Systems and methods for utilizing a low-friction rotating coalescer contact seal
Rotating coalescer crankcase ventilation (CV) systems are described. The described CV systems utilize a contact seal to seal a gap between a static side of a housing and a rotating coalescer inlet. The rotating coalescer may be driven mechanically, electrically, hydraulically, or the like. The contact seal can be formed via a soft solid or a liquid film created by oil. Accordingly, the contact seal is a hydrodynamic soft seal. The contact seal prevents the blowby gases from bypassing the filter element of the rotating coalescer. At the same time, the contact seal may be broken during positive blowby gas recirculation circumstances because the contact seal is a hydrodynamic soft seal.
1. A crankcase ventilation system comprising:
a housing;
an inlet configured to receive blowby gases from an internal combustion engine and to provide the blowby gases to the housing;
an outlet configured to provide filtered blowby gases from the housing and to at least one of an intake of the internal combustion engine and an ambient;
a rotating coalescer positioned within the housing, the rotating coalescer including:
an endcap, and
a filter media; and
an oil inlet providing oil to a gap between a stationary portion of the housing and the endcap such that a hydrodynamic seal is formed by the oil positioned in the gap during an operating condition of the rotating coalescer, the hydrodynamic seal preventing a negative recirculation of the blowby gases;
wherein when the rotating coalescer rotates above a threshold rotational velocity and creates a pumping pressure that causes a high pressure within the housing on a clean side of the filter media and a low pressure on a dirty side of the filter media, thereby causing a positive recirculation of the blowby gases in which a portion of already filtered blowby gas from the clean side of the filter media returns through the gap to the dirty side of the filter media, such that the hydrodynamic seal is broken.
2. The crankcase ventilation system of claim 1 , wherein the oil inlet provides oil to a groove that defines the gap.
3. The crankcase ventilation system of claim 2 , wherein the endcap includes a tongue that partially extends into the groove and further defines the gap.
4. The crankcase ventilation system of claim 3 , wherein the tongue is structured to provide axial vibration damping of the rotating coalescer with respect to the housing.
5. The crankcase ventilation system of claim 1 , wherein the hydrodynamic seal is formed in part by a radial oil groove around a circumference of the stationary portion of the housing.
6. The crankcase ventilation system of claim 1 , wherein the filter media is non-pleated.
7. A crankcase ventilation system comprising:
a housing;
an inlet configured to receive blowby gases from an internal combustion engine and to provide the blowby gases to the housing;
an outlet configured to provide filtered blowby gases from the housing and to at least one of an intake of the internal combustion engine and an ambient;
a rotating coalescer positioned within the housing, the rotating coalescer including:
an endcap, and
a filter media; and
an oil inlet providing oil to a gap between a stationary portion of the housing and the endcap such that a hydrodynamic seal is formed by the oil positioned in the gap during an operating condition of the rotating coalescer, the hydrodynamic seal preventing a negative recirculation of the blowby gases,
wherein the filter media is selected such that
π
·
κ
·
ω
2
·
h
·
(
D
3
2
-
D
0
2
)
4
·
Q
·
v
·
ln
(
D
2
D
1
)
<
1
is satisfied, where:
ρ is gas density of the blowby gases,
ω is the rotational speed of the rotating coalescer,
h is a media height of the filter media,
D 0 is an inside diameter of a rotating annul portion of the rotating coalescer, the rotating annul portion representing the outer diameter of the gap,
D 1 is an inner diameter of the filter media,
D 2 is an outer diameter of the filter media,
D 3 is an outer diameter of the rotating coalescer,
μ is a viscosity of the blowby gases,
ν is a kinematic viscosity of the blowby gases,
Q is a flowrate of the blowby gases, and
κ is a permeability of the filter media.
8. The crankcase ventilation system of claim 6 , wherein the filter media comprises multiple layers of filter media.
9. The crankcase ventilation system of claim 1 , wherein the filter media is pleated.
10. A crankcase ventilation system comprising:
a housing;
an inlet configured to receive blowby gases from an internal combustion engine and to provide the blowby gases to the housing;
an outlet configured to provide filtered blowby gases from the housing and to at least one of an intake of the internal combustion engine and an ambient;
a rotating coalescer positioned within the housing, the rotating coalescer including:
an endcap, and
a filter media; and
an oil inlet providing oil to a gap between a stationary portion of the housing and the endcap such that a hydrodynamic seal is formed by the oil positioned in the gap during an operating condition of the rotating coalescer, the hydrodynamic seal preventing a negative recirculation of the blowby gases,
wherein the filter media is selected such that
κ
·
N
·
h
·
(
D
2
2
-
2
D
1
D
2
cos
(
π
N
)
+
D
1
2
)
1
2
·
ω
2
·
(
D
3
2
-
D
0
2
)
8
·
Q
·
v
·
t
<
1
is satisfied, where:
ρ is gas density of the blowby gases,
ω is the rotational speed of the rotating coalescer,
h is a media height of the filter media,
t is a thickness of the filter media that is normal to a flow direction through the filter media,
N is a number of pleats of the filter media,
D 0 is an inside diameter of a rotating annul portion of the rotating coalescer, the rotating annul portion representing the outer diameter of the gap,
D 1 is an inner diameter of the filter media,
D 2 is an outer diameter of the filter media,
D 3 is an outer diameter of the rotating coalescer,
μ is a viscosity of the blowby gases,
ν is a kinematic viscosity of the blowby gases,
Q is a flowrate of the blowby gases, and
κ is a permeability of the filter media.
11. The crankcase ventilation system of claim 1 , wherein the stationary portion is a drain pan of the housing.
12. A crankcase ventilation system comprising:
a housing;
an inlet configured to receive blowby gases from an internal combustion engine and to provide the blowby gases to the housing;
an outlet configured to provide filtered blowby gases from the housing and to at least one of an intake of the internal combustion engine and an ambient;
a rotating coalescer positioned within the housing such that a gap exists between a portion of the rotating coalescer and a stationary portion of the housing; and
an elastomeric gasket that provides a seal between the rotating coalescer and the stationary portion of the housing:,
wherein when the rotating coalescer rotates above a threshold rotational velocity and creates a pumping pressure that causes a high pressure within the housing on a clean side of the filter media and a low pressure on a dirty side of the filter media, a positive recirculation of the blowby gases collapses a portion of the elastomeric gasket to provide passage of a portion of already filtered blowby gas from the clean side of the filter media through the gap to the dirty side of the filter media, such that the seal is broken.
13. The crankcase ventilation system of claim 12 , wherein the rotating coalescer includes:
an endcap, and
a filter media.
14. The crankcase ventilation system of claim 12 , wherein the elastomeric gasket is V-shaped.
15. The crankcase ventilation system of claim 12 , wherein the elastomeric gasket is U-shaped.
16. The crankcase ventilation system of claim 12 , wherein the elastomeric gasket is a lip seal.
17. The crankcase ventilation system of claim 12 , wherein the elastomeric gasket includes a metallic stiffening component.
18. The crankcase ventilation system of claim 17 , wherein the metallic stiffening component comprises a spring that increases a sealing force of the elastomeric gasket.