US1295086A - Jet apparatus. - Google Patents

Description

W. B. EDDISON.

JET APPARATUS.

APPLICATION FILED JULY 2,1917.

1 ,2953086 Patented Feb. 18, 1919.

' 2 SHEETSSHEEI l.

i: C i Er 3a 5 tijv-flnifi v E I W. B. EDDISON.

JET APPARATUS.

APPLICATION FILED JULYZ. 1911.

Patented Feb. 18, 1919.

2 SHEETS-SHEET 2.

WIT/VESSE'S.

Jew 1 represented in the fol WILLIAM BARTON EDDISON, OF IRVINGT COMBUSTION 00., INCORPORATED, 0]? Y0 ON, NEW YORK, ASSIGNOR TO THE SURFACE NEW YORK, N. Y., A CORPORATION OF NEW 3' ET APPARATUS.

Specification of Letters Patent.

Patented Feb. is, 1919,

Application filed July 2. 1917. Serial No. 178,821.

1 '0 all whom it may concern:

Be it known that I, WILLIAM BARTON ED- DISON, a citizen of the United States, res1ding at Irvington, in the count of Westchester and State of New Yor have 1nvented Certain new and useful Improvements in Jet Apparatus fully descrrbed and lowing specification and the accompanying drawings, forming a part of the same.

This invention relates to jet apparatus for forming and supplying a mixture of gases, and more particularly to an apparatusln which the mixture is formed and supplled under the desired pressure through the utilization of the pressure energy of a gas which forms a minor constituent of the resulting mixture. 0

' The invention has been made especlally with the idea of providing an apparatus for supplyin air and uel gas to the burner dlscharge orifices of a surface combustion furnace at a pressure above a predetermined minimum and in quantities variable at will and without changing the proportions of the constit uent gases, that is, to meet the conditions of constant proportions, variable quantlty, and exit pressure sufficient to prevent back-flash- The usual city or town gas requires from five to six parts by volume of air to one part of the fuel gas to form an explosive mixture containing gas and air in approximately combining proportions. The efiiciency of jet mixing apparatus heretofore used for supplying under pressure a mixture of gases formed by the entraining and inducing action of a jet of gas supplied under comparatively high pressure and discharged into the entrance cone of a Venturi tube decreases as the ratio of driven gas in the mixture increases, so that when it comes to supplyin an explosive mixture of air and fuel gas the energy of a jet of the fuel gas, the efliiency of the apparatus is low, with the result that the prwure under which such an explosive mixture can be so supplied to a surface combustion burner is so low compared to the initial gas pressure that only a very limited range of mixture supply is possible with the fuel gas supplied under the usual and most desirable high pressure distribution supply pressures of from 10 to 15 pounds.

an explosive gaseous mixture of gas to driving The present invention has been made with the idea of overcoming this disadvantage and providing a jet apparatus suitable for supplying an explosivemixture of air and fuel gas to the burner discharge orifices of a surface combustion furnace which shall have a comparatively high efliciency and give a greater range of mixture supply pressure with resulting increased range of variation in the amount of mixture that may be supplied and discharged through a given area of burner discharge orifice or orifices. The invention is'not, however, limited in its application to apparatus for such purpose, but is generally applicable to jet apparatus for supplyi a mixture of gases formed by the energy 9% a jet of the gas which forms a minor constituent of the mixture, and it is also not limited in its application to conditions which call for variation in the quantity of mixture supplied under a given available pressure of the driving gas. or which call for maintenance of proportions in the mixture under variations in the quantity of mixture supplied.

Obviously the drivin gas and the driven gas need not be gases 0 different kinds, and the expression mixture of gases as used herein would include a mixture of diflerent portions of gas of the same kind but drawn from difierent sources.

en a jet of gas is discharged at high velocity into the entrance cone of an ordinary Venturi tu'be havingathroat or critical cross-section of negligible length, to the entrance cone of which other gas has access, and the throat being of suflicient size for the production of a mixture containing an amount of the driven gas equal to several times that of the driving gas, the flow velocity at and near the axis of the throat is so greatly in excess of the velocity at and near its side walls as to greatly interfere with the building up of pressure in the discharge cone of the Venturi tube, and unless the discharge nozzle of the driving gas is set back a suitable distance from the entrance cone of the Venturi tube, the drawing in of the desired proportionate amount of the driven gas will not be attained. Satisfactory operation of such an apparatus, but with comparatively low efiiciency, may be secured by setting the driving gas nozzle back from the Venturi throat sufliciently to permit such an amount of the driven gas to be entranced by the open jet of the driving gas that the moving stream or jet entering the entrance cone of the venturi will contain a substantial portion of the whole proportionate amount of driven gas desired in the mixture. But even with-such an arrangement, the velocity of the central portion of the stream passlng from the Venturi throat into the discharge cone is so much greater than the velocity at the outer portions thereof, that the eificiency of the apparatus in changing the velocity energy of the gaseous mixture back into pressure energy is comparatively very low. The entraining or inducing efficiency is also low, and the arrangement also has other disadvantages.

To get the most efficient transformation of velocity energy into pressure energy in the expanding or discharge cone of the Venturi tube, it is necessary to have as near as possible a uniform velocity across the stream of gas at the point where such transformation begins. I have found that by suitably elongating the throat or portion of minimum cross-section of the Venturi tube of a jet mixture supply apparatus, the pressures across the stream of mixed gases may be substantially equalized, the core of the stream giving u some of its velocity to the peripheral portions, and the stream then passing from the throat into the discharge cone with the velocities of its inner and'outer portions s0 nearly equalized that a comparatively high efliciency in transforming velocity energy of the stream into pressure energy is obtained. Furthermore, the elongated throat has the effect of increasing the entraining or driving action of the driving et, so that the general efliciency of the appa-v ratus in supplying under desired pressures a mixture containing a proportionate amount of entrained gas equal to several times the amount of the entraining or driving gas is very much greater than that of the ordinary jet inspiratin device having a Venturi throat of negligible length. The efliciency of the apparatus varies substantially inversely as the ratio of the entrained to the entraining gas, and this ratio depends practically on the relative size of the jet noz zle to the Venturi throat cross-section, and also depends on the relative size of the orifice or orifices through which the mixture is discharged and the pressure against which the mixture is discharged.

I In supplying an explosive mixture of fuel gas and air to the burners of a surface combustion furnace, it'is, as before pointed out,

necessary that the mixture supply pressure he maintained above a predetermined minimum in order that the mixture shall be discharged through the burner orifices with a velocity in excess of the rate of propagation of inflammation through the mixture so as to prevent back flashing, and it is desirable take .Pla'ce.

'jet apparatus made in accordance with the present invention, an explosive mixture of fuel gas and air, that is, a mixture which with ordinary city gas should contain usually from 5% to 6 parts of air to one of gas, may be supplied to a surface combustion furnace at the required pressure through a comparatively Wide range of quantity control with the gas supplied to the apparatus at a pressure of, say, 10 pounds, for example. In order that proportions of theconstituent gases in the mixture may be maintained approximatelyconstant under variations in quantity of mixture supplied, the entrained gas, that is, air in the particular case under consideration, should be supplied under a pressure approximately equal to the furnace pressure or the pressure against which the mixture is discharged from the burner orifices. This condition is met by drawing the air-for the mixture direct from the surrounding atmosphere when the furnacepressure is approximately atmospheric pressure. Furthermore, the flow of the air into theVenturi throat and the flow of the mixture should most desirably be controlled pressure cone of the Venturi tube, while yet being large enough so that there may be a sufliciently low pressure and correspondingly low resistance to flow in theVe'ntu'ri-throat for the desired proportionate flow ofair to With an apparatus made in accordance with the present invention, the aggregate burner discharge orifice area may e substantially smaller than is practicable with an apparatus in which the Venturi throat is of negligible length.

By the term surface combustion as used herein is meant the combustion of an explosive gaseous mixture which is supplied at a velocity in excess of the rate of propagation of inflammation through the mixture so as to prevent back-flashing through the supply nozzle or orifice, the mixture being, then caused to spread out with rapid increase of its stream cross-section and consequent reduction of its flow velocity, and combustion taking place in a zone or surface at which the flow velocity of the mixture is equal to its rate of propagation of inflammation. Such surface combustion is disclosed in U. St Letters Patent of Dr. Charles E. Lucke among which may be mentioned N0. 7535,3 76, dated March 22, 1904, and No. 1,146,724 dated July 13, 1915. While apparatus embodying the present invention is especially adapted for supplying explosive gaseous mixture for surface combustion furnaces, yet as before pointed out the invention is not to be considered as limited to such use or such apparatus, but it is to be understood that the invention is intended for and is capable of use generally for supplymg gaseous mixtures under pressure, and especially where the amount of the driven gas in the mixture is substantially in excess of the amount of the driving gas.

A full understanding of the invention can best be given by a detailed description of an approved form of apparatus embodying all the features of the invention, and such a description will now be given in connection with the accompanying drawings showing such an apparatus for supplying an explo sive mixture of fuel gas and air to a surface combustion furnace, and in which Figure 1 is a plan view of the apparatus and of part of the furnace to which the apparatus is attached;

Fig. 2 is a sectional view on a larger scale of the jet mixing and proportioning device;

Fig. 3 is a view in elevation looking in the direction of the arrow 3 of Fig. 2;

Fig. 4 is a broken sectional view of a part of the furnace taken on line 44 of Fig. l and showing one of the burner tubes in section; and

Figs. 5 and 6 are sectional views of modified forms of the Venturi tube of the apparatus.

Referring to the drawings, the fuel gas which is to serve as the driving or inducing or entraining gas is supplied under a suitable pressure from a source of supply such as a high pressure distribution main, being supplied through a supply pipe 10 to a chamber 11, an adjustable restriction or valve 12 being provided in the supply pipe for controlling the supply of gas to the chamber 11 and the pressure maintained therein. The gas chamber 11 is formed in an extension of the inspirator body or casing 13 which also provides an air chamber 14: separated from the gas chamber by a partition and connected therewith by a gas discharge orifice 15. Air enters the chamber 14 through inlet opening 16 and the apparatus is provided with means for closing these openings and for adjusting the effective size thereof for the purpose hereinafter explained.

The Venturi tube 20 is mounted with its entrance cone 21 opening into the air chamber 11 in position to receive the jet of gas issuing from the gas orifice 15, and the end of the discharge or pressure cone 22 of the Venturi tube is connected to suppl the mixture to the mixture discharge ori ces of the burner nozzles. The entrance end of the Venturi tube most desirably extends into the air chamber to a point beyond the air inlet openings 16 so as to provide a space about the tube to insure an even flow of air into the entrance cone of the tube Without other means for battling the air to insure such even flow. The tube may be of any suitable construction, but when of the shape here shown is most desirably formed of a single casting of metal or other suitable material, and it is conveniently cast with a shouldered flange at a suitable distance from its inner end formed to set in anopening in the end wall of the body casing 13, the tube being removably secured in position as by tap bolts as shown. I find that if in casting such a tube care is taken to have a smooth core no finishing of the inner surface of the tube is necessary.

The entrance cone and the expanding portion forming the discharge or pressure cone are or may be of usual form, care being taken, however, that these parts shall be of suitable limited angles between their sides,

when, as in the apparatus shown, approxi-' mately constant proportions of fuel gas and air in the mixture are to be maintained under variations in quantity of mixture delivered. and also in order that the energy of the driving gas may be most efliciently employed to supply the mixture under desired pressure. If the angle between the sides of the discharge cone of the tube is too great, an eflicient transformation of velocity energy into pressure energy is not secured, and furthermore the presence of eddy currents is liable to interfere with the maintenance of constant proportions of the constituent gases in the mixture. On the other hand, too small an anglewould mean an excessive length of the cone and involve excessive friction losses. An angle of 10 between the sides of the discharge cone has been found to work well under usual conditions of operation.

If the included angle between the walls of the entrance cone 21 is too large, the first part of the elongated throat of the tube will not be properly filled with the entering air and eddy currents will result, interfering with the desired entraining and inducing action and with the maintaining of proportionality under variations in quantity of cent. This angle may be Varied considerablywithout bad results but should not be so small as to cause the entering air to encounter excessive friction in reaching the throat. A comparatively short entrance is suflicient and desirable and a length equal to or even somewhat less than the diameter of the throat has been found to work Well.

The enturi tube should therefore have its entrance and discharge cones of such limited angles that the air and gas will hug the sides of the discharge cone and maintain the position of the limit of minimum jet cross-section stationary in the throat of the tube, and that the desired rise in pressure will be developed and the necessary change of velocity energy back into pressure energy effected without excessive friction losses.

The throat or portion 23 of smallest crosssection of the Venturi tube instead of being of negligible length iselongated and made of a length which is great as compared to its diameter. Without suchan elongated throat the comparatively fast flowing central portion or core of the jet of gas and entrained air tends to drive through the central portion of the throat and into the pressure cone .with the portions of the stream nearer the walls moving much more slowly, so that an efficient building up of pressure in the pressure cone is impossible. The elongated throat which I provide serves as a means for equalizing the flow velocity across the stream of mixture and causing the stream to enter the pressure cone with such an approximation to uniform velocity in all its parts that an efiicient transformation of velocity energy into pressure energy in the pressure cone is secured, -With'such a throat the jet nozzle need not be so set back from the-entrance cone of the tube-as has been necessary with'tub'es having throats of negligible length. A greatly increased entraining or driving action is also secured, such increased entraining or driving efwhich occur, when the jet passes as an open jet across an intervening space from thenozzle to the Venturi tube are substantially eliminated, and that in addition to the frictionalentrainment of air there isa substantial entraining or driving action due to induction. Thel elongated throat thus acts entrainingtube. The exact length of the velocity ing and entraining throat of the tube may vary considerably without losing all benefits which it imparts 'to the" app'a'- both as a velocity equalizing tube and as an ratus, and the best lengthfor any' 'given 3 throat diameterwill vary somewhataccordingto h Shape of th tube and the fol-m; size and relative positions, Homer-parts and the use to be made of the apparatus. With a'size Number 4:7 Morse twist drill nozzle which is .07 85 inches in diameter, discharging gas under a pressure of 10 pounds per square inch into a Venturi tube having an entrance cone of the form shown and a throat of uniform a" diameter throughout its length, that is, one having its sides parallel, as shown by Fig. 5, the nozzle being set close to the entrance end of the tube as shown, it has been found that a length of 5 inches or 8 diameters, gives the maximum amount of air passing with a substantial equalization of the flow velocity, and therefore gives the best condition for transforming the velocity energy back to the maximum pressure energy in the pressure cone without limiting the proportionate amount of air in the mixture. A shorter throat does not give such good equalization of velocities, and with increase in the length of the throat the aggregate velocity and conto the tube axis substantially less than the angle to the tube axis of the walls of the discharge or pressure cone. The walls of the throat may be considered-as in all cases extending at an angle to the tube axis which is substantially less than the angle to the tube axis of the walls'of the pressure cone and which may vary from zero to the maximum less than the angle to the tube axis of the Walls of the pressure cone. In practice I find that the angle of the walls of the throat to the tube axis should not exceed about 2% and the best results are secured as this angle approaches zero. ficiency being'probably due to'the fact that: with the'driving jet inclosedby the elon gated throat the lossesdue to eddy currents.)

Manufacturing considerations'have led to the use of a throat of the form shown in Fig. 2, the sides of which extend at zero angle to the tube axis, or which is of uniform diameter, for a portion of its length and the junction of the throat and the pressure cone.

Manufacturing considerations and reliabil- I ity in operation also make it more desirable $ualizenturi to use a single throat with each jet nozzle rather than a compound throat comprising two or more throats of increasing size arranged tandem, one discharging into another. While, therefore, I do not wish in jprotecting the invention to be limited exa-ctly' as to, the angle to the tube axis of the sides of the elongated throat, or to the use of a single throat, 1 intend to claim specifistraight or approximately straight run of a length equal to or somewhat greater than its diameter, that is, sufiicient to properly direct and form the jet. For convenience in manufacture and in order to permit ready change of the gas orifice as desired, a removable nozzle piece 25 is provided secured in position by being threaded to screw into a tapped hole in the partition between the gas chambenand the air chamber, the nozzle bein protided most desirably with a, removab e tip 26. The wall of the gas chamber opposite the artition wall is formed with an openin t rough which access may be readily ha for setting or removin the gas nozzle, this opening being normal y closed as by means of a cap piece 27 held in place by a screw extending through a yoke 28.

The gas nozzle should for best results be set with its extreme tip end close to, and most desirably approximately in the plane of, the end of the entrance cone of the Venturi tube, as shown, so that, the nozzle orifice being of suitable relative size, the driving jet at the point of entrance into the throat Will have a cross-area which is only a fractional part of the cross-area of the throat. When so set close to the end of the Venturi tube, the outside of the nozzle and of its tip should be formed so as not to interfere with the flow of air into the Venturi tube, that is, the nozzle should project suflicien-tly into the air chamber to permit the entrance end of the Venturi tube to be set off from the partition wall between the air and gas chambers sufliciently for free flow of air into the Venturi tube, and the nozzle should be of such external size and shape as not to interfere with such flow.

The relative size or cross-area of the nozzle orifice and of the Venturi throat will vary according to the proportions of driving and driven gases in the mixture to be produced, increase in the proportion of the driving gas requiring a larger nozzle orifice, and vice versa. For producing and supplying under suitable pressure to a surface combustion furnace an explosive mixture of air and fuel gas in the proportion of about 5% to 1, with the Venturi throatofthe form shown in Fig. 2, the area of the throat should be from 50 to 100 times that of the nozzle orifice. The exact relative areas will be determined by other conditions and especially the aggre te burner dischar e orifice area. I have fc iiind it best to use No. 47 Morse twist drill nozzle with a Venturi tube having an elongated throat 5" in diameter for supplying burners having an aggregate discharge orifice area equal to about 1% of the area of the Venturi throat.

In an apparatus such as shown for supplying an explosive mixture of fuel as and air, the relative size of the gas ori ce will thus vary according to the character of the fuel gas to be used, the richer the gas the smaller the orifice, and vice versa. Change in mixture proportions may thus be accomplished by changin the area of the gas orifice, this bein rea ily accomplished in the construction s own by changing the nozzle tip. Slight variations or ad ustment of proportions is most conveniently efi'ected, however, by controlling the supply of air to the air chamber 14, and for this purpose in the construction shown a shutter 30 which is adapted to open and close the air inlet openings or ports 16 has adjusta'bly connected to it a plate 31' by which the size of the shutter openings may be varied. The ports 16 are of such size relatively to the enturi' throat that when they are fully open approximately full atmospheric pressure will be maintained in the air chamber. When, however, the plate 31 is adjusted to partly close the shutter openings, the flow of air into the air chamber is restricted and the pressure in the air chamber lowered and a smaller proportionate amount of air enters the Venturi throat with the gas. A limited adjustment of proportions may be effected by such means without substantially affecting the maintenance of proportions under variations in the amount of mixture supplied within the usual Working range of the apparatus. In order to prevent back draft from the furnace chamber through the inspirator when the gas is shutofi', the shutter 30 may be connected by a link 32 to the handle of a shut-off valve 33 in the supply pipe 10 so that when the gas is shut off the air inlets 16 will also be closed.

The inspirating, apparatus is shown in Fig. 1 as connected to supply a plurality of burner nozzles or mixture discharge tubes 40 of an impact-jet surface combustion furnace for burnmg explosive gaseous mixtures according to the method of U. S. Patent N 0. 1,146,724, anted July 13, 1915 on an ap lication of r. Charles E. Lucke. The urnace, a broken section of which is shown by Fig. 4, comprises ,a structure providing a furnace chamber 41 provided with a porous and permeable combustion supporting bed 42 of refractory material against which jets of the explosive mixture are directed from the nozzles 40 set in the furnace wall 43. The jet of mixture, moving with a velocity in excess of the rate of propagation of inflammation of the mixture, strikes against the combustion bed, the mixture being thereby deflected and caused to rapid loss of flow velocity and burnin at the surface of or within the bed as descri ed in said patent.

In order that the proportionality of the mixture may be maintained under variations in the quantity supplied, eachv of the burner nozzles is formed with a discharge orifice of substantially constant coefiicient form, and the connecting passages between such orifices and the Venturi tube, that is, the passages through the burner nozzles and the con.-

necting pi ing, are of such relatively large size that t ere will be no or substantially no pipe resistance to afiect the flow of the mixwould, in the absence of some means for com-- pensatin for the increase in back pressure,

cause a c nge inthe proportions 0 gas and air in the mixture, since the increase in back' pressure by increasing the pressure in the.

expansion cone of the Venturi tube would result in a reduction of the flow velocity through the Venturi throat and a reduction in the proportionate amount of air entering Such heating of the mix- 'ture in the burner nozzle also reduces the the Venturi tube.

amount of mixture flowing from the nozzle under the available pressure. Such undesirable results are best avoided by using burner nozzles having anapproximately] v BXPlOSIVG'mIXtlII'G of fuel gas and 'air' to an constant pressure-capacity charcteristic, this characteristic of the nozzles being secured by forming the nozzles so that the wallsjof the discharge passage shall be prevented from becoming excessively heated'in operation. Such a nozzle'is more fully described in U. S. Patent No. 1,242,114, granted Octo-' her 2, 1917, on an application of Richardson, Eddisonand Read. This is accomplished inthe burner nozzle shown-in the drawings by having the nozzle formed and set in the furnace wall so that only a small portion of the end or nose of thenozzle is exposed tothe I furnace heat, the balance thereof being protected by the surrounding wall of poor heat conducting material, and by forming the nozzle of-the body of metal of sufficient con-v tinuous mass to rapidly conduct away to'the outer portions of the nozzle body .orjtube such heat as is absorbed by the exposed nose of the nozzle, and by forming or providing the outer end of the nozzle tube withmeans spread out with dissipating fins or plates 45;

The high efliciencyof the apparatus in entraining and pressure building 'ves considerable latitude with regard to t e aggregate burner discharge orificearea which may be employed with a given throat area ofv the Venturi tube. Of course the area of the burner discharge orifice must not be so great as :toprevent the building up of the'necessary mixture pressure for causing'the re-.. quired excessvelocity of discharge from the nozzle, or as to unduly limit the range of quantity control, and on the other hand, the burner discharge orifice area must not be so small. as to prevent sufficient pressure reduction at the Venturi throat and cause too great a resistance to flow in the throat for for discharging 'the heat, such-as the heat.

the desired proportionate flow of air to'take place. The aggregate burner discharge orifice area will, however, always be quite definitely related to the orifice area of. the gas jet nozzle,since for determining proportions in the mixture the principal governing factor within the limits imposed by a given throat size is the area of the gas nozzle orifice against the aggregate burner discharge orifice area. For example, in the apparatus the dimensionsof parts of which are given on page 5, the ratio of the burner dischargeorifice' area to the orifice area of the gas jet nozzle is approximately to 1. Increas-. I ingth'e size of the gas nozzle orifice or. de-

creasing the aggregate burner orifice area increases the proportionate amount of fuel gas,or'driving gas, in the mixture, and decreasing the size of the gasnozzle orifice or increasing the aggregate. burner discharge orifice'area' decreases the richness of the mixture, or the" amount of driving gas in the mixture I have already given an example c'if tli'e relative, 'roportions which I'einploy in apparatus suc as shown for sup-plying an impact-jet surface, combustion furnace.

In the operation of the apparatus, the gas being under a suitable pressure and the ap-v paratus being adjusted to secure the desiredproportions ior any flow rate, {then the amountof m xture supplied may be varied as desired within the working limits of the i2 Venturi tube increases and decreases proportionately, and the final deliveryfpressuiie of the mixturefito the burner orifices .rises and falls correspondingly, the quantity of mixturedischarged from the burner orifices thus being" varied-but the proportionality ofthe maintained approximately mixture being constant.

The term orifice as used-in the claims is to be understoodto mean an opening which is restricted as compared to the adjacent flow passage or space and so formed as to control the flow of gas therethrough according to the typical flow law of orifices (V=C /2gh), true when the pressure or head it is not too large, and an orifice having a constant coefficient, or a constant coeflicient orifice, is to be understood as an orifice the coeflicient of discharge of which is approximately constant within the normal working range of the apparatus, or for which the areaof the contracted vein of the jet is itself constant. It is desirable that the coeflicient of the orifices controlling the flow of air and of the mixture should be approximately 100%. It may be pointed out that the air inlet ports as varied in size by adjustment of the shutter plate 31 act as constant coefiicient orifices under the low head under which the air passestherethrough.

Subject matter disclosed but not claimed herein is claimed in my co-pending applications Serial No. 130,887 filed November 11, 1916, and Serial No. 174,818, filed June 14, 1917.

What is claimed is:

1. Jet apparatus for supplying a mixture of gases, comprising a nozzle for discharging a high velocity jet of the driving gas, an elongated and smooth-walled entraining and velocity-equalizing tube into which the jet of gas is discharged, the sides of said tube being approximately parallel and the length thereof being suflicient to substantially equalize the velocities across the stream,

and means for transforming velocity energy of the stream of gases from said tube into pressure energy, the nozzle being so formed and so located that the cross-area of the jet at the point of entrance into said tube shall be only a fractional part of the crossarea of the tube.

Jet apparatus for supplying a mixture of gases,comprisingmeans for supplying one i of the gases under pressure to serve as the driving gas, means providing an orifice for discharging a high velocity jet of said gas, an elongated and smooth-walled entraining and velocity-equalizing tube into which the jet of gas is discharged, the cross-area of said tube being many times greater than the cross-area of said orifice and the orifice being so close to the end of the tube that the jet at the point of entrance into the tube will have a cross-area which is only a fractional part of the cross-area of the tube, the sides of said tube being approximately parallel and its length being equal to several times its diameter, whereby the flow velocity across the stream of gases is substantially equalized. and a pressure cone for transforming velocity energy of the stream of gases from said tube into pressure energy.

3. Jet apparatus for supplylng a mixture of gases, comprising a Venturi tube, and means providing an orifice for discharging into the Venturi tube in the direction of flow through the tube a high velocity driving jet of gas having at the oint of entrance into the throat of the i enturi tube a cross-area which is small compared to the cross-area of the throat, the Venturi tube having between its entrance cone and its pressure cone an elongated smooth-walled entraining and velocity-equalizing throat the sides of which are approximately parallel and the length of which is equal to several times its diameter, whereby the flow velocity across the stream of gases is substantially equalized.

4. Jet apparatus for supplying a mixture of gases, comprising a Venturi tube, and means for directing into the Venturi tube in the direction of flow through the tube a high velocity jet of gas which is to serve as the driving gas having at the point of entrance into the throat of the Venturi tube a cross-area which is small as compared to the cross-area of the throat, the Venturi tube having between its entrance cone and its pressure cone a smooth-walled elongated entraining and velocity-equalizing throat the length of which is several times its diameter and the walls of which extend at an angle to the tube axis less than the angle to the tube axis of the walls of the pressure cone, whereby the flow velocity across the stream of gases is substantially equalized.

5. Jet apparatus for supplying a mixture of gases, comprising a Venturi tube, and means for discharging into the Venturi tube in the direction of flow through the tube a high velocity jet of the gas which is to serve as the driving gas having at the point of entrance into the throat of the Venturi tube a cross-area which is small as compared to the cross-area of the throat, the Venturi tube having between its entrance cone and its pressure cone a smooth-walled elongated entraining and velocity-equalizing throat the walls of which extend at zero angle to the tube axis from the entrance cone for a distance which is great compared to the diameter of the throat, whereby the flow velocity across the stream of gases is substantially equalized.

6. Jet apparatus for supplying a mixture of gases, comprising a Venturi tube, and means for directing into the Venturi tube in the direction of flow through the tube a high velocity jet of the gas which is to serve as the driving gas having at the point of entrance into the throat of the Venturi tube a cross-area which is small as compared to the cross-area of the throat, the Venturi tube having between its entrance cone and its pressure cone a smooth walled elongated entraining and velocity-e ualizing throat, the length of the throat being several times its diameter and its walls extending from the entrance cone for a substantial portion of its length at zero angle to the tube axis and thereafter diverging at an angle which is less than the angle of divergence of the walls of the pressure cone, whereby the flow velocity across the stream of gases is substantially equalized.

7. Jet apparatus for supplying a mixture of gases, comprising a Venturi tube, and means for directing into the Venturi tube in the direction of flow through the tube a high velocity jet of the gas which is to serve as the driving gas having at the point of entrance into the throat of the Venturi tube a cross-area which is small as compared to the cross-area of the throat of the Venturi tube, the Venturi tube having between its entrance cone and its pressure cone a smoothwalled elongated entraining and velocity equalizing throat the length of which is several times its diameter and which is of uniform diameter throughout at least a substantial portion of its length, whereby the flow velocity across the stream of gases is substantially equalized.

8. Jet apparatus for supplying a mixture of gases, comprising a Venturi tube, and a nozzle set with its tip approximately at the plane of the end of the entrance cone of the Venturi tube to discharge a high velocity jet of the driving gas into the Venturi tube in the direction of flow throu h the tube, the cross-area of the nozzle or ce being small as compared to the crossarea of the throat of the Venturi tube, and the Venturi tube having between its entrance cone and its pressure cone a smooth-walled elongated entraining and velocity equalizing throat the length of which is equal to several times its diameter and the walls of which extend at an angle to the tube axis less than the angle to the tube axis of the walls of the pressure cone, whereby the flow velocity across the stream of gases is substantially equalized.

9. Jet apparatus for supplying a mixture of gases, comprising a Venturi tube, and a nozzle set to discharge a high velocity jet of the driving gas into the Venturi tube in the direction of flow through the tube, the Venturi tube having between its entrance cone and its pressure cone a smoothwalled elongated entraining and velocityequalizing throat the length of which is equal to several times its diameter and the walls of which extend at an angle to the tube axis less than the angle to the tube axis of the walls of the pressure cone, whereby the flow velocityacross the stream of gases is substantially equalized, the cross-area of said throat being many times greater than the cross-area of the nozzle orifice, and the nozzle being set with its tip so close to the end of the throat that the high velocity jet at the point of entrance into the throat will have a cross-area which is only a fractional part of the cross-area of the throat.

10. Jet apparatus for supplying a mixture of gases, comprising means forming a supply chamber, a Venturi tube having its entrance end' projecting into said chamber and provided with a short entrance cone, a nozzleextending from the chamber wall opposite the end of the Venturi tube in position to discharge a high velocity jet of gas into the Venturi tube, the cross-area of the nozzle orifice being small as compared to the cross-area of the throat of the Venturi tube and the nozzle being set with its tip so close to the end of the throat that the cross-area of the jet as it enters the throat shall be small as compared to the cross-area of the throat, means for supplying gas under pressure to said nozzle, and means providing a flow controlling orifice for supplying an- I other gas to said chamber, the Venturi tube having between its entrance cone and its pressure cone an elongated entraining and velocity-equalizing throat the walls of which extend at an angle to the tube axis less than the angle to the tube axis of the walls of the pressure cone and the length of which 1s suflicient to substantially) equalize the velocity across the stream of gases flowing therethrough.

11. Jet apparatus for supplying a mixture of gases in approximately constant proportions, comprising a Venturi tube, means for dischargin into the entrance cone of the Venturi tu e in the direction of flow through the tube a high velocity jet ofthe gas which is-to serve as the driving gas having at the oint of entrance into the throat of the enturi tube a cross-area which is only a fractional part of the crossarea of the throat, means comprising an inlet orifice for supplying another as to the entrance cone of the Venturi tu e, means providing a flow controlling orifice for con trolling the flow of the gaseous mixture received from the Venturi tube, means for varying the supply of the driving gas in order to vary the quantity of the mixture produced, and means for varying the size of said inlet orifice for varying the proportions of the gases in the mixture, the Venturi tube having between its entrance cone and" its pressure cone an elongated velocity equalizing throat the length of which is equal to several times its diameter and the walls of which extend at an angle to the tube axis less than the angle to the tube axis of the walls of the pressure cone, whereby the flow velocity across the stream of gases is substantially equalized.

12. Apparatus for supplylng and burning an explosive mixture of fuel gas and air in approximately constant proportions, comprising a Venturi tube, means for supplying the fuel gas under pressure to serve as the driving gas, a nozzle set to discharge into the Venturi tube in the direction of How through the tube a high velocity jet of the fuel gas having at the point of entrance into the throat of the Venturi tube a crossarea which is only a fractional part of the cross-area of the throat, an inlet orifice for supplying air to the entrance' cone of the Venturi tube from a source of supply under pressure substantially equal to the pressure against which the mixture is discharged, a burner nozzle through which the mixture is discharged to be burned, said burner noz zle being formed to control the flow of the mixture according to the flow law of orifices having constant co-elficients, and a connecting passage between the orifice of the burner nozzle and the Venturi tube formed and proportioned to avoid pipe, bend and eddy losses, the Venturi tube having its entrance cone and its pressure cone of such limited angles that the air and gas will hug the sides of the tube, and having an elongated velocity-equalizing throat between its entrance cone and its pressure cone the length of which is several times its diameter and the walls of which extend at an angle to the tube axis less than the angle of the tube axis of the walls of the pressure cone, whereby the flow velocity across the stream of gases is substantially equalized.

13. Apparatus for producing and burning an explosive gaseous mixture of fuel gas and air in approximately constant proportions, comprising means providing an air chamber, a Venturi tube set with its entrance cone open to the air chamber, means for supplying the fuel gas under pressure to serve as the driving gas, a nozzle extending into the air chamber and set to discharge into the entrance end of the Venturi tube in the direction of flow through the tube a high velocity jet of the fuel gas having at the point of entrance into the throat of the Venturi tube a cross-area which is only a fractional part of the crossarea of the-throat, an inlet orifice for admitting air under atmospheric pressure to the air chamber, adjusting means for varying the size of said inlet orifice to vary the proportions of fuel gas and air in the mixture, a burner nozzle through which the mixture is discharged to be burned, said burner nozzle being formed to control the flow of the mixture according to the flow law of orifices having constant coefficients, and a connecting passage between the orifice of the burner nozzle and the Venturi tube formed and proportioned to avoid pipe, bend and eddy losses, the Venturi tube having between its entrance cone and its ressure cone an elongated velocity equallzing throat the length of which is equal to several times its diameter and the walls of which extend at an angle to the tube axis less than the angle to the tube axis of the walls of the pressure cone, whereby flow velocity across the stream of gases is substantially equalized.

14. Apparatus for producing and burning an explosive mixture of fuel gas and air, comprising means for supplying the fuel gas under pressure to serve as the driving gas, a nozzle for discharging a high Velocity jet of said gas, an entraining and velocity-equalizing tube into which the jet of gas is discharged, the cross-area of said tube eing many times greater than the crossarea of the nozzle orifice and the nozzle being set with its ti so close to the end of the tube that the liigh velocity jet at the point of entrance into the tube will have a cross-area which is only a fractional art of the cross-area of the tube, and the sldes of said tube being approximately parallel and its length being sufficient to substantially equalize the velocities across the stream, a pressure cone for transforming energy of the stream of gases from said tube into pressure energy, and a burner nozzle having a restricted orifice to which the gaseous mixture is supplied from said pressure cone and through which the mixture is discharged to be burned.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

W. BARTON- EDDISON.

Witnesses H., F. WHITE, JOHN H. BARTLETT, Jr.

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