Device For Driving A Fluid

Abstract

Device for driving a secondary fluid by a primary fluid comprising a first intake pipe for the primary fluid and a second intake pipe for the secondary fluid which is coaxial to the first pipe, at least one symmetrical bulb is lodged coaxially in the second pipe, with the downward end of the first pipe providing a slit between it and the upward portion of the bulb for the flowing of the primary fluid therethrough whereby the primary fluid issues from the slit in a path substantially tangential to the outer profile of the bulb from upward to downward, the downward end of the bulb being truncated.

Description

The present invention relates to improvements to the driving of an important mass of fluid by a smaller mass of fluid of high energy. The invention relates also to the industrial applications of the said improvements.

Many applications of the Coanda effect are already well known but it has been observed that the cross section of the nozzle throat kept down frequently the effectiveness and thus the efficiency of this latter. Tests have been carried out and have shown that when the Coanda slit was opened at a given dimension, the total flow produced (driven fluid and driving fluid) was such that the throat was in effect saturated, i.e., that its cross section was not big enough to let the total flow pass without braking it.

The research work carried out in order to eliminate this drawback and to hold and if possible to develop the full advantages of the Coanda effect, has lead to observe that this performance was very simply reached with a nozzle, which can be termed "external nozzle," cooperating with a slit whose extended lip is located externally from the rolled profile of a streamlined body, which will be referred to as "bulb" in the description hereafter.

Proceeding from this basis, the improvements to the carrying into effect of the Coanda effect consist essentially, according to the present invention, in sending under pressure a driving or primary fluid on the upstream edge of intake edge of a streamlined body in form of symmetrical bulb, immersed into a fluid to be driven or secondary fluid, the arrival of the primary fluid taking place coaxially with the axis of the said bulb, and the coming out of this primary fluid into the secondary fluid being tangential to the curvature of the bulb from upstream to downstream. The input of the fluid under pressure can take place internally or externally from the bulb, but in every case in such a manner that the flow of the outcoming fluid be always tangential to the curvature of the bulb from upstream to downstream, and following the curvature of said bulb.

The carrying into effect of these improvements is ensured by a device consisting essentially, in its more general form, of a profile rolled around an axis and having the shaped of a streamlined body or symmetrical bulb, by tubular means coaxial with the said bulb and opening in the vicinity of the upstream surface of the bulb for driving there the primary fluid, and by means suitable for driving the said primary fluid to be tangent to the curvature of the bulb from upstream to downstream.

According to another feature of the invention, the above-mentioned improvements include the arrangement of a chamber either cylindrical or of a diameter higher than the maximum diameter of the bulb, either in a shape of truncated, convergent or divergent cone, but in all cases coaxial with the bulb. The said chamber can stretch from a point located before the intake edge up to a point located at a given distance below the rear end of the bulb. The bulb can also be located completely on the axis of the cylindrical room and before this latter, by selecting, will be disclosed later on, the respective dimensions of the bulb and of the chamber as well as the distance between the entrance of the chamber and the rear end of the bulb. The chamber can particularly be made of a complete venturi or of its conical portions, eventually interconnected by a cylindrical portion.

It has been observed that, under the conditions explained hereabove, the secondary fluid flow obtained was much higher than with a simple external bulb nozzle of same characteristics, while a lower efficiency was normally expected in view of the load losses resulting from the fluid coming into contact with the wall of the cylindrical chamber.

The primary fluid and the secondary fluid can be similar or different. The primary fluid supply can be continuous or pulsatory, for example it can be provided by the exhaust gas of an engine.

The bulb can be fitted as indicated hereabove, either completely above the chamber pipe, or partly at the external side above the said pipe and partly into the chamber pipe, or partly below this pipe. The position of the bulb in relation with the chamber pipe can be selected in terms of the desired velocity of the flow at the outlet of the device according to the invention, and dependent on the mass of fluid whose driving is desired.

The bulb can be made of a surface of revolution which can be total or partial; it can also have the shape of a single wing, or of a double, preferably symmetrical, wing, with the wall enveloping the bulb being then made of at least one plane parallel to the axis of the wing. The surface of the bulb can also be interrupted at a certain distance below the main cross section, which allows to increase the diffusion of the mass coming out from the device.

The outlet of the primary or driving fluid can be made of a regular slit, of an interrupted slit or of a series of holes.

Inside a chamber and according to the desired performances, it is possible to fit either several identical or different parallel-axis bulbs or one single bulbous body made of bulbs mutually overlapping in order to form lobes. Adjacent to each other it is also possible to arrange several cylindrical chambers mutually overlapping in form of lobes, and to set up a bulb inside of each lobe.

It has been observed that, in a general manner, with D being the diameter of the bulb at the main cross section and d being the diameter of the slit, .DELTA. being the diameter of the cylinder surrounding the bulb or the bulbous body, it was recommended that:

D/d 2, in relation with the pressure of the primary fluid, .DELTA. be selected on the one side in relation with the result desired, with a value eight or 10 times higher than d when speed of the total flow is desired at the exhaust, and a value higher than 20 d when a big flow of the stream is desired. It has also been observed that, according to the invention, the highest induction ratio was obtained with low primary pressures (in the order of 20 g./cm..sup.2 approximately) and thin slits (in the order of 0.1 mm.).

As for the length L of the cylinder, it has been observed still according to the invention, that the best driving action of the secondary fluid by the primary one is obtained with the following relation between L and .DELTA., the bulb being located at the upstream input of the cylinder: 3.DELTA.<L <5.DELTA..

On the other side, the position of the bulb in relation with the input of the chamber pipe, does not apparently load to a noticeable variation of the efficiency of the device.

The process and the device according to the invention are likely to have many industrial applications, such as: driving of air to provide ventilation effects --production of high velocity streams in order to allow for very remote localized aerations--mixing of two or more fluids, for example for burners--extraction of gas by means of the local depression produced by the coming out of the primary gas, improving namely the exhaust of internal combustion engines --spraying of liquids for different processes --handling of pulverulate or granulate materials. These different applications of the device according to the invention have efficiencies and an effectiveness much higher than those obtained with the already known apparatus.

With some of these applications, it is possible to use to the best the wall effect resulting from the presence of the chamber pipe or other, by proving the modification of the said pipe diameter; it is also possible to modify the length of the pipe with or without air input into wall, by using for example a concentric tube, a hole made free by sliding, a telescopic tube or other.

Among the above-mentioned applications, it was found the mixing of one or more fluids, intended for being used in burners; in this case, a grid could be fitted at the outlet of the external chamber of the device for carrying into effect the said improvements. In such a case of gas burner, it has been indicated above that a practically total automaticity of adjustment of the oxydizing air in relation with gas was obtained, with any type of gas, volume and pressure whatsoever, as the flow can only be adjusted by the pressure of the primary gas (fuel).

A form of embodiment particularly advantageous of a gas burner, where this burner consists, on the one side, of a mixer portion made of a bulb according to a main patent, of a pipe feeding coaxially with the bulb the fuel primary gas and driving it into a slit made between the end of the pipe and the upstream portion of the bulb around this latter, of a pipe whose both ends are opened and conically flared upstream and downstream in order to accommodate an inlet for the ambient fluid (oxydizer) between the upstream portion of the bulbous body and the downstream portion of the pipe, the conical upstream portion of said pipe stretching up to a small distance above the slit for injection of the primary gas in order to form a primary chamber for mixing the primary fluid and and oxydizing fluid, and a cylindrical channel surrounding the whole said pipe stretching beyond the downstream end of said pipe, on the other side of a grid fitted at the outlet of the final mixing chamber comprised between the upstream end of the conical pipe and the channel, the final mixture being inflamed by any appropriate means at the grid outlet.

In the case when several bulbs are mounted in series in the intake pipe for the primary fluid, there is advantageous to use one bulb element along, composed of bulbs which are solidarized from the one to the other through their respective upward and downward ends, the maximum diameters of which decreasing from the one to the other and which are individually provided on its upward front with a slit receiving the primary fluid issued from the preceeding bulb element and possibly mixed with secondary driven fluid, so that the fluid issuing from said second element penetrates into the slit of the third bulb element and so on, the last bulb element being truncated at its downward end.

By referring to the appended drawings, some examples of the carrying into effect of improvements and applications according to the invention.

In these drawings:

FIG. 1 is a diagrammatic view in axial cross section of the device according to the invention;

FIG. 2 is similar view of another embodiment;

FIGS. 3 and 4 are respectively views in longitudinal cross section according to the line 4-4 of FIG. 3 of a lobed device;

FIG. 5 illustrates in axial cross section a device for fluids spraying;

FIG. 6 is a sectional view of a device for the handling of materials;

FIGS. 7, 8 and 9 represent respectively: diagrammatic sectional views of a tandem of bulbs according to the invention, a bulb fed by a nozzle and of a nozzle fed by a bulb according to the invention;

FIG. 10 illustrates an adjustable aeration device;

FIG. 11 illustrates an adjustable slit device;

FIG. 12 is graph showing the results obtained with an aeration device according to the invention.

FIG. 13 is longitudinal axial section view of an example of preferred embodiment of a mixer burner according to the invention;

FIG. 14 is a schematical sectional views of another embodiment of the device shown on FIG. 7.

In the drawings, the device according to the invention is illustrated with a bulb 1 having an upstream portion 2, a main cross section 3 and a streamlines downstream portion 4, which can moreover be real only up to a certain distance from its tip. The primary fluid supply is provided by a pipe 5 coaxial with bulb 1. In the case of FIG. 1, the pipe 5 is flared with a slit 6 between the upstream portion 2 and a wall 7. In FIG. 2, the pipe 5 enters the upstream body 2 and opens externally above the main cross section 3, by an annular slit 6. The bulb 1 is located coaxially into a cylindrical pipe 8: it has been observed that this pipe facilitated the driving effect produced on the the secondary fluid by the primary fluid coming out, tangentially from the bulbous body, from the slit 6. In case the device has to be used as a gas burner, a grid can be fitted at the output hole of the external chamber (FIG. 11).

The device of FIGS. 3 and 4 embodies three bulbs 1, 1.sub.1 and 1.sub.2 located into a chamber 8 with three lobes 8.sub.1, 8.sub.2 and 8.sub.3 which have a primary fluid supply provided by a pipe 5 fitted with branches 5.sub.1, 5.sub.2 and 5.sub., each of them being connected to one of the slits of the three bulbs. A variable volume ventilation can thus be provided by the working of one or more bulbs of the lobe. The arrows illustrate the path of the fluid.

The device illustrated into FIG. 5 is particularly convenient for the spraying of a driven fluid. In this example, the bulb 1 has its downstream portion 4 truncated in 4' and an arrival 9 of liquid is arranged internally of the bulb at the surface of which it comes out from holes 9 uniformly distributed at the vicinity of the main cross section 3. A ring or similar 10 allows to vary, if desired, the free surface of flow of the openings 9. A modified device consists of a bulb 1 at the output of the sleeve 8, the liquid to be sprayed arriving on the external surface of the bulb by any appropriated means already known. Under these conditions, we obtain in one or another embodiment, an extreme fragmentation of the liquid which is thus perfectly sprayed. The truncated portion 4' favors still more this spraying when the arrival of the liquid to be sprayed is made at the downstream end of the bulb and even at a certain distance downstream on the axis of the bulb; we obtain thus locally a very strong eddy effect which avoids any deposition and dripping, as the spraying is only produced externally from the sleeve.

The device illustrated in FIG. 6 is intended for transporting pulverulate material. In this effect, the pipe 5 for the primary fluid supply has a conical cap 11 on which the material 12 arrives, driven by the secondary fluid used as support. The material is then driven with the secondary fluid. The conical cap 11 could be replaced by an helicoidal surface; we could also simply provide a slit of a circular series of additional holes 11' at the vicinity of the outcoming pipe 5 on the downstream portion 2 of bulb 1. The holes or helix provide centrifugal ejection of the particulate material into the secondary fluid and the material handling is carried out as desired. In FIG. 7, two bulbs 1' and 1" constituting a bulb unit are mounted in tandem, the first one 1' being placed in a cylindrical chamber 5" providing a curved connection. The second bulb 1" is placed in a pipe 8. The pipe 5' discharges through a slit 6' between the flared end of the pipe 5' and the adjacent end of the bulb 1'. The cylindrical chamber 5" discharges through a slit 6" between the mutually adjacent ends of the chamber 5" and the bulb 1".

In the case of FIG. 8, a Coanda nozzle 11 of known type is made to stream directly by its venturi 14 into the slit 15 of a bulb 1 located coaxially into a pipe 8.

The FIG. 9 illustrates a bulb 1 fed by a pipe 5 and located into the cylindrical pipe 8 in such a manner that the bulb and the pipe outlets are located approximately into the throat of the known type Coanda nozzle 16. We observe that a very favorable action is thus obtained on the homogeneity of the output stream.

The device illustrated in FIG. 10 is made on the one side of a bulb 1 with its supply 5 in primary fluid such as air in order to drive a secondary fluid such as air, for ensuring the aeration of premises, on the other side of a pipe made of two parts 8.sub.1 and 8.sub.2 which can mutually slide, with a gap 17 between them. In the position illustrated in the upper part of FIG. 10, the gap 17 is opened and we obtain the driving of a constant air volume at low velocity. In the position illustrated in the lower part of FIG. 10, the two parts 8.sub.1 and 8.sub.2 of the pipe are entered and we obtain the driving of a constant volume of air at high velocity. If the bulb 1 is mounted inside the first pipe, concentric to an external pipe used as channel, we can obtain a high flow ventilation under low pressure.

The device according to the invention can work with a high versatility when the dimensions of the driving slits are made to vary as illustrated as example in FIG. 11. We see there a bulb 1 rotatably mounted by any appropriate means already known inside a cylinder 21 with curved surface, in order to form at the vicinity of the bulb 1 an essentially cylindrical channel. The slit 6 is then of such a shape that its free depth is constant for the different slopes of the bulb 1 in relation with the axis. We can also fit the cylinder pipe with any known device likely to modify its diameter.

A numerical example of the tandem arrangement according to the FIG. 7 has been subjected to different tests. We have used a ventilation apparatus where the bulb 1' had a slit 6 of a 26 mm. diameter, a main cross section 3' of a 48 mm. diameter and a length of 160 mm. The internal diameter of the pipe 5' was 100 mm., its length 310 mm. The diameter of the slit 6' was 130 mm. The bulb 1" had a main cross section 3" of a 176 mm. diameter. Its length was 420 mm. The pipe 8 had an internal diameter of 410 mm. and a length of 1,000 mm. The performances obtained have been plotted on the graph (FIG. 12) for an opening of the slit 6' of 0.125 mm. and for an opening of the slit 6" of 10 mm. The pressures in bars have been plotted horizontally, and the flow in liters per second vertically rightwards for the primary flow in liters and leftwards for the total flow. The solid-line curve indicates the total flow in liters per second; the primary flow in liters per second is indicated by the dashed lines, and the curve in mixed lines indicates the ratio "total flow/primary flow."

FIG. 13 shows a bulb 1 of the type described into the main patent, with an axial pipe 2 for the fuel fluid supply, this pipe 2 opening into a slit 3 on the wide upstream portion 4 of the bulb 1. The bulb 1 is located coaxially with the internal part of the venturi 5, with a converging short section 6 and a long diverging section 7, connected through the throat 8 essentially at the same level as the slit 3. Finally, the whole venturi 5 and bulb 1 is located coaxially inside a cylindrical envelop 9 which extends from the level of the throat 8 to the downstream side of the end of the diverging part 7. A grid 10 is mounted perpendicularly to the axis of the whole, at the downstream end of the envelop 9. The above-mentioned device is mounted for example on supports 11, into an environment 12 of oxydizer such as air.

The operation of the device is as follows: the fuel gas, for example propane or butane, is driven under the desired pressure through the pipe 2, wherefrom it comes off the slit 3 along the wide upstream portion 4 of the bulb 1; the fluid drives air from the environment 12 into the annular channel 13 accommodated between the venturi 5 (converging part 6, throat 8), the bulb 1 and the diverging part 7. A first mixture of fuel fluid and oxydizing air is thus formed into the space inside the diverging part. At the outlet of the diverging part 7, ambient air is added to this premixture which it receives from the annular channel 14 included between the envelop 9 and the external part of the diverging portion 7. The final mixture is then driven to the grid 10 where it can be inflamed for any proposed application.

In the embodiment according to FIG. 14, the device comprises a bulb unit 11', disposed in line along the inlet axes of the primary and secondary fluids, inside of the piping 8 for the driven air (secondary fluid) and in prolongation to the intake pipe 5 of primary fluid (driving air). The unit is here formed with element 111.sub.1, 111.sub.2 and 111.sub.3, which provide maximal diameters 103.sub.1, 103.sub.2, 103.sub.3 decreasing from upward to downward and which are connected from the one to the other by a thinner portion 104.sub.1, 104.sub.2, 104.sub.3 ; on the upward front of each element there is provided a slit, respectively 106.sub.1, 106.sub.2, 106.sub.3. The pipe 5 for the primary air must be located on the front of the first element 111.sub.1 ; the primary fluid passes through the slit 106.sub.1 and drives therewith secondary fluid (driven air) tangentially to the outer profile of element 111.sub.1, wherefrom its issues being added with a supplemental quantity of secondary fluid, and is in turn driven tangentially into the slit 106.sub.2 of the second element 111.sub.2, to come then into the slit 106.sub.3 of element 111.sub.3 and so on.

If the device works as a burner, we have observed the remarkable fact as follows: under the conditions of the device according to the invention, it is always obtained a complete automaticity of the adjustment of the oxydizing air in relation with the gas, with any gas, volume or pressure whatsoever, i.e., the invention allows here to be in any case under the optimum conditions of mixture combustion, as the thermal flow can be adjusted by only acting on the pressure of the primary gas (fuel) by maintaining a practically optimum carbureted mixture. This is of course of great practical interest, namely in view of the quality of the heating and of the safety, which are automatically ensured.

Claims

What I claim is:

1. Device for driving a secondary fluid by a primary fluid comprising a first intake pipe for the primary fluid and a second intake pipe for the secondary fluid which is coaxial to the first pipe, at least one symmetrical bulb lodged coaxially into the second pipe with its maximum diameter disposed on the upward side of the intake pipes, the downward end of said bulb being truncated, said first pipe entering axially into the upward front portion of said bulb and extending into a channel opening tangentially through the outer wall of said upward front portion of said bulb, a gap between the downward end of said first pipe and the upward portion of said bulb, said gap being so arranged that the primary fluid flowing therethrough circulates in a substantially tangential flow along the outer profile of the bulb from upward to downward.

2. Device for driving a secondary fluid by a primary fluid comprising a first intake pipe for the primary fluid and second intake pipe for the second fluid, both pipes being coaxial, a bulb unit disposed coaxially within said pipes, said unit comprising at least two bulbs with the maximum diameter disposed on the upward side of the intake pipes and decreasing from the upward bulb to the downward bulb, a curved connection between the downward end of the upward bulb and the upward front end of the next downward bulb, the downward end of said downward bulb being truncated, a slit between the downward end of the first intake pipe and the upward front portion of the upward bulb, whereby the primary fluid issues from the slit in a path substantially tangential to the outer profile of the upward bulb from upward to downward and follows then the connection and the profile of the downward bulb.

3. In a device as claimed in claim 2, means to provide a slit around the slightest diameter of the connection between two successive bulbs and the upward front portions of the following bulb.