diameter passage, and may vary between 4.5 times the diameter of said throat and 10 times the diameter of the throat. The end of the nozzle 2 in this assembly is preferably located at the throat of the passage l8, but may occupy a position at either axial side of this throat to a distance (A) up to functioning as a source of for the ejector.

s .5 of the throat diameter (DB)of the passage ll. The foregoing dimensions may be expressed in terms of the following formulae:

DB=DN 1.3 to DNXL'I A, the distance of the end of the nozzle 2, in either direction the throat of the passage l8, may vary within the limits of zero to DBX .5.

In the above formulae the limits specified have been found. to define a critical or optimum range of dimensions or angles, outside of which maximum suction effects are not obtainable at the ejector.

It will thus be seen that the most important dimension or range of dimensions relates to the diameter DN of the nozzle passage, and that once this dimension is obtained by using the known maximum brake horsepower of the engine .as a basis for the calculations, the length of the nozzle passage LN, the diameter of the throat of the bore dN, etc., may be readily determined.

Hence, by the invention presented herein it is a relatively simple matter to associate with anyinternal combustion engine of known maximum brake horsepower, the proper ejector mechanism to accomplish. optimum maximum suction effects.

The maximum known brake horsepower of a particular engine is generally set forth in the specifications of the engine and hence is a known quantity. Such factors as the areaof the pistons in inches, the pressure in pounds weight per square inch, the length of the stroke in inches, the number of strokes per minute, the number of cylinders, etc" all contribute to the determination of the maximum brake horsepower for any given internal combustion engine and as these factors bear a very definite relation to maximum volumetric displacement of the engine when considering said engine as an forth, I have found further (DB) of the throat of the axially, from exhaust gas compressor, 1 have discovered that above, I have found it possible with the pressures available from the exhaust of an internal combustion engine, which pressures are seldom in excess of 25- pounds, to lift water vertically through heights as great as 24 feet, this lift being far in excess of the lift previously obtainable by ejector action from such exhaust pressure source. While it is known that prior to theapplicants invention attempts have been made to utilize ejectors operated from the exhaust of an internal combustion engine for the purpose of priming pumps, such attempts within the knowledge of the applicant have failed in commercial application by reason of inability to produce by this means lifts ofadequate height. The present invention finds an application of particular value in connection with centrifugal pumps employed in fire fighting apparatus wherein the priming operation may frequently involve lifts of water from the source to the pump of considerable heights. It is customary in modern fire fighting apparatus to provide thevehicle with an internal combustion engine employed to propel the vehicle, or to operate the pumping equipment on the vehicle such as a centrifugal pump or the like. It is therefore a matter of great convenience to utilize. the internal combustion engine mounted on the vehicle as a source of pressure fluid for operating an ejector adapted to create maximum suction effects for pump priming and/or other purposes.

I claim:

1. A suction mechanism comprising an ejector connected to the exhaust of an internal combustion engine of. known maximum brake horsepower which engine functionsas a source of pressure fluid for operating the ejector, said ejector including a nozzle having a cylindrical passage through which the exhaust passes, a body member having a bore arranged in axial alignment with the nozzle passage and extending following formulae:

aximum brake H. P. of engine where DN is the diameter in inches of the nozzle passage, LN is the length of the nozzle passage, DB is the. diameter of the throat of said bore, 0 is the angle of divergence of said bore, .A is the distance of the forward end of said nozzle from said throat in either direction axially of the bore,

Maximum brake H. P. of engine which is selectively LB is the length of said bore, and dN is the. thickness of the wall of the nozzle at the forward end thereof which lies in proximity to the throat of said bore.

nozzle and communicating with said bore, said first nozzle passage being cylindrical in form and having an internal diameter in inches equal to from A to A of the square root of the maximum brake horsepower of the engine with which said ejector is to be connected whereby eificient operation of said engine for production' of pressure fluid for suction effects may be obtained. I

3. A suction mechanism as defined in claim 2, wherein the first nozzle passage has an efl'ective length equal to from 1 to 5 times the internal diameter of said nozzle passage.

RICHARD B. SARGENT.

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