Venturi devices resistant to ice formation for producing vacuum from crankcase gases
A device for producing vacuum using the Venturi effect, systems utilizing the device, and methods of making the device are disclosed. The device has a housing defining a Venturi gap, a motive passageway converging toward the Venturi gap and in fluid communication therewith, a discharge passageway diverging away from the Venturi gap and in fluid communication therewith, and a suction passageway in fluid communication with the Venturi gap. The suction passageway has an interior surface with a surface topography that renders the interior surface hydrophobic and has an oleophobic coating applied to the interior surface while maintaining the surface topography.
1. A device for producing vacuum using the Venturi effect comprising:
a housing defining a Venturi gap, a motive passageway converging toward the Venturi gap and in fluid communication therewith, a discharge passageway diverging away from the Venturi gap and in fluid communication therewith, a suction passageway in fluid communication with the Venturi gap, and a suction chamber housing the Venturi gap and into which a spout defining a discharge entrance or defining a motive exit protrudes a distance;
wherein the spout is disposed spaced apart from all sidewalls of the suction chamber for suction flow around the entirety of an exterior surface of the spout, wherein the exterior surface of the spout is generally frustoconical and converges inward within the suction chamber;
wherein the suction passageway has an interior surface with a surface topography that renders the interior surface hydrophobic and has an oleophobic coating applied to the interior surface while maintaining the surface topography.
2. The device of claim 1 , wherein a cross-sectional area of the motive exit is smaller than a cross-sectional area of the discharge entrance.
3. The device of claim 1 , wherein the suction chamber has a generally rounded interior bottom below the discharge entrance.
4. The device of claim 1 , wherein the suction chamber has an internal width of about 10 mm to about 25 mm.
5. The device of claim 1 , wherein the motive passageway and the discharge passageway both diverge in a cross-sectional area away from the Venturi gap as a hyperbolic or parabolic function.
6. The device of claim 1 , wherein the surface topography is plasma etched or laser etched into the material defining the suction passageway.
7. The device of claim 1 , wherein the surface topography is a coating or film comprising particles of material of selected size and shape to render the interior surface hydrophobic.
8. The device of claim 1 , wherein the surface topography is mechanically etched into the material defining the suction passageway.
9. The device of claim 1 , wherein the oleophobic coating comprises a fluoropolymer, a silicone, or combinations thereof.
10. The device of claim 9 , wherein the oleophobic coating comprises polytetrafluoroethylene.
11. A system comprising:
the Venturi device of claim 1 ;
a source of higher pressure fluidly connected to the motive passageway;
a source of lower pressure, relative to the source of higher pressure, fluidly connected to the discharge passageway; and
blowby gases from a crankcase fluidly connected to the suction passageway.
12. The system of claim 11 , wherein the source of higher pressure is atmospheric pressure or is boost pressure from a compressor of a turbocharger or supercharger.
13. A method of making a Venturi device comprising:
providing a housing defining a suction chamber, a motive passageway converging toward the suction chamber and in fluid communication therewith, a discharge passageway diverging away from the suction chamber and in fluid communication therewith, a suction passageway in fluid communication with the suction chamber, and a suction chamber housing the Venturi gap and into which a spout defining a discharge entrance or defining a motive exit protrudes a distance;
wherein the spout is disposed spaced apart from all sidewalls of the suction chamber for suction flow around the entirety of an exterior surface of the spout, wherein the exterior surface of the spout is generally frustoconical and converges inward within the suction chamber;
texturing the interior surface of the suction passageway to have a surface topography that renders the interior surface hydrophobic; and
subsequent to texturing the interior surface, coating the interior surface with an oleophobic coating while maintaining the surface topography.
14. The method of claim 13 , further comprising texturing the interior surface of the suction chamber to have a surface topography that renders the interior surface hydrophobic, and subsequently coating the interior surface of the suction chamber with an oleophobic coating while maintaining the surface topography.
15. The method of claim 14 , further comprising texturing the interior surface of the discharge chamber to have a surface topography that renders the interior surface hydrophobic, and subsequently coating the interior surface of the discharge chamber with an oleophobic coating while maintaining the surface topography.
16. The method of claim 13 , wherein texturing the interior surface comprises plasma etching or laser etching a surface topography into the material defining the suction passageway.
17. The method of claim 13 , wherein texturing the interior surface comprises applying a coating or a film that has particles of material of selected size and shape therein to render the interior surface hydrophobic.
18. The method of claim 13 , wherein texturing the interior surface comprises mechanically etching the surface topography into the material defining the suction passageway.
19. The device of claim 1 , wherein the oleophobic coating consists of a fluoropolymer, a silicone, or combinations thereof.