AirWolf  

 

                             DROPLET  SPECTRUM  GEOMETRY

 

                                                 By Richard Howe

 

 

Over the past 24 years Howe Enterprises has treated some 37 million acres for mosquito control in South Florida.  The last 8 years we have treated 13 million acres, using my prototype High Pressure Spray System.  The High Pressure Spray System, is the only purpose built aerial adult mosquito control system in use today.

 

With the exception of my High Pressure Spray System, every system used today, for adult mosquito control was designed for agricultural use.  These systems were designed  to deposit insecticide on a crop.  However to control adult mosquitoes, aerosol size droplets are necessary. The larger droplets simply drop to the ground.  If it were not for the occasional small droplets breaking off the agricultural system spray pattern, the insecticide used in these systems would not kill mosquitoes.  The definition of an aerosol droplet is one less than 20 microns.  An aerosol droplet is not affected by gravity.  It behaves as a gas that suspends in the air column.        

                                   

The average DV 50 (volume mean diameter size droplet) for the agricultural system that I have used to treat 24 million acres for mosquito control was 80 microns.  The High Pressure Spray System using an “impingement” nozzle, has the ability to produce a DV 50 size droplet of 8 microns.  The 80 micron droplet contains enough insecticide, to produce approximately 2000, 8 micron droplets.

 

I have included as documentation, an excerpt from the journal of, The American Mosquito Control Association, dated December, 2006 page 715 written By Dr. Jonathan  Hornby, et al.  It is about, optimum droplet size, for control of adult mosquitoes.  This article discusses size ranges that are most effective for this purpose, being in the range of  2 to 16 microns, with 8 microns  the median optimal size.  I will quote from the first highlighted area of this article, that states, “Lofgren et al. (1973) applied soybean oil to mosquitoes, by using a truck-mounted aerosol generator and a nebulizer, in the field and laboratory, respectively, and they found that droplets, under 2 microns and over 16 microns do not impinge on mosquito wings as effectively as droplets within the 2-16 micron size range”.   Also LaMer et al. (1944) emphasized that droplets greater than 8 microns “far exceed” the critical dose required, resulting in excessive toxicant waste.

 

October 18, 2002 Dr. Hornby and I, ran an experimental nozzle that I brought to him, using the Lee County, Mosquito Control, wind tunnel, equipped with  a Malvern Lazer, measuring device, to establish accurate droplet diameter size and volume.  This nozzle produced an 8 micron DV50, with 80% of the material  atomized in the 2 to 16 micron range.  I hold a “use” patent on this nozzle, for aerial adult mosquito control.  It is an integral part of a system, that has the registered trade name, AeroMister.  U. S. patents #6,886,784 and #7,004,431 have been issued to me in the recent past, for the High Pressure Spray System.  In addition (O.A.P.I.) African Intellectual Property Organization (this organization includes 17 West African countries at this time) has issued a patent on my system #13,506 on June 29 2007.

 

The benefits of my High Pressure Spray System are two fold, economic                                                     and environmental.  The environmental benefits are, none of this material hits the ground, it stays suspended in the atmosphere, where the mosquitoes are flying.  The economic benefits are the most important.  This system has the potential to cost effectively eradicate mosquito vector borne diseases, such as malaria, in the developing world. 

         

The geometry of the High Pressure Spray System, droplet spectrum, has everything to do with the efficiency of this system.  The 80 micron droplet produced by the agricultural system I used for 24 million acres, wastes the equivalent of 2000 usable droplets.  The 80 micron droplet has enough volume to produce the equivalent of 2000 usable droplets.  This makes the High Pressure Spray System 2000 times more efficient than the agricultural systems in use today.  I will illustrate, using a formula to establish how, halving the area of a cube or a sphere affects volume.  When the size of a sphere or a cube is reduced by ½, the volume of the area is reduced by 8.  If an 80 micron droplet, the one that is equivalent in size to the one produced by the agricultural system, was reduced to 8 microns, the size produced by the High Pressure Spray System, the number of usable droplets would increase by 2000 over the conventional systems in use today.  I am going to illustrate using this breakdown

 

80 microns = 1 droplet

40 microns = 8 droplets

20 microns = 64 droplets

10 microns = 512 droplets

5 microns = 4,096 droplets

2.5 microns = 32,768 droplets

1.25 microns = 262,144 droplets

.062 microns = 2,097,152 droplets

 

So if my system produces an 8 micron droplet, each one, a lethal dose, then this system is approximately 2000 times more efficient than the conventional systems in use.  To date, due to political pressure from the insecticide industry, I have only been allowed to reduce my rates by a factor of 7.5 to 1. Even this modest reduction has allowed my primary customer Palm Beach County, to save on average, over 1 million dollars per year.  I would like to take this technology to the limit, and see if these numbers are valid.  I am looking for a user friendly country, where it would be possible to explore these parameters.  The potential of this technology to benefit humanity, as a cost effective tool, in the eradication of malaria in Africa, for example is enormous.