US3266552A

US3266552A - Burner for producing a stable flame with a high concentration of heat stabilized by a shock wave

Info

Publication number: US3266552A
Application number: US291600A
Authority: US
Inventors: Denis Michel
Original assignee: Institut de Recherches de la Siderurgie Francaise IRSID
Current assignee: Institut de Recherches de la Siderurgie Francaise IRSID
Priority date: 1959-02-21
Filing date: 1963-06-25
Publication date: 1966-08-16
Anticipated expiration: 1983-08-16
Also published as: US3333619A; FR1226568A

Description

M. DEms 3,266,552 BURNER FOR PRODUCING A STABLE FLAME WITH A HIGH Au 16, was

CONCENTRATION OF HEAT STABILIZED BY A SHOCK WAVE 6 Sheets-Sheet 1 Filed June 25, 1963 G I F M. DENIS Aug. 16, I966 BURNER FOR PRODUCING A STABLE FLAME WITH A HIGH CONCENTRATION OF HEAT STABILIZED BY A SHOCK WAVE 6 Sheets-Sheet 2 Filed June 25, 1965 v P 1 b Aug. 16,1966

BURNER FOR PRODUCING STABLE FLAME WITH A HIGH CONCENTRATION OF HEAT STABILIZED BY A SHOCK WAVE Filed June 25, 1963 M DENIS 6 Sheets-Sheet 5 Aug. '16, 1966 MDEN s BURNER FOR PRODUCING A STABLE FLAME WITH A HIGH CONCENTRATION OF HEAT STABILIZED BY A SHOCK WAVE 6 Sheets-Sheet 4 Filed June 25, 1965 5 6 II F a 2 p W P 0 f a f 3 F m 3 H 3/ W i w m "R rm W.

PFIiSl/Pf #500627? W P a f H a w 1966 M. DENIS BURNER FOR PRODUCING A STABLE FLAME WITH A HIGH Aug. 16,

i CONCENTRATION OF HEAT STABILIZED BY A SHOCK WAVE 6 Sheets-Sheet 5 Filed June 25, 1963 j- AW/ WI- 7 g, 1966 M. DENIS BURNER FOR PRODUCING A STABLE FLAME WITH A HIGH CONCENTRATIQN OF HEAT STABILIZED BY A SHOCK WAVE 6 Sheets-Sheet 6 Filed June 25, 1965 United States Patent 3,266,552 BURNER FOR PRODUCING A STABLE FLAME WITH A l-HGH CONCENTRATION OF HEAT STABILIZED BY A SHOCK WAVE Michel Denis, Saint Germain-en-Laye, France, assignor to Institut de Recherches de iaSiderurgie Francaise, Saint Germain-en-Laye, France, a professional institution of France Filed June 25, 1963, Ser. No. 21,600 Claims priority, application France, Feb. 21, 195%, 787,384, Patent 1,226,568; Dec. 29, 1959, 814,323, Patent 76,826; Feb. 12, 1960, 818,271, Patent 1,256,669; July 6, 1962, 903,196, Patent 1,335,143 5 Claims. (Cl. 158-76) The present application is a continuation-in-part application of the copending application filed February 9, 1961, under the Serial No. 88,140, now abandoned, and entitled Burner for Producing a Stable Flame with a High Concentration of Heat Stabilized by a Shock Wave, which in turn is a continuation-in-part application of the application filed February 17, 1960, with the Serial No. 9,256, and now abandoned.

The present invention relates to burners and more particularly to a burner for producing a stable flame with a high concentration of heat stabilized by a shock wave.

Various burners are known in the art for producing a flame of high calorific value up to two hundred millions K. cal. per hour and cubic meter of combustion fluid. One type of such burners, usually called high intensity burners uses a combustion chamber located at the end of the burner wherein almost the whole of the combustion is performed. The maximum temperature obtainable with such burners, however, is limited to the maximum temperature the liner of the combustion chamber will withstand. The flame temperature producible with such burners is therefore limited to a value lower than two thousand centigrades.

Other burners are known which do not use a combustion chamber and which are usually called injection type burners in which a combustible fluid and a combustion sustaining agent are mixed in an injection nozzle and in which the combustion mainly occurs outside of the injection nozzle at the outlet end thereof. Since the combustion fluid and the combustion sustaining agent are mixed in this type of burners in the injection nozzle and since the injection nozzle reache during extended use a temperature higher than that required for ignition, the flame will propagate itself back into the incoming air-fuel stream at from 15 to 40 feet per second. The velocity of the mixture leaving the burner must therefore exceed this speed in order to prevent flareb-acks and therefore exit velocities of 130 to 1000 feet per second are used in such burners. With such great exit speeds such burners usually require the use of a pilot flame to maintain the combustion in the high fluid speed field. Furthermore, such injection burners necessarily using a high exit speed of the combustion fluid will produce a long flame with which high temperatures cannot be obtained Applicants invention is directed to a burner for producing a stable flame of high calorific value which avoids the drawbacks of burners known in the prior art.

One object of the present invention is to provide for a burner which produces a flame of high calorific value stabilized without the aid of a pilot flame and not using a combustion chamber which necessarily limits the temperature obtainable with the burner.

It is another object of the present invention to provide for such a burner which consists only of a few and simple parts, which can be produced at reasonable cost and which will properly stand up under extended use.

It is an additional object of the present invention to provide for such burner which can also advantageously be used when one of the combustion fluids carries dust or grit, for instance pulverized coal, in suspension which will produce an abrasive action in the burner.

It is yet an additional object of the present invention to provide for a burner in which the abrasive action of such pulverized material is reduced as far as possible and/ or in which the parts subjected to such abrasive action can be easily replaced, when, after extended use, such replacement appears necessary.

It is a further object of the present invention to provide for such a burner in which the flame of the burner can be easily regulated.

It is also an object of the present invention to provide for such a burner which can be advantageously used in a blast furnace and in which wear or consumption of the material at the burner end can be easily compensated for.

Finally, it is also an object of the present invention to securely prevent a flareback of the flame into the injection nozzle even during variations in the pressure of the gaseous mixture.

With these objects in view the burner of the present invention for producing a stable flame of high calorific value in a high speed fluid field mainly comprises passage means for guiding a fuel fluid and a combustion sustaining agent fluid under pressure and at sub-sonic speed separated from each other, means at the region of the outlet end of these passage means for mixing the fluids with each other, and means at said outlet end for accelerating the speed of said mixture to supersonic speed so as to produce a shock wave, whereby the combustion of the mixture is maintained. In applicants burner this shock wave producing means forms the only means of the burner for maintaining combustion of the mixture.

The means for mixing the fluids with each other and for accelerating the speed of the mixture to supersonic speed are preferably constituted by Venturi means haVing a convergent section, a throttled section and a divergent section at the region of the outlet end of the passage means. The passage means may be constituted by rectilinear tube in axial alignment with the Venturi means and connected to the convergent section thereof for feeding a gaseous fluid, which may or may not contain solid particles in suspension into the Venturi means. The passage means may further include a second tube for feeding a second combustion fluid, liquid or gaseous into the Venturi means so that the second combustion fluid becomes mixed with the first combustion fluid. This second tube may be arranged substantially concentric with the first mentioned supply tube, with the outlet end of the second tube located in the throttled section or slightly downstream of the throttled section of the Venturi means. The second tube may also be arranged outside the first mentioned supply tube. In this case a plurality of passages are formed extending through the wall of the Venturi means inclined to the axis thereof and communicating with the inner ends thereof with the region of the throttled section of the Venturi means, whereas the second tube communicates with the other ends of these passages for feeding a second combustion fluid under pressure into throttled section of the Venturi means so that a second combustion fluid may be mixed with the first combustion fluid fed by the first mentioned supply tube into the Venturi means.

Preferably the throttled section of the Venturi means is constructed with such a cross sectional area normal to the axis of the Venturi means, so that when fluids are fed into the burner at a rate necessary for the minimum burner output the fluids entering the Venturi means at pressure and sub-sonic speed will obtain sonic speed in the throttled section of the Venturi.

The throttled section of the Venturi means may be constituted by a cylindrical element, especially when the sec- 3 nd combustion fluid is peripherally injected into the throttled section.

Preferably also the diverging section of the Venturi means is constructed with a semi-angle of divergence not more than 4 and the inner surface of the divergent section is machined to perfect smoothness.

The length of the divergent section is calculated in such a way that with a total-tangle of divergence of less than 8 and the perfect smoothness of the inner surface thereof, the fluids which have sonic speed in the throttled section of the Venturi means will be accelerated to supersonic speed in the divergent section under simultaneous expansion of the fluid to a pressure below ambient pressure.

A shock wave is thereby produced at the outlet end of the divergent section of the Venturi means and this shock wave will produce a violent and complete mixture of the two combustion fluids passing through the Venturi means to produce thereby a stable flame of high heat concentration.

The means for producing the shock wave may also include a discontinuity of the inner surface of the divergent section of the Venturi means of the outlet end thereof, for instance a sudden increase of the inner diameter at the outlet end of the divergent section of the Venturi means.

If the injection of the second fluid taking part in the combustion is effected in the divergent part of the nozzle the injection has to take place at a portion of the divergent section which is always upstream from the position of the shock wave which corresponds to the normal output of the burner, and this position may be calculated by known formulas of thermodynamics in which the rate of flow of the burner is used.

If the injection of the Second fluid is made through peripheral passages having outlet ends in the divergent section of the Venturi means adjacent the throttled section thereof, then the second fluid is preferably injected under such a pressure that the size of the outlet openings of the peripheral passage may be held to a minimum to avoid creating during the injection a disturbance in the supersonic flow into which they open.

As mentioned above it is also an important feature of the present invention to provide for a burner which can also be advantageously used when one of the combustion fluids contains combustible material in powder form suspended therein. When the passage means for feeding the two combustion fluids separated from each other include an outer tube and an inner tube coaxially arranged in the outer tube, then the combustion fluid in which the powdered combustible material is suspended is preferably fed into the outer tube by a feed tube extending transversely to the axis of the outer tube and communicating with the interior thereof in substantial tangential direction, and a wear-resistant sleeve is mounted in the region in which the feed tube enters into the outer tube to take the brunt of the abrasive action of the powdered material suspended in the combustion fluid.

If the second fluid is injected through peripheral passage means into the throttled section of the Venturi means or into the divergent section adjacent to the throttled section, then the arrangement is preferably made in such a way that the Venturi means and the tube connected to the convergent section of the Venturi means can be easily removed from the burner arrangement.

According to a further development the burner of the present invention may also comprise first conduit means having a straight axis, for guiding a combusition sustaining fluid therethrough, fed under pressure at sub-sonic speed into one end of the first conduit means which has an outlet end opposite the one end, and second conduit means for guiding a fuel fluid therethrough fed under pressure at subsonic speed into one end of the second conduit means, in which the second conduit means is coaxially arranged in the first conduit means spaced from the inner surface thereof. In this arrangement the second conduit means have a maximum cross section in the region of the outlet end of the first conduit means and the inner surface of the first conduit means and the outer surface of the second conduit means are constructed in such a manner to form in the region of the outlet end an annular convergent-divergent passage having a minimum cross section such that the fluid passing therethrough will obtain sonic speed. The arrangement is made in such a manner that the second conduit means communicates with the first conduit means in the divergent portion of the passage so that the fluids passing respectively through the conduit means will mix in the divergent portion, and the length of said divergent portion is made such so as to produce in the divergent portion a reduction of the pressure of the mixture passing therethrough below the ambient pressure at the outlet end of the burner.

In this arrangement the first conduit means may have substantially cylindrical configuration throughout the whole length thereof, or the first conduit means may have at the outlet end a slightly divergent or a slightly convergent frusto-conical end portion. Preferably, the second conduit means are mounted in the interior of the first conduit means movable in axial direction with respect to the first conduit means.

The convergent-divergent passage of the burner may be formed by a body fixed to and coaxially arranged with an end of the second conduit located rearwardly of the outlet end of the first conduit, in which the body is constructed to have a first outer cone surface having its apex rearwardly of the aforementioned end of the second conduit and a second outer cone surf-ace having its apex substantially at the outlet end of the first conduit and in which the cone surfaces have a common base circle arranged in a plane substantially normal to the axis of the conduits so that the outer cone surfaces form with the inner surface of the first or outer conduit an annular convergent-divergent passage having its smallest cross section in the plane of the common base circle. In this arrangement the body is formed with a plurality of passage means therethrough communicating at the inner ends thereof with the interior of the second conduit and at the outer ends thereof with the divergent portion of the aforementioned passage, so that the fuel fluid which may be either a liquid or a gas passing through the second conduit will mix with the combustion sustaining fluid, which is preferably in gaseous form, passing through the first conduit in the divergent portion of the passage.

In this arrangement the aforementioned cross section or the neck of the convergent-divergent passage is again dimensioned in such a manner that the gas passing therethrough will obtain sonic speed and the length of the divergent portion is again made such to produce in the divergent portion reduction of the pressure of the mixture below the ambient pressure at the outlet end of the burner.

The arrangement will also produce a shock wave at the outlet end of the burner, which will cause reduction of the fluid speed to subsonic speed and simultaneously compression of the fluid permitting the discharge thereof from the outlet end. The shock wave will also produce a complete atomizing of the fuel fluid and the intimate mixture thereof with the combustion sustaining agent. The intense molecular agitation of the fluids produced by the shock wave will result in a rapid combustion and produce a very short flame of high caloric intensity in a high speed fluid field which though subsonic will still have greater speed than that maintained in burners of known construction. Furthermore, the shock wave will separate the zone of subsonic speed at the outlet end of the burner from the zone of sonic speed at the aforementioned neck of the passage and form in this way a barrier through which the flame may not flash back into the interior of the burner.

The aforementioned smallest cross section of the convergent-divergent passage has to be dimensioned in such a manner that the fluid passing therethrough will obtain at least the speed of sound for the minimum amount of fluid fed into the burner during its operation and the length of the divergent portion of the passage has to be held to such a dimension to assure an expansion of the mixture to reduce the pressure thereof considerably below the ambient pressure at the outlet end of the burner. If the expansion would lead to a pressure very near the ambient pressure at the outlet end, Mach waves instead of shock waves would be produced, and such Mach waves are not able to fix the flame at a definite location and such waves do not provide for sufficient energy to assure a perfect atomization of the combustible material. Therefore, the length of the divergent portion of the passage has to be made such to assure an extended expansion of the mixture passing therethrough under consideration of the angle of divergence of the divergent portion. An additional advantage of the arrangement in which a central body of double cone configuration as described above is used, is that the angle of divergence can be made considerably greater than in the arrangement in which standard Venturi means as described before are used for forming the convergent-divergent passage of the burner. In the construction using the central double coned body it is possible to use a total angle of divergence up to 30 degrees without producing an undesired detachment of the fluid flow from the surfaces defining the divergent portion, which would lead to turbulence in the fluid flow and premature reduction of the speed to subsonic speed. The surfaces forming the divergent portion of the aforementioned passage have to be polished to perfect smoothness, since any roughness in these surfaces would produce eddy-currents and premature reduction of the speed of flow to subsonic speed.

The last described embodiment is especially adapted for the injection of combustible material into an electric arc furnace or into a blast furnace. In an electric arc furnace the outer conduit of the burner arrangement may constitute one of the electrodes of the furnace provided with an axial bore therethrough in which the second or inner conduit with the aforementioned double-coned body connected therethrough is arranged. Any wear or consump tion of the electrode material at the end thereof can then be compensated by axial adjustment of the outer conduit and simultaneous axial adjustment of the inner conduit with the body attached thereto, relative to the adjusted outer conduit. Of course, when the outer conduit is'used as electrode, the outer conduit has to be electrically insulated from the means for feeding the combustion sust-aining gas into the outer end of this conduit.

The arrangement may also be used for the injection of combustible material into a blast furnace with complete atomization of the combustible materials for instance by pure oxygen.

If the outlet end of the first or outer conduit has a divergent or convergent frusto-conical end portion, as described above, it is also possible to regulate the burner in an expedient manner and especially to regulate the minimum output of the burner by moving the second conduit means in axial direction With respect to the first conduit means. Of course, if the outer conduit is made with a frusto-conical divergent end portion, this divergent end portion has to have an angle of divergence so that the total angle of divergence between the inner surface of the divergent end portion of the outer conduit and the outer cone surface having its apex at the outlet end of the outer conduit does not become too great to produce a detachment of the fluid flow from the surfaces defining the divergent portion of the passage. When due to axial displacement of the second or inner conduit with the body attached thereto the smallest cross section or the neck of the passage is changed it is possible to vary the amount of gas discharged through the outer conduit even if this gas is fed at constant pressure into the outer conduit and to vary thereby the output of the burner.

It'is mentioned that even if the shock Wave forms in the interior of the divergent portion of the passage, in which case a portion of the flame will be located in this divergent portion, the elements forming the divergent portion will be protected from direct contact with the flame by the existence of a boundary layer which prevents excessive transfer of heat onto the wall portions forming the divergent portion of the burner. In an experimental burner constructed according to the present invention, in which fuel oil with pure oxygen was used and in which a heat output of 8,000,000 calories per hour was produced it was not necessary to provide special cooling means when the burner was used in the open air. A special cooling jacket was necessary only when the burner was used in the interior of a furnace to protect the burner from the heat created in the interior of the furnace.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of spe cific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a cross section taken along the axis of the burner and showing one modification of the burner according to the present invention;

FIG. 2 is a cross section, taken along line -22 of FIG.

3 and showing a different modification of a burner according to the present invention;

FIG. 3 is a cross section along line 33 of the burner shown in FIG. 2;

FIG. 4 is also a cross section of a burner taken along the longitudinal axis of the burner and showing a third modification of a burner accordingto the present invention;

FIG. 5 is a schematic illustration of the burner arrangement of the present invention and illustrating the auxiliary equipment connected to the burner;

FIG. 6 is a partial cross sectional view of an additional modification of the burner according to the present invention which is similar to the embodiment shown in FIG. 1;

FIG. 7 is a partial sectional view of a further modification of the burner of the present invention and this modification is similar to the embodiment shown in FIG. 4;

FIG. 8 is a longitudinal cross section through a further modification of the burner according to the present invention;

FIG. 9 is a partial cross section similar to FIG. 8, in which the outer conduit has a convergent frusto-conical end portion;

FIG. 10 is a partial cross section similar to FIG. 8, in which the outer conduit has a convergent frusto-conical end portion; and

FIG. 11 is a partial cross section of the end portion of the arrangement shown in FIG. 8 and showing a slight modification thereof.

Referring now to the figures of the drawings and first to FIG. 1 thereof, it will be seen that the burner of the modification illustrated in FIG. 1 includes an outer tube 1 and an inner tube 2 arranged coaxially with the outer tube and spaced from the inner surface thereof. The rear end of the inner tube 2 curves outwardly and passes fluid tightly sealed through the wall of the outer tube 1. Venturi means 3 are provided in axial alignment with the outer tube 1 and supported in the outlet end thereof. This Venturi means 3 has a convergent section 4 blending with the inner surface of the outer tube -1, a throttled section 5 having a smaller diameter than the inner diameter of the outer tube 1, and a divergent section 6 downstream of the throttled section 5. A discontinuity 7 is provided at the inner surface of the divergent section 6 at the outlet end of the latter and this discontinuity is constituted by a sudden increase of the diameter of the CJI adapted to feed a fuel fluid and a combustion sustaining agent fluid under pressure and at sub-sonic speed separated from each other into the Venturi means 3. Outer tube 1 and inner tube 2 constitute therefore passage means for guiding two combustion fluids separated from each other into the Venturi means. The fluid passing through tube 1 may for instance be oxygen which may or may not contain powdered combustion material such as for instance coal dust suspended therein and the fluid passing through tube 2 may for instance be fuel oil or any other combustible material in liquid or gaseous form. However, at least one of the fluids has to be in gaseous form.

The two combustion fluids are fed into tube 1 and 2, respectively, preferably under pressure greater than atmospheric pressure and at sub-sonic speed. The cross section of the throttled section of the Venturi means is calculated for the minimum output of the burner in such a manner that the fluid passing therethrough will reach sonic speed. The divergent section 6 of the Venturi means 3 is formed with a semi-angle of divergence not greater than 4 and the inner surface of the divergent section is machined with perfect smoothness. The length of the divergent section 6 is calculated in such a way that the speed of the fluids passing therethrough will be accelerated to supersonic speed under simultaneous expansion of the fluids to a pressure below ambient pressure, i.e. below atmospheric pressure. A shock wave is thereby produced at the outlet end of the divergent section 6 of the Venturi means and this shock wave not only produces a violet and complete mixture of the two combustion fluids with each other, but the shock wave also separates the high speed fluid region in the divergent nozzle section, necessary for avoiding flashback into the burner, from a low speed region at the outlet end necessary for obtaining a short flame to produce a flame of high calorific value. Consequently, the front of the flame downstream of the plane of the shock wave is stabilized by means of the shock wave which separates the two speed regions from each other.

For the proper working of the burner it is essential that the shock wave is produced and maintained downstream of the place in which the second combustion fluid is injected into the Venturi means and mixed with a first combustion fluid.

This position of the shock wave may be calculated by known formulae of thermodynamics for the specific type of Venturi and for a specific rate of flow through the Venturi. In other words for calculating the Venturi nozzle a certain pressure of the combustion fluids is taken as a basis, the position of the shock wave is calculated, then the ratio of the cross section at the outlet end and the throttled section is computed and the throttled section is calculated according to the minimum flow of fluid through the burner so as to produce for the fluids flowing through the burner at sonic speed at the throttled section.

Following is an example of a burner constructed according to the present invention. For this burner oxygen was used as the first combustion fluid or as the combustion sustaining agent and this oxygen was fed at a rate of 648 cubic meters per hour under a pressure of 5 atmospheres into the burner. The other combustion fluid was gas oil fed into the burner at a rate of 350 kg. per hour. In this case the throttled section of the Venturi means had a cross section of 2 square centimeters and the length of the diverging section was 7.4 centimeters with a cross section at the outlet end of the diverging section of 5 square centimeters. The thermal output of this burner was 3,240,000 kg. calories per hour.

Of course the dimensions of the burner will vary from the above specified dimensions when different combustion fluids are used fed into the burner at a rate and pressure different from the above.

The means for producing the shock wave preferably also comprises a discontinuity at the inner surface of the divergent nozzle section, which is preferably formed by a sudden increase of the inner diameter of the divergent section at the outlet end thereof as shown at 7 in FIG. 1. As shown in FIG. 1 the divergent sections 6 of the Venturi means has at the outlet end a substantially cylindrical inner surface portion of a diameter greater than the portion of the divergent section adjacent thereto so as to form a sharp inner edge at the shoulder between the enlarged cylindrical portion 7 and the end of the divergent portion 6.

A discontinuity at the inner surface of the divergent nozzle section as shown at 7 in FIG. 1 is, however, not absolutely necessary for producing a shock wave at the outlet end of the Venturi means. A shock wave will also be produced at the outlet end of the Venturi means when the throttled section thereof is constructed with such a cross sectional area that sonic speed is obtained in the gas mixture passing through the Venturi means at the throttled section thereof and if the divergent section of the Venturi means, preferably made with an angle of divergency less than 8, is made long enough and with a perfectly smooth inner surface to accelerate the speed of the gas mixture passing therethrough to supersonic speed in simultaneous expansion of the mixture to a pressure below ambient. In such a case the shock wave will form at the outlet end of the divergent section of the Venturi means when the gas mixture leaving at supersonic speed and a pressure below ambient pressures impacts against the outer atmosphere. Such a construction in which the discontinuity in the inner surface of the divergent nozzle section is omitted is shown in FIG. 6, which illustrates only the front end of the burner. The upper non-illustrated end may be the same as illustrated in FIG. 1 or in FIG. 2. The Venturi means 3" differs from the Venturi means shown in FIGS. 1 and 2 in that the divergent section 6" is continued up to the outlet end of the Venturi means and that the discontinuity 7 is omitted.

The outer tube 1 is preferably surrounded by a water jacket 9 having an inner tubular portion 10 communicating at the bottom end thereof with an outer tubular portion 11 surrounding the inner tubular portion 10. Both tubular portions of the water jacket 9 are closed at the upper ends thereof and a pair of passage means 12 and 13 communicate respectively with the interior of the inner tubular portion 10 and the interior of the outer tubular portion 11 of the water jacket for feeding cooling water in the direction as indicated by the arrows in these passage means into and out of the cooling jacket 9.

A modification of the burner differing from the embodiment described above is shown in FIGS. 2 and 3. This modification is especially suitable for burners of the type described in which one of the combustion fluids contains combustible material in powder form suspended therein, for instance one of the combustion fluids may be oxygen with powdered coal suspended therein. The burner as shown in FIGS. 2 and 3 comprises also an outer tube 1' closed in the region of the rear end thereof, shown in the drawing as the upper end of the outer tube 1, by removable closure means 14, that is a cap screwed onto the threaded rear end of the outer tube 1'. The cap 14 is provided with a central opening through which the inner tube 2 passes into the interior of the outer tube 1 coaxially arranged with the latter. A Venturi means 3 is supported in the same manner as described above in connection with FIG. 1 in the interior of the outlet end of the outer tube 1 and this Venturi means comprises a convergent section 4, a throttled section 5 and a divergent section 6 downstream of the throttled section 5 and having a discontinuity 7 at the outlet end thereof, all arranged and constructed as described in connection with FIG. 1. The outlet end 8 of the innertube is located in the region of the throttled section preferably a few millimeters downstream of the throttled section. A water jacket 9 as described before surrounds the outer tube 1' and this Water jacket is provided with a pair of passage means 12 and 13 for feeding cooling water into and out of the water jacket in the direction as indicated by the arrows. One combustion fluid which may for instance be oxygen with a combustible material in powder or grit form suspended therein is fed into the interior of the outer tube 1' through a feed tube which extends transverse to the axis of the outer tube and which communicates with the interior of the latter in tangential direction as best shown in the cross section of FIG. 3. A liner 16 formed from abrasion-resistant material is provided in the region of the rear end of the outer tube 1 into which the feed tube 15 enters. The outer surface of the liner 16 abuts against the inner surface of the outer tube 1 and the liner 16 is formed with an opening therethrough aligned with the feed tube 15 so that the fluid passing through the feed tube may enter into the interior of the outer tube 1'. The liner 16 is preferably formed at the upper end thereof as shown in FIG. 2 with a shoulder 16' sandwiched between the upper end of the outer tube 1' and the inner surface of the closure cap 14. After removal of the closure cap the liner mzy thereby conveniently move from the interior of the tu e 1'.

In this construction the liner 16 will take the brunt of the abrasive action produced by the powdered material suspended in the fluid passing under pressure through the feed tube 15 and wear on the outer tube 1' is thereby reduced to a minimum. The tangential introduction of the suspended abrasive material will also produce an eddying movement so that the wear of the sleeve 16 will be very small.

A further modification of the burner of the present invention is shown in FIG. 4. This burner differs from the above described modifications mainly by a different arrangement for feeding the second combustion fluid into the region of the throttled section of the Venturi means. Furthermore, the arrangement shown in FIG. 4 is constructed in such a manner that the Venturi means can be easily removed from the arrangements together with the tube carrying the Venturi means so that replacement of the Venturi means and the tube connected thereto can be carried out in a convenient and efficient manner when such replacement appears necessary.

The burner shown in FIG. 4 comprises a tube 18 for feeding a first combustion fluid at a predetermined pressure and at sub-sonic speed into the burner. The tube 18 has an outlet end 18 to which a Venturi means 3' is connected in axial alignment with the tube 18. The Venturi means 3 has a convergent section 4', a throttled section 5' and a divergent section 6' downstream of the throttle section 5'. The throttled section 5' preferably has the form of a short cylinder. The sections 4, 5' and 6' of the Venturi means are again constructed and arranged as described in detail in connection with FIG. 1.

The tube 18 is surrounded :by a water jacket 9' constructed in a slightly different manner than the water jacket 9 shown in FIGS. 1 and 2. The water jacket 9' comprises an inner tubular portion 19, an outer tubular portion 21 and an intermediate tubular portion located between the inner and the outer tubular portion of the Water jacket 9. As can be seen from FIG. 4 the inner tubular portion 19 of the water jacket extends further to the rear or upper end of the tube 18 then the outer tubular portion 21 whereas the intermediate tubular portion 20 ends intermediate the ends of the inner and outer tubular portions of the water jacket 9'.

Caps

26 and 27 are respectively provided at the rear ends of the intermediate and outer

tubular portions

20 and 21 for closing these portions at the rear ends thereof. An end piece 22 having preferably wall sections heavier than the other wall sections of the water jacket 9' is provided at the front or bottom end as viewed in FIG. 4 of the water jacket and this end piece surrounds the Venturi means 3' and connects the bottom end of the inner tubular portion 19 with the outer tubular portion 21 of the water jacket 9, whereas the front end of the intermediate tubular portion 20 ends short of the inner surface of the end piece 22. A pair of passage means 12' and .13 are provided which respectively communicate with the space between the inner tubular portion 19 and the intermediate tubular portion 20, and the space between the intermediate tubular portion 20 and the outer tubular portion 21 of the water jacket so as to feed cooling water or any other cooling fluid into and out of the cooling jacket 9' as indicated by the arrows in these passage means. The rear or upper end of the inner tubular portion 19 is provided with a reinforcing ring 28 preferably welded thereto and this reinforcing ring 28 is provided with an outer screw thread onto which a closure cap 29 is screwed. The closure cap 29 is formed with a central opening 29' through which the tube 18 passes. A ring 30 is located in the interior of the closure cap 29. Ring 30 surrounds the tube 18 and is fixedly connected thereto, preferably by welding. Ring 30 is engaged by the transverse wall portion of the closure cap 2h when this cap is screwed onto the reinforcing ring 28.

The end piece 22 of the water jacket which surrounds the Venturi means 3' is formed in the region of the convergent section 4' of the Venturi means with a frustoconical inner surface 23 tapering towards the outlet end of the Venturi means and engaged by a correspondingly shaped fr-usto-conical outer surface of the Venturi means. Therefore, when the closure cap 29 is screwed onto the reinforcing ring, a downwardly directed pressure is imparted through the ring 30 onto the tube 18 which in turn will press the outer frusto-conical surface of the Venturi means 3' connected to tube 18 against the frustoconical surface 23 of the end piece 22 of the water jacket so that these two surfaces will tightly engage each other.

On the other hand, when the closure cap 29 is unscrewed from the reinforcing ring 28 the tube 18 and the Venturi means 3' connected thereto can be easily removed from the arrangement so that the Venturi means 3' and the tube 18 connected thereto can be easily exchanged if a replacement of the Venturi means or the tube 18 should become necessary.

The Venturi means 3' is formed in the outer surface thereof engaging the fnusto-conical surface 23 of the end piece 22 with a peripheral groove 24 and a plurality of passage means or bores 25 extending downwardly inclined to the axis of the Venturi means from the peripheral groove 24 into the interior of the Venturi means. The passage 25 are uniformly distributed about the axis of the Venturi means and the inner ends thereof and, as shown in FIG. 4, at the throttled cylindrical section 5 of the Venturi means. The passages 25 may, however, also be arranged in such a way that the inner ends thereof communicate a few millimeters downstream of the throttled section 5 with the divergent section 6' of the Venturi means.

A feed tube 32 is used to feed the second combustion fluid into the burner shown in FIG. 4. This feed tube 32 passes through the cover 26, between the inner and intermediate

tubular sections

19 and 20 of the water jacket 9' and feed tube 32 communicates at the lower end thereof, as shown in FIG. 4, with the peripheral groove 24 in the Venturi means 3' so that the combustion fluid fed through feed tube 32 enters through the passages 25 into the region of the throttle section 5' of the Venturi means to be mixed with the combustion fluid passing through tube 18.

A discontinuity of the inner surface of the divergent section of the Venturi means is also preferably provided in the burner construction shown in FIG. 4 and this discontinuity is in this case formed by a substantially cylindrical bore in the end piece 22 of the water jacket, ar-

ranged coaxially with the axis of the Venturi means and having a diameter greater than the maximum diameter of the divergent section of the Venturi means at the outlet .end thereof.

FIG. 7 shows a variation of the embodiment illustrated in FIG. 4 and the embodiment shown in FIG. 7 differs from the forementioned one in that the Venturi means 3" ends flush with the end surface of the end piece 22' of the water jacket so that the discontinuity 33 formed by a large diameter portion of the end piece 22 shown in FIG. 4 is omitted. The shock Wave in this case will form, in the same way as described in connect-ion with FIG. 6, at the outlet end of the divergent section 6" of the Venturi means.

A general arrangement of the burner and the auxiliary equipment connected thereto is chematically illustrated in FIG. 5. The burner B shown therein is the burner shown in detail in FIG. 4 and for clarity sake this burner is shown to a larger scale than the auxiliary equipment connected thereto. The arrangement shown in FIG. is strictly schematic and the various elements of the auxiliary equipment are not shown in the right proportions with respect to the burner. The auxiliary equipment used with the burner of the present invention includes, as shown in FIG. 5 a tank T, which may contain oxygen under pressure, connected to a pressure reducer V from which a pipe connection 34 leads into the flow meter M and from there into the tube 1 8 of the burner B. A pressure gauge G is connected to the pipe 34 so that the pressure of the oxygen fed from the tank T through pipe 34 into the tube 18 of the burner and obtained by properly setting the pressure reducer V may be checked at the pressure gauge G. The second combustion fluid, for instance gas oil, is fed from the fuel tank T through a fuel feed pump P through the feed tube 32 which passes through the space between the inner and intermediate

tubular sections

19 and 20 of the water jacket as described in connection with FIG. 4 in detail. A flow meter M, is provided in the feed tube 32 to check the rate of flow of the fuel passing therethrough. Water is supplied to the water jacket of the burner from a water tank T" through a pipe 36 communicating with the passage means 12' of the Water jacket to feed water thereinto and water is fed from the passage means 13' of the water jacket through pipe 37 which communicates with the bottom portion of the water tank T". A water feed pump P" located in the pipe 37 serves to continuously circulate the water through the tank T" and the water jacket 9' of the burner.

The fuel feed pump and water feed pump shown in FIG. 5 are driven by any means known in the art and not illustrated and the speed of these pumps can preferably be regulated.

The burner of the present invention is operated as follows:

To start the burner, the pressure reducer V connected to the oxygen tank T is set to a desired value of flow and pressure checked on the flow meter M and the pressure gauge G. The fuel pump P is started and the flow of the fuel of the burner through tube 32 is checked on the flow meter M. The mixture of the two combustion fluids for instance oxygen and gas oil thus obtained at the outlet end of the burner is ignited by any means, not shown in the drawings, for instance a torch held at the outlet end of the burner. The rate of flow of the combustion means and the pressure thereof is set to such a volume so that sonic speed will be obtained in the throttled section of the Venturi and this sonic speed is then accelerated in the divergent section of the Venturi means to supersonic speed under simultaneous expansion of the fluid mixture to a pressure below ambient or atmospheric pressure. Due to this arrangement a shock Wave is formed at the outlet end of the Venturi means which separates the high speed fluid region in the divergent section of the Venturi from a low speed fluid region at the outlet end thereof. A stable short flame is thus created at the outlet end of the burner and flashback of the flame into the interior of the burner nozzle is positively prevented. The short flame thus produced will have a high calorific value greater than obtainable with burners according to the prior art. It should be further noted that the short flame is stabilized and continuous combustion maintained only by the shock wave produced at the outlet end of the burner.

No separate pilot flame is necessary for maintaining combustion of the mixed fluids.

FIGS. 8-11, show a further development of the burner according to the present invention. Referring first to FIG. 8 which shows one modification of the burner in longitudinal cross section, it will be seen that this burner includes first conduit means formed by a substantially cylindrical circular conduit 41 screwed at its upper end into the threaded end portion of a bore 49, formed in a bushing 48 which is substantially closed at the upper end thereof by a plug 51. A tube 50 extending at an angle to the axis of the conduit 41 passes through a bore in the bushing 48 fluid-tightly connected thereto by soldering or welding, and communicating at the inner end thereof with the bore 49. The outer end of the tube 50 not shown in the drawing is connected to a source of combustion sustaining fluid, for instance oxygen under pressure, so that this combustion sustaining fluid may be fed at a given pressure at subsonic speed into the interior of the conduit 41.

Second conduit means are coaxially arranged in the first conduit means spaced from the inner surface thereof and these second conduit means include a conduit 52 having an inner end spaced from the outlet end of the conduit 41 and a central body 42 coaxially fixed to the inner end of the second conduit 52. This central body 42 has a first oute-r cone surface 43 having its apex rea-rwardly of the inner end of the second conduit 52. and a second outer cone surface 44 having its apex substantially at the outlet end of the first conduit 41. Cone surfaces 43 and 44 have a common b-ase circle 57 arranged in a plane substantially normal to the axis XX of the burner. A passage is thus formed between the inner surface 41 of the conduit 41 and the outer cone surfaces 43 and 44 which has a convergent portion 45 around the cone surface 43 and a divergent portion 46 around the cone surface 44 and a smallest cross section 47 in the plane of the common base circle 57. The body 42 is foamed with a plurality, for instance 6 passage means 55 therethrough communicating with the inner ends thereof with the inter-ior of the second conduit 52 and having their outer ends at the cone surface 44 so that passage means 55 communicate with the divergent portion 46 of the aforementioned passage. Conduit 52 passes through a bore formed in the plug 51 and through a coaxial bore formed in an additional plug 53 screwed into a correspondingly threaded cavity formed in plug 51 coaxial with the bore therethrough. A sealing Washer 54 formed from elastically compressible material, for instance neoprene, is arranged in the space between the end face of the cavity formed in the plug 51 and the corresponding end face of the plug 53. By screwing the plug 53 into the cavity formed in the plug 51, the washer 54 will be compressed in axial direction and be tightly pressed against the outer surface of the conduit 52 so as to hold conduit 52 in fixed relation with respect to conduit 4-1. By screwing the plug 53 in outward direction the pressure produced by the compressible washer 54 on the conduit 52 may be reduced so that the conduit 52 with the central body 4-2 fixed thereon may be adjusted in axial direction with respect to the outer conduit 41.

Plugs

51, 53 and the compressible washer 54 constitute therefore means for mounting the second conduit means 52, 42 movable in axial direction with respect to the first conduit means 41, 49 and 50. The outer end of conduit 52, not shown in the drawing, is connected to a source of combustion fluid, for instance fuel oil under pressure, so

13 that fuel oil may be fed through conduit 52 and passage means 55 into the diverging portions 46 of the aforementioned passage.

According to the basic principle of the present invention,

the minimum cross section of the passage defined by the outer surface of the central body 42 and the inner surface 41' of the conduit 41 at the neck 47 of the passage has to be made in such a manner that during feed of the minimum amount of gas through conduit 4-1 the gas will obtain at the neck of the passage 47 the speed of sound. In this case, the expansion of the gas or the expansion of the mixture of gas and fuel fluid will take place in the divergent portion 46 of the passage according to the following formula:

I ev l A is the cross section of the divergent portion of the passage at a point of a pressure P,

Ac is the cross section at the neck 47 of the passage,

P is the pressure upstream of the convergent section of the passage,

, is the specific heat of the gas at constant pressure and volume; and

(p is the Hugoniot number of the gas, and the speed of the gas continues to grow and the pressure to diminish during the flow thereof through the passage.

When the length of the divergent section is made long enough to assure that an expansion of the mixture takes place until the pressure thereof is inferior to the ambient pressure surrounding the outlet end of the burner, a shock wave producing recornpressio-n of the gas will form in the divergent portion 46 of the passage permitting discharge of the gas and fluid mixture from the burner. Such a shock wave may form at the place as indicated by the dotted line 56 in the divergent portion 46 of passage. The passage means 55 have to communicate with the divergent portion 46 of the passage upstream of the place at which the shock wave forms and the outer surface of the cone 44 and the inner surface 41' of the conduit 4d have to be made perfectly smooth to prevent any turbulence and premature forming of a shock wave.

A burner of the present invent-ion was built for introducing of fuel oil into a blast pipe of a blast furnace whereby pure oxygen was used as the combustion sustaining agent and for automizing the fuel oil. The burner was built with an internal diameter of the conduit 41 of 20 mm. and with a maximum diameter of the body 42 of 18 mm. whereas the cone angle of the cone surface 44 was held at 30 degrees. Fuel oil was fed at a pressure of .10 kg. per .crn. at the rate of 360 kg. per hour was fed into-the conduit 12 while oxygen was introduced into the .tube 50 at a pressure of kg. per cm. at an amount of 360 N m! per hour. The amount of oxygen fed into the burner equals approximately half of the stoichiometric amount necessary for complete combustion which then took place completely in the hot air blown into theblast furnace. In this case a shock wave was formed slightly upstream of the outlet end of the burner approximately at the location as indicated by the dotted lines 56 in FIG. 1 and the position of the shock wave was maintained in the divergent portion 46 and proper function of the burner maintained even during variations of feed of the in which:

oxygen up to 50%.

The use of such a burner in blast furnaces provides E4 the end of the conduit 41 can be easily compensated for by longitudinal displacement of the second conduit means, that is the conduit 52 and the central body 42 attached thereto, in longitudinal direction with respect to the conduit 41.

FIG. 9 shows a slight modification of the above described arrangement illustrated in FIG. 8. The embodiment shown in FIG. 9 differs from the embodiment illustrated in FIG. 8 in that the conduit 41a has a frustoconical end portion 41b the inner surface 410 thereof is formed with an apex angle of about 8 degrees. In this case the maximum diameter of the central body 42a is preferably made substantially equal to the inner diameter of the conduit 4111 at the cylindrical portion thereof; The central body 42a comprises again two cone surfaces 4311 and 44a and passage means 55a having their outer ends at the cone surface 4411 so as to form between the cone surfaces and the inner surface 41c a converging-diverging passage having its smallest cross section at 47a. The upper portion of the burner illustrated in FIG. 9 is not shown in this figure and the upper portion thereof is identical to that shown in FIG. 8. In this arrangement, one can change the minimum cross section 47a of the passage between practically zero, and a maximum amount depending on the axial adjustment of the conduit 52 and the central body 42a thereon relative to the frusto-conical end portion 41b of the conduit 41a. This permits to wary the amount of gas, for instance oxygen, fed into the burner, to a very great extent even if the gas is fed with constant pressure into the burner. In adjusting the position of the central body 42a the degree of expansion of the mixture in the divergent portion of the passage is also adjusted and this flow adjustment is made to form an optimum shock wave. This provides for an especially efficient regulation of the burner and regulation of the heat produced by the flame.

A further slight variation of the burner according to the present construction is shown in FIG. 10 and this modification differs from the above described modification shown in FIGS. 8 and 9 in that the outer conduit 41d has a frusto-conical end portion 412 the inner surface 41 slightly converges instead of diverging as shown in FIG. 9. In vthis arrangement the minimum cross section of the passage formed between the inner surface 41 and the cone surfaces of the central body 42 may also be varied by adjusting the posit-ion of the central body 42 together with the conduit 52 in axial direct-ion.

Final-1y, FIG. 11 illustrates a further modification and this modification in which only [the end portion of the burner is shown differs from the arrangement illustrated in FIG. 8 in that the central body 42b has a truncated cone having an end face 57 normal to the burner axis. In this case, a sudden expansion of the gas mixture passing through the outlet end of the burner is obtained in the plane of the end face 57 and the turbulence produced at the end of the truncated cone 4212 which will assure formation of a shock wave at this place. This arrangement is especially advantageous when the burner is subjected to sudden and considerable variations.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of burners differing from the types described above.

While the invention has been illustrated and described as embodied in a burner producing a stable flame with a high concentration of heat stabilized by shock waves, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A burner for producing a stable flame in a high speed fluid field comprising, in combination, first conduit means having a straight axis for guiding a combustion sustaining fluid therethrough fed under pressure and at subsonic speed into one end of said first conduit means, said first conduit means having an outlet end opposite said one end; second conduit means for guiding a fuel fluid therethrough fed under pressure and at subsonic speed into one end of said second conduit means, said second conduit means being coaxially arranged in said first conduit means spaced from the inner surface thereof; and a body fixed to said second conduit means coaxially therewith in the region of said outlet end, said body comprising a pair of cone surfaces which taper in opposite directions and have a common base circle, thus defining within said first conduit means an annular convergentdivergent passage having a minimum cross section in the plane of said base circle such that the fluid passing therethrough will obtain sonic speed, said second conduit means communicating with said first conduit means only in the divergent portion of said passage so that the fluids passing through said conduit means will mix in said divergent portion, and the length of said divergent portion being such to produce in said divergent portion reduction of the pressure of said mixture below the ambient pressure at said outlet end.

2. A burner for producing a stable flame in a high speed fluid field comprising, in combination, first conduit means having a straight axis for guiding a combustion sustaining fluid therethrough fed under pressure and at subsonic speed into one end of said first conduit means, said first conduit means having an outlet end opposite said one end and having at said outlet end a divergent frusto-conical end portion; second conduit means for guiding a fuel fluid therethrough fed under pressure and at subsonic speed into one end of said second conduit means, said second conduit means being coaxially arranged in said first conduit means spaced from the inner surface thereof; and a body fixed to said second conduit means coaxially therewith in said frusto-conical end portion of said first conduit means, said body comprising a pair of cone surfaces which taper in opposite direction and have a common base circle, thus defining within said frustoconical end portion an annular convergent-divergent passage having a minimum cross section in the plane of said base circle such that the fluid passing therethrough will obtain sonic speed, said second conduit means communicating with said first conduit means only in the divergent portion of said passage so that the fluids passing through said conduit means will mix in said divergent portion, and the length of said divergent portion being such to produce in said divergent portion reduction of the pressure of said mixture below the ambient pressure at said outlet end.

3. A burner for producing a stable flame in a high speed fluid field comprising, in combination, first conduit means having a straight axis for guiding a combustion sustaining fluid therethrough fed under pressure and at subsonic speed into one end of said first conduit means, said first conduit means having an outlet end opposite said one end and having at said outlet end a convergent frusto-conical end portion; second conduit means for guiding a fuel fluid therethrough fed under pressure and at subsonic speed into one end of said second conduit means, said second conduit means being coaxially arranged in said first conduit means spaced from the inner surface thereof; and a body fixed to said second conduit means coaxially therewith in said frusto-conical end portion of said first conduit means, said body comprising a pair of cone surfaces which taper in opposite direction and have a common base circle, thus defining within said frustoconical end portion an annular convergent-divergent passage having a minimum cross section in the plane of said base circle such that the fluid passing therethrough will obtain sonic speed, said second conduit means communicating with said first conduit means only in the divergent portion of said passage so that the fluid passing through said conduit means will mix in said divergent portion, and the length of said divergent portion being such to produce in said divergent portion reduction of the pressure of said mixture below the ambient pressure at said outlet end.

4. A burner for producing a stable flame in a high speed fluid field comprising, in combination, first conduit means having a straight axis for guiding a combustion sustaining fluid therethrough fed under pressure and at subsonic speed into one end of said first conduit means, said first conduit means having an outlet end opposite said one end; second conduit means for guiding a fuel fluid therethrough fed under pressure and at subsonic speed into one end of said second conduit means, said second conduit means being coaxially arranged in said first conduit means spaced from the inner surface thereof; and a body fixed to said second conduit means coaxially there with in the region of said outlet end, said body comprising a pair of cone surfaces which taper in opposite directions and have a common base circle, thus defining within said first conduit means an annular convergentdivergent passage having a'minimum cross section in the plane of said base circle such that the fluid passing therethrough will obtain sonic speed, said second conduit means communicating with said first conduit means only in the divergent portion of said passage so that the fluids passing through said conduit means will mix in said divergent portion, and the length of said divergent portion being such to produce in said divergent portion reduction of the pressure of said mixture below the ambient pressure at said outlet end; and means mounting said second conduit means movable in axial direction with respect to said first conduit means.

5. A burner for producing a stable flame in a high speed fluid field comprising, in combination, a first cylindrical conduit having a straight axis for guiding a combustion sustaining gas therethrough fed under pressure and at subsonic speed into one end of said first conduit, said first conduit having an outlet end opposite said one end; a second cylindrical conduit coaxially arranged in said first conduit spaced from the inner surface thereof for guiding a fuel fluid therethrough fed at one end under pressure and at subsonic speed into said second conduit, said second conduit having an other end rearwardly of said outlet end of said first conduit; a body fixed to said other end of said second conduit coaxial therewith, said body having a first outer cone surface having its apex rearwardly of said other end of said second conduit and a second outer cone surface having its apex substantially at said outlet end of said first conduit, said cone surfaces having a common base circle arranged in a plane substantially normal to said axis so that said outer cone surfaces form with the inner surface of said first conduit an annular convergent-divergent passage having its smallest cross section in the plane of said common base circle, said smallest cross section dimensioned so that the gas passing therethrough will obtain sonic speed; and a plurality of passage means formed in said body communicarting with one end with said other end of said second conduit and at the other end thereof only with said divergent portion of said passage so that the fluid passing through said second conduit will mix with said gas passing through said first conduit in said divergent portion of said passage, and the length of said divergent portion being such to produce in said divergent portion reduction 17 18 of the pressure of said mixture below the ambient pressure OTHER REFERENCES at said Outlet Gas Ignition Behind the Schock Wave; B-azhenova and Soloukain; pages 8 66- 976; Seventh Symposium (Inter- Refelellces Cited y the Examine! national) On Combustion; published 1958 by Butter- 5 h Scientific Publications London En land co in UNITED STATES PATENTS S y g PY Scientific Library and in 158-28 Group 380. 1 1,434,238 10/ 19212 Weber r |15876 2,692,480 10/1954 Via d t 1, 6() 39 72 FREDERICK L. MATTBSON, JR., Primary Examiner.

MEYER FERDIN, JAMES W. WESTHAVER, FOREIGN PATENTS 10 Examiners.

576,365 5/ 19158 Italy. E. G. FAV-ORS, Assistant Examiner.