USRE21416E

USRE21416E - Suction mechanism

Info

Publication number: USRE21416E
Authority: US
Publication date: 1940-04-02

Description

April 2, R. B. SA'RGVENT Re. 21,416

sue-non 112cm: s

Original Filed-Dec. 18, 1937 I ma a Apr. 2, 1940 UNITED STATES SUCTION mechanism Richard B. sail-gent, Philadelphia, Pa., assignor to The Hale Fire Pump 00., Inc., Conshohocken, Pa., a corporation of Pennsylvania Original No. 2,180,259, dated Novemberdd, 1939,

Serial No. 180,654, December 18, 1937. Application tor reissue February 8, 1940, Serial No.

3 Claims. (Cl. 230-95) This invention relates to improvements in suction mechanism of the type utilizing for motivation the fluid pressure generated in the exhaust 01 an internal combustion engine. Such. mechanisms may be employed, forexample, for priming centrifugal pumps, and are of particular utilityin connection with fire flghting apparatus wherein the internal combustion motor of the flre engine is commonly employed to drive the pump or pumps forming essential elements of the equipment.

A principal object of the present inventionis 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 degrees of vacuum. a

The invention further resides in certain novel structural details and arrangements of parts hereinafter described and illustrated in the at-.- tached drawing, in which:

Figure l 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.v 5 is a line drawing 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 I. The housing I is provided at one end with a threaded port 4 for connection with the exhaust manifold or exhaust pipe oi an internal combustion engine, and is provided at itsopposite end with an outwardly projecting annular flange I having tapped holes for reception of screws 8 which secure the body member 3 to the housing.

.- Intermediate its ends the housing has in its in- 1 er wall an annular recess I, and a tapped port I i'ormedinabosst onthe wall oi'thehousing "communicates with said chamber. The housing further is'provided with an internal flange II Kwliich provides a solid abutment or seat for the nozzle 2.

The nozzle 2 is formed at its rear and, namely,

neatly flt within the bore of the housing I, and

that end which in assembly abuts the flange II, with a cylindricahsurface I2, and this surface, as shown in Fig. 4,'neatly flts the bore of the housing I. From this end the body of the nozzle 2 tapers inwardly to a cylindrical extension I3 of 5 relatively small external diameter. Ribs Iliextend outwardly at the base of the extension I3, and the outer surfaces of these ribs flt neatly against the inner wall surface of the housing I, as shown in Figs. 2 and 3. These ribs, with the surface I2, form an extended bearing for the nozzle upon the housing and maintain the nozzle 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 poi'tion terminates in a cylindrical passage I6 which extends through the extension I3 of the nozzle.

' The body member 3 is formed at one end to is.provided intermediate its ends with an outwardly extending flange II through which the bolts 6 pass. It will be noted that in assembly the'flange II does not engage the flange 5 of the housing, so that when the bolts 5 are tightened, the inner end of the body member 3,-which engages the end edges of the ribs I4, 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 in the assembly by means solely of the bolts 6, and by removing these bolts the nozzle structure may be disassembled without disturbing the connections at the ports 4 and 8 01' the housing. The body member 3 provides a rearwardly tapered passage l8 which at its inner end communicates directly with the nozzle passage I6, and as shown in Fig. 2, the passage ll of the body member communicates at its rear or inner end with a conical terminal recess I9, which through the spaces between the ribs I4 of the nozzle 2 is in direct communication with the annular chamber I. By reason of the neatly fltted contacting surraces or 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 or ,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 thepump in well known manner.

of an ejector adapted 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, pre? sented a problem of considerable complexity involving deflnitedeparture from the conventional design practice. It was n to consider not only the characteristicsof'the ejector per so at the available pressures, but also the effect of the presence of the e'jector in theexhaust 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 developedin the exhaust is a motion of engine operation, the eiii- I ciency of which operation, whensaid engine is functioning as an exhaust gas compressor, being determined by the diameter and form of thenomle e 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 compressor, is not sufilcient toprovide maximum suction at the ejector, due to the fact that the exhaust gases pass too freelythrough the nozzle without building up a sufiicient back pressure. I have discovered, on the-other hand, that ifthediameter ofthenozzleistoosmall,theexhaust pressure or pressure will be too great between the engine and the ejector to permit the efficient operation of the engine when said engine is acting as an exhaust gas compressor, due to the fact that the excessive exhaust back pressure existing between the en-y gine and the ejector will materially interfere with the operation of the engine, 1. 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 anozzleinsertedin-theexhaustofaninternal combustion engine and the exhaust pressure of that engine and that it is possible to design a nomle which, within definable limits of size and shape, will be productive of the development ofmaximum attainable exhaust pressures by the engine when said engine is functioning as an exhaust gas compressor and, therefore, of maximum yelocities -of gas discharge through the nozzle. Velocity alone ispot s'uiiicient, 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 dimen sions 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 a these relations are substantially constant, and that they may, therefore, he expressed in terms of formulae permitting y application of the principle involvedto the reduction of ejectors for use with substantially any character of internalg combustion engine and capable of ail'ord-' ing, 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 the exhaust gases of an internal combustion engine through a nozzle e of the cylindrical form shown where the diameter (DN) of the e, in inches, is approximately 35 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 anozzle passage of this with the ejector connected to the exhaust of an internal comhustiorr engine when said,.engine is functioning as an exhaust gas compressor, the exhaust pressure may be developed toestahlish the maximum suction at the ejector. This is accomplished by .running the internal combustion engine withthe throttle thereof at the wide open position, for it is at this pofltion of the throttle that the engine develops its maximum brake horsepower. with a nozzle passage of a diameter in inches of approximatelylfi ofthesquarerootofthemaxb' mum brake horsepower of the internal combustion engine, maximum velocity and pressure ef-' fects will be obtained at the ejector and the said engine will operate smoothly and efficiently as an exhaust gas compressor. i. e., no excessive back pressure will be built up between the elector and engine which would tend to affect adversely thenormal operation of the engine as an exhaust gas compressor and the. nozzle e is such thattheexhaustgasdoesnotpasstooreadily therethl'ough. I have found further that exceptionally good rsults may be obtained by variation ofthese dimensions in either direction between certain limits. Thus the diameter of the nozzle emayvarybetweenyi andl of the square root of the maximum brake horsepower of the engine, and the length of the nozzle may vary between 1% times thediameter of the nome e and five\ times said. diameter. These .-therefore, may be express in tergns 'of the following formulae:

---braie iiliaxlimufmbrake 8 engine 15 30 VILN=DNX 1% to mvxs The limits specified in the above formulae have been foundto define a critical or optimum range of dimensions, outside of which maximum suction effects are not obtainable at the ejector. If the diameter of the nozzle passage exceeds the above specified maximum, theexhaust-e gases pass too readily through the nozzle, whereas if the diameter of the nonle passage, is less than the above specified minimum, the ,back pressure is too great and affects adversely the efficient operation .of the internal combustion engine. when I refer to the emcient operation of the engine, it will be understood that I refer only to the efficiency of the engine to function as an exhaust gas compressor, i. e., I am not at all concerned throat diameter (DB) of the passage It. The

- 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 functioning as a source of exhaust gas pressure for the ejector.

As previously set forth, I have found further 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 ll through the body member 3 should diverge forwardly from a point of maximum restriction adjoining the nozzle 2, and this angle of divergence (a) should be approximately 2, and may vary between 1 and 3". The diameter of the throat of the passage l8, 1. e., the diameter (DB) at the point of maximum restriction, should for best results be approximately 1.5 times the diameter (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 proximity to the throat of the passage l8 should be from 9;" 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 (DB) of the throat of the 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 II, but may occupy a position at either axial side of this throat to a distance (A) up to .5 of the foregoing dimensions may be expressed in terms of the following formulae:

dN=DN+JW to DN+ a. DB=DN 1.3 to DNxL'l a =1 to 3 .LB=DB- 4.5 to DB 210 A, the distance of the end of the nozzle 2, in either direction axially,

from the throat of the passage ll, may vary within the-limits of zero to DBx .5;

ejector.

It will thus be seen that the most important dimension or range ofdimensions 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 DB, et'c., may be readily determined. Hence, by the invention presented herein it is a relatively simple matter to associate with any internal 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 area of 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., al1 contribute to the determination of the maximum brake horsepower for any'given 'maybeusedasabasisfo -metric displacement of the engine when considering said engine as an exhaust gas compressor.

I have discovered that the maximum brake horsepower of an internal combustion engine calculating the dimensions of the componen parts of an ejector, which ejector, when connected to the exhaust of the selected internal combustion engine and said engine operated at wide open" throttle, will develop maximum suction eflects at the ejector.

with an ejector constructed as described above, I have found it possible with the pressures avail able 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 my 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 my knowledge have failed in commercial application by reason of inability to produce by this means lifts of adequate 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 watei from the source to the pump of considerable heights. It is customary in modern fire fighting apparatus to provide the vehicle with an internal combustion engine which is selectively 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 functions as 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 forwardly from the latter, said bore diverging towards its forward end and said nozzle being arranged with its forward end in proximity to the throat of said bore, and means providing a suction chamber outwardly of said nozzle and communicating with the rear end of said bore, said nozzle structure conforming to the terms of the following formulae:

Maximum brake H. P. of engine Maximum brake H. P. of engine LB=4.5DB to IODB DN- to where DN is the dimeterin inches of the nozzle passage, L N 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 oi the forward end oi said nozzle from said throat in either direction axially oi the bore,LBisthelensthotsaid bore,anddNis the outside diameter of the nozzle at the forward end thereof which lies. in proximity to the throat 01 said bore.

2. A suction mechanism comprising an ejector connected tothe exhaust of an internal combustion engine oi known maximum brake horsepower, which engine functions as a source 01 pressure fluid for operating the ejector, said ejector includink a first nomle having-apassage through which the exhaust a second nozzle having a bore axialLv aligned with and extending-forwardly from the forward end oi the first. nozzle, and a chamber outwardly of. said first nomle'and communicating with the rear end of said bore, said first nozzle e being cylindrical in term and having an internal diameterininchesequaltofi'om A toys oithe square root at the maximum brake horsepower oi the ensine with which said ejector is to be connected whereby emcient operation 01' saidensine for production of pressure fluid for suetion effects may be obtained.

3. A suction mechanism as defined in claim 2, wherein the first nozzle diameter of said nozzle mcnarm B. sananu'r.

e has an efiectivefi length equal to from 1% to timesthe internal