ULTRASONIC ATOMIZING VIBRATORY ELEMENT

Abstract: An ultrasonic atomizing vibratory element (10) comprises a elongated shank (14), and the tip of the elongated shank is formed with an edged portion (22) having at least one flat portion (24) which is formed stepwise. Liquid fuel is supplied from a pipe (30) to the flat portion (24) of the edged portion (22) along a groove (28) in the shank, and the liquid is atomized at the edged portion by ultrasonic vibration applied to the shank (14).

Description: Technical Field The present invention relates generally to an ultrasonic atomizing apparatus, and particularly to a vibrating element for use with an ultrasonic atomizing apparatus for atomizing liquid either intermittently or continuously. Such an element may be effectively used with (1) automobile fuel injection devices such as electronically controlled gasoline injection valves and electronically controlled diesel fuel injection valves, (2) gas turbine fuel nozzles, (3) burners for use on industrial, commercial and domestic boilers, heating furnaces and heating devices, (4) industrial liquid atomizers such as drying atomizers for drying liquid materials such as foods, medicines, agricultural chemicals, fertilizers and the like, spray heads for controlling temperature and humidity, atomizers for calcining powders (pelletizing ceramic), spray coating devices and reaction promoting devices, and (5) liquid atomizers for uses other than industrial ones, such as spreaders for agricultural chemicals and antiseptic solution. Background Art Pressure atomizing burners or liquid atomizers have been heretofore used to atomize liquid in the various fields of art as mentioned above. The term "liquid" herein used is intended to mean not only liquid but also various liquid materials such as a suspension, a solution or the like. In the injection nozzles used on such spray burners and the liquid atomizers, the liquid is atomized by virtue of the shearing action between the liquid injected from the nozzles and the ambient air (atmospheric air). Accordingly, in order to atomize the liquid supplied, it is required to increase the liquid supply pressure, resulting in making the liquid supplying facility such as pumps, piping and the like complicated and large-sized ones. Further, regulation of the flow rate of injection is effected by varying either the pressure of the liquid supplied or the area of the nozzle injecting port. However, the former method provides poor liquid atomization at a low flow rate (under a low pressure), as a remedy for which air or steam has additionally been used on medium-sized or large-sized boilers to aid in atomization of the liquid fuel supplied. Therefore apparatus become more and more complicated and enlarged. On the other hand, the latter method requires an extremely intricate structure of nozzle which is troublesome to control and maintain. To improve the defects of such prior art injection nozzles, attempts have been made to impart ultrasonic waves to a liquid material as the liquid material is injected from the injection port of the injection nozzle under pressure. However, the conventional ultrasonic liquid injection nozzle cannot be used in circumstances which require a large amount of atomized liquid because it has extremely small capacity for pulverization. As a result of extensive researches and experiments conducted on the ultrasonic liquid atomizing mechanism and the configuration of the ultrasonic vibrating element so as to accomplish atomization of a large amount of liquid, the present applicants have found that by providing an edged portion at the end portion of an ultrasonic vibrating element and supplying liquid to the edged portion in a film form, a large quantity of liquid can be atomized at the edged portion, and have proposed an ultrasonic injection method and an injection nozzle on that basis (see European Patent Application EP-A-0 159 189). The present invention relates to improvements in the ultrasonic atomizing apparatus described above, and particularly to improvements in the vibrating element for use with the atomizing apparatus. Accordingly, an object of the present invention is to provide an ultrasonic atomizing vibratory element which is capable of accomplishing satisfactorily either continuous or intermittent liquid supply. Another object of the present invention is to provide an ultrasonic atomizing vibratory element which is capable of stably and effectively atomizing liquid either in a large amount or a small amount and therefore providing an extremely large turn-down ratio as well as mixing the atomized liquid with air for combustion, particularly in fuel injection nozzles for use in domestic heating boilers, gas turbines, automobiles and the like. A further object of the present invention is to provide an ultrasonic atomizing vibratory element which is capable of accomplishing stable atomization without fluctuating the states of atomization (flow rate and particle size) of the supplied liquid. In particular, the element of the present invention may be suitably used for a horizontally disposed combustor. Summary of the Invention The present invention provides an ultrasonic atomizing vibratory element comprising an elongated shank and an edged portion which has at least one flat portion stepwise formed at the tip of the elongated shank, the flat portion of said edged portion being supplied with liquid to atomize said liquid. Brief Description of the Drawings One way of carrying out the present invention will now be described in detail by way of example with reference to Fig. 1 of the accompanying drawings which is a fragmentary perspective view of an embodiment of an ultrasonic atomizing vibratory element in accordance with the present invention, FIG. 2 being a sectional view of a conventional ultrasonic atomizing apparatus which will be described in detail, by way of comparison. Detailed description with reference to the accompanying drawings. With reference first to Fig. 2, the conventional apparatus, namely, a fuel atomizer 1 for use with a kerosene heater used as a burner for a domestic heater, for example, is provided with a vibrating element 10 in a sideways position. The vibrating element 10 includes a body portion 12 positioned on the right in this embodiment, an elongated, cylindrical shank 14 of the vibrating element having a diameter smaller than that of the body portion 12 and a transition portion 16 connecting the body portion 12 and the shank 14. The body portion 12 is provided with an enlarged diameter flange 18 which is supported by a holder 20, and the vibrating element 10 is secured to a heater body (not shown) through the holder 20. The tip of the vibrating element 10, that is, the tip on the left of the shank 14 in this embodiment is formed with an edged portion 22. Further, one or more fuel supplying pipes 30 are disposed adjacent to the edged portion 22 of the shank 14, which feed the fuel to the edged portion 22. The fuel supplying pipes are supplied with the liquid fuel from a fuel supplying source (not shown) through external supplying lines (not shown). The flow and flow rate of fuel are controlled by supplying valves (not shown) disposed in the external supplying lines. With the construction described above, the vibrating element 10 is continuously vibrated by an ultrasonic vibration generating means 100 operatively connected to the body portion 12. Accordingly, liquid fuel is supplied through the lines, the supplying valves and the supplying pipes 30, to the edged portion 22 where the fuel is atomized and outwardly injected. The edged portion 22 of the vibrating element 1 is usually formed either with four annular steps having progressively increased diameters or with a plurality of annular steps having equal diameters as shown. The atomizing apparatus having such construction operates extremely effectively. However, the present inventors have found that the atomizing apparatus such as fuel injection nozzles for use with a boiler, a gas turbine or an automobile, and the like in which the flow rate and thus supplying speed of fuel varies in response to the running load has various drawbacks. Particularly, with the construction of the atomizing apparatus of the type as shown in Fig. 2 in which a vibrating element is horizontally disposed, and constructed as shown in Fig. 2, at an increased flow rate of fuel supply a part of the fuel may fall in drops without being fed to the edged portion, or the particle size of the liquid being pulverized may be increased. The occurrence of such phenomena causes incomplete combustion resulting in increasing hydrocarbon, carbon monoxide and soot in the exhaust gas. On the other hand, at a low flow rate of fuel the mixing of fuel and air for combustion is insufficiently effected resulting in lowering combustion efficiency and increasing hydrocarbon, carbon monoxide and soot in the exhaust gas similar to the above-mentioned. The ultrasonic atomizing vibratory element according to the present invention and shown in Fig. 1 will now be described in detail with reference to Fig. 1. While the present invention may be effectively used in various applications as mentioned above, in the present embodiment, the present invention will be described as being used as a fuel atomizer for a kerosene heater as explained in connection with Fig. 2. Fig. 1 merely shows an edged portion 22 at the tip of the vibratory element of the atomizer. According to the present invention, the edged portion 22 of a vibrating element 10 is formed with a plurality of flat portions 24 and 26 which are stepwise formed at the tip of the vibrating element 10 (or the edged portion 22) and progressively reduced in the height of step in the direction from right to left in Fig. 1 in the present embodiment. The shape of the edged portion 22 as seen in the direction indicated by arrow X is suitably a circular shape but is not limited to such a shape. In the present embodiment, the edged portion is formed with two flat portions, namely a first flat portion 24 and a second flat portion 26 but the configuration of the edged portion 22 is not limited to this two step configuration and may comprise one step or more than two such steps. Further, while the flat portions 24 and 26 are separately formed in horizontal planes in the present embodiment, they may be formed in planes slanted in any direction other than horizontal, if desired. Furthermore, respective flat portions may be slanted in different directions. Further, a shank 14 of vibrating element 10 is formed with a groove 28 in the outer periphery of the shank 14 which groove receives fuel from a fuel supplying pipe 30. The groove 28 is adapted to guide the fuel along the shank to the first stage flat portion 24. The groove 28 is progressively enlarged in cross-section from an upstream portion 28 a which receives the fuel discharged out of the fuel supplying pipe 30 to a downstream portion 28 b whereat the fuel is discharged to the flat portion 24. Preferably, the bottom surface of the groove is inclined downwardly in the direction from the fuel receiving portion 28 a to the fuel discharging portion 28 b , to facilitate the flow of the fuel along the groove. Further, the groove may be of a U-shaped or V-shaped cross-section. With the construction of vibrating element described with reference to, and as shown in, Fig. 1, the fuel which is supplied to the shank 14 of the vibrating element may be guided by the groove 28 to flow efficiently to the first flat portion 24. The fuel which is supplied to the first flat portion 24 may be spread over the first flat portion resulting in increasing the contacting area of the fuel and the edged portion. The fuel may be atomized at the flat portion 24 and its peripheral edges. The surplus fuel which is not atomized at the first flat portion 24 flows from the first flat portion to the second flat portion 26 to be again spread over the second flat portion 26 and to be atomized at the second flat portion and its peripheral edges. Thus, the present invention accomplishes an increased efficiency of pulverization and cooling of supply liquid. In addition according to the present invention, it is possible to accomplish consistent liquid atomization and eliminate the trouble that the fuel supplied to the edged portion 22 in the prior art Fig. 2 construction falls in droplets. Advantages of the Invention With the construction as herein described according to the present invention with reference to Fig. 1, the ultrasonic atomizing vibratory element can stably and efficiently atomize either a large amount of, or a small amount of, liquid at the flat portion(s) formed in the edged portion, and resulting in providing a large turn down ratio and eliminating the problem of falling of the liquid in droplets. Further, it is possible to accomplish stable combustion and reduction of hydrocarbon (HC), carbon monoxide (CO) and soot in exhaust gases in fuel injection nozzles for use with fuel atomizers for kerosene heaters, boilers, gas turbines, atuomobiles and the like, to a large extent. In addition the vibratory element of Fig. 1 can accomplish consistent liquid atomization in that there is no substantial change in the conditions of atomization (flow rate and particle size), so that particularly the vibratory element of Fig. 1 may effectively be used in a horizontal combustor.

Claims: An ultrasonic atomizing vibratory element (10) comprising an elongate shank (14) and an edged portion (22) which has at least one flat portion (24,26) stepwise formed at the tip of the elongate shank (14), said flat portion (24,26) of said edged portion (22) being supplied with liquid to atomize said liquid. An ultrasonic atomizing vibratory element according to claim 1, wherein said flat portion (24,26) is in a substantially horizontal plane. An ultrasonic atomizing vibratory element (10) according to claim 1 or claim 2, wherein said shank (14) is formed with a groove (28) for guiding the liquid to said flat portion (24,26) of the edged portion (22). An ultrasonic atomizing vibratory element according to claim 3, wherein said groove (28) is progressively enlarged in section in the direction from a portion (28a) to receive the liquid to a portion (28b) to discharge the liquid to the flat portion (24) and the bottom surface of the groove (28) is inclined downwardly in the direction from said liquid receiving portion to said liquid discharging portion. An ultrasonic atomizing vibratory element as claimed in any preceding claim, wherein the edged portion (22) comprises more than one step (24,26). An ultrasonic atomizing vibratory element as claimed in claim 5, wherein the steps (24,26) both lie in horizontal planes. An ultrasonic atomizing vibratory element as claimed in claim 5, wherein the steps (24,26) lie in planes intersecting one another.

Inventors: ISHIKAWA, KIYOE, KUROKAWA, HITOSHI, TAKEZI, HIROYUKI, TANAKA, YASUHISA
Applicants: TONEN CORPORATION
Application year: 1987
Main classification: B05B17
IPC codes: B05B17, B06B1