GB2120958A - Atomizer - Google Patents

Abstract

Liquid is injected from a single hole injector (1) and atomized by the use of an impingement body (3). The liquid expanded by the body (3) is formed into a turbulent liquid film of diameter D by properly selecting the diameter of nozzle, the liquid pressure, and the configuration of the impingement body (3). The liquid film is broken up at its edge into fine particles by means of the high-frequency vibration of the liquid film. The pressure P of the jet is selected from a range in which the rate of change of D relative to P is less or equal to zero. <IMAGE>

Description

SPECIFICATION Atomiser Background of the invention Field of the invention The present invention relates to an atomizer for atomizing liquid, usable for combustors, internalcombustion engines, humidifiers or other air conditioning equipments, sprayers for spraying agricultural chemicals, powder driers, sprayers for paints and so forth. More particularly, the invention is concerned with an atomizer capable of improving the performance of the apparatus mentioned above through the generation of liquid fine particles. More specifically, the invention pertains to an atomizer improved to obtain spray having a smaller liquid particle diameter, which is naturally excellent in floatability and evaporation speed, thereby to make it possible to improve the intrinsic characteristics of the above-mentioned apparatus.

Description of the prior art Hitherto, various methods have been devised as means for atomizing liquid. The invention is intended to improve the atomizer of impingement atomization type, which is the simplest in construction. Although the impingement atomization type atomizer has been partly put into practical use, it has not been widely spread due to the following reasons.

Namely, (1 ) the particle diameter of the liquid atomized by the impingement atomization type atomizer is larger than that atomized by the air biast atomization type atomizer (employing a high-speed air flow, e.g., carburetors, industrial burners, etc), which is representative of atomizers; and (2) it is difficult to atomize all the liquid to be atomized, since some of the liquid adheres to a solid impingement body.

Due to the above-mentioned disadvantages, the impingement atomization type atomizer has been regarded as unsuitable for practical use in spite of advantages thereof, i.e., a simple construction, an efficient atomization with a smaller power, etc.

Summary ofthe invention Object of the invention Accordingly, a first object of the invention is to make the liquid particle diameter smaller thereby to obviate the first-mentioned problem of the prior art.

A second object of the invention is to eliminate the liquid which is not atomized owing to its adhesion to the impingement body thereby to overcome the second-mentioned problem of the prior art.

Briefsummary of the invention To these ends, according to the invention, there is provided an atomizer having an injector for injecting a liquid jet from its tip and an impingement body disposed facing the liquid jet in order to expand the liquid jet into a liquid film and produce broken-up fine particles at extremities of the liquid film, characterized in that the liquid pressure P of the injector is set within a range where the relationship between the liquid pressure P and the outside diameter D of the liquid film satisfies dD/dP0.

The above and other objects, features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings.

Brief description of the drawings Figure 1 is a sectional view of a first embodiment of the atomizer in accordance with the invention; Figure 2 is a characteristic chart showing the relationship between the liquid pressure and the liquid film diameter; Figures 3 and 4 schematically illustrate the atomization mechanism of the first embodiment; Figure 5 is a characteristic chart showing the relationship between the liquid pressure and the break-up length; Figures 6 and 7 schematically illustrates liquid jets and the atomization mechanism of a second embodiment of the atomizer in accordance with the invention, respectively.

Figures 8 and 9 schematically illustrate the atomization mechanisms of third and fourth embodiments of the atomizer in accordance with the invention, respectively; and Figures 10 and 11 showfifth and sixth embodiments of the atomizer in accordance with the invention, respectively.

Detailed description of the preferred embodiments Preferred embodiments of the invention will be described hereinunder in detail with reference to the accompanying drawings.

Figures 1 and 2 in combination show a first embodiment of the atomizer in accordance with the invention.

Referring now to Figure 1, a liquid is injected toward an impingement body 3 from a nozzle 2 of an injector 1. The nozzle 2 has an inside diameter of 100 pW, while the impingement body 3 has an outside diameter of 500 ij. Moreover, kerosene is employed as the liquid.

Under the above-mentioned conditions, as the liquid is pumped to the injector 1 by means of a pressurizing pump 6, the liquid linearly flows out from the nozzle 2 and impinges upon the center of the impingement body 3 sufficiently ground to have a mirror surface.

After the impingement, the liquid spreads so as to form a disk-shaped thin film and then breaks up at the radial ends of the liquid film. There are also cases where, when the liquid pressure is extremely low, the radial ends of the disk-shaped liquid film bend toward the center thereof again to form a spherical liquid film. The diameter D (the maximum outside diameter of the liquid film) of such a liquid film enlarges with the increase in the liquid pressure P in the region where the velocity V of the injected liquid, i.e., the liquid pressure P is low (Figure 2 shows the relationship between the liquid film diameter D and the liquid pressure P). In such a region, the liquid film diameter D increases in proportion to the square of the velocity V of the liquid jet.In addition, since the liquid jet velocity V is proportional to the square root of the liquid pressure P, the liquid film diameter D increases in proportion to the liquid pressure P.

In this case, the liquid film is smooth or flat and hardly has turbulency in the flow within the film. If the liquid had no surface tension, the liquid film would infinitely spread (although this is impossible in practice). Actually, the surface tension of the liquid acts in the direction opposite to the direction of movement of the liquid film. In other words, the surface tension of the liquid works so as to bring back the liquid film toward the point of impingement.

The liquid film diameter is determined by the balance of the spreading force of the liquid film to the surface tension of the liquid. More specifically, the momentum of the jet in scattering does not change with the increase in the liquid film diameter (since the quantity of the liquid which continuously flows is constant with respect to the liquid film diameter D, and since also the flow velocity of the liquid is conserved within the liquid film and hence does not change). On the other hand, the surface tension increases as the liquid film diameter D becomes larger, since the film area naturally enlarges with the increase in the liquid film diameter D.

The relationship between the liquid pressure P and the liquid film diameter D is explained by the relationship between such two forces.

Within the region, i.e., the smooth or flat liquid film region where dD/dP > 0 is satisfied, the iiquid losing in velocity at radial ends of the liquid film breaks up from the liquid film, producing particles having a relatively large diameter.

The mechanism for generating the large-diameter particles is considered as follows through observation. The liquid film having lost its radial velocity at an extremity thereof is concentrated in the form of a string radially extending from the extremity thereof under the surface tension acting circumferentially.

Then, the string-shaped liquid breaks up into gigantic particles (see Figures 3).

Examples of the conventional impingement atomization type atomizer employing this smooth or flat liquid film region include an atomizer in which a high-speed airflow is adapted to break up the liquid film.

In the embodiment, it has been found that as the liquid pressure P is further raised, the liquid film diameter D gradually lowers the rate of change dD/dP, and finally a region of dD/dP = 0 is reached, i.e., a region in which the liquid film diameter D does not change with the increase in the liquid pressure P.

Aiso a region of dD/dP < 0 has been discovered, i.e., a region in which the liquid film diameter D decreases with the increase in the liquid pressure P. In addition, it has been confirmed that the fine particle diameter is minimized in the region of dD/dP < 0.

In such a region, unlike the above-mentioned smooth or flat film, the liquid film is a wavy turbulent film having a high-frequency vibration.

Although the scattering velocity of the liquid film increases in proportion to the increase in the liquid jet velocity V, the liquid film becomes turbulent when the liquid jet velocity exceeds a certain value.

Therefore, the liquid film starts to break up on a smaller radius before the above-described two forces balance with each other. The increase in the liquid jet velocity makes the turbulency larger. For this reason, the region of dD/dP I 0 is finally reached.

In this turbulent film region, the extremity of the liquid film breaks up in the form of a substantial ring, which continues spreading while still maintaining the radial velocity and then breaks up into particles (see Figure 4).

The ring immediately before the breakup has a thickness smaller than that of the string-shaped liquid produced at the extremity of the abovedescribed smooth or flat liquid film. This is because the latter is formed by the liquid film concentrated into a string-shaped liquid, while the former is produced by the breakup of the liquid film itself.

Accordingly, the fine particle diameter in the turbulent film region is small.

Moreover, it is often that the above-mentioned ring is not a perfect ring but is constituted by a group of split arcs. In addition, such a phenomenon occurs near the region of dD/dP = 0 and is more clearly observed in the region of dD/dP < 0. Further, the diameter of the impingement body 3 and that of the nozzle 2 have large effects on obtaining such a region of dD/dP ~ 0. This point will be described hereinunder.

First of all, the liquid jet flows from the nozzle 2 toward the impingement body 3 and circumferentially spread thereon. The liquid jet largely loses its velocity on the impingement body 3 by means of friction. Accordingly, the smaller the diameter of the impingement body 3, the higher the scattering velocity of the liquid film.

The scattering velocity of the liquid film governs the turbulency as described above. Tehrefore, when the diameter of the impingement body 3 is smaller, the turbulent film region can be obtained at a lower liquid jet velocity V.

According to an experiment, the liquid pressure required to obtain the region of dD/dP = 0 by employing the nozzle 2 having a diameter of 100 ,a was 12 to 15 kgf/cm2 for a diameter of the impingement body 3 of 1 mm; 5 to 6 kgf/cm2 for a diameter of 0.5 mm; and 4 to 5 kgf/cm2 for a diameter of 0.2 mm.

Thus, it has been proved that as the diameter of the impingement body 3 is smaller, the liquid jet velocity V is more effectively converted into a liquid film scattering velocity and moreover, the turbulent film can be produced at a lower liquid pressure. It is a matter of course that any impingement body 3 smaller than the diameter of the nozzle 2 cannot be an impingement body.

Moreover, the relationship between the liquid pressure and the diameter of the impingement body 3 also differs in accordance with the diameter of the nozzle 2. As the diameter of the nozzle 2 becomes smaller, the momentum of the liquid decreases, and also the momentum of the liquid film decreases.

Therefore, the impingement body 3 having a smaller diameter must be selected to obtain the region of dD/dP = < 0 As will be apparent from the above description, there is a certain relationship between the three, i.e., the diameter of the nozzle 2, the liquid pressure and the diameter of the impingement body 3. It is, however, possible to form a turbulent film and spray a predetermined amount of fine particles by determining the diameter of the nozzle 2 and the liquid pressure according to the desired amount of spray and the delivery pressure of the pump 6 and then by expeimentally selecting the diameter of the impingement body 3 corresponding to the region of dD/dP = 0 with respect to the diameter of the nozzle 2 and the liquid pressure.The selection of the diameter of the impingement body 3, as a matter of course, differs in accordance with the kind of the liquid to be atomized.

Since the conditions for obtaining the region of dD/dP =' 0 differ in accordance with not only the liquid pressure, the diameter of the nozzle 2 and the diameter of the impingement body 3 but also the kind of the liquid, it is impossible to numerically specify the relationship therebetween. It is, however, a common fact that the region of dD/dP =' 0 exists regardless of the kind of liquid and moreover, the atomization characteristics are excellent in that region.

Further, in carrying out the invention, it is extremely important to ensure the relative positional relationship between the injector 1 and the impingement body 3. Means therefor will be described hereinunder.

As has been described in the above embodiment, the diameter of the impingement body 3 is less than ten times as large as that of the nozzle 2 at most.

Moreover, it is necessary to make the jet impinge upon the center of the impingement body 3. The reason is that if the jet impinges upon a point off the center, the atomization becomes nonuniform and moreover, the velocity of the liquid film scattering from the impingement body 3 becomes uneven, resulting in a partial smooth or flat film, which is apt to produce gigantic particles.

In order to eliminate such a drawback, in the embodiment, the impingement body 3 is directly mounted to the injector 1 through a support 4.

The support 4 has a U-shaped configuration with one end thereof secured to the injector 1 and the other end secured to the impingement body 3. The U-shaped configuration allows the support 4 to avoid contact with the liquid film.

Moreover, in order to avoid the vibrations caused by the pressure of the jet, the support 4 employs a material having a diameter larger than that of the impingement body 3 so as to obtain a rigidity larger than that of the latter.

In addition, the support 4 has at a portion thereof a regulator 5 for regulating the relative positions of the nozzle 2 and the impingement body 3. By such a construction, the positions of the nozzle 2 and the impingement body 3 are accurately regulated, and it is possible to make the positional relationship therebetween stable and hard to be disordered.

Further, in case of employing the invention for an apparatus generating heat of high temperature, such as a spray combustor or the like, if a material of low thermal expansion coefficient, such as ceramic or crystailized glass, is employed for the support 4 for the impingement body 3, it is possible to stabilize the relationship between the nozzle 2 and the impingement body 3.

Figure 5 is a characteristic chart for determining a liquid pressure region in a second embodiment of the atomizer in accordance with the invention.

It will be apparent from Figure 2 showing the relationship between the liquid film diameter D and the liquid pressure P described above that although within the region of dD/dP =' 0, as the liquid pressure increases, the turbulency intensity becomes larger and the atomized liquid particle diameter becomes smaller, the liquid film diameter suddenly decreases near a liquid pressure of 15 kgf/cm2 in the Figure.

This is because the relationship between the length of the smooth jet shown in Figures 6A and 6B and the liquid pressure P changes in the region of dCldP =' 0 as shown in Figure 5 owing to the fact that the vibration wave jet obtained in such a region impinges upon the impingement body 3.

This phenomenon and effect thereof will be described hereinunder in detail.

Referring to Figures 5 and 6A, 6B the jet injected from the single hole injector 1 is first a smooth jet but gradually becomes a vibrating nonlinear jet and then breaks up as the vibration develops. The break-up length e, which is a length of the smooth jet from the nozzle 2 to a point at which the smooth jet becomes the vibration wave jet, changes with the liquid pressure P. The break-up length e becomes longer with the increase in the liquid pressure to a certain liquid pressure range (dB/dP > 0). However, as the liquid pressure exceeds a certain value, the break-up length e gradually decreases (dCldP =' 0).In addition, although the break-up length e differs in accordance with the kind of liquid, the nozzle diameter and configuration of the nozzle, the tendency of change of the break-up length e with respect to the liquid pressure P is completely the same. The time (T = KVW: K is a constant) required for the smooth jet to become the vibration wave jet is substantially constant independently of the liquid presure in the region where the relationship between the break-up length e and the liquid pressure P satisfies dCldP > 0, i.e., the region of low liquid pressure. The time, however, rapidly decreases in the region of dW/dP =' 0.This means that the jet starts to have a strong turbulencywhen the relationship between the break-up length e and the liquid pressure P enters the region of dW/dP =' 0.

According to photographic observation, it has been found that the shape of the vibration wave jet of the liquid jet within the region of de/dP > 0 tends to be such as shown in Figure 6A, while the shape of the vibration wave jet of the liquid jet within the region of dW/dP = < 0 tends to be such as shown in Figure 6B. The difference between the vibration wave jet shape is mainly attributable to the difference in turbulency intensity between the jets.

In addition, the turbulency generated in such a jet has an extremely short wavelength. Although the wavelength is not always constant, it is mainly composed of wavelengths three to five times as much as the diameter of the nozzle. For example, if a jet of JIS No. 1 kerosene having a flow velocity of 50 mls is produced from a nozzle having a diameter of 0.1 mm, then the jet vibrates at a frequency of about 150 to 250 kHz, which is a ultrasonic region.

In the case where a jet having a high-frequency deformation vibration as described above is made to impinge upon the impingement body 3, the liquid film produced is naturally subjected to the vibration of the jet itself and spreads in the form of a disk while vibrating with the same wavelength as that of the jet.

In the first embodiment described hereinbefore, the liquid film is a wavy turbulent film the vibration of which develops as the film gradually spreads toward the outer periphery as shown in Figure 4.

Accordingly, in this case, the liquid film is broken up in the form of a substantial ring at a portion having a relatively large liquid film diameter. At this portion, the liquid film has a decelerated flow velocity.

Therefore, the ring-shaped liquid produced becomes large in thickness owing to the surface tension as well as is apt to break up into gigantic particles. In other words, since the kinetic energy required for the ring to expand in the ring shape is small, the surface tension acts so as to bring back the ring.

In the second embodiment, however, unlike the first embodiment, the vibration of the liquid film scattering from the impingement body 3 is extremely large owing to the deformation vibration of the jet itself as shown in Figure 7, and hence, the liquid film is broken up in the form of ring immediately after leaving the impingement body 3.

The scattering velocity of the broken-up ring is ciose to the velocity of the liquid jet itself, so that the ring is expanded at a high velocity. As the expanding force, i.e., the force by means of the kinetic energy expands the ring against the surface tension, the ring becomes smaller in thickness and then is broken up by means of the turbulency newly caused in the ring.In addition, since, as described above, the intensity of turbulency of the jet in the case where a vibration wave jet obtained in the region of dCldP '= 0 is made to impinge is larger than that in the case where a vibration wave jet obtained in the region of deldP > 0 is made to impinge, the above-described phenomenon makes it possible to obtain fine particles distinctively and more effectively. In this case, since the turbulency is strong, the diameter of the liquid film produced is only slightly larger than that of the impingement body. The liquid film becomes so small that it is almost invisible to the naked eye.

Moreover, the region of dD/dP = 0 inevitably includes the region of deldP 0. This is because the liquid film becomes turbulent at a lower liquid pressure than the liquid jet, since the latter is more stable in construction than the former. It is a matter of course that also in the second embodiment, it is possible to obtain the conditions for attaining the region of dD/dP =' 0 obtained in the first embodiment. In addition, the region of dD/dP =' 0 can be obtained by even applying a vibration wave jet obtained in the region of de/dP = 0 to the impingement body. However, in such a case, the effect offered by the vibration of the liquid jet is not satisfactory.Employing the region satisfying both dD/dP = 0 and dCldP =' 0 permits the liquid film to be most effectively broken up into fine spray particles.

In addition, the above-described effect of the vibration wave jet obtained in the region of ddP 0 is not damaged, whether the liquid jet is continuous or broken up.

Figure 8 shows a third embodiment of the atomizer in accordance with the invention.

In the firstt and second embodiments, the velocity of the liquid jet is converted into the radial velocity (of the liquid film and the ring) by means of the impingement body 3, and as the converted velocity becomes higher, the liquid film becomes more unstable and more easily becomes turbulent, or the ring produced is expanded at a higher speed and more easily becomes small in thickness.

Accordingly, the third embodiment maily relates to the construction of the impingement body 3 for effectively spreading the velocity of the liquid jet radially as follows.

It is necessary to conserve the momentum of the fuel jet on the impingement body 3 as much as possible. Therefore, the impingement surface is mirror-finished in order to decrease the friction at the surface of the impingement body 3. However, when flying out to space from the periphery of the impingement body 3, the liquid film spreading on the impingement body 3 is forced to reduce its radial velocity by the affinity between the side surface of the impingement body 3 and the liquid fuel and also wets the side surface of the impingement body 3. For this reason, the liquid film formed undesirably becomes large in thickness, so that it is impossible to make the particle diameter of the produced spray sufficiently small.Moreover, all the liquid fuel injected from the nozzle 2 cannot be atomized, and some of the liquid fuel adheres to the side surface of the impingement body 3, producing sugs.

The third embodiment has attained improvement in the atomization characteristics and the atomization efficiency by reforming the configuration of the impingement body thereby to overcome the abovementioned disadvantages.

The impingement body 3 is circular and mirrorfinished similarly to the conventional impingement body. However, the distal end of the impingement body 3 is formed into an inverted cone, and the impingement surface and an impingement body side surface 3a adjacent thereto make an acute angle at the periphery of the impingement body 3. Conse quently,the liquid fuel expanded into a liquid film in the impingement body 3 contacts only a sharp edge portion 7 when flying out into space. For this reason, unlike the conventional columnar impingement body, the impingement body in accordance with this embodiment permits the reduction in the radial velocity of the liquid film to be extremely small.

Moreover, such a configuration allows the surface tension of the liquid fuel to overcome the affinity between the liquid fuel and the impingement body side surface 3a, so that there is no possibiiity that the liquid fuel wets the impingement body side surface 3a. In consequence, the radial velocity of the liquid jet within the liquid film is conserved substantially as it is. Accordingly, the liquid film formed becomes small in thickness, so that extremely small spray particles are produced and moreover, it is possible to atomize almost all the fuel injected from the nozzle.

Figure 9 shows a fourth embodiment of the atomizer in accordance with the invention.

The fourth embodiment has the same object as the third embodiment as follows.

The impingement body 3 is constituted by a circular thin plate and is supported by the support 4 having a diameter smaller than that of the impingement body 3, being connected at its rear side to the support 4. The impingement body and the support are conventionally formed into one body, and the impingement surface is conventionally formed by mirror-finishing the impingement body end surface on the grounds of the atomization characteristics. By employing such a construction as that in this embodiment, however, the surface per se of the thin plate as the material is a mirror surface; hence, it becomes unnecessary to specially mirror-finish the impingement body surface, so that the production cost is greatiy cut down.Moreover, since the impingement body 3 is generally required to have wear resistance, it is conventionally necessary to employ an expensive hard material for the impingement body 3 including also the support portion. In the embodiment, however, it is only necessary to employ a wear-resistant material only for the impingement body 3, and the support 4 is not required to have such a property and is able to employ, for example, a synthetic resin or the like as the material therefor. Accordingly, also the material cost is cut down.

Further, constituting the impingement body 3 by a thin plate makes it possible to minimize the adverse effect of the side surface of the impingement body 3 on atomization. More specifically, when flying out into space, the liquid fuel expanded into a liquid film on the impingement body 3 contacts only the edge portion 7 at the periphery of the impingement body.

Therefore, the reduction in the radial velocity of the liquid jet within the liquid film is lessened, unlike the conventional columnar impingement body. Moreover, the surface tension of the liquid fuel overcomes the affinity between the liquid fuel and the impingement body side surface, so that there is no possibility that the liquid fuel wets the impingement body side surface. In other words, the radial velocity of the liquid jet within the liquid film is conserved substantially as it is. Thereby, the liquid film formed becomes small in thickness, so that extremely small spray particles are produced and moreover, it is possible to atomize almost all the liquid fuel injected from the nozzle 2.

Figure 10 shows a fifth embodiment of the atomizer in accordance with the invention, which is as follows.

Referring now to Figure 10, the liquid pressurized by the pump 6 for pressurizing liquid is injected as a linear liquid jet from the single hole injector 1 toward the impingement surface of the impingement body 3. The liquid jet injected to impinge upon the impingement body 3 spreads as a radial liquid film, producing fine particles at the radial ends of the liquid film. The support 4 is formed integrally with the impingement body 3. The end portion of the support 4 including the impingement body 3 which is positioned within the spray region is downward obliquely disposed in the spray region.

Referring now to Figure 11 showing a sixth embodiment of the invention, the impingement body 3 and the injector 1 are provided horizontally facing each other, and the end portion of the support 4 including the impingement body 3 which is positioned within the spray region is obliquely disposed in the spray region.

The advantages of the above-mentioned constructions will be described hereinunder with reference to Figure 10.

The fine particles produced at the radial ends of the liquid film adhere to the impingement body 3 and the support 4 for supporting the same and become droplets 8. The droplets 8 are dropped onto the rear surface of the liquid film by their own weights or the negative pressure produced by the fine particles flying off from the impingement body 3.

The droplets 8 dropped onto the rear surface of the liquid film are scatterd again as substatially uniform fine particles by the action of the liquid film radially formed on the impingement body 3.

On the other hand, as in the case of the embodiment shown in Figure 11, the droplets 8 resulting from the accumulation of the fine particles having adhered to the support 4 flow into the negative pressure portion at the rear surface of the liquid film as well as drop from the impingement body 3 onto the rear surface of the liquid film. The droplets 8 having dropped onto the rear surface of the liquid film are scattered again as substantially uniform fine particles by the action of the liquid film.

As described above, by the atomizer in accordance with these embodiments, it is possible to scatter the droplets again as substantially uniform fine particles, since the liquid pressurized by the pump 6 is injected as a linear liquid jet toward the impingement body 3 to form a radial liquid film as well as produce broken-up fine particles at the radial ends of the liquid film, and since the droplets 8 having adhered to the impingement body 3 and the support 4 for the same and accumulated thereon are made to drop onto the rear surface of the liquid film.

Accordingly, the atomization amount is not practically reduced by the existence of the support and the impingement body.

Although the invention has been described through specific terms, it is to be noted here that the described embodiments are not exclusive and various changes and modifications may be imparted thereto without departing from the scope of the invention which is limited solely by the appended

Claims (6)

claims. CLAIMS

1. An atomizer having an injector for injecting a liquid jet from its tip and an impingement body disposed facing said liquid jet in order to expand said liquid jet into a liquid film and produce brokenup fine particles at extremities of said liquid film, characterized in that the liquid pressure P of said injector is set within a range where the relationship between said liquid pressure P and the outside diameter D of said liquid film satisfies dD/dP ' 0.

2. An atomizer according to claim 1, wherein said liquid jet is a vibration wave jet obtained within a range where the relationship between the smooth jet length e and said liquid pressure P satisfies dW/dP ' 0.

3. An atomizer according to either one of claims 1 and 2, wherein the surface of said impingement body upon which a liquid fuel impinges and another constituent surface adjacent thereto make an acute angle.

4. An atomizer according to either one of claims 1 and 2, wherein said impingement body is constituted by a thin plate, which is supported by a support having a diameter smaller than that of said thin plate from the rear side of the impingement surface thereof.

5. An atomizer according to either one of claims 1 and 2, wherein droplets produced on said impingement body and a supporting means therefor are made to drop onto the rear surface of said liquid film.

6. An atomizer substantially as hereinbefore described with reference to the accompanying drawings.