FLUIDS MIXING DEVICE AND METHOD FOR MIXING FLUIDS THEREOF

Abstract: Fluids mixing device, of the type apt to inject a first fluid, coming at a first pressure from a supply source (9), in a gaseous state comprising a second fluid, in order to obtain a mixture of both fluids. According to the invention, said mixing device (14) comprises mixing means (23) consisting of a first element (24) and a second element (28), hermetically associated together for delimiting a chamber (30), where to the first fuel is conveyed, and a third element (26) bearing actuating means (26A) apt to produce a localized distortion or spacing between said first element (24) and said second element (28), said distortion or spacing (34) delimiting the orifice where through the first fluid contained in the chamber (30) spills into the conveying duct of the second fluid (2, 7). The invention is particularly advantageous for application in manfacturing fuel injectors, such as for internal combustion engines, where the first fluid is a fuel and the second fluid is air (comburent).

Description: FLUIDS MIXING DEVICE AND METHOD FOR FLUIDS THEREOF. DESCRIPTION The present invention relates to a fluid mixing device, of the type apt to inject a first fluid, coming at a first pressure from a supply source, in a gaseous state comprising a second fluid, in order to obtain a mixture of both fluids. These devices are known and utilized e.g. for manufacturing fuel injectors for internal combustion engines, where the first fluid is a fuel and the second fluid consists of air (comburent). Endothermic reciprocating engines with spark ignition, among them also the turbo-compressed engines, are fed obtaining an air-fuel mixture upstream the combustion chamber. This air-fuel mixture is usually obtained taking the fuel from a tank by means of a suitable electro-pump and conveying it to an electric injector. Said electric injector will injects the fuel nebulizing it inside the intake duct, wherein the air flows. Through the intake duct the air-fuel mixture is then conveyed to the combustion chamber. Said injection method is called Single Point Injection (SPI); another injection method, i.e. the Multi Point Injection (MPI) is also known, which provides for an electric injector in each one of the cylinders, located near the cylinder inlet. SPI and MPI injection methods employ electric injectors with electromagnetic control, consisting of a needle sliding inside a body whereto the fuel flows. The needle is provided at its end with a shutter, whose movement allows or prevents the fuel to flow out under pressure from an exit nozzle. The control is electromagnetic, so that the needle is provided on its middle with a magnetic keeper, while inside the injector body a suitable coil is located for magnetic control of the needle, according to the known pattern of a solenoid valve. Also injectors are known which, instead of the electromagnetic control, employ piezoelectric means for opening the electric valve. Common injectors, being located sideways of the intake duct, do not allow an optimal mixing of the fuel with the air flowing in the duct. Moreover, said injectors often produce a nebulization of the fuel in drops, which is not sufficient for an optimal combustion. In fact, if the size of the fuel drop injected in the air is greater than a determined value, it may happen that a portion of the drop is not burnt, so impairing the engine efficiency. Such injectors also show a high inertia typical of the electromechanical systems, so that the injecting frequency is limited to a few hundreds of Hz, resulting in a not so flexible injection control. Furthermore, such injectors work with an injection pressure of a few bars, so that the fuel is always under pressure, with evident risks in case of breakage of the fuel conveying ducts, for instance due to an accident, so requiring the additional presence of inertial breakers in the fuel feeding circuit. It is the object of the present invention to solve the above drawbacks and provide a mixing device, in particular a fuel injector for internal combustion engines, having an improved and more efficient structure in respect of the known solutions. In this frame, it is the main object of the present invention to provide a fluid mixing device and/or a method for the mixing of fluids, which allow for obtaining micronization of a first fluid at the moment of the creation of the mixture with the second fluid. A further object of the present invention is to provide a fluid mixing device and/or a method for the mixing of fluids, which allow for obtaining a homogeneous mixing of the first fluid in the second fluid. A further object of the present invention is to provide a fluid mixing device and/or a method for the mixing of fluids, which allow for the use of fuel substantially at low pressure. A further object of the present invention is to provide a fluid mixing device and/or a method for the mixing of fluids, which allow for controlling and changing the amount/flowrate of the first fluid in the second fluid. In order to achieve such aims, it is the object of the present invention to provide a fluid mixing device, in particular a fluel injector for internal combustion engines, and/or a method for the mixing of fluids, incorporating the features of the annexed claims, which form an integral part of the description herein. Further objects, features and advantages of the present invention will become apparent from the following detailed description and annexed drawings, which refer to a fuel injection system for internal combustion engines, and are supplied by way of non limiting example, wherein: - Fig. 1 shows the basic schematic diagram of a fuel injection system for internal combustion engines, according to the present invention; - Fig. 2 shows the basic schematic diagram of a mixer device in the form of a fuel injector for internal combustion engines, according to the present invention; - Fig. 3 shows the perspective diagram of a detail of the fuel injection device according to Fig. 1; - Fig. 4 shows the basic schematic diagram of a detail of the fuel injection device according to Fig. 1. In Fig. 1 is illustrated a schematic diagram of a fuel injection system 1 according to the invention, realized according to the teaching of the present invention. There is shown an intake duct 2, conveying the air required for the combustion mixture from the air inlets, not shown here, of the motor vehicle. The intake duct 2 has an air filter 3, and downstream the filter is located a butterfly body 4, comprising a butterfly valve 5. Downstream the butterfly body 4 there is located an air "plenum" 6, from which departs a plurality of intake ducts 7 ending in a cylinder head, not shown. The elements described above are all known and will not be described in detail. A fuel tank 9 is also provided, from which an hydraulic fuel conveying circuit 10 is departing, indicated by a thicker line. This hydraulic fuel conveying circuit 10 is operated by means of a fuel pump 11 ; downstream the pump there is located a fuel filter 12. The arrangement of these elements is also commonly known. Downstream the fuel filter 12, the hydraulic fuel conveying circuit 10 comprises a dosing device 13. Inside the intake duct 2 there is located a mixing device or injector 14. Said injector device has a housing 15 with streamlined shape, which is hold up by proper supports 19, so that the housing 15 is axially arranged in respect of the intake duct 2. On the circumference of the housing 15 there are provided a number of slots 20. The hydraulic fuel conveying circuit 10 continues beyond the dosing device 13 to reach inside of the housing 15 thanks to one of the supports 19, which is appropriately hollow and has the shape of a pipe. There is further provided an electronic control unit 16, which is also known in itself, and is provided with electrical connections 17 to the injector device 14 located inside the intake duct 2. Through an electrical connection 18, the electronic control unit 16, in turn, receives a signal about the position of the butterfly valve 5. In Fig. 2 there is shown the basic schematic diagram of a mixing device or injection device 14 according to the present invention. It should be noticed how in this figure the sizes of the various components of the invention, as further described, are magnified with respect to the housing 15, so as to obtain a clearer representation of them. The injection device 14, as said, consists of the housing 15, having a typical streamlined shape, the function of which is to delimit, together with the walls of the intake duct 2, a number of conduits having a profile of a Venturi tube. It should be noticed that one of the supports 19 continues inside of the profile and connects to an axial duct 22, which ideally ends the hydraulic fuel conveying circuit 10. In the above example, the axial duct 22 also acts as a support for four mixer 23. Each mixer 23 substantially comprises: a dosing disk 24, made of ferromagnetic material, with a central hole for its keying or fastening on the duct 22; a disk counterplate 28, provided on its perimeter with a raised rim 29, in sealed cooperation with the disk 24; also the counterplate 28 has a central hole for its keying or fastening on the duct 22. Each raised rim 29 of the counterplate 28 and the surface of the dosing disk 24 are sealed overlapped, so that between the dosing disk 24 and counterplate 28 a substantially cylindrical chamber 30 is delimited; to this purpose, at least the edge 29 will be made of a suitable material apt to warrant the required hermetical sealing. The axial duct 22 has a number of holes 31 in line with every chamber 30, in order to let it be filled with the fuel coming from the feeding circuit 10, through the support 19. Reference 26 indicates a supporting element with a set of electromagnets 26A on its surface facing the dosing disk 24, which form a round crown as a whole. Said electromagnets 26A are driven and energized by the control unit 16 so as to locally draw the dosing disk 24. Thus, the dosing disk 24 is locally distorted, so as to delimit an outlet orifice for the fuel contained in the chamber 30. According to a possible embodiment, the control unit 16 may be programmed for the sequential driving of the electromagnets 26A. In so doing, a travelling wave is in fact obtained, which runs the circumference of the dosing ring 24; in other words, the sequential drive of the electromagnets 26A will cause the above local distortion of the dosing disk 24 "to run" along the perimeter of the disk. Since the dosing disk 24 cannot revolve, its local distortion which moves in a circular direction, tends to move the dosing disk away from the raised rim 29 of the counterplate 28 in the passage points, so creating a number of orifices or nozzles, which let micro amounts of the fuel spill sequentially along the whole perimeter of the dosing disk 24. In Fig. 3, reference 34 shows in fact the above orifice, which is determined by the distortion of the dosing ring 24, said distortion being obtained by feeding the electromagnet indicated with 26A'; in this figure, reference 35 indicates the above micro amounts of fuel, represented here by drops. As illustrated, the system may comprise a plurality of chambers 30. In the above example, each supporting element 26 may have crowns of electromagnets 26A on both its faces; thus, each supporting element 26 can drive two different dosing chambers 30. Similarly, the counterplate 28 can advantageously lay between two dosing disks 24; in this case, both opposite surfaces of the counterplate 28 will be provided with a raised edge 29, capable of sealing cooperation with a respective dosing disk 24. Therefore, the injection device 14 operates as follows: the fuel is conveyed through the fuel pump 11 in the fuel conveying duct 10. The dosing device 13 is used to feed the mixing device or injector 14 and supply the fuel amount required plus a slight overpressure due to the hydrostatic pressure of the fuel contained in the section of the fuel conveying circuit 10, comprised between the dosing device 13 and the axial duct 22. However, in the intake duct 2, in line with the slots 20 where the housing 15 delimits the gorge of the Venturi tube, a vacuum is generated by the Venturi itself. Therefore, the mixer 23, due to the effect of the travelling distorsion of the dosing disk 24, generates a spill, which moves along the circumference. The combined effect of the overpressure inside the fuel conveying circuit 10 and pressure drop due to the housing 15 has the effect of micronizing the fuel drops 35 of the spill and move them quickly away from the raised rim 29, so improving their mixing with the air. The electronic control unit 16 receives the information about the position of the butterfly valve 5 through the connection 18, so that it can conveniently control the sequential feed frequency of the electromagnets 26A, and consequently the rotation speed of the travelling wave or distortions in the injector device 14. In this way, at any rotation speed of the engine, an optimal feeding is ensured as regards fuel consumption and compliance with the anti-pollution rules. The electronic control unit 16 has moreover the possibility of modulating the feed voltages of the electromagnets 26A, changing the amplitude of the distortion or travelling wave and, consequently, the local distance between the dosing disk 24 and the counterplate 28, (or better the edge 29 of the latter), and therefore the size of the injected drop. Each mixer comprises therefore a first element, the dosing disk 24, a second element, the counterplate 28, and a third element, the support 26 of the electromagnets 26A, where the first and second elements delimit the chamber 30. The action of the electromagnets 26A creates a local controlled spacing (a few μm) of the dosing disk 24 from the counterplate 28; this spacing delimits a nozzle 34 where through the fuel spills into the intake duct 2, under the action of the slight pressure established inside the chamber 30. The effect of the distortion or travelling wave is therefore so, that such nozzle or orifice 34 is moving with a substantially circumferential motion along the dosing disk perimeter 24, delimiting an injection point that is moving in the time, apt to make the injection more even and control it by means of the frequency and amplitude of the voltage signals. In Fig. 4 there is shown the dosing device 13, which receives in input the hydraulic fuel conveying circuit 10 and delivers in output, through an outlet duct 38, the fuel to the mixer device 14. Inside the dosing device 13 there is located a float 39, provided on the top with a pin shutter 40. The fuel pushed by the fuel pump 11 enters the dosing device 13 and flows through the outlet duct 38 to the mixer device 14. When the fuel level inside the dosing device 13 is such that the pin shutter 40 on the float 39 closes the fuel conveying circuit 10, fuel feeding will stop. The fuel feeds the mixer device 14 by gravity, until the fuel level decreases and the pin shutter 40 will open again the fuel conveying circuit 10. However, the dosing device 13 can be removed, sizing the fuel conveying circuit 10 in the way that it is a closed circuit, namely by means of a return line to the tank, so assuring a constant fuel pressure in the chamber 30. The same effect can be achieved by pressing the dosing disk 24 on the counterplate 28 with a tightening force being compatible with the described system operation. The mixer device 14, shown in Fig. 2, is provided with four mixers 23, which are fastened and kept in place by suitable tightening nuts 32 and/or spacers 33. Of course the number of mixers 23 located in the axial duct 22 may also be greater, and such a number will be calculated as a function of the flowrate requested by the specific application. Similarly, the number of electromagnets 26A forming each crown arranged on the support 26 will be calculated as a function of the size of the drops or micro amounts of fluid to be obtained. Furthermore, in order to optimize the fuel injection the control unit 16 can control the mixers 23 in a different way. For instance, assuming that three mixers 23 are provided, they can be driven by means of signals shifted in phase by 120° to each other, so that the corresponding distortions or travelling waves in the relevant three chambers 30 will be consequently delayed in phase and generate an even distribution of the injected fuel, avoiding any interference. From the above description the features of the present invention as well as the relevant advantages thereof are clear. The fluid mixing device according to the present invention, in particular a fuel injector for internal combustion engines, advantageously allows for nebulizing a first fluid (fuel) directly inside the conveying duct of a second fluid (air - comburent), favoring micronization and mixing, so improving the ratio managing capability between both fluids and in conclusion their consumption/performance ratio for the application in internal combustion engines. Advantageously, moreover, the first fluid or fuel is distributed along the whole circumference of the mixer or injector, so improving both the injection uniformity and mixture quality. Moreover, the fuel mixing device described above advantageously allows for an easy and efficient dosing of the first fluid, also controlling both the rotation frequency of the distortion or travelling wave, through the frequency of the voltage signals generating it, and the size of the injected drops through the amplitude of such signals. Advantageously, moreover, the device according to the invention allows to operate with a low pressure in the intake circuit of the first fluid or fuel, to the injector device. In the case described, the pressure needed at the fuel pump is about 1 bar, so that a simple cheap membrane pump can be used, directly driven by the engine, or in the case of a favorable layout of the hydraulic circuit, a pump may even be dispensed of, taking advantage of the hydrostatic pressure. Additionally, the use of a low pressure involves clear advantages in the design of the hydraulic feeding circuit of the first fluid or fuel. For instance, it may allow for avoiding the need of an inertial breaker in order to stop fuel flow in the case of an accident, since there is no longer a pressure of 4-6 bar to push the fuel out of a broken duct, independently from the engine operation. It is obvious that many changes are possible for the man skilled in the art to the fluid mixing device and/or fluid mixing method described above by way of example, without leaving the novelty principles of the inventive idea, and it is also clear that in practical actuation of the invention the components may often differ in form, size, proportions and materials employed from the ones described above, and be replaced with technical equivalent elements. According to a possible implementation, the control unit 16 may be programmed for obtaining a non sequential energization of the electromagnets 26A of each crown, but simultaneously, i.e. based on an activation logic of the electromagnets of pulsing type. As it can be noticed, this will no longer produce a localized distortion in just one peripheral point of the dosing disk 24, but a distortion of the whole disk, so as to obtain the maximum flowrate obtainable by the mixing system, said distortion of the whole disk 24 being obtained by the set of single local distortions generated by each electromagnet 26A. Obviously, both energizing systems (sequential and simultaneous or pulsing) do not exclude each other, but they create a further flexibility element for controlling the system. The supporting component 26 of the electromagnets 26A, as well as their arrangement, does not necessarily have a ring shape. It is also clear that appropriate driving of the electromagnets 26A may bring to a simultaneous production of several distortions or traveling waves 34 on one same dosing disk, which will determine several orifices at the same time. It shall be possible, taking advantage of a greater number of mixer 23 according to the invention, namely more chambers 30 available, to associate a different fluid to each mixer device; in the case of engines using more than one type of fuel, one of the mixer may inject oil. One or more mixer 23 may also be assigned for gas or fuel additives injection. On the other hand, the mixer 23 shall also inject other materials that can be absorbed by fluids or gas, such as finely ground powders, e.g. powdered coal. Therefore, the invention is also applicable for the mixing and/or injection of all fluids compatible with the size of the hydraulic circuit. It is also clear that the ability of injecting or mixing a wide range of fluids makes the device according to the invention apt to different uses other than described in the case of an internal combustion engine, wherever a precise dosing of micro amounts of fluid is required. Possible applications are for instance their use as dosing devices in chemical, pharmaceutical or heating plants, etc. The injector device can also be used in association not only with the intake duct of an engine, but additionally as an alternative to, or in connection with the air conveying ducts to the cylinders, in analogy with MPI technique. In the example described above, it is assumed to utilize an attraction force generated by electromagnetic way, so as to obtain distortion of the dosing disk 24; however, the above system may also be changed, according to procedures clear for the man skilled in the art, in order to obtain this distortion taking advantage of an electromagnetic repulsion force. Instead of providing two electromagnet sets on opposite faces of the supporting element 26, the latter may bear only one set of through electromagnets, the ends of which would extend out towards two different dosing disks 24, each end being polarized and energized appropriately, according to procedures clear for the man skilled in the art.

Claims: CLAIMS 1. A fluid mixing device, of the type apt to inject a first fluid, coming at a first pressure from a supply source (9), in a gaseous state comprising a second fluid, in order to obtain a mixture of both fluids, characterized in that said mixer device (14) comprises mixing means (23) consisting of a first element (24) and a second element (28), hermetically associated together for delimiting a chamber (30), whereto the first fuel is conveyed, and a third element (26) comprising actuating means (26A) apt to produce a localized distortion or spacing between the first element (24) and the second element (28), said distortion or spacing delimiting an orifice (34) wherethrough the first fluid contained in the chamber (30) spills into the conveying duct of the second fluid (2,7). 2. A device according to claim 1, characterized in that said actuating means (26 A) are electromagnetic actuating means. 3. A device according to claim 1 or 2, characterized in that the position of the orifice (34) is identified by a point, which is moving in time. 4. A device according to claim 3, characterized in that the orifice (34) follows a substantially circular path. 5. A device according at least to one of the claims from 2 to 4, characterized in that said electromagnetic actuating means (26A) create a distortion or travelling wave in the first element (24), said distortion (33) having a substantially circular motion. 6. A device according to claim 2, characterized in that said electromagnetic actuating means (26A) are borne by the third element (26) and are apt to generate distortion in the first element (24), said distortion having in particular a direction mainly parallel to the axis of the conveying duct of the second fluid (2,1). 7. A device according to claim 2, characterized in that said electromagnetic actuating means (26A) are arranged like a ring on the third element (26). 8. A device according to claim 2, characterized in that said electromagnetic actuating means (26A) are obtained trough a plurality of electromagnets, in particular distributed along the perimeter of the third element (26). 9. A device according to claim 8, characterized in that it provides means (16) for sequential driving and/or feeding of the electromagnets (26 A). 10. A device according to claim 8, characterized in that it provides means (16) for simultaneous driving and/or feeding of the electromagnets (26A), in particular for obtaining a distortion of the first element (24) formed by a plurality of local distortion. 11. A device according to claim 2 or 8, characterized in that it provides means (16) for controlling and/or changing the supply voltage to the electromagnetic actuating means or electromagnets (26A), and/or the actuation frequency of the electromagnetic actuating means or electromagnets (26A), and/or the number of activated electromagnetic actuating means or electromagnets (26A), so as to optimise the flowrate of said first fluid. 12. A device according to claim 1, characterized in that said second element (28) is provided with a raised rim (29), which delimits a wall of the chamber (30), said first element (24) resting in particular on said edge (29). 13. A device according to claim 1, characterized in that said mixing means (23) are more than one, in particular one of them injecting a different fluid from the others. 14. A device according to the previous claim, characterized in that said actuating means (26A) of each mixing means (23) are apt to cause distortion or spacing of the respective first element (24) rotating out of phase between them. 15. A device according at least to one of the previous claims, characterized in that the first pressure is higher than the pressure outside the chamber (30) of the first fluid. 16. A device according at least to one of the previous claims, characterized in that said mixing means (23) are located inside the conveying duct of the second fluid (2, 7). 17. A device according at least to one of the previous claims, characterized in that said mixing means (23) are associated to fluid dynamics means (15) apt to create a pressure drop in the conveying duct of the second fluid (2,7). 18. A fluid mixing device, of the type apt to inject a first fluid, coming at a first pressure from a supply source (9), in a gaseous state comprising a second fluid, in order to obtain a mixture of both fluids, characterized in that it comprises electromagnetic means (26A) creating a travelling distortion (34), said travelling distortion having a substantially circular motion. 19. A fluid mixing device, of the type apt to inject a first fluid, coming at a first pressure from a supply source (9), in a gaseous state comprising a second fluid, in order to obtain a mixture of both fluids, characterized in that it comprises electromagnetic means (26A) creating the distortion of a dosing element of the first fluid (24), said distortion being formed by a plurality of local distortion generated by a plurality of said electromagnetic means (26A). 20. A mixing device according at least to one of the previous claims, characterized in that it is used as a fuel injector for an internal combustion engine. 21. A method for the mixing of fluids, of the type that provides the nebulization of a first fluid through mixing means (23) in a gaseous phase comprising a second fluid, characterized by the steps of: - sending said first fluid to a chamber (30) comprised in said mixing means (23), delimited by a first element (24) and a second element (28) associated hermetically; - generating by electromagnetic way a local distortion of at least a portion of said first element (24), so that the latter is spaced from the second element (28) in line with said portion; - using said spacing (34) caused by said distortion to allow for a spill of the first fluid outside the chamber (30). 22. A method according to claim 21, characterized in that it causes the local distortion of said first element (24) to move in time, in particular along a circular path. 23. A method according to the previous claim, characterized in that said spacing is obtained by means of the sequential driving and/or feeding of a plurality of electromagnets (26A), substantially arranged as a circular crown. 24. A method according to claim 21, characterized in that it provides for simultaneous driving and/or feeling of several electromagnets (26A) so as to obtain a distortion of said first element (24), said distortion being formed by a plurality of local distortions. 25. A method according to claim 23 or 24, characterized in that it provides the change of the feed voltage of the electromagnets (26A), and/or of the activation frequency of the electromagnets (26A), and/or of the number of the activated electromagnets (26A), so as to optimise the flowrate of said first fluid with respect to said second fluid. 26. A method for the mixing of fluids, of the type that provides the nebulization of a first fluid through mixing means (23) in a gaseous phase comprising a second fluid, characterized by the steps of: - sending said first fluid to a chamber (30) comprised in said mixing means (23), delimited by a first element (24) and second element (28), associated hermetically; - causing a local distortion at least of a portion of said first element (24), according to a substantially normal direction with respect to the input direction of the first fluid in the chamber (30), so as to generate a distortion of the first element (24), which in line with said portion is spaced from the second element (28); - using said spacing (34) caused by said distortion to allow for the spill of the first fluid outside the chamber (30). 27. A method for the mixing of fluids, which provides the nebulization of a first fluid through mixing means (23) in a gaseous phase comprising a second fluid, characterized by the steps of: - conveying said first fluid into a chamber (30) obtained by hermetically associating a first element (24) to a second element (28); - controlling actuating means (26A) associated to a third element (26), for generating a local distortion of the first element (24) and a consequent spacing between the latter and the second element (28), so causing a loss of tightness of the chamber (30) and allow for a consequent spill of the fuel. 28. A method according to one or more of the previous claims, characterized in that it is used for fuel injection in internal combustion engines.

Inventors: COZZARI GIULIANO, COZZARI, GIULIANO
Applicants: COZZARI GIULIANO, COZZARI, GIULIANO
Application year: 2001
Main classification: F02M69
IPC codes: F02M51, F02M69