Perfected burner for heat generator

Abstract: Perfected burner for heat generators, which can be used in cooperation with heating plants such as boilers, hot air generators etc. for heating rooms in general, the burner comprising at least a containing structure (11) associated with the outer wall of a combustion chamber (26) and defining inside at least the seating for a flame pipe (17) and a ventilator unit (13), the flame pipe (17) containing inside itself a fuel feed pipe (22) and having at its periphery a slit (33) for air to pass through associated with the ventilator unit (13), the ventilator unit (13) having an air propellor (40) carried by an actuating motor (37) supported by a mounting flange (53), the slit (33) cooperating with a shutter (34) element, the fuel feed pipe (22) having at its end a nozzle-type outlet (30) cooperating with a turbulence disk (31), there also being present an intake opening (15), the containing structure (11) defining, at the side of the air propellor, an area (48) through which the air passes and which becomes progressively wider until it reaches a width at least 30% of the diameter of the air propellor (40) in the area substantially diametric to its initial part, and around the flame pipe (17) an annular recircling conduit (45) communicating at its inlet with this area (48) and the air propellor (40) defining inside itself a housing area for at least part of the motor (37), between the motor (37) and the inner diameter of the air propellor (40) there being longitudinal fins (41,42) substantially diametrically arranged and defining, together with the air propellor (40), a lower intake area (44) communicating with the opening (15) and a higher intake area (43) communicating with the annular recircling conduit (45), between the air propellor (40) and the inner side of the containing structure (11) on the side of the flange (53) there being an annular space (54) to convey the air.

Description: This invention concerns a perfected burner for heat generator as set forth in the main claim. The perfected burner according to the invention is applied to heating systems substantially for domestic use either inside or immediately outside the room to be heated. The burner according to the invention can also be applied in cooperation with heating systems of a certain size to heat halls, gymnasiums, warehouses etc. The burner according to the invention may be of the type which uses liquid fuel, such as oil, or gas fuel. The need to obtain heat generators is known, particularly for domestic use or similar, which have all the characteristics of safety, simplicity of use and adjustment, high efficiency, ease and speed of installation and/or maintenance. It is also known that there are problems in the state of the art when the user needs to get to the heat generator to carry out even the simplest adjustments and overhauls. In some cases in the state of the art, some characteristics have been favoured over others when it was not possible to reach a compromise between the various needs. There are for example some burners known to the state of the art which are difficult to install and/or maintain quickly because the designers tried to make them more compact and to reduce the space they occupy. For the same reason, it is not always simple to carry out the necessary adjustments for a correct functioning. In other cases, in the attempt to achieve high efficiency and reduced consumption, bulky and unfunctional burners have been designed. Often, in order to put together as many functional characteristics as possible, burners have been made which are suitable only for one type of heat generator and therefore cannot be adapted for generators which have a combustion chamber of a different type. Another serious problem which is found in burners known to the state of the art, particularly in those which use blown air, is that of the pulsations at the beginning caused by the sudden overpressure which occurs at the moment of lighting. That may cause the flame to be extinguished and therefore it becomes necessary to repeat the lighting procedure several times or even, in the worst case, a blow-back of the flame, with extremely dangerous consequences for the user. Moreover, these initial pulsations often cause the exhaust gases to leak from the combustion chamber. This problem is partially resolved, in the state of the art, by increasing the dimensions of the burners and thus creating problems in the size and compactness of the structure of the heat generator itself. In particular, some solutions known to the state of the art conform the air inlet to the ventilator in a suitable way, but this in any case causes an increase in the total size. DE-C-4232178 teaches to use a ventilator system which obtains at least a partial recircling of the air propelled by the air propellor, in order to increase the prevalence of the air and thus limit any excessive pressure at the moment of ignition. In this document, however, given the reciprocal positioning of the propellor and the chassis of the ventilator, only a very limited quantity of air is subject to a recircling action, and therefore the increase in the steepness of the prevalence/flow curve is very limited. Moreover, this document does not include the body of the motor inside the ventilator, nor does it allow the motor to be included therein, and this causes an enormous increase in the axial bulk of the heat generator in its entirety. FR-A-2 211 106 discloses a ventilator structure to feed a burner where the flame pipe is entirely associated with the chassis of the ventilator, which makes it impossible to perform any kind of adjustment and positioning without modifying the overall bulk of the heat generator. Moreover, it is substantially impossible to perform any kind of maintenance work and/or replacement of internal parts without dismantling the entire structure, and this can only be performed by the appropriately authorised and specialised staff. The present applicants have designed, tested and embodied this invention to overcome the shortcomings of the state of the art and to realise a simplified burner, of compact size, extremely functional in its installation, its maintenance and its adjustments, as well as to achieve further advantages. This invention is set forth and characterised in the main claim, while the dependent claims describe variants of the idea of the main embodiment. The purpose of this invention is to obtain a simple burner, easy to install, adjust and maintain, which gives a high operating efficiency while maximizing safety and minimizing the size. The invention concerns a perfected burner for a heat generator as defined in claim 1. According to a further feature of the invention the various parts of the burner are connected by means of attaching elements which also act as elements to adjust the burner easily and in a way which is immediately accessible from outside, even for someone of no specific skill in the art, thus assisting and accelerating assembly operations and any necessary work on the internal components or parts. By means of these adjustment elements it is possible to adjust with extreme precision the functioning parameters of the burner, guaranteeing extreme versatility and flexibility of the whole plant which can be adapted to different applications and vary its operating conditions according to necessity. Moreover, according to an advantageous feature of the invention, the type of connection between the various components of the burner guarantees an airtight seal between the inside and outside of the burner. The burner further comprises a chassis of such a shape as to guarantee, in an extremely limited space, both the support and/or containment of the various components, and also a flow of air suitable for an efficient and complete combustion and an efficient discharge of the fumes. The chassis, or containing structure, is equipped with attachment means to attach it to the outer wall of the combustion chamber associated with the burner. The chassis defines an inner seating where the flame pipe is inserted, and the front end of the flame pipe faces inside the combustion chamber. Inside the flame pipe, advantageously in a coaxial position with the pipe, there is the fuel feed pipe, connected outside to the fuel feed means. According to a further feature of the invention, the rear, or outer, end of the flame pipe is associated with a cover element by means of which the flame pipe is attached to the chassis of the burner. According to a further feature of the invention, the connection between the cover element and the chassis can be adjusted from the outside by means of screws, in cooperation with at least one replaceable spacer element. This makes it possible to move the flame pipe axially so that its front end protrudes more or less inside the combustion chamber. This adjustment makes it possible to adapt the flame of the burner to the different configurations of the combustion chamber and the different types of heat generator to which the burner is applied. The fuel feed pipe, which is inside the flame pipe, has a nozzle conformation in correspondence with its front end outlet. In front of this nozzle there is a disk element, the function of which is to make the comburent air fed to the burner turbulent, and therefore to optimize the mixture with the fuel given by the fuel feed pipe to the nozzle. According to a further feature of the invention, by acting on an adjustment accessible from the outside, the fuel feed pipe can be made to run axially to the flame pipe. This adjustment is advantageously screw-type, and is arranged on the cover element associated with the rear end of the flame pipe. By varying the reciprocal position between the turbulence disk and the front end of the flame pipe outlet, the adjustment makes it possible to vary the turbulence of the flow of comburent air and therefore to vary the mixture of comburent material and combustible material. By adjusting the axial position of the fuel pipe, it is also possible to vary the position of the air shutter which regulates the flow of comburent air fed to the burner. According to a further feature of the invention, the position of this shutter, which is placed downstream of the air intake propellor, can be adjusted autonomously and independently of the position of the fuel feed pipe by acting on specific adjustment means accessible from outside. In the preferred embodiment of the invention, the adjustment means for the position of the shutter are screw-type too, and are arranged on the cover element. This double adjustment makes it possible to optimize the combustion in an extremely precise way and therefore both to reduce consumption and to adapt the functioning of the heat generator to the specific requirements. The whole adjustment unit is easily removable for checking and maintenance inside the burner, even without removing the burner itself from the wall of the combustion chamber. Since the whole adjustment system is on the flame pipe, rather than on the air inlet opening on the chassis, the air inlet area, in the burner according to the invention, can be put in a pipe and therefore the initial intake point can be placed at a considerable distance from the burner. One possible case is that an air intake point is placed outside the building where the heat generator is found. This allows a balanced flow of air to be achieved and thus guarantees greater safety and comfort; moreover, it is possible to install auxiliary devices, such as filters or silencers, on the pipes which feed the air to the burner. According to a further feature of the invention, the air propellor which feeds the comburent air to the burner acts as a housing for the motor of the ventilator, which considerably reduces the space occupied. Moreover, the conformation of the air propellor and the motor is such as to guarantee at least a partial recircling of the air aspired for combustion, which causes on one side an increase in the prevalence of the air, or rather the vertical height to which the air can be lifted, and on the other side an accentuation of the steepness in the prevalence/flow curve. By obtaining a high steepness in this curve, it is possible to combat efficiently the high pressures which occur at the moment of ignition, and thus to limit significantly the problems connected with these pressures, including the leakage of exhaust gas from the combustion chamber. According to a further feature of the invention, this partial recircling of the aspirated air is obtained by allowing the air which has not entered the flame pipe to circle outside the flame pipe and then move near the air propellor again. This recircled air, which is already under pressure, is directed along a peripheral zone of the propellor, and then later picked up by the propellor itself, from which it receives new energy. The new air, aspired through the opening in the body of the burner, is attracted both by the normal depression determined by the action of the propellor and by the induction effect generated by the flow of air under pressure generated by the recircling air thus obtained. The attached figures are given as a non-restrictive example and show a preferred embodiment of the invention as follows: Fig. 1 shows a longitudinal cross section of the perfected burner according to the invention; Fig. 2 shows the diagram of a perfected burner according to the invention, with particular reference to the area of the ventilator; Fig. 3 shows a cross section seen from A of the burner according to the invention; Fig. 4 shows the flow/prevalence curve of the flow of air given by the ventilator of a state of the art burner and the same curve obtained by a burner according to the invention. Fig. 1 shows the preferred embodiment of the perfected burner 10 according to the invention. The burner 10 comprises a chassis 11 which has at its lower end a hole 12 which allows for the installation of a suitable ventilator 13, which has an air propellor 40 and a motor 37, and defines the opening 15 for the flow of air, indicated by 14. The chassis 11 is attached to the outer wall of the combustion chamber 26, in this case, by means of a screw attachment element. In the upper part of the chassis 11 there is a through hole 16 into which the flame pipe 17 is inserted in such a way that its forward end, a truncated cone 17a, is substantially placed inside the combustion chamber 26. The rear end of the flame pipe 17 is associated with a cover element 18 by means of a solid connection by the attachment element 24. Between the cover element 18 and the flame pipe 17 there are holding elements 19, in this case an O-ring packing, which make the flame pipe 17 airtight with the outside. In this case, the holding elements 19 are inside a relative channel 20 which follows the perimeter edge of the cover element 18. In this case, the cover element 18 is attached to the chassis 11 of the burner by means of a screw-type attachment element. Between the attachment element 25 and the chassis 11 there is a spacer element 28 which can be replaced or modified. The attachment element 25, cooperating with the spacer element 28, makes it possible to adjust the axial position of the flame pipe 17 inside the chassis 11 and, therefore, the position of the forward end 17a with respect to the combustion chamber 26 with which the burner 10 is associated. The length of the spacer element 28 can be adapted according to requirements, or replaced. By varying the position of the forward end 17a of the flame pipe 17 with respect to the combustion chamber 26, it is possible to adapt the flame of the burner 10 to the various forms and dimensions of the combustion chamber 26 and the different applications, such as boiler, hot air generators, etc., which can be used with the burner 10. The cover element 18 has a hole 21, in this case situated on the axis, inside which there is the fuel feed pipe 22. On the outside too, in cooperation with the hole 21 there is a channel 20 in which an 0-type packing is inserted. On the outside the fuel feed pipe 22 has an attachment 38 to the conventional fuel feeding means, whether they be liquid or gas. The fuel feed pipe 22, contained in the flame pipe 17, can be made to run axially through the hole 21. The axial position of the fuel feed pipe 22 in the flame pipe 17 can be adjusted, in this case, by acting on a screw-type attachment and adjustment element 23. This element 23 is solid with the fuel feed pipe 22 and its position can be adjusted with respect to the cover element 18. By acting on the attachment and adjustment element 23, the fuel feed pipe 22 is moved backwards or forwards axially inside the flame pipe 17. The axial movement of the fuel feed pipe 22 is assisted, in this case, by a runner element 29, of a shape mating with the inner section of the flame pipe 17, which is also used to support and guide the fuel feed pipe 22. The fuel feed pipe 22 has at its ends nozzle-type outlet means 30 in front of which there is a turbulence disk 31. In this way, by moving one way or the other the fuel feed pipe 22 with respect to the flame pipe 17, it is possible to vary the turbulence of the comburent air fed into the combustion area, and therefore it is possible to vary the combustion itself. The rear or outer end of the fuel feed pipe 22 is associated with a removable plug 32 where a device to preheat the fuel could possibly be housed. The flame pipe 17, in that part of its surface contained inside the chassis 11 and facing the ventilator 13, has a slit 33 through which the air fed by the ventilator 13 passes. The section of this slit 33 through which the air passes is determined by the position of an air shutter 34 contained inside the flame pipe 17 and positioned, in this case, downstream of the ventilator unit 13. The position of the air shutter 34 can be adjusted independently of the flame pipe 17 by acting on the appropriate screw-type adjustment element 35, arranged on the cover element 18, of which the activating mechanism is accessible from the outside. In this way, the flow of air fed to the combustion area at the outlet of the fuel feed pipe 22 can be adjusted in an extremely quick and simple way to vary the combustion. By dismantling the cover element 18, which can be done extremely easily even by non-specialist users, it is possible to accede to the inside of the burner 10 very quickly, to check it or for maintenance. Figure 2 shows a partial drawing of the perfected burner 10 according to the invention. In this Figure, it can be seen how the space occupied is very small as the motor 37 of the ventilator 13 is substantially housed in the space defined by the air propellor 40 itself. The motor 37 is attached to the chassis 11 by means of a flange 53. In this way, most of the motor 37 is contained inside the space taken up by the chassis 11, and, in this case, only the pump 39 remains outside this space. In the perfected burner 10, moreover, the opening 15 for the flow of air 14 is on the same side as the motor 37 and this gives a further reduction in the overall space occupied. Figure 3 shows a cross section seen from A of the perfected burner 10 according to the invention. In this case, on the outer surface of the motor 37 there are two fins in a diametric position: upper longitudinal fin 41 and lower longitudinal fin 42. In cooperation with the inner surface of the propellor 40, these fins 41 and 42 define an upper intake area 43 and a lower intake area 44. The chassis 11, on its lower part, defines an area 48 where the air passes through. This area 48 widens progressively from its initial area until it reaches a width equal to at least 30% of the width of the propellor 40 in the area substantially diametric to the initial area. The flow of air 14 aspired from the outside through the opening 15 is pushed by the air propellor 40 towards the slit 35 of the flame pipe 17. This flow of air is conveyed through a space 54 which communicates with the slit 33, the space 54 being between the head of the air propellor 40 and the inner wall of the chassis 11 which is placed on the side of the flange 53 which mounts the motor 37. In this case, the head of the propellor 40 is closed by a screen 55 which prevents air entering. In this case, the width of the area 48, together with the rounded conformation of the inner surface of the chassis 11, causes part of the air, indicated by 49, to enter the recircling conduit 45 which is placed around the flame pipe 17, rather than entering directly the flame pipe 17 itself through the slit 33. From the recircling conduit 45 the recircled air, which already has a certain pressure, is aspired downwards through the conveyor space 54, as it is prevented from entering the slit 33 by the deflector element 46. The deflector element 46 is attached to the chassis 11 on the inner side from where the flange 53 is positioned and extends substantially on a horizontal plane to cover approximately the width of the propellor 40. The recircled air, indicated by the arrows 50, is confined in the upper intake area 43 by the diametric fins 41 and 42, after passing over the deflector element 46. From here it is forced by the propellor 40 into the sickle-shaped tangential area 47 between the propellor 40 and the chassis 11, acquiring new energy from the propellor 40. The tangential area 47 grows progressively wider towards the bottom and is found substantially at the same axial height as the air propellor 40. The recircled air, indicated by 51, mixes with the flow of new air, indicated by 52, aspired by the air propellor 40 itself through the opening 15, which is found substantially in correspondence with the end of the tangential area 47. According to this configuration, the new air is therefore aspired by the double depression created by the air propellor 40 and the induction effect determined by the flow of recircled air fed through the upper intake area 43 and the sickle-shaped tangential area 47. This makes it possible to modify the characteristics of the air sent to the flame pipe 17 in terms of flow/prevalence, as shown in the graph in Fig. 4. The graph, where the flow expressed in cu.m. per hour is indicated in x-coordinate and the prevalence expressed in mm. using a column of water as a parameter of measurement is indicated in y-coordinate, gives a curve L which is obtained with a substantially conventional burner, and a curve L' which is obtained with the perfected burner 10 according to the invention. The greater steepness of the curve L' causes, when the system is working, a good compensation of the overpressures which occur during ignition and which cause the initial pulsations known to the state of the art. This guarantees a more efficient combustion and makes it possible to overcome efficiently the resistences which the fumes encounter in conventional burners as they leave the heat generator.

Claims: Perfected burner for heat generator, which can be used in cooperation with heating plants such as boilers, hot air generators etc. for heating rooms in general, the burner comprising at least a containing structure (11) associated with the outer wall of a combustion chamber (26) and defining inside the seating for at least a flame pipe (17) and for a ventilator unit (13), the flame pipe (17) containing inside a fuel feed pipe (22) and having at its periphery a slit (33) through which the air passes associated with the ventilator unit (13), the ventilator unit (13) having an air propellor (40) carried by an actuating motor (37) supported by a mounting flange (53), the slit (33) cooperating with a shutter element (34), the fuel feed pipe (22) having at its end a nozzle outlet (30) cooperating with a turbulence disk (31), there also being an intake opening (15) for the air aspirated by the propellor (40), wherein the containing structure (11) defines, laterally to the air propellor (40), an area (48) through which the air passes which increases progressively to a width equal to at least 30% of the diameter of the air propellor (40) in the area substantially diametric to its initial part, and around the flame pipe (17) an annular recircling conduit (45) which communicates at its inlet with that area (48), the burner being characterised in that the air propellor (40) defines inside a housing space for at least part of the motor (37), between the motor (37) and the inner diameter of the air propellor (40) there being longitudinal fins (41, 42) substantially diametrically arranged and defining, together with the air propellor (40), a lower intake area (44) communicating wih the opening (15), and a higher intake area (43) communicating with the annular recircling conduit (45), between the air propellor (40) and the inner side of the containing structure (11) on the side of the flange (53) there being an annular space (54) to convey the air. Burner as in Claim 1, in which between the annular recircling conduit (45) and the upper intake area (43) there is a deflector element (46) which extends on a substantially horizontal plane as far as the proximity of the flame pipe (17) and the proximity of the slit (33) through which air passes, the deflector element (46) being solid with the inner side of the containing structure (11) on the part opposite the flange (53) and extending at a right angle as far as the width of the air propellor (40), between the air propellor (40) and the containing structure (11) there being a tangential area (47) which communicates at its upper end with the upper intake area (43) and at its lower end with the air intake opening (15). Burner as in Claim 2, in which the tangential area (47) is substantially at the same axial height as the air propellor (40), is sickle-shaped and becomes progressively wider towards the bottom. Burner as in any of the claims hereinbefore, in which the air propellor (40) has a screen (55) to close the annular space (54) which conveys the air. Burner as in any of the claims hereinbefore, in which the air intake opening (15) communicates with the lower intake area (44) and substantially begins at the lower longitudinal fin (42). Burner as in any of the claims hereinbefore, in which at least the axial position of the flame pipe (17) with respect to the combustion chamber (26) can be adjusted manually and independently of the other components of the burner (10). Burner as in Claim 6, in which the means to adjust the axial position of the flame pipe (17) are accessible from outside, at the front of the burner (10) and comprise at least screw-type adjustment means (25) and replaceable deflector means (28). Burner as in any of the claims hereinbefore, in which at least the axial position of the shutter (34) with respect to the flame pipe (17) can be adjusted manually and independently of the other components of the burner (10). Burner as in Claim 8, in which the means to adjust the axial position of the air shutter (34) are accessible from the outside at the front of the burner (10) and have at least screw-type adjustment means (35). Burner as in any of the claims 7 to 9, in which the adjustment means (25,28, 35) are anchored on a removable cover element (18) associated with the rear end of the flame pipe (17). Burner as in any of the claims hereinbefore, in which the insertion seating of the flame pipe (17) is defined by a hole (16) made in the cover element (18) and has means (19) to create an airtight seal at its periphery. Burner as in any of the claims hereinbefore, in which the insertion seating of the fuel feed pipe (22) is defined by a hole (21) made in the cover element (18) and has means (19) to create an airtight seal at its periphery.

Inventors: BOGHETTO GIANVITTORE, BOGHETTO, GIANVITTORE
Applicants: F I M FONDERIA IND MECCANICHE, F.I.M.- FONDERIA INDUSTRIE MECCANICHE SPA
Application year: 1997
Main classification: F23D11
IPC codes: F23D11, F04D25, F23D14