BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a rear view of an atomizer spray plate according to an exemplary embodiment of the present invention.
FIG. 2 is a cross-sectional view (A-A) of the atomizer spray plate shown in FIG. 1.
FIG. 3A is a front view of the atomizer spray plate shown in FIG. 1.
FIG. 3B is a cross-sectional view (B-B) of the atomizer spray plate shown in FIGS. 1 and 3A.
FIG. 4 is a cross-sectional view of an exemplary atomizer assembly including the atomizer spray plate shown in FIG. 1.
FIG. 5 is graph illustrating performance of an atomizer spray plate according to an exemplary embodiment of the present invention.
FIG. 6 is another graph illustrating performance of an atomizer spray plate according to an exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a rear view of an atomizer spray plate 100 according to an exemplary embodiment of the present invention. The spray plate 100 includes a body 102. The body 102 may have any shape or size. For example, the shape and size may be selected to accommodate a particular application of the spray plate 100. In the present embodiment the body has a substantially cylindrical shape.
The spray plate 100 further includes an inlet portion having an inlet surface 110. In some embodiments, the depth of the inlet portion is shorter than inlets generally found in conventional mechanical atomizers. The inlet surface 110 includes a plurality of elongated protrusions or fluid deflectors 130 (e.g., islands). Better illustrated in FIG. 2, each protrusion 130 extends outward from the inlet surface 110. The protrusions 130 extend radially from an inner edge 112 and towards an outer edge 114 about the inlet surface 110. The protrusions 130 are preferably also situated at an angle (a) with respect to the inner edge 112, e.g., to assist in initiating rotation and/or generating a swirling motion. The angle α is the exemplary embodiment is less than ninety degrees (e.g., with respect to a tangent at or around the base of the protrusion 130).
The spray plate 100 further includes a swirl chamber 120, which is preferably frustoconical or hemispherical in shape. The swirl chamber 120 is adjacent to the inner edge 112 of the inlet surface 110, and receives fluid from the inlet portion and/or inlet surface 110 wherein the fluid rotates and forms a thin conical sheet of fluid.
Each of the protrusions 130 on the inlet surface 110 has a particular shape defining a venturi passage or swirl slot 118 between adjacent protrusions 130 and leading to the swirl chamber 120. As one of ordinary skill in the art will understand, the shape of the protrusions 130 provides for a reduced pressure at the inlet and an increased velocity in accordance with Bernoulli's principle and the Venturi effect. Fluid is accelerated through each of the swirl slots 118 and about the protrusions 130 into the swirl chamber 120. In the exemplary embodiment, velocity of the fluid entering the swirl chamber 120 is approximately 65% greater than velocities achieved in conventional mechanical atomizers. Rotational velocity in the swirl chamber 120 is thus substantially increased and a thinner sheet of fluid is formed therein. As one of ordinary skill in the art will understand, the thinner sheet then provides for the formation of smaller fluid droplets.
FIG. 3A shows an exit or exit surface 140 of the atomizer spray plate 100 and FIG. 3B shows a cross-sectional view (B-B) of the exemplary spray plate 100. The atomizer spray plate 100 includes atomizer hole 122 extending through the body from the swirl chamber 120 to the exit 140. In the exemplary embodiment, the hole 122 is a cylindrical hole having an axis 150. The exit surface 140 may simply include an outlet edge of the atomizer hole 122 (not shown). However, in some embodiments, the exit surface 140 further includes a shaped surface having two or more discharge slots 142, e.g., for directing the fluid from the atomizer spray plate 100 and/or providing a particular spray pattern. For example, the exit surface 140 may include five discharge slots 142 extending radially from the atomizer hole 122. In some embodiments, the spray pattern provided by the discharge slots 142 advantageously reduces the formation of nitrogen oxide (“NOx”).
FIG. 4 shows an atomizer 200 according to the present invention. The atomizer 200 includes a spray plate 100 such as the exemplary embodiment described above. The atomizer 200 further includes a back plate 210 situated adjacent to the inlet surface 110 of the spray plate 100. The back plate 210 includes one or more channels 212 for providing fluid, such as fuel oil, to the inlet surface 110 of the spray plate 100. In some embodiments, the back plate 210 further includes one or more return channels 214 for receiving fluid from the spray plate 100. Each of the spray plate and back plate 210 are housed in a retaining nut 200.
FIGS. 5-6 illustrate performance of a prototype of an atomizer spray plate 100 according to an exemplary embodiment of the present invention. FIG. 5 shows a graph of delivered fuel flow in gallons per minute (gpm) as a function of fuel supply pressure in pounds per square inch gauge (psig) for the spray plate 100. Performance of the exemplary spray plate 100 is also shown under several pressure differential conditions including simplex (no return), 250 pounds per square inch differential (psid), 300 psid, and 350 psid. As shown in FIG. 5, at 300 psid a delivered fuel flow of 16 gpm correlates to approximately 940 psig of fuel supply pressure.
FIG. 6 shows a graph of spray quality or Sauter mean diameter (“SMD”) in microns (μm) as a function of delivered fuel flow for an exemplary atomizer spray plate 100. As one of ordinary skill in the art would understand, mechanical atomization has always been limited to larger droplet sizes when compared to a generally preferred target of 100 SMD microns. 100 SMD μm has been achievable when by dual fluid atomization but very difficult when the lower cost mechanical atomization is used. However, as indicated in FIG. 8, the exemplary atomizer spray plate 100 provides a droplet size of 110 SMD μm at the delivered fuel flow of 16 gpm. Smaller droplet sizes are also provided at increased fuel flows. A conventional plate has a typical result of at least 141 SMD microns under similar conditions. This reduction in droplet size provided by the present invention results in better burnout of the fuel, lower excess oxygen in the boiler, lower opacity, lower sulfur trioxide (“SO3”) and lower NOx.
Although the invention has been described with reference to a particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements or features, and indeed many modifications and variations will be ascertainable to those of skill in the art.
Patent Application
20070241210
