Patent Publication Number: US-4320875-A

Title: Burner nozzle

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The invention relates to a burner nozzle comprising an outer body having a longitudinal hole therethrough, a nozzle body which is inserted in the end portion of the longitudinal hole and has a coaxial nozzle orifice, with a vortex pocket provided at the inner end of the nozzle orifice communicating, through at least one channel, with a first annular cavity extending at the outer end of the channel or channels, and a pin which is inserted in the longitudinal hole of the outer body and bounds a passage for supplying fuel to the nozzle body. 
     From Swiss Pat. No. 553,379, there is known an oil burner with a burner nozzle comprising an axially symmetrical outer body tapering toward the nozzle tip. In the tip of the outer body, a nozzle plate is inserted having a nozzle orifice at its center. Adjoining the nozzle plate is a vortex body whose contacting surface is provided with channels which extend from the outer edge of the vortex body to the area of the nozzle orifice. The vortex body is pressed into contact with the nozzle plate by a hollow pin which is snugly screwed into the outer body. An annular gap is provided between the front end of the pin and of the vortex body and the inside surface of the outer body. On its front end, the pin is further provided with slots through which, during operation, the oil can flow from the oblong hole of the pin into said annular gap. Then, the oil flows through the slot to the outer ends of the channels provided in the vortex body. The pin end remote from the nozzle plate is provided with radial bores opening into the oblong hole thereof. In the zone of these radial bores, the pin is surrounded by a fine-meshed screen. During operation, the oil passes through the screen serving as filter and through the radial bores into the oblong hole of the pin. 
     Thus, during operation of this prior art burner nozzle, the oil is filtered through the screen surrounding the rear portion of the pin. Experience has shown, however, that in spite of this arrangement, dirt still passes to the channels of the vortex body and may cause their clogging. This is the case particularly with burner nozzles which are intended for relatively low heating capacities and in which the channels of the vortex body have correspondingly small sectional areas. For example, for heating equipments of small single-family houses, and of vehicles, burners are needed in which the channels have widths and depths in the magnitude of 0.12 to 0.3 mm. 
     Attempts have already been made to prevent a clogging of the channels by providing a collar at the front end of the pin of the prior art burner disclosed in Swiss Pat. No. 553,379. The collar has been dimensioned to obtain a radial width of the annular gap between the inside surface of the outer body and the collar, in the zone of the collar,in the magnitude of 0.1 mm, so that dirt particles also be held back. This design of the oil burner did reduce the frequency of clogging the channels. However, tests have shown that dirt particles, particularly fibre-like particles, still penetrate to the channels of the vortex body and may cause clogging. Further known, from German Offenlegungschrift No. 24 41 833, is a burner nozzle having a hollow outer body in which, at one of its ends, a substantially disc-shaped body and a vortex body with a channel for producing turbulence are inserted. On the vortex body side remote from the nozzle body, a hollow bolt with a stepped outer surface is provided which is screwed into the outer body. An annular gap is provided between the outer surfaces of the nozzle body, of the vortex body, and of the adjoining end of the hollow bolt and the inside surface of the outer body. The bolt end adjoining the vortex body is provided with radial ports connecting the cavity to the annular gap. A filter in the form of a cylindrical sleeve surrounds the bolt end provided with the radial ports, the vortex body, as well as a portion of the nozzle body, and applies against their outer surfaces. The oil to be burned is supplied through the hollow of the bolt and passes through the radial ports of the bolt and said annular gap into the channel of the vortex body, and is to be filtered by the filter. 
     The filter of a burner nozzle designed in accordance with the German Offenlegunschrift No. 24 41 833 and known to the inventor is made from a metal gauze which certainly is cut out of a piece of gauze and then welded to a sleeve. Thus, the prior art burner nozzle has the disadvantage that a separate filter must be made of a wire mesh and engaged on the nozzle body, the vortex body, and the end of the bolt. Since the filter must be very fine-meshed to perform its function, its manufacture and engagement on the parts is relatively time consuming and very exacting. In addition, it is hardly possible to engage the filter on the nozzle body, the vortex body, and the bolt in such a way as to ensure everywhere a close fit and to prevent dirt particles from escaping past the filter edges. In particular, since the filter is provided with a weld which necessarily increases thickness and causes rigidity, there is a great chance that the filter will not perfectly apply in the area of the weld and that dirt particles will there be allowed to escape. Moreover, the weld itself also may have defective spots where dirt particles may penetrate through. Further, there is a considerable risk that during the cutting of the wire mesh and engaging of the filter, the wires forming the filter will partly be cut through or otherwise damaged and that later, during operation, wire lengths will break off and clog the channel of the vortex body. 
     Another disadvantage of the burner nozzle known from German Offenlegungschrift No. 24 41 833 results from the fact that the heating oil usually contains semi-solid, paraffinic particles. In general, these particles are about ball-shaped and may temporarily be deformed. While temporarily so deformed, they might pass through an aperture of a lattice filter, even though in their initial spherical shape, they have a diameter exceeding the size of the filter aperture. If such particles pass into a channel serving to produce turbulence and having a clear cross section smaller than the ball diameter, but being substantially longer than the ball diameter, particles frequently can no longer deform to a sufficient extent to pass through the channel and cause clogging. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a burner nozzle in which a clogging of the channels is prevented as securely as possible, even if a vortex body is used having channels of a very small sectional area. In spite of that, the burner nozzle must be easy to assemble and, in particular, the necessity of manufacturing and mounting a filter as a separate component part is to be eliminated. This problem is solved by providing a burner nozzle of the kind mentioned above and having the features set forth in claim 1. Further particularly advantageous embodiments of the invention follow from the dependent claims. 
     The inventive burner nozzle comprises at least one filter which is formed by a circular row of grooves. Advantageously, the length of the grooves is at least three times, preferably five times, and, for example, 10 to 20 times, their width as well as their depth. This makes sure with a great probability that the filter will prevent the passage therethrough also of paraffinic and other deformable particles which might clog the vortex channels. 
     The grooves of the filter of the inventive burner nozzle also provides another advantage over the lattice-type filter of German Offenlengunschrift No. 24 41 833. That is, the grooves increase the friction and, consequently, the temperature of the fuel oil flowing therethrough, with the result that the volume of the oil slightly increases prior to reaching the vortex channels. This reduces the density and the specific calorific value which is related to the volume. In addition, the frictional effects in the grooves increase the drop in pressure. For these reasons, and with a definite predetermined nominal performance of the burner, the grooves make it possible to enlarge the cross section of the channels, which further reduces the risk of clogging. 
     In accordance with the invention, a burner nozzle is provided which includes an outer body having a longitudinal bore extending therethrough from an entrance end to an exit end for passing a fuel therethrough. A nozzle body is mounted in the bore adjacent to the exit end. The nozzle body has an orifice coaxially disposed in respect to the axis of the longitudinal bore for passing the fuel. A vortex body is mounted in the bore spaced from the outer body to provide a first annular cavity between the outer body and the periphery of the vortex body. The vortex body has a front face designed for reception on the nozzle body. The front face includes a tapering pocket immediately adjacent to and in alignment with the orifice and a channel interconnecting the first annular cavity and the tapering pocket. A pin member is mounted in the bore. The pin member has a passage for supplying fuel to the nozzle body. The pin member also has an annular groove near an end thereof adjacent to the vortex body to provide a second annular cavity between the outer body and the periphery of the pin member. The pin member has a surface portion intermediate the second annular cavity and the first annular cavity which contacts a surface portion of the outer body which bounds the longitudinal bore. One of the surface portions has a plurality of grooves interconnecting the first cavity and the second cavity. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the subject matter of the invention is explained by referring to the embodiment shown in the drawings, where 
     FIG. 1 is a longitudinal sectional view of a burner head accommodating a burner nozzle; 
     FIG. 2 is an enlarged longitudinal sectional view of a burner nozzle; 
     FIG. 3 is a top plan view still enlarged relative to FIG. 2 of the front face of the vortex body which is provided with the channels; 
     FIG. 4 is a section taken across the vortex body shown in FIG. 3; 
     FIG. 5 is a view, enlarged relative to FIG. 2, of the front end of the pin, carrying the circular row of grooves; 
     FIG. 6 is a top plan view, still enlarged relative to FIG. 5, of the end of the pin, taken in the direction of arrow VI of FIG. 5; 
     FIG. 7 shows a variant of a burner nozzle in which a circular row of grooves is provided on the vortex body; and 
     FIG. 8 is a longitudinal sectional view of a burner nozzle in which the circular row of grooves serving the purpose of filtering is provided on the vortex body. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The burner head shown in FIG. 1 comprises a flame tube 1 accommodating a burner nozzle 5 which is secured to a burner rod 3, an ignition electrode 7, and a baffle plate 9. The baffle plate has an aperture 9a which is coaxial with burner nozzle 5. 
     Burner nozzle 5, separately shown in FIG. 2, comprises a metallic, substantially rotationally symmetrical outer body 21 which conically tapers toward its end forming the tip of the burner nozzle and is provided, close to its other end, with an external thread by which it can be screwed into burner rod 3 which has a longitudinal hole for receiving the externally threaded end. Outer body 21 is provided with a coaxial longitudinal hole or bore 21a extending therethrough. Hole 21a includes a circularly cylindrical, main midportion 21b which is followed, in the vicinity of the conical end of the outer body, by a cylindrical portion 21c having a slightly smaller diameter and being limited, on its end remote from midportion 21b, by a radial shoulder face. At the side of the midportion 21b remote from the conical end, a slightly wider tapped hole portion 21d is provided. The opposite end 21e of hole 21a, remote from the conically tapered end of the outer body, is again circularly cylindrical and has a slightly larger diameter than the tapped portion. 
     In hole portion 21c, a disc-shaped nozzle body 23 is inserted having a circular contour and being provided with an orifice 23a which extends therethrough and is coaxial with the axis of rotational symmetry of outer body 21. Orifice 23a is necked in its mid-portion and enlarges to both sides. Nozzle body 23 is followed by an also disc-shaped vortex body 25 having a circularly cylindrical outer contour. 
     The radial front face 25a of vortex body 25, which is received on, that is, applies against nozzle body 23, is provided, at its center, with a conically tapering pocket hole 25b, as best shown in FIGS. 3 and 4, adjacent to and in alignment with the orifice 23a. Two extend from the outer circumference of the vortex body 25 and open into the pocket hole. The two channels 25c are symmetrical relative to the center of the vortex body, however, they do not extend radially, but are tangential to an imaginary circle which is coaxial with the vortex body axis. Channels 25c have a rectangular cross section and their depth measured parallel to the longitudinal axis of burner nozzle 5 is indicated at a and their widths measured perpendicularly thereto is indicated at b. The outer diameter of the vortex body 25 is smaller than the inner diameter of the main hole portion 21b into which the vortex body is inserted. Therefore, an annular cavity 43 is formed in the zone of the peripheral ends of channels 25c, between the circumferential surface of vortex body 25 and the inside surface of outer body 21. 
     Burner nozzle 5 further comprises a substantially cylindrical pin 27 which is provided with an external thread 27a extending over a part of the pin length and screwed into the tapped hole portion 21d of outer body 21. The end of pin 27 which is enclosed in outer body 21 is provided with a recess forming a seat for a portion of vortex body 25 whose front face 25a is pressed by the pin into in some degree tight contact with nozzle body 23. In the direction of vortex body 25, external thread 27a is followed by a portion 27b which has a circularly cylindrical outer surface and whose diameter is approximately equal to the inner diameter of main portion 21b of hole 21 of the outer body. Near the pin end facing the vortex body, portion 27b is followed by an annular groove 27c. On its outermost end portion, the end portion proper 27d facing the vortex body of the pin is provided with a conical taper, and on its cylindrical outer surface, with a circular row of grooves 27 e. 
     Grooves 27e, which are best shown in FIG. 5 and 6, are bounded by teeth and uniformly distributed over the circumference of pin 27, and they are provided in a number of at least thirty, and preferably about ninety. Grooves 27e extend parallel to the longitudinal axis of symmetry of burner nozzle 5. Grooves 27e have a triangular cross-section with the vertex at their bottom. The depth of the grooves measured between their deepest point and the envelope 29 is indicated at t in FIG. 6. The maximum widths of the grooves measured tangentially of the envelope is indicated at w in FIG. 6. 
     Pin 27 is further provided with a coaxial blind bore 27g which is drilled from its side facing the vortex body. In the pin portion projecting from outer body 21, two diametrally opposite, radial bores 27i are provided which open into blind bore 27g. Two other radial, diametrally opposite bores 27h connect blind bore 27g to the annular cavity 41 which is bounded by groove 27c and the inner surface of outer body 21. 
     An unthreaded rear end portion 27k of the pin, projecting from outer body 21, is slightly thicker than the adjoing threaded pin portion 27a, and is provided with a cross slot, thus forming a screw head. Further provided on the rear portion of pin 27 is a fine-meshed metal lattice or screen 31 embracing this portion. The screen extends from the shoulder formed by the pin end portion 27k into the hole portion 21e of the outer body thus covering particularly the outer openings of radial bores 27i. 
     Burner rod 3 as already mentioned, is provided with a longitudinal hole into which outer body 21 is screwed. Between the pin portion projecting from the outer body and embraced by screen 31 and the inside surface bounding the longitudinal hole of burner rod 3, a passage having a circular cross section is formed through which, during operation, the fuel to be burned is supplied. The external thread 27a and the cylindrical portion 27b of the pin, along with the corresponding opposite surfaces of outer body 21 provide a joint by which, in practice, the fuel passage is tightly sealed off. In the same way, the opening of blind hole 27g is practically sealed off by vortex body 25. Further, nozzle body 23 tightly seals the longitudinal hole 21a of the outer body towards the outside. Consequently, the fuel flows through screen 31 serving as filter into bores 27i and through blind bore 27g and the bores 27h into the annular cavity 41 bounded by groove 27c and the inside surface of the outer body. Therefrom, the fuel passes through grooves 27e into the annular cavity 43 which is formed between the circumferential surface of vortex body 25 and the inside surface of outer body 21. Thereupon, the fuel flows through channel 25c into the vortex space 45 which is bounded by the conical pocket hole 25b and the inner portion of nozzle orifice 23a. In this space, the fuel is set into a whirling motion and atomized. The fuel then leaves the nozzle as a mist and flows through the orifice 23 a, approximately as indicated in FIG. 1 at 11, within a conical space, through aperture 9a of baffle plate 9 out of the burner head. Air is supplied through flame tube 1, as indicated by arrows 13 in FIG. 1. The air mixes with the fuel mist, so that the fuel is combusted. 
     The burner nozzles are intended particularly for the heating equipment of single-family houses or vehicles, for example, driver cabins of trucks. In such applications, about 1 to 5 kg of fuel per hour are consumed, the fuel being either fuel oil or diesel oil. In such burner nozzles, the depth a and the width b of vortex-body channels 25c are less than 0.5 mm, usually about 0.1 to 0.3 mm, depending on the wanted heating capacity. The dimensions a and b are approximately equal to each other, so that channels 25c have about a square cross section. Grooves 27e are so proportioned to the design of the vortex body that their maximum sectional area is smaller than the maximum sectional area of channels 25c. More particularly, the maximum depth d and maximum width w of the grooves are smaller than both the channel depths a and the channel width b. Depending on the provided burner capacity, the depth t of grooves 27e is smaller than 0.15 mm, preferably smaller than 0.07 mm. It may be about 0.03 to 0.05 mm, for example. The width w of grooves 27e is about twice their depth t. Consequently, depending on the provided burner capacity, the maximum width w of the grooves is smaller than 0.3 mm, preferably smaller than 0.15 mm and, for example, 0.05 to 0.1 mm. Otherwise, the manufacturing tolerances of outer body 21 and of pin 27 are defined to the effect that the teeth 27f bounding the grooves 27e either contact the inside surfaces of the outer body or that maximum radial clearances are allowed therebetween which are smaller than the groove depth, and amount of about 0.01 mm at most. 
     In consequence, dirt particles present in the fuel and having passed through screen 31 or entrained from the further passages through which the fuel flows, are intercepted to a large extent at the entrance of grooves 27e. In particular, intercepted are any dirt particles which could clog channels 25c. This makes it possible to use burner nozzles with very small channel cross sections. This further permits to provide small diameters of the nozzle body, vortex body, and the outer body, which is important with low heating capacities, in order to obtain a satisfactory efficiency. 
     An accumulation of dirt particles at the entrance of grooves 27e may clog individual grooves. However, in view of the great number of grooves 27e, the free passage area for the fuel still remains sufficiently large, even if some of the grooves are clogged. 
     FIG. 7 shows a modified design of a pin 127 corresponding to pin 27, which may be received in outer body 21 as a substitute for pin 27. Pin 127 differs from pin 27 in that not a single circular row of grooves, but three portions 127d, 127m, 127n each with a circular row of grooves 127e around the pin, are provided between annular groove 127c which communicates with longitudinal hole 127g through radial bores 127h and the front face turned to the vortex body of pin 127. Annular grooves 127p and 127q, in which the fuel can flow around the circumference of the pin, are provided between the respective portions 127d, 127m and 127n following each other. 
     The burner nozzle 205 shown in FIG. 8 comprises an outer body 221. A nozzle 223 having a nozzle orifice 223a, a vortex body 225, and a pin 227 are received in the longitudinal hole 221a of body 221. Pin 227 presses vortex body 225 into contact with nozzle body 223. The front face 225a of vortex body 225 opposite to the nozzle body is conically tapered, provided with channels 225c, and projects into the nozzle orifice 223a whose inner portion forms the vortex space 245. Vortex body 225 is provided on its circumferential surface with a circular row of grooves 225e which extend in the axial direction and correspond in their function to grooves 27e of the first embodiment described above. The pin portion 227c adjacent the vortex body 225 has a smaller diameter than the following, cylindrical pin portion 227b and longitudinal hole 221a, so that an annular cavity 241 is formed between the outer surface of end portion 227c and the inner surface of longitudinal hole 221a. Pin 227 has a longitudinal bore 227g which communicates with cavity 241 through radial bore 227h. Cavity 241 communicates through grooves 225e with an annular cavity 243 which surrounds the vortex body 225 in the zone of the outer ends of channels 225c. 
     The grooves 127e of pin 127 shown in FIG. 7 and the grooves 225e of the vortex body 225 shown in FIG. 8 are of analogous design and their dimensions are identical with those of grooves 27e of the first embodiment of the burner nozzle, so that their filtering effect is similar. 
     Grooves 27e, 127e and 225e may be produced by means of an impact slotting tool, for example. 
     The cross-sectional shapes and dimensions of the grooves may, of course be modified in different ways and it is not necessary that the grooves extend exactly parallel to the longitudinal axis of symmetry of the burner nozzles. However, the grooves must provide a connection between two annular cavities of which one communicates with the peripheral ends of the channels serving to produce the whirling motion and the other communicates with the passage or passages through which the fuel is supplied. 
     It would further be possible, instead of providing the grooves on the circumferential surfaces of the vortex body or the pin through which the fuel is supplied, to provide them on the inside surface of the outer body. 
     Also, instead of providing the channels intended for producing the whirling motion in a vortex body, they might be provided on the inner front face of the nozzle body.