Crankcase ventilation system with pumped scavenged oil

1. A crankcase ventilation system for an internal combustion engine generating blowby gas in a crankcase containing engine oil and oil aerosol, said system comprising an air/oil separator having an inlet receiving blowby gas and oil aerosol from said crankcase, and having an air outlet discharging clean blowby gas, and an oil outlet discharging scavenged separated oil, and a jet pump pumping said scavenged separated oil from said oil outlet of said separator to said crankcase, wherein said separator has a pressure drop thereacross such that the pressure at said inlet and in said crankcase is higher than the pressure at said air outlet and at said oil outlet, the pressure differential between said crankcase and said oil outlet normally tending to cause backflow of oil from the higher pressure crankcase to the lower pressure oil outlet, said jet pump supplying pumping pressure greater than said pressure differential to overcome said backflow tendency and instead cause suctioning of scavenged separated oil from said oil outlet and pumping same to said crankcase, said jet pump is an air-driven jet pump having a pressurized drive input receiving pressurized motive air from a compressed air source, a suction input receiving separated oil from said oil outlet of said separator, and an output delivering jet-pumped oil and motive air to said crankcase.

2. The crankcase ventilation system according to claim 1 wherein said engine has a turbocharger delivering pressurized air for combustion, and said compressed air source comprises said turbocharger, and said pressurized drive input receives pressurized motive air from said turbocharger.

3. The crankcase ventilation system according to claim 1 wherein said separator comprises an inertial impactor.

4. The crankcase ventilation system according to claim 1 wherein said separator comprises a coalescer.

5. The crankcase ventilation system according to claim 1 wherein said separator comprises a combined inertial impactor and coalescer.

6. The crankcase ventilation system according to claim 1 wherein said impactor is upstream of said coalescer.

7. The crankcase ventilation system according to claim 6 wherein separated oil from said coalescer drains to said oil outlet of said separator, and wherein separated oil from said impactor through said coalescer and then to said oil outlet of said separator.

8. The crankcase ventilation system according to claim 6 wherein separated oil from said coalescer drains to said oil outlet of said separator, and wherein said separator has an auxiliary drain channel draining separated oil from said impactor to said oil outlet of said separator and bypassing said coalescer.

9. The crankcase ventilation system according to claim 8 wherein said auxiliary drain channel has a flow-limiting bleed orifice therein.

10. The crankcase ventilation system according to claim 6 wherein separated oil from said coalescer drains to said oil outlet of said separator, and wherein said separator has a second oil outlet draining separated oil from said impactor to said suction input of said jet pump.

11. The crankcase ventilation system according to claim 6 wherein said separated oil from said coalescer drains to said oil outlet of said separator, and wherein said separator has a second oil outlet draining separated oil from said impactor to said crankcase.

12. The crankcase ventilation system according to claim 11 wherein said separate oil from said impactor drains through said second oil outlet to said crankcase by gravity, without passage through said jet pump.

13. The crankcase ventilation system according to claim 1 wherein said jet pump has a jet provided by said pressurized drive input, and a mixing bore provided by an output delivering jet-pumped oil to said crankcase, said mixing bore having a cross-sectional area greater than or substantially equal to the cross-sectional area of said jet.

14. The crankcase ventilation system according to claim 13 wherein said cross-sectional area of said mixing bore is greater than the cross-sectional area of said jet by a ratio up to 100:1.

15. The crankcase ventilation system according to claim 13 wherein the cross-sectional area of said mixing bore is substantially equal to the cross-sectional area of said jet to provide venturi effect suction at said suction input.

16. The crankcase ventilation system according to claim 13 wherein said mixing bore is round, and said jet is round.

17. The crankcase ventilation system according to claim 13 comprising a plurality of jets feeding said mixing bore.

18. The crankcase ventilation system according to claim 1 comprising a first conduit supplying said pressurized motive fluid to said drive input of said jet pump, and a second conduit delivering said jet-pumped oil to said crankcase from said output of said jet pump, and comprising at least one check valve in one of said first and second conduits permitting one-way flow therethrough.

19. The crankcase ventilation system according to claim 18 comprising two said check valves, a first check valve in said first conduit, and a second said check valve in said second conduit.

20. A crankcase ventilation system for an internal combustion engine generating blowby gas in a crankcase containing engine oil and oil aerosol, said system comprising an air/oil separator having an inlet receiving blowby gas and oil aerosol from said crankcase, and having an air outlet discharging clean blowby gas, and an oil outlet discharging scavenged separated oil, and a jet pump pumping said scavenged separated oil from said oil outlet of said separator to said crankcase, wherein said separator has a pressure drop thereacross such that the pressure at said inlet and in said crankcase is higher than the pressure at said air outlet and at said oil outlet, the pressure differential between said crankcase and said oil outlet normally tending to cause backflow of oil from the higher pressure crankcase to the lower pressure oil outlet, said jet pump supplying pumping pressure greater than said pressure differential to overcome said backflow tendency and instead cause suctioning of scavenged separated oil from said oil outlet and pumping same to said crankcase, wherein said jet pump is a fluid-driven jet pump having a pressurized drive input receiving pressurized motive fluid from a source of pressurized fluid, a suction input receiving separated oil from said oil outlet of said separator, and an output delivering jet-pumped oil to said crankcase, and comprising a first conduit supplying said pressurized motive fluid to said drive input of said jet pump, and a second conduit delivering said jet-pumped oil to said crankcase from said output of said jet pump, and comprising at least one check valve in one of said first and second conduits permitting one-way flow therethrough, wherein said jet pump is an air-driven jet pump having a pressurized said drive input receiving pressurized motive air from a compressed air source.

21. The crankcase ventilation system according to claim 20 wherein said engine has a turbocharger delivering pressurized air for combustion, and said compressed air source comprises said turbocharger.