Liquid atomization methods and devices

Details Liquid atomization methods and devices Liquid atomization methods and devices

2002-06-06

2003-08-05

Evans, Robin O. (Department: 3752)

Fluid sprinkling, spraying, and diffusing

Processes

Of fuel injection

C239S128000, C239S130000, C239S132000, C239S135000, C239S136000

Reexamination Certificate

active

06601776

ABSTRACT:

FIELD OF THE INVENTION
The present invention is directed to methods and devices for atomizing liquids. More specifically, the liquids are atomized at the exit of an elongated, small diameter tube or a small internal surface area chamber, with an optional heating device for directly heating the liquid within the tube or chamber. The atomization devices are useful in many applications including, but are not limited to: flame and plasma based atomic spectroscopy, nano-powder production; particle/droplet seeding for laser-based flow diagnostics; spray drying for the production of fine powders; nebulizers for inhalation in delivery of medication and for atomizing fuel for use in combustion chambers.
BACKGROUND OF THE INVENTION
Atomizers are already used in many applications for producing finely divided aerosols with uniform droplet size distribution. While some of the prior art atomizers are at least partially effective, there is still a need for an atomizer that can produce a finely atomized spray with controlled and uniform droplet size distribution. The article on pages 2745-2749 of Analytical Chemistry 1990-62, entitled “Conversion of an Ultrasonic Humidifier to a Continuous-Type Ultrasonic Nebulizer for Atomic Spectrometry” and authored by Clifford et al., discusses the most commonly used solution nebulizers for atomic spectrometry. U.S. Pat. No. 4,582,731 issued on Apr. 15, 1986 to Smith, discloses a supercritical fluid molecular spray film deposition and powder formation method. The generation of particles and seeding in laser velocimetry is described by James F. Meyers in the von Karman Institute for fluid dynamics, lecture series 1991-08. This reference also discusses the increase in accuracy of laser measurements when uniform size particles are used. A nebulizer device for the delivery of medication is described in U.S. Pat. No. 5,511,726 issued to Greenspan et al. on Apr. 30, 1996. The device uses a piezo-electric crystal and control circuit to apply a voltage to a sprayed solution.
In addition to the above prior art atomizers, various methods and apparatus for preheating or atomizing fuel have been developed over recent years. While some of these devices are partially effective, there is still a need for an atomizer that can completely vaporize the fuel, as well as raise the temperature of the fuel to avoid condensation downstream of the atomizer. This is particularly useful during the cold start and warm-up cycle of an internal combustion engine. After an engine has been allowed to cool significantly below operating temperature (as little as several minutes after shutting it off, depending on the weather) and is then started, the fuel entering the combustion chamber is often in vapor, large droplet and liquid form. Large portions of the fuel that is in droplet or liquid form does not burn completely. This results in reduced engine efficiency (used but unburned fuel) and an increase in the production of unburned hydrocarbons. Not only is the engine not hot enough to effectively burn the non-atomized fuel, but the after-treatment (i.e. catalytic converter) is non-operational during this heavy pollution producing period of operation. In fact, seventy to eighty percent of all hydrocarbon emissions are generated prior to the catalytic converter coming on line. By decreasing the size of the fuel droplets and increasing the vaporization of the fuel entering the combustion chamber, the percentage of the fuel that is burned is increased, thereby producing more heat and reducing the time needed to bring the engine and catalytic converter to operating temperature.
U.S. Pat. No. 4,011,843 issued to Feuerman on Mar. 15, 1977, discusses vaporizing fuel for use in internal combustion engines. A spray valve for a fuel injected, IC engine is taught in U.S. Pat. No. 4,898,142, issued on Feb. 6, 1990 to Van Wechem et al. U.S. Pat. No. 5,118,451, issued on Jun. 2, 1992 to Lambert, Sr. et al. is drawn to another fuel vaporization device. In U.S. Pat. No. 5,609,297, issued on Mar. 11, 1997 to Gladigow et al., several embodiments of a fuel atomization device are described. A fuel injector with an internal heater is disclosed in U.S. Pat. No. 5,758,826, issued on Jun. 2, 1998 to Nines. U.S. Pat. No. 5,778,860, issued on Jul. 14, 1998 to Garcia, teaches a fuel vaporization system. SAE Technical Paper Series #900261 entitled “The Effect of Atomization of Fuel Injectors on Engine Performance”, and written by Kashiwaya et al., discusses the use of injectors with swirl patterns. SAE Technical Paper Series #970040 entitled “Fuel Injection Strategies to Minimize Cold-Start HC Emissions”, and written by Fisher et al., describes the effect of changing fuel injector and control parameters on cold-start emission levels. SAE Technical Paper Series #1999-01-0792 entitled “An Internally Heated Tip Injector to Reduce HC Emissions During Cold-Start”, and written by Zimmermann et al., is drawn toward measuring the effect of internally heated fuel injectors on HC emissions prior to an engine reaching operating temperature.
SUMMARY OF THE INVENTION
The present invention involves controlled atomization of liquids for various applications such as particle/droplet seeding for laser-based measurements of flow velocity, temperature, and concentration; flame and plasma based atomic spectroscopy; nano-powder production; spray drying for generation of uniform-size powder; chemical processing (i.e. phase transformation, dispersions, catalysis, and fuel reformation); nebulizers for inhalation applications and for atomizing fuel for use in combustion chambers. In these and other atomizer applications the control of droplet and/or particle size and uniformity is critical. In some applications extremely small droplets are preferred (less than a micron), while in others, droplet diameters on the scale of several microns are required. However, most of the above-mentioned applications require finely dispersed spray with droplets sufficiently uniform in size (i.e. mono-dispersed). Other applications desire very fine droplets for increased surface area interaction for improved reactions, thermal and chemical equilibrium rates, phase transformations and uniformity. The atomizer of the present invention has the flexibility of forming droplets with controlled size, wherein not only the size of the average droplet can be adjusted, but the range of sizes may be adjusted as well. The methods of using the atomizer are described below with reference to the specific application.
The use of laser technology in the measurement community has increased significantly over the past few decades and continues to gain acceptance as new and improving technology evolves. An advantage of laser technology is that the light is non-intrusive and non-destructive and the condensed intensity inherent to laser beams allows for very accurate sensing of very small particles making very small changes. One such application is the use of laser beams to make velocity measurements, and is known as laser Doppler velocimitry (LDV). The laser beam is directed at moving particles, and the velocity of the particles is measured. Often, this type of measurement is used to study the velocity characteristics of a gas flow, such as air, through a duct. To provide an object for the laser beam to be reflected by in air and other gases, one must introduce some medium that is large enough to be illuminated. In demonstrations, this is typically accomplished with smoke. However, measurements such as LDV typically require a slightly larger particle in the sub-micron to several micron range. In addition to the size sensitivity, the reflecting medium can change the parameters that are being measured as well. To study the velocity characteristics of a gas flow, one must ‘seed’ the gas flow with enough sub-micron to several micron particles to make measurements possible, while at the same time not affecting or degrading the gas flow. This seeding requirement is often the most difficult requirement to achieve for accurate and reliable LDV measurements. Currently available

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