EP0915292A1 - Universal device for mixing two gaseous fluids - Google Patents

Abstract

The gas mixer has two concentric chambers each with a nozzle supplying a gas at medium pressure. The two nozzles contain valves which are actuated together so gas mixes in a downstream chamber in proportions defined by the dimensions of the nozzles. The air-gas supplier for multiple burners in industrial units, preferably supplying a mixture with a set calorific power. Universal mixing device for two gases, with chamber (110) containing first and second concentric chambers (111,121). A first pipe opens into the first chamber, supplying it with the first gas at medium pressure, and a second pipe opens into the second chamber to supply the second gas at medium pressure. A first sonic nozzle of variable throat is mounted in the first chamber and a second similar nozzle in the second chamber. Each nozzle has a hollow element of convergent-divergent revolution acting as the seat for a valve. The first valve forms an axial boring at least partly defining the first and second chambers. The second nozzle is in this boring and the two elements of revolution are placed relative to the chamber so the two valves can be mechanically linked to a single operator to ensure a synchronized displacement. The two homothetic gases from the two coaxial nozzles open into the same downstream chamber where they mix in a ratio defined by the dimensions of the nozzles. A third chamber connected to the first by orifices and a third nozzle with a third valve which acts in the opposite way to the first two allows the surplus of the first gas to be cleared from the chamber. The first gas is air and the second is a fuel such as propane and/or butane. The gases are introduced at a pressure of 1.3 bar, or with the first gas at 150 millibar and the second at 1.3 bar.

Description

The present invention relates to a universal mixing device for two gaseous fluids and its application to various types of supply installations in mixtures of air and combustible gas.

It is often necessary to mix two different gases.

In particular, the use of combustible gases such as natural gas or liquefied petroleum gas (LPG) goes through processes of mixing with air. The mixtures are generally made at pressures close to the pressure atmospheric.

For these applications, fuel gas, which is often available under medium pressure, is relaxed to a few millibar to be brought into contact with the oxidizing gas which is most often atmospheric air.

The many mixing devices currently used have the following default their range of use which remains narrow to maintain the best operating conditions on the chosen domain. So when it comes to burners or carburetors, combustion is rarely maintained stoichiometric over the entire range of use of the installation. Likewise, in the in the case of air / LPG generators, the calorific value of the distributed gas is affected by the imprecision of mixing devices whose dynamics hardly exceed 10 with current systems.

• les systèmes à action discrète pour lesquels le mélange air/gaz est préréglé à partir d'orifices dont la section de passage et la pression d'alimentation sont pré-définies de façon à obtenir la combustion recherchée, dans le cas d'un brûleur, ou un pouvoir calorifique supérieur (PCS) constant, dans le cas d'un générateur air/GPL. Ces dispositifs sont les plus utilisés notamment pour les brûleurs de chaudières de forte et moyenne puissance qui disposent de systèmes pré-réglés à une, deux ou trois allures ;
• les systèmes modulants dans lesquels le mélange air/gaz est maintenu constant par l'action conjointe de deux vannes à ouverture synchronisée, l'une sur le gaz, l'autre sur le registre d'air. Ces systèmes sont également pré-réglés, au moyen de dispositifs mécaniques à came, qui permettent d'ajuster pour chaque position de vanne le mélange désiré. On trouvera le même principe avec des générateurs air/GPL ;
• les systèmes modulants gérés par automates et calculateur lesquels, à partir d'une ou plusieurs informations (analyse de fumées, température d'un procédé, débit des gaz, etc.) agissent sur les vannes d'admission de gaz et d'air.

Among these existing mixing devices, a distinction will be made:

• discrete-action systems for which the air / gas mixture is preset from orifices whose passage cross-section and the supply pressure are pre-defined so as to obtain the desired combustion, in the case of a burner, or a constant higher calorific value (PCS), in the case of an air / LPG generator. These devices are the most used in particular for burners of high and medium power boilers which have pre-adjusted systems with one, two or three stages;
• modulating systems in which the air / gas mixture is kept constant by the joint action of two synchronized opening valves, one on the gas, the other on the air damper. These systems are also pre-adjusted, by means of mechanical cam devices, which allow the desired mixture to be adjusted for each valve position. The same principle will be found with air / LPG generators;
• modulating systems managed by automata and calculators which, on the basis of one or more pieces of information (smoke analysis, process temperature, gas flow, etc.) act on the gas and air intake valves.

With regard to the air / LPG mixture generators, for example the air / propane mixers, we currently know two different techniques. The first, called high or medium pressure, uses compressed air and LPG to a pressure of a few bar, and allows to deliver fairly high powers. The second, called low pressure, uses atmospheric air and LPG under pressure of a few bars.

Mixers intended for medium pressure distribution networks (for example 2 bar) use compressed air and LPG at a pressure generally between 4 and 10 bar. Such known mixers include a first line for compressed air and a second line for LPG.

These two lines meet in a nurse where the mixing takes place before being dispensed under a pressure ranging from a few millibar to 1 or 2 bar. The pressure limitation is linked to the risk of condensation of LPG, when the climatic conditions of the distribution site reach temperatures too low.

The mixing ratio is obtained by means of pneumatic valves proportional. Each line is fitted with a control valve, the piloting is ensured by a pneumatic device which causes a reaction simultaneous of the two valves, whose sections and opening laws have been previously defined. Recent systems use enslavements which, all keeping the previous architecture, can significantly improve the performance of this type of mixer in terms of accuracy on the PCS and dynamic. These servos use instant debit information delivered by turbine meters placed on each line, and those of a Wobbmeter which reacts to the report setpoint. An automaton associated with a calculator manages the various parameters.

• inadaptation aux régimes variant rapidement en raison d'un temps de réponse relativement long dû aux deux vannes à gérer ;
• installations gourmandes en énergie (nécessité d'un compresseur pour l'air, réchauffage des deux fluides afin d'éviter les phénomènes de recondensation) ;
• installations complexes, et de ce fait très coûteuses, nécessitant une main d'oeuvre spécialisée pour la maintenance et la mise au point.

These different systems have the following shortcomings in common: weak flow dynamics for which the PCS is stable, since this depends, in most cases, on that of the meter which rarely exceeds 20; pressure regulation difficult to stabilize, especially at low pressure, because the piloting must permanently manage the precise position of the two valves (on air and on LPG);

• unsuitability for rapidly varying regimes due to a relatively long response time due to the two valves to be managed;
• energy-hungry installations (need for a compressor for the air, heating of the two fluids in order to avoid recondensation phenomena);
• complex installations, and therefore very expensive, requiring specialized manpower for maintenance and development.

Air / LPG generators for low pressure applications generally use a battery of venturi nozzles whose unit flow allows arithmetic progression (for example: 10-20-40-80 m ³ / h) the combination of the different nozzles making it possible to achieve a regulation by discrete action. The mixture is obtained by suction of atmospheric air, by the induction effect of the jet of LPG which entrains the air in the nozzle. The operation in all or nothing mode of the different nozzles requires the use of buffer gasometers in order to "smooth" the resulting pressure in the network.

The advantage of this type of generator lies in the fact that it is autonomous in energy because it works using only LPG pressure.

The disadvantages are linked to the need to have a gasometer, for example bulky and expensive nature, to perform pressure regulation which is, for principle, unstable due to the cyclic operation of the nozzles. Finally the precision obtained on the "Higher Calorific Power" (PCS) is low because this type of installation generally includes nozzles which are adjusted once and for all, without the use of correction devices pressure and temperature.

The present invention aims to remedy the drawbacks of the prior art and to allow to ensure in a convenient, simple and reliable way, with dynamics of important operation, the mixture of two gaseous fluids.

These aims are achieved, in accordance with the invention, thanks to a device for universal mixture of two gaseous fluids, characterized in that it comprises an enclosure defining first and second concentric chambers, a first conduit opening into the first chamber to supply the latter with a first medium pressure gas, a second conduit opening into the second chamber to supply the latter with a second medium gas pressure, a first sonic nozzle with a neck of variable section arranged in the first chamber and a second sonic nozzle with a variable section neck arranged in the second chamber, in that the first sonic nozzle comprises a first hollow element of convergent-divergent revolution serving as a seat for a first arched valve and the second sonic nozzle includes a second hollow element of convergent-divergent revolution serving as a seat for a second wedge-shaped valve, in that the first valve defines a bore axial and at least partially delimits the first and second chambers, in that that the second sonic nozzle is disposed inside said axial bore, in that that the first and second hollow elements of revolution converge-diverge have a determined position relative to the enclosure while the first and second valves are mechanically linked to each other and associated with an actuator single ensuring synchronized movement of the first and second valves and in what the first and second gas having passed through the first and second coaxial and homothetic sonic nozzles open axially in the same downstream chamber where the first and second gases are mixed according to a ratio of predetermined mixture conditioned by the dimensions of the first and second sonic nozzles.

Each of the first and second gases is introduced respectively into the first and second chamber at a pressure equal to or greater than 1.3 bar.

Insofar as the first and second nozzles have valves, which are mechanically linked, and have precise and synchronized movements from a single actuator, a continuous variation of the air flows is generated and gas, the ratio of which is kept constant over the entire operating range thanks to the perfect homothety of the nozzles. The operating dynamics can for example, be of the order of 50: 1.

According to a particular embodiment, the universal mixing device of two fluids further comprises a third chamber communicating by ports with the first chamber and a third section neck sonic nozzle variable arranged in the third bedroom; the third sonic nozzle includes a third hollow element of convergent-divergent revolution identical to said first hollow element of revolution but arranged in alignment axially opposite to it in a determined position with respect to the enclosure and serving as a seat for a third valve in the shape of a warhead whose shape and the dimensions are identical to those of the first valve; the third valve is mechanically linked to the first and second valves but is placed in opposition relative to these, so that the third sonic nozzle works from antagonistic to the first sonic nozzle and that the third sonic nozzle is in the open position when the first sonic nozzle is in closed position and vice versa, and that the third chamber includes orifices arranged downstream of the third sonic nozzle so that the surplus of the first gas from the third sonic nozzle can be discharged from the enclosure.

The first gas is introduced into the first chamber at a pressure greater than or equal to 150 millibar and the second gas is introduced into the second chamber at a pressure greater than or equal to 1.3 bar.

Advantageously, each of the sonic nozzles is produced so modular and includes a removable valve allowing to modify, by the modification of the taper of the valve the capacity or the mixing ratio of the mixing device. The fixed part of the sonic nozzles can itself be also made so as to be removable.

The presence of a third antagonistic nozzle at the first nozzle, and of identical functional characteristics to this, ensures regulation automatic pressure of the first gas, whatever the positions of the mixer, and allows to operate on gases whose pressures are relatively low (a few tens of millibar to a few hundred millibar).

• la figure 1 est une vue en coupe axiale d'un premier exemple de dispositif de mélange de gaz selon l'invention, à deux tuyères soniques,
• la figure 2 est une vue en coupe axiale d'un deuxième exemple de dispositif de mélange de gaz selon l'invention, à trois tuyères soniques,
• la figure 3 est une vue schématique d'un exemple d'installation d'un mélangeur selon l'invention, et
• la figure 4 est une vue en coupe axiale d'une variante du deuxième mode de réalisation à trois tuyères soniques.

Other characteristics and advantages of the invention, as well as different applications of the universal mixing device according to the invention will emerge from the following description of particular embodiments, given by way of examples, with reference to the appended drawings, in which :

• FIG. 1 is a view in axial section of a first example of a gas mixing device according to the invention, with two sonic nozzles,
• FIG. 2 is a view in axial section of a second example of a gas mixing device according to the invention, with three sonic nozzles,
• FIG. 3 is a schematic view of an example of installation of a mixer according to the invention, and
• Figure 4 is an axial sectional view of a variant of the second embodiment with three sonic nozzles.

In the example of Figure 1, which is applied to the mixture of air and a gas fuel, the mixing device 100 comprises a cylindrical enclosure 110 to the interior of which two concentric coaxial chambers 111 are defined, 121. A lateral combustion air supply duct 112 opens into the outer chamber 111 while a lateral gas supply conduit 122 fuel flows into the interior chamber 121.

A first sonic nozzle 130 with a neck of variable section is arranged in the first chamber 111, downstream of a perforated plate 113 used to straighten the air flow introduced through the duct 112 into the chamber 111. The nozzle 130 comprises a hollow convergent-divergent element of revolution 131 which serves as a seat for a valve 132 in the shape of a warhead.

A second sonic nozzle 140 with a neck of variable section is disposed at inside the valve 132 of the first nozzle 130. The nozzle 140 comprises a hollow convergent-divergent element of revolution 141 which is integral with the enclosure 110 by means of a flange 116 and is placed in a bore of the valve 132 and in contact via a seal with this bore so as to allow the valve 132 to slide relative to the hollow element 131 and so watertight with respect to the hollow element 141. The hollow element 141 serves as a seat for a check valve 142 in the form of a warhead whose upstream end 144 is threaded so as to be able to be made selectively integral with a thread formed in the valve 132. The valves 132 and 142 are thus joined together and connected to the downstream end of an axial rod control 145 itself connected by a coupling mechanism 146 with an actuator 150, which can be of pneumatic, electric or hydraulic.

The disassembly of the valves 132 and 142 in the shape of a warhead makes the device modular. Thus, by simply replacing the valves 132, 142 with valves in the form of warheads of different conicity, it is possible to modify the capacity or the ratio of the mixing device. The fixed hollow element 131, which is screwed into the tubular enclosure 110 can also be replaced easily.

The upstream portion 133 of the valve 132 is in the form of a hollow cylinder and is engaged so that it can slide axially tightly in the bore a cylinder 123 which constitutes a boundary wall between the central chamber 121 for fuel gas supply and the outer annular chamber 111 combustion air supply. The fuel gas introduced through the radial duct 122 in the chamber 121 can enter the hollow upstream part 133 of the valve 132 and reach the convergent-divergent space of the nozzle 140 through passages 143 provided in the valve 132.

The enclosure 110 of the mixing device may have the form of a cuff with an outer cylindrical wall 114 and planar walls transverse end 115, 116 forming flanges. The downstream end wall 116, which is used in particular to support the fixed but removable part 141 of the nozzle 140, can be connected to the upstream flange 161 of an element defining a mixing and receiving on the one hand the flow of fuel gas from the divergent space of the internal sonic nozzle 140 and on the other hand the air flow coming from the divergent space annular of the external sonic nozzle 130. The internal wall of the downstream mixture 160 can be fitted with a sound absorbing material 163. This material 163, as well as material 162 inserted between the flange elements 116, 161 of the enclosure 110 and of the downstream mixing chamber 160, constitute a silent device at the outlet of the two concentric nozzles 130, 140, which silent system reduces acoustic emissions linked to relaxation and promotes mixing the mixture.

Note that in the prior art, sonic nozzles with section neck are generally used on a gas supply line to ensure triple the gas expansion function, gas flow measurement and regulation of the gas flow or the calorific power conveyed by a fuel gas.

Examples of flow control and measuring devices sonic nozzles with variable necks are given for example in documents FR-A-2341131, FR-A-2514163, FR-A-2580803 and FR-A-2630184. The sonic nozzle technology described in the above documents is applicable to the mixing device according to the invention. In the prior art, in the case using concentric nozzles as in document FR-A-2 514 163, a single gas supplies the two nozzles. The central auxiliary nozzle is used simply to receive a small bypass flow from the main gas stream to regulate and the auxiliary nozzle opens into a separate pipe leading to a counter. If the architecture presented in document FR-A-2 514 163 did not not in the role of ensuring a mixture between gases of different natures, it it is however possible, within the framework of the present invention, to use the technology for manufacturing sonic nozzles known in particular by aforementioned documents.

The device of FIG. 1 is not limited to the production of air-gas mixtures combustible, and can be applied to various pairs of gaseous fluids. However, interesting applications exist when the first gas introduced in the duct 112 is air and the second gas introduced in the duct 122 is a combustible gas such as natural gas or a petroleum gas, such as propane, butane or a mixture of propane and butane.

To obtain sonic flow conditions at the throat of the nozzles 130, 140, it is necessary that the air and the gas introduced into the conduits 112, 122 have a minimum pressure of 1.3 bar absolute.

The fuel gases are generally distributed between 1.3 and 4 bar for the natural gas and between 2 and 7 bar for LPG. In this case, it is not necessary to insert a booster between the fuel gas source and the gas inlet 122. In however, a source of compressed air at medium pressure is not always available. In the case where atmospheric air is applied via a fan whose discharge pressure is for example between 20 and 50mbar, a booster must be inserted between the fan and the air inlet 112, or implement a mixing device with three nozzles such as that which will be described later with reference to Figure 2.

The nozzles 130, 140 have dimensions and shapes (in particular taper angle of valves 132, 142 and converging-diverging fixed parts 131, 141) which are defined beforehand to obtain an opening report which corresponds, in a first approach, to the desired mixing ratio. So at For example, in the case of an application to a propane air generator, the mixing ratio can be 30% LPG for 70% air. This report is determined taking into account the supply pressure conditions and the maximum power desired.

From the initial conditions pre-defined by the geometry of the nozzles, and which can be easily adapted or modified, taking into account the design the sonic nozzles, the displacement of the two valves 132, 142 of the nozzles 130, 140 by the actuator 150 generates a continuous variation of the flow rates air and gas, the ratio of which is kept constant over the entire range of operation thanks to the perfect homothety of the two nozzles 130, 140. It is possible thus obtain operating dynamics far superior to systems known, for example 50: 1.

The gas mixing device according to the invention, as described with reference in Figure 1, can be used for different applications.

According to a particular application, the mixer according to the invention can be integrated in a fuel air-gas mixture installation industrial process such as a multi-burner heat treatment oven.

In some heat treatment furnaces, several burners are distributed spatially inside the oven. If these different burners are supplied from a conventional air-gas mixer, when the air changes the flow of one or more oven burners, the initial power, and therefore the quality of the mixture are affected.

On the contrary, thanks to the present invention, it is possible to set up operates an air-gas mixer with sonic nozzles with which any modification of the one or more furnace burners operates an automatic flow transfer, added or subtracted, to unmodified burners, and keeps the overall power of the oven and the quality of the mixture.

Figure 3 shows an example of installation incorporating a mixer according to the invention and which can be used, for example, to supply an air-gas mixture to a industrial process such as a set of burners from the same oven, the different burners that can be adjusted to produce flames of shaped and very varied characteristics without affecting the quality of the air-gas mixture applied to different burners.

In the installation of Figure 3, we see a line 11 of air supply compressed and a line 21 for supplying fuel gas at a medium pressure greater than 1.3 bar.

On the air supply line 11, a fan 12 is associated with a low pressure switch 13, a pressure regulator 14 and organs 15 of pressure and temperature measurement. The regulated air flow is applied to the mixer 100, on the inlet 112 for introducing the first gaseous fluid (FIG. 1).

On line 21 for supplying medium pressure fuel gas, there are successively a quarter turn valve 22, a filter 23, a set safety solenoid valves 24, 25, a pressure regulator 26 and members 27 of pressure and temperature measurement. The regulated gas flow is applied to the mixer 100, at the inlet 122 for introducing the second gaseous fluid (FIG. 1).

The outlet of the mixer 100 is fitted with a high pressure switch 9 and a safety solenoid valve 8.

The air-gas mixture is available on a line 31, to be applied to the process to be fed such as a set of burners. A module 7 allows the control of the position of the valves 132, 142 of the sonic nozzles 130, 140 of the mixer 100. The module 7 can in particular be equipped with a position sensor valves 132, 142.

The pressure regulators 14, 26 regulate the supply pressures of the 100 air and gas mixer, at desired values to obtain the mixture required. A PID (proportional-integral-derivative) regulator that can be classic is integrated in module 7 to adjust the position of the valves 132, 142 from mixer 100 to the power required for the process.

The addition of a command on one or other of the pressure regulators 14, 26 or both at the same time allows, by simply modifying the pressure initially set for medium pressure air supply or the gas supply at medium pressure, to change the aeration rate of the flame, in the case where reducing or oxidizing atmospheres are required, and this without modifying the position of the valves in the form of warheads 132, 142 of the mixer 100.

It can also be noted that the use of nozzles 132, 142 with a neck of variable section, operating in sonic regime, provides the output of these, in the downstream mixing chamber 160, of diffusers with high loss of filler, the shapes of which provide turbulence and homogeneity of the mixture. This is carried out without affecting the flow rates and power of the installation.

The mixing device of Figure 1 can also be used in the context an air / LPG generator, which produces a mixture of air and petroleum gases (butane, propane or mixture of butane and propane) in very precise proportions, in order to obtain a gas whose calorific value is predetermined at a value constant and can serve as a substitute gas for natural gas. For example, a mixing approximately 55% propane with 45% air to combustion characteristics very similar to those of natural gas for a wide range variety of combustion equipment.

Insofar as compressed air is available at a pressure greater than approximately 3 bar, the mixer 100 of FIG. 1 can be used, for example example with additional elements such as those shown in the figure 3, to receive on the one hand compressed air on line 11 and on the other hand petroleum on line 21, and supply on line 31 an air / LPG mixture of predetermined characteristics, with a pressure which can be for example of 2 bar, or lower. The mixing ratio and the capacity of the installation are previously defined a priori, by the dimensions of the variable nozzles 130, 140, and the supply pressure available on lines 11 of air and 21 of LPG.

Downstream pressure regulation is carried out using the control module 7 which acts on the position of the valves 132, 142 in the shape of a nozzle cone of mixer 100.

The control module 7 can include a totally servo-controlled pneumatic, the two valves 132, 142 being made integral with a servomotor direct or pilot action type, depending on the precision or speed sought on the regulated pressure.

As a variant, the control module 7 can also include other types of regulation which combine PID type regulators and electric actuators, such as stepper motors or electro-pneumatic actuators.

A mixer 100 according to the invention can also be incorporated into a air / LPG generator intended for low pressure applications, where no has no source of compressed air at a pressure higher than 1.3 bar. In this case, the mixer 100 has the configuration shown in FIG. 2 and includes an additional nozzle 170.

In Figure 2, all elements similar to those in Figure 1 bear the same references and will not be described again. In particular, the conduits inlet 112, 122, the concentric chambers 111, 121 and the nozzles 130, 140 can be carried out similarly in the case of the embodiments of the Figures 1 and 2.

In the embodiment of Figure 2, we see that the enclosure 110 is extends beyond the radial wall 115, by an enclosure portion 117, by example in the form of a cuff connected to the radial wall 115, which portion of enclosure 117 defines a third chamber 181 which communicates, through orifices 182 formed in the radial wall 115, with the first chamber 111. The nozzle additional sonic 170 with variable section neck is arranged in the chamber 181 and comprises a hollow convergent-divergent element of revolution 171, the geometric and dimensional characteristics are identical to those of the hollow element 131 of the nozzle 130, but which is arranged in axial alignment with opposite to the hollow element 131, in a determined position relative to the enclosure portion 117 extending the enclosure 110. The hollow element 171 serves as a seat a check valve 172 in the form of an ogive whose shape and dimensions are identical to those of the first valve 132.

The valve 172 is mechanically linked to the valves 132, 142 by the stem of control 145, but is placed in opposition to the valves 132, 142 of so that the sonic nozzle 170 operates in an antagonistic manner with respect to to the first sonic nozzle 130 and that the nozzle 170 is in the open position when the nozzle 130 is in the closed position (as shown in the figure 2) and vice versa.

A flange-shaped end piece 174 is arranged radially by relative to the cylindrical wall of the enclosure portion 117, on the side opposite the wall 115, downstream of the nozzle 170 and comprises orifices 175 so that the surplus air from the nozzle 170 can be evacuated outside the enclosure 110, 117.

The control rod 145 which provides the mechanical connection of the valves 172 and 132, 142, is extended by an additional rod 173, which passes through the valve 172 by being integral with it and also crosses in leaktight and sliding manner the end piece 174 to be connected to an actuator, not shown in FIG. 2, but which can be analogous to the actuator 150 of FIG. 1, and an example of which is shown in figure 4.

The implementation of a third nozzle 170 acting in an antagonistic manner relative to the first nozzle 130 makes it possible to use the mixer 100 according to the invention, in its configuration of FIG. 2, and with the elements complementary represented on figure 3, to constitute a generator / LPG in the context of a low pressure application, and in the event that a high pressure compressed air source is not available. In this case, it is sufficient that the centrifugal fan 12 placed on the air line 11 uses a minimum pressure of 150 mbar which constitutes the lower limit for obtaining a sonic flow. It is naturally possible to provide a fan supplying air under a higher pressure, for example 300 mbar, but this increases consumption in electrical energy necessary for the operation of the fan.

In a mixer 100 with three nozzles 130, 140, 170 whose valves in ogive shape 132, 142, 172 are integral and synchronized in their movements, the constant flow of air supplied by the fan 12 passes either to the mixture 160, either towards the outlet to atmosphere 175, or finally, and this is the most frequent, towards these two destinations at the same time when the valves 132, 172 of the nozzles 130, 170 of identical dimensions and placed in opposition are in position intermediate.

The petroleum gas supply pressure at the inlet pipe 122 may be of the order of a few hundred millibar.

The control module 7 includes a valve position sensor 132, 142, 172 of variable sonic nozzles 130, 140, 170. As already indicated in with reference to FIG. 3, means 15, 27 for measuring the temperature and the fluid pressure are provided upstream of the chambers 111, 121, means 9 for pressure measurement of the mixture of air and petroleum gas are provided downstream of the mixer 100 and regulating means act on the pressure regulator 26 from the gas supply source or on a valve positioning device 132, 142, 172 of the nozzles 130, 140, 170 to maintain a downstream pressure predetermined mixture of air and calorific value gas (PCS) predetermined.

Downstream pressure regulation can be done using circuits enslavement in a manner analogous to what has been described with reference to a air / LPG generator using a mixer with two nozzles 130, 140.

A particular advantage, which results from the use of three nozzles 130, 140, 170 including two concentric nozzles 130, 140 resides in the fact that the air produced by fan 12 undergoes heating which is directly recoverable to promote the evaporation of LPG and avoid the condensation phenomena that we meet with conventional systems, and which leads to the implementation of heaters on both fluids to overcome this drawback. The disposition coaxial nozzles 130, 140 indeed promotes temperature exchanges between air and LPG. In addition, the permanent evacuation of the air supplied by the fan 12 through one or the other of the opposing nozzles 130, 170 allows the temperature upstream of the air nozzle 130 to remain stable over time.

With the embodiment of Figure 2, it is possible, as in that in Figure 1, to have a silencer forming device 163 at the outlet of nozzles 130, 140, in the mixing chamber 160. The nozzle 170 through which air escapes to the atmosphere can also be fitted with a muffler 179 which reduces nuisance in the room where the air / LPG generator is installed (see figure 4).

A mixer 100 of gaseous fluids with three nozzles 130, 140, 170, such as that shown in Figure 2, and can cooperate with external elements such as those shown in Figure 3, can still be implemented in the other installations, such as a power supply installation air-gas mixture of a supply air boiler burner.

This type of burner is generally used in boilers producing water hot for central heating with powers of a few tens of kW at several thousand kW.

Boilers use network gas (natural gas) delivered at a pressure on the order of a few hundred millibar, for example 300 mbar, and supplied air by a fan at a pressure of a few tens of bars. These boilers operate in all or nothing or all or little mode, from fixed settings (small pace, great pace).

In this case, a mixer with three nozzles 130, 140, 170, such as that shown in Figure 2 can be used advantageously, air being introduced by the conduit 112 and the network gas being introduced by the conduit 122.

The sum of the air flow rates of the first and third sonic nozzles 130, 170 antagonists is equal to the constant flow of the fan which corresponds to the flow at full opening of only one of the first and third sonic nozzles 130, 170, where it follows that for a given power of a nominal flow of the source gas supply, there is an automatic regulation of the air pressure.

For a given power of blower or nominal flow, we obtain with the provision of two opposing nozzles automatic regulation of the air pressure equal to the constant value sought, and this for all positions valves 132, 142, 172 of the mixer 100. Furthermore, taking into account permanent evacuation of pressurized air supplied by the ventilator to duct 112, the temperature upstream of the air nozzle remains stable over time.

Thanks to the stability of the air regulation, it is possible with this system of implement a modulating power regulation which adapts perfectly and gradually on demand. On the contrary, in classical systems, this regulation takes place in all or little or all or nothing mode which has the effect of inducing some malfunctions in the detent / metering station of the dispenser (overpressure on closing, overcounting of certain types of meters particularly sensitive to cyclic variations in flow, etc.).

FIG. 4 represents an alternative embodiment of the device for mixing gas previously described with reference to Figure 2.

The variant of FIG. 4 is entirely modular. So the fixed parts 131, 171 of the nozzles 130, 170 are not formed in one piece with the enclosure 110 as according to the drawing in FIG. 2, but consist of pieces of separate revolution which are removable and come to position inside the tubular enclosure 110 thanks to threaded parts. Such a mounting type of the fixed part 131 of the nozzle 130 has moreover already been shown in FIG. 1 for the embodiment with two concentric nozzles.

We also see in Figure 4, in the downstream mixing chamber a transverse plate 164 provided with perforations 165 and supporting on its front face a plate 166 made of porous material. The assembly 164, 166, which is removable, in being sandwiched between the flanges 116, 161, acts as a rectifier which regulates the flow of the mixture avoiding the formation of a vortex while also providing a sound absorbing function helping to reduce noise generated by the expansion of the gas. The set 164, 166 could also be applied to the embodiment of Figure 1 if necessary.

Similarly, a cuff 177 attached to the flange 174 comprises an air outlet duct 178 to the atmosphere, which is equipped with a material sound absorber 179 advantageously defining a channel whose portion located near the exit is conical and widens towards the exit.

FIG. 4 also shows an example of an actuator 150 which incorporates a pneumatic type servo to act on an axial rod 176 connected to the additional rod 173.

The pneumatic type actuator 150 shown in FIG. 4 comprises at by way of example a downstream chamber 154 which is in communication by a nozzle 153 with a source of gaseous fluid under pressure and is delimited on the one hand by a fixed rigid transverse plate 155 and on the other hand by a flexible membrane 151 supported by a rigid plate integral with the axial rod 176 and against which acts a spring 152. The control of the actuator 150 can naturally be more complex or be of a different nature from that of a bondage pneumatic.

Claims (13)

Universal mixing device for two gaseous fluids, characterized in that it comprises an enclosure (110) defining first and second chambers (111, 121) concentric, a first conduit (112) opening into the first chamber (111) for supplying the latter with a first medium-pressure gas, a second conduit (122) opening into the second chamber (121) to supplying the latter with a second medium pressure gas, a first nozzle sonic (130) with variable section neck arranged in the first chamber (111) and a second sonic nozzle (140) with a neck of variable section arranged in the second chamber (121), in that the first sonic nozzle (130) comprises a first convergent-divergent hollow element of revolution (131) serving as a seat for a first valve (132) in the shape of a warhead and the second sonic nozzle (140) comprises a second hollow convergent-divergent element of revolution (141) serving as a seat for a second valve (142) in the form of a warhead, in that the first valve (132) defines an axial bore and at least partially delimits the first and second chambers (111, 121), in that the second sonic nozzle (140) is disposed inside said axial bore, in that the first and second hollow elements of convergent-divergent revolution (131, 141) have a determined position relative to the enclosure (110) while the first and second valves (132, 142) are mechanically linked to each other and associated with a single actuator (150) ensuring synchronized movement of the first and second valves (132, 142), and in that the first and the second gas having passed through the first and second coaxial sonic nozzles (130, 140) and homothetics open axially in the same downstream chamber (160) where the first and second gases are mixed according to a mixing ratio predetermined conditioned by the dimensions of the first and second nozzles sonic (130, 140). Device according to claim 1, characterized in that it further comprises inside the enclosure (110) a third chamber (181) communicating by orifices (182) with the first chamber (111), a third sonic nozzle (170) to neck of variable section arranged in the third chamber (181), in that the third sonic nozzle (170) includes a third hollow element of revolution convergent-divergent (171) identical to said first hollow element of revolution (131), but disposed in axial alignment opposite to it in a determined position relative to the enclosure (110) and serving as a seat for a third valve (172) in the form of a warhead whose shape and dimensions are identical to those of the first valve (132), in that the third valve (172) is linked mechanically to the first and second valves (132, 142), but is placed in opposing them, so that the third sonic nozzle (170) operates in an antagonistic manner with respect to the first sonic nozzle (130) and the third sonic nozzle (170) is in the open position when the first sonic nozzle (130) is in the closed position and vice versa, and in that the third chamber (181) comprises orifices (175) arranged downstream of the third sonic nozzle (170) so that the surplus of the first gas from the third sonic nozzle (170) can be evacuated from the enclosure (110). Device according to claim 1 or 2, characterized in that it comprises in addition to a flow rectifier (113) arranged in the first chamber (111) in upstream of the first sonic nozzle (130). Device according to any one of Claims 1 to 3, characterized in that that it further comprises an element (163, 166) of sound absorbing material disposed in the downstream mixing chamber (160). Device according to any one of Claims 1 to 4, characterized in that that the first gas is made up of air and the second gas is made up of a combustible gas such as natural gas or petroleum gas such as propane, butane or a mixture of propane and butane. Device according to claims 1 and 5, characterized in that the first gas is introduced into the first chamber (111) at a higher or equal pressure at 1.3 bar and the second gas is introduced into the second chamber (121) at a pressure greater than or equal to 1.3 bar. Device according to claims 2 and 5, characterized in that the first gas is introduced into the first chamber (111) at a higher or equal pressure at 150 millibar and the second gas is introduced into the second chamber at one pressure greater than or equal to 1.3 bar. Device according to any one of Claims 1 to 7, characterized in that that each of the sonic nozzles (130, 140, 170) is produced in a modular fashion and includes a removable valve (132, 142, 172) for modifying, by modification of the taper of the valve (132, 142, 172), the capacity or the ratio of mixing of the mixing device. Installation for supplying air-gas mixture to an industrial process such that a set of heat treatment furnaces with multiple burners, characterized in what it includes a medium pressure air supply source comprising a fan (12) and a pressure regulator (14); a source fuel gas supply line comprising a gas supply line to medium pressure on which a filter (23) is arranged, at least one safety solenoid valve (24, 25) and a pressure regulator (26); a device (100) of universal mixture according to any one of claims 1 to 8, of which the first and second chambers (111, 121) are respectively connected to the air supply source and fuel gas supply source, and a safety solenoid valve (8) disposed at the outlet of the mixing device (100) universal. Installation according to claim 9, characterized in that it comprises at at least one control means acting on at least one of the regulators of pressure (14, 26) to change the aeration rate of the flame by simple change in pressure initially set for medium air supply pressure or medium pressure gas supply. Air-gas mixture supply installation of an air boiler burner soufflé, characterized in that it comprises a universal mixing device (100) according to claim 2, a gas supply source at a pressure of the order of a few hundred millibar, which is connected to the second chamber (121) of the mixing device, a source of air supply at a pressure of the order of a few tens of millibar, which includes a fan (12) and is connected to the first chamber (111) of the mixing device, which first chamber (111) is itself in communication with the third chamber (181), so that the sum of the air flow rates of the first and third sonic nozzles (130, 170) antagonists is equal to the constant flow of the fan which corresponds to the flow at full opening of only one of the first and third sonic nozzles (130, 170), where it follows that for a given power of a nominal flow of the source gas supply, there is an automatic regulation of the air pressure. Generator of a mixture of air and petroleum gas whose power heat value (PCS) is predetermined at a constant value, characterized in that it comprises a universal mixing device (100) according to claim 1, a source of petroleum gas at a pressure of the order of a few bars, which is provided with a pressure regulator (26) and is connected to the second chamber (121) of the mixing device, a source of air supply at a pressure of the order of a few bars, which is provided with a pressure regulator (14) and is connected to the first chamber (111) of the mixing device (100), a sensor (7) of the position of the first and second valves (132, 142) of the first and second sonic nozzles (130, 140), means (15, 27) for measuring the temperature and the fluid pressure upstream of the first and second chambers (111, 121), means (9) for measuring the pressure of the mixture of air and petroleum gas downstream of the mixing device (100), and of regulation means acting on the pressure regulator (26) of the gas supply source or on a device for positioning of the first and second valves (132, 142) of the first and second nozzles (130, 140), for maintaining a predetermined downstream pressure of the mixture of air and gas of predetermined calorific value (PCS). Generator of a mixture of air and petroleum gas whose power heat value (PCS) is predetermined at a constant value, characterized in that it comprises a universal mixing device (100) according to claim 2, a source of petroleum gas at a pressure of the order of at least a few hundred millibar, which is fitted with a pressure regulator (26) and is connected to the second chamber (121) of the mixing device, a source supply air at a pressure of the order of at least 150 millibar, which is fitted with a pressure regulator (14) and is connected to the first chamber (111) of the mixing device (100), itself in communication with the third chamber (181) of the mixing device (100), a sensor (7) of the position of the first, second and third valves (132, 142, 172) of the first, second and third sonic nozzles (130, 140, 170), means (15, 27) for measuring the temperature and fluid pressure upstream of the first and second chambers (111, 121), means (9) for measuring the pressure of the air mixture and petroleum gas downstream of the mixing device (100), and means for regulation acting on the pressure regulator (26) of the supply source gas or on a first, second and third positioning device valves (132, 142, 172) of the first, second and third nozzles (130, 140, 170) to maintain a predetermined downstream pressure of the air and gas mixture predetermined calorific value (PCS).

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