A Twin- Fluid Internally Mixed Swirl Atomizer Field of Invention
The present invention relates to an atomizer, which provides controlled liquid spray for a wide range of viscosities. The invention particularly relates to a twin fluid internally mixed swirl atomizer device, in which two fluids are mixed in a chamber and pass through a helical passage, a spin chamber and an atomizer orifice for releasing the fluid mixture at high velocity with a swirling motion in the form of hollow cone spray or solid cone spray, depending upon the application.
Background and Prior Art of the Invention
Atomization of liquids is widely used in several applications, e.g. spray combustion, spray-painting, spray dying, crop spraying and many other applications. Spray combustion is used in domestic heating burners, industrial heating furnaces, gas turbines, diesel engines and rockets. For the different applications a wide range of spray devices have been developed, and they are generally designed as atomizers as nozzles.
Spray may be produced in various ways. The process of atomization is a process where a liquid jet or sheet is broken up by the kinetic energy of the liquid itself or by exposure to high-velocity air or gas. Some atomizers accomplish this by discharging liquid at high velocity into a relatively slow-moving steam of air or gas. Examples of this type of atomizers include various forms of pressure atomizers and also rotary atomizers that eject the liquid at high velocity from the periphery of a rotating disc. An alternative approach is to expose a relatively slow-moving liquid to a high-velocity air steam. This method is generally known as twin-fluid, air-assist or air-blast atomization.
In the context of the present invention, it is worthwhile to mention about the conventional swirl atomizer and an internally mixed atomizer reported in the prior art. In swirl atomizer liquid is made to flow through a swirler before it exists from the atomizer, providing a tangential motion to the liquid. This swirling liquid forms a hollow cone outside the atomizer and this cone breaks up into droplets once the kinetic energy of the molecules of the cone overcomes the surface energy of the liquid. In an internally mixed atomizer, a small amount of gas is introduced into the liquid inside the injector forming a two-phase mixture of liquid and gas. This two-
phase mixture produces liquid droplets owing to two-phase flow dynamics. However, due to the absence of any tangential velocity component in the flow (because it is a one dimensional flow), this atomizer always forms a solid cone spray.
US Patent No. 6,547,163 Bl describes about Hybrid Atomizing fuel Nozzle. In this air is provided in the mixing chamber after the swirler so that two phase flow does not pass through the swirler. This is an air blast atomizer and not air assisted atomizer.
DE Patent 19918120 describes atomizer jet for dispensing liquid with disc shaped helical element up stream of outlet aperture. This is similar to traditional pressure swirl atomizers and cannot be considered as twin fluid atomizer, thus differing from the atomizer of the present invention.
US Patent No.6,186,417 Bl describes front plunger pressure-swirl atomizer which is applied to a fuel atomizer of a micro gas turbine engine which is different from the atomizer of the present invention.
US Patent No.6, 601,776 Bl describes the liquid atomization methods and devices which are different from the twin-fluid atomizers of the present invention. This is an electrostatic atomizer and uses electrical heating of the liquid inside the atomizer, thus, changing the surface tension and viscosity of the liquid.
US Patent Pub No. 2003/0080215 Al describes the fuel oil atomizer and method for atomizing fuel oil. It describes a sprayer plate flow restrictor assembly of a fuel oil atomizer, which, in combination with other atomizers, can provide better distribution of spray inside a combustor.
The function and the outcome of the twin-fluid internally mixed swirl atomizer of the present invention are different from all the above-mentioned prior arts. In the atomizer of the present invention a two-phase air liquid is created by injecting a small amount of air into liquid inside the atomizer. Then this two-phase mixture is made to flow through a helical swirler, which imparts a tangential motion to the two-phase flow. This creates a two dimensional flow of air-liquid mixture in the spin chamber of the atomizer, thus providing flow dynamics of a two-dimensional two-phase flow which is different from a one-dimensional two-phase flow or a two-dimensional single phase (liquids) flow. The two dimensionality achieved, brings in the differences in the performances of the present invention with respect to the prior art atomizers. In addition, the flow inside the atomizer lies in different flow regimes of two-phase flow for different ratios of air and liquid flow rates and thus, produces
different types of spray at different operating conditions. The proper order and combination of the components of the atomizer is also critical in the present invention leading to surprising results of two-dimensional two-phase flow, which has not been achieved by any of the prior art atomizers.
Brief description of the accompanying drawings
Figure 1 represents schematic of the twin-fluid internally mixed swirl atomizer
Figure 2 represents various spray patterns and droplet size distributions for the constant water flow rate of 0.34 LPM.
Figure 3 represents various spray patterns for same air flow rate of 4 Kgf/cm2
Figure 4 represents Atomization of highly viscous engines oil (Kinematic viscosity 13.5 to 15.5 cst) n
Figure 5 shows variation of Liquid Flow Rate with Air Flow Rate, wherein max. liquid flow rate = 10.1 g/s for air flow rate of 0.01 g/s at a pressure of 80 PSI.; min. liquid flow rate = 2.9 g/s for air flow rate of 0.03 g/s at a pressure of 20 PSI.; flow rate can be further increased by increasing the liquid supply pressure and decreased by reducing the liquid supply pressure.
Figure 6 shows variation of spray cone angle with liquid flow rate obtained by changing the air flow rate; wherein minimum Angle: 36°; for liquid flow rate of 2.96 g/s at 20 PSI pressure; maximum Angle: 79°; for liquid flow rate of 10.1 g/s at 80 PSI pressure; For same liquid supply pressure, the spray angle increases with increase in liquid flow rate which is accompanied by reduction in air flow rate.
Figure 7 shows variation of spray cone angle with air-liquid mass ratio for the data presented in fig. 6
Figure 8 shows variation of spray solidity with liquid flow rate obtained by changing the air flow rate; Maximum solidity: 89% for liquid flow rate of 2.96 g/s at 20 PSI pressure; Minimum Solidity: 35.3% for liquid flow rate of 9.5 g/s at 70 PSI pressure; For same supply pressure, the solidity increases with decreasing liquid flow rate due to an increase in ALR as shown in Fig. 9.
Figure 9 shows variation of spray solidity with air-liquid mass ratio for the data presented in Fig. 8.
Figure 10 shows a performance map of the atomizer; wherein Spray cone angle is varied from 36° to 79°; spray solidity is varied from 35.3% to 89%; Vertical
line in the plot: Range of spray solidity (50% - 79%) for constant spray angle
of 64° Horizontal line in the plot: Range of Spray cone angle (48° to 66°) for a
constant spray solidity of 74%) Figure 11 shows hollow cone spray and solid cone spray at the same liquid supply
pressure Figure 12 shows hollow cone spray and solid cone spray for the same liquid flow rate
of 7.12g/s. Figure 13 shows hollow cone and solid cone spray for the same air flow rate of 0.033
g/s.
Detailed description of figure 1
1. Liquid Inlet - Through this port the liquid to be atomized enters the atomizer.
2. Air Inlet - Through these holes the atomizing air enters the atomizer, which mixes with the liquid and assists in the atomization process. This is not present in conventional pressure swirl atomizer.
3. Air settling chamber - The atomizing air settles in this chamber before being introduced into the atomizer. This chamber allows for an equal distribution of air through all the air inlet holes to the atomizer. Also, the pressure of air in that chamber is total air pressure, which is higher than the static pressure present at the tip of air injection holes, and, thus, to certain extent prevents the back flow of liquid into the air passage. This is also not present in a conventional pressure swirl atomizer.
4. Helical passage - The air-liquid mixture flows through this helical passage before it goes to the spin chamber. This passage converts the flow of the mixture from purely axial to a rotating flow that has a tangential and an axial component by providing a swirling motion to it. This is not present in a conventional air assisted atomizer.
5. Spin Chamber - Here the air-liquid swirling flow develops into a fully developed swirling flow with a well-defined air core. The pattern of the flow inside this chamber depends on the ratio of mass flow rates of the air and the liquid. This is not present in a conventional air assisted atomizer.
6. Atomizer Orifice - Through this hole or orifice the liquid air mixture comes out of the atomizer at high velocity and with a swirling motion.
Statement of invention
The present invention provides a twin fluid internally mixed swirl atomizer device, comprising of: first inlet port (1) for allowing entry of first fluid which is to be atomized, plurality of second inlet holes (2) providing entry of second fluid in a direction perpendicular to the first fluid flow, settling chamber (3) for the second fluid, which is transversely and fluidly connectable to first fluid flow path, wherein settling chamber is to achieve first fluid - second fluid mixture, a helical passage (4) providing swirling means for converting the first fluid-second fluid mixture flow from purely axial to a rotating and transverse flow resulting in both tangential and axial components of first fluid - second fluid mixture; a spin chamber (5), for fully developing the first fluid - second fluid mixture swirling flow with a well-defined core, and an atomizer orifice (6), for releasing the first fluid - second fluid mixture at high velocity with a swirling motion in the form of hollow cone spray or solid cone spray. The first fluid is a liquid selected from group consisting of fuel including aviation turbine fuels (ATF), paints, agricultural liquids, liquid medicines and water and the second fluid is selected from group consisting of a gas, gaseous mixture, liquid and/or mixtures thereof.
Detailed description of the present invention
Accordingly, the present invention relates to twin fluid internally mixed swirl atomizer device, comprising of:
a. first inlet for allowing entry of first fluid which is to be atomized,
b. second inlet having plurality of holes providing entry of second fluid in a
direction perpendicular to the first fluid flow,
c. settling chamber for the second fluid, which is transversely and fluidly
connectable to first fluid flow path, said second fluid settling chamber
providing for the settling and equal distribution, of second fluid through
all the inlet holes, to the atomizer to achieve first and second fluid
mixture,
d. a helical passage providing swirling means for converting the first fluid-
second fluid mixture flow from purely axial to a rotating and transverse flow
resulting in both tangential and axial components of first fluid - second fluid
mixture;
e. a spin chamber provided for fully developing the first fluid - second fluid
mixture swirling flow with a well-defined core, and
f. an atomizer orifice, for releasing the first fluid - second fluid mixture at high
velocity with a swirling motion in the form of hollow cone spray or solid cone
spray.
In an embodiment of the present invention, the first fluid is liquid which is to be atomized, selected from group consisting of fuel including turbine fuels (ATF), paints, aviation agricultural liquids, liquid medicines and water.
Another embodiment of the invention, the second fluid is selected from group consisting of a gas, gaseous mixture, liquid and/or mixtures thereof, wherein the liquid may be selected from fuel, paints, Aviation Turbine fuels (ATF), agricultural liquids, liquid medicines and water
In another aspect of the invention the rate of first fluid which is to flow through the inlet port is in the range between 2.96 gm. to 10.1 gm. per second.
The inlet pressure of first fluid is varied from 20 PSI to 80 PSI.
The rate of flow of second fluid flowing through the inlet holes ranges between 0.0045 gm and to 0.0600 gm per second.
Another important aspect of the invention is the diameter of atomizer orifice which ranges between 0.40 and 1.00 mm.
In another embodiment of the invention relates to atomizer device, wherein the spray cone angle achieved is in the range of36°to79°.
Another embodiment relates the mass ratio second fluid to first fluid which is in the range of 0.0007 to 0.0117.
Another embodiment, the spray solidity obtained from the device of this present invention is in the range of 35.3% to 89%.
This atomizer utilizes the principles of a simplex pressure-swirl atomizer and an internally mixed, twin-fluid, air-assisted atomizer. A schematic of the developed atomizer is shown below in the figure. The first half of the present invention is similar to a traditional internally mixed atomizer in which a small amount of air is introduced into the liquid flow inside the atomizer, creating a two-phase air-liquid mixture. The center core of this atomizer consists of a simplex type pressure swirl atomizer through which the air-liquid mixture flows. The swirling motion to the mixture is provided by a properly design helical passage. The helical passage was fabricated by inserting a double-ported, double turn, screw element with specified acme thread machined onto
it. The mixture flows inside the passage between the thread, and thus, a helical motion is imparted to the two-phase flow. In the absence of atomizing air, the liquid, with a spinning motion, feels the spinning chamber inside the atomizer, where an air core develops due to the free vortex created by the swirling motion of the liquid. This swirling liquid, with an axial and a tangential velocity component, forms a hollow cone liquid jet outside the atomizer. Owing to the increased surface area of the hollow-cone jet, the surface forces cannot keep the jet intact and it breaks into liquid droplets. This atomizer provides reasonably good atomization in the absence of atomizing air, but, introducing a small amount of air into the liquid stream, upstream of the helical passage (as shown in the figure 1), significantly improves the atomization. The improvement in the atomization depends on the amount of air added to the liquid flow. The introduction of air forms a two-phase air-liquid mixture inside the atomizer, whose flow is governed by two-phase fluid dynamics. When a very small amount of air is introduced in the internally mixed atomizer, the mixture produced is a bubbly mixture with air bubbles imbedded inside the liquid flow. This mixture goes through the helical passage and gets a swirling motion and comes out of the atomizer as a hollow cone spray. Since the air bubbles occupy a finite area inside the atomizer, the liquid is squeezed to a smaller available area. This causes an increase in the liquid velocity or kinetic energy and helps in the atomization process. Secondly, the increase in air core reduces the sheet thickness of the hollow-cone spray and thus improves atomization. Thirdly, the air bubbles, which are at higher pressure than the ambient pressure, explode when they emerge from the atomizer. This bubble explosion introduces localized instabilities to the liquid jet and improves atomization. Therefore, introduction of a small amount of air improves the atomization to a greater extent. By varying the air flow rate, the flow structure inside the atomizer can be changed from bubbly flow to slug to frothy flow and finally to an annular flow. When the air-liquid flow becomes annular, the air flows in an outer annulus over the liquid core. This pushes the liquid in, and reduces and finally eliminates the air core inside the injector. Secondly, the squeezing of liquid core in the axial direction increases the axial velocity of the liquid. These two effects collapse the hollow-cone jet into a solid cone jet. But, owing to the large kinetic energy of the liquid jet and the large shear stresses acting on the liquid core due to annular flow of air, the atomization is of very good quality.
Though the product utilizes the principles of swirling atomization and twin-fluid atomization, the final product gives much better spray than the one achieved by using either one of them. Hence, the atomizer of the present invention can find application in many fields, where an atomizer of the prior art cannot perform the same when used in isolation or by a mere in combination with another atomizer.
The atomizer of the present invention provides sprays with varied spray cone angle and spray solidity. The varied and constant spray cone angle, spray solidity; can be achieved while maintaining constant liquid flow rate and varied liquid flow rates respectively traversing along a horizontal line as represented in Figures 2 and 4 respectively. Further, variation of spray and angle independent of spray solidity and spray solidity independent of spray cone angle is achieved by traversing along a horizontal line as represented in Figure 6.
The atomizer can provide sprays with a wide range of Spray cone angle. Hence, the atomizer can be used for various applications such as wetting larger areas (agricultural sprays to cover wider ground area, spray painting for initial coating, etc.) and providing wider cone angles for spraying. For more concentrated applications as in treatment of specific plants by agricultural sprays, final surface finish in spray painting, drug delivery using nebulizers, etc., smaller cone angles are preferred. Intermediate cone angle ranges are preferred for fuel sprays in automobile and gas aircraft engines. The same atomizer can provide sprays in all these angle ranges
The atomizer can provide sprays with wide range of Spray Solidity. Solidity is the percentage of the total spray cone area covered by the liquid phase. A solid cone spray has higher solidity compared to a hollow cone spray. A solid cone spray is required in many applications of an atomizer. Some examples are:
a. Spray painting for fine surface finish.
b. Agricultural sprays of pesticides to treat specific effected areas.
c. Medical sprays to provide proper concentration of medicines.
d. Liquid combustors: near the combustor walls to provide better fuel/air
mixing in the boundary layer with minimum wastage of fuel.
e. In RAMJET and SCRAMJET engines for more uniform fuel/air mixing.
At the same time, some applications of the atomizer require hollow cone
sprays to mention some are provided in the previous paragraph.
A major advantage of the present invention is that the solidity of the spray cone can be altered without changing the consumption rate of the liquid, as shown in Fig. 4 (by traversing along a vertical line on the plot).
Air-Liquid ratio is one of the controlling parameter in the present invention. As shown in the figures, the spray pattern was controlled by simultaneously varying the ALR and the liquid supply pressure.
The present invention was tested for a range of control parameters. The working range was obtained from those test results. The ALR could not be increased beyond the given values because the liquid flow becomes unstable beyond those values. The air flow rate and the liquid flow rate could not be reduced further as they were beyond our measurement capabilities.
The following examples are for illustration only and should not be construed to limit the scope of the present invention. Any average person skilled in the art can able to perform the invention without doing any undue experimentation.
Examples
Example 1
a. Atomizer device is constructed as per figure 1 and by varying the parameters
like, flow rate of first fluid i.e. the liquid which is to be atomized and flow rate of second fluid namely air, spray cone angle, data have been generated and represented graphically (Figures 5 to 10)
b. Experiments conducted by varying Liquid Flow Rate with Air Flow Rate.
Max. liquid flow rate = 10.1 g/s for air flow rate of 0.01 g/s at a pressure of 80
PSI.;
Min. liquid flow rate = 2.9 g/s for air flow rate of 0.03 g/s at a pressure of 20 PSI; Pressure: 20 psi to 80 psi
Flow rate can be further increased by increasing the liquid supply pressure and decreased by reducing the liquid supply pressure. The values are plotted in a graph (figure 5.)
c. Experiments conducted by changing of spray cone angle with liquid flow
rate obtained by changing the air flow rate
Minimum Angle: 36°; for liquid flow rate of 2.96 g/s at 20 PSI pressure; Maximum Angle: 790; for liquid flow rate of 10.1 g/s at 80 PSI pressure;
For same liquid supply pressure, the spray angle increases with increase in liquid flow rate which is accompanied by reduction in air flow rate (figure 6)
d. Experiments conducted by varying spray cone angle with air-liquid mass
ratio for the data presented (c). (Refer to figure 7)
e. Experiments conducted by varying of spray solidity with liquid flow rate
obtained by changing the air flow rate.
Maximum solidity: 89% for liquid flow rate of 2.96 g/s at 20 PSI pressure; Minimum Solidity: 35.3% for liquid flow rate of 9.5 g/s at 70 PSI pressure; For same supply pressure, the solidity increases with decreasing liquid flow rate due to an increase in ALR as shown in Fig. 9. (Refer to figure 8)
f. Experiments conducted for several of spray solidity with air-liquid mass
ratio for the data presented in Fig. 8. (Ref figure 9).
Example 2
The atomizer of the invention is used for atomizing liquid with air under varying conditions as per the following table. The type of spray obtained is illustrated
in figures 11 to 13.

(Table Removed)
Main Advantages of the present invention
1. Provides good atomization with small pressure drop (reduction in operating cost).
2. Both hollow-cone and solid cone spray from single atomizer assembly is achieved.
3. Possible to atomize very viscous liquid because of large kinetic energy available by introduction of small amount of air.
4. Clogging due to solid impurities in the liquid is avoided because of self cleaning provided by the atomizing air.
5. The liquid flow rate and atomization quality can be controlled independent of each other by simultaneously varying liquid and air supply pressures.
6. The Atomizer of the present invention provides wide range of applications.
a. Same atomizer can provide sprays with a wide range of Spray cone
angle
b. Same atomizer can provide sprays with wide range of Spray Solidity.
7. While maintaining a constant liquid flow rate, various spray cone angle can be obtained - (by traversing along a vertical line on Fig. 2)
8. While maintaining a constant liquid flow rate (by traversing along a vertical line on Fig. 4) various spray solidity can obtained
9. By keeping constant spray angle for a range of liquid flow rates can be maintained (by traversing along a horizontal line on Fig. 2)
10. By keeping constant spray spray solidity for a range of liquid flow rates can be maintained (by traversing along a horizontal line on Fig. 4)
11. It is possible to vary the spray cone angle independent of the spray solidity (by traversing along a vertical line on Fig. 6)
12. It is possible to vary the spray solidity independent of the spray cone angle (by traversing along a horizontal line on Fig. 6)

I/We claim:
1. A twin fluid internally mixed swirl atomizer device, comprising:
a first inlet (1) for allowing entry of a first fluid, which is to be atomized; a second inlet having a plurality of holes (2) providing entry of a second
fluid in a direction perpendicular to a first fluid flow direction to achieve a first
fluid - second fluid mixture; and
an atomizer orifice (6) for releasing the first fluid - second fluid mixture, characterized in that, the atomizer device comprises:
a settling chamber (3), wherein the second fluid is transversely and fluidly connectable to a first fluid flow path, and wherein the settling chamber (3) provides settling and equal distribution of the second fluid, through the holes (2), to the atomizer to achieve the first fluid - second fluid mixture;
a helical passage (4) providing swirling means for converting a flow of the first fluid - second fluid mixture from a purely axial to a rotating and transverse flow resulting in both tangential and axial components of the first fluid - second fluid mixture; and
a spin chamber (5), configured between the helical passage (4) and the orifice (6), wherein the spin chamber (5) is provided for fully developing the swirling flow of the first fluid - second fluid mixture with a well-defined core, and wherein the first fluid - second fluid mixture at a high velocity with the developed swirling flow is released from the orifice (6) in the form of a hollow cone spray or a solid cone spray.
2. The device as claimed in claim 1, wherein the first fluid is a liquid selected from a group consisting of fuel, paints, Aviation Turbine fuels (ATF), agricultural liquids, liquid medicines and water.
3. The device as claimed in claim 1, wherein the second fluid is selected from a group consisting of a gas, gaseous mixture, liquid and/or mixtures thereof.
4. The device as claimed in claim 3, wherein the liquid is selected from fuel, paints,
Aviation Turbine fuels (ATF), agricultural liquids, liquid medicines and water.
5. The device as claimed in claim 1, wherein the first fluid has a rate of flow through
the first inlet (1) in a range from 2.96 to 10.1 gram per second.
6. The device as claimed in claim 1, wherein the first fluid has an inlet pressure in a
range from 20 PSI to 80 PSI.
7. The device as claimed in claim 1, wherein the second fluid has a rate of flow
through the holes (2) in a range from 0.0045 to 0.0600 gram per second.
8. The device as claimed in claim 1, wherein the atomizer orifice (6) has a diameter
in a range from 0.40 to 1.00 mm.
9. The device as claimed in claim 1, wherein the cone spray has a spray cone angle
in a range from 36° to 79°.
10. The device as claimed in claim 1, wherein the device has a second fluid-to-first
fluid liquid mass ratio in a range from 0.0007 to 0.0117.
11. The device as claimed in claim 1, wherein the spray has a spray solidity in a range from 35.3% to 89%.