Circulating coolant fluid in hybrid electrical propulsion systems

1. A hybrid propulsion system comprising:

a heat engine configured to drive a heat engine shaft;

an electric motor configured to drive a motor shaft;

a transmission system connected to receive rotational input power from each of the heat engine shaft and the motor shaft and to convert the rotation input power to output power;

a first lubrication/coolant system connected for circulating a first lubricant/coolant fluid through the heat engine;

a second lubricant/coolant system in fluid isolation from the first lubrication/coolant system, wherein the second lubricant/coolant system is connected for circulating a second lubricant/coolant fluid through the electric motor;

a turbine gearbox connecting between the heat engine and a shaft for rotation of a compressor and a turbine at a rotational speed different from that of the heat engine; and

a pressure pump operatively connected to be powered by the turbine gearbox, wherein the pressure pump is connected in a coolant line of the first lubrication/coolant system between a sump tank and the heat engine for driving flow of the first lubricant/coolant from the sump tank to the heat engine.

2. The system as recited in claim 1 , further comprising: a cooler in the coolant line between the sump tank and the heat engine downstream of the pressure pump for cooling the first lubricant/coolant with a flow of ambient air.

3. The system as recited in claim 2 , further comprising:

a filter in the coolant line between the sump tank and the heat engine; and/or

a coolant pressure sensor in the coolant line between the sump tank and the heat engine downstream of the cooler; and/or

a coolant temperature sensor in the coolant line between the sump tank and the heat engine downstream of the cooler.

4. The system as recited in claim 1 , wherein the coolant line branches into respective coolant sub-lines connected for circulating the first lubricant/coolant to the heat engine, the turbine gearbox, the compressor, and the turbine.

5. The system as recited in claim 4 , wherein the coolant line includes a coolant sub-line that connects through a hydraulic motor to the sump tank.

6. The system as recited in claim 4 , further comprising a plurality of scavenge passages connecting for return of the first lubricant/coolant fluid from the heat engine, the turbine gearbox, the compressor, and the turbine.

7. The system as recited in claim 6 , wherein a respective scavenge passage from the compressor to the sump tank includes a first scavenge pump operatively connected a hydraulic motor to drive scavenge flow of the first lubricant/coolant from the compressor to the sump tank, and wherein a respective scavenge passage from the turbine to the sump tank includes a second scavenge pump operatively connected the hydraulic motor to drive scavenge flow of the first lubricant/coolant from the turbine to the sump tank.

8. The system as recited in claim 7 , further comprising a chip detector in a line downstream from at least one of the first and second scavenge pumps.

9. The system as recited in claim 1 , wherein the pressure pump provides driving potential for the first lubrication/coolant system entirely.

10. The system as recited in claim 1 , wherein the pressure pump is located in a u-bend in the coolant line.

11. The system as recited in claim 1 , wherein the sump tank includes an anti-siphon device connected to the coolant line.

12. The system as recited in claim 1 , wherein no anti-siphon device is included connecting the sump tank to the coolant line, and wherein a chip detector is included within the sump tank.

13. The system as recited in claim 1 , further comprising:

a first scavenge passage from the compressor to the sump tank including a first scavenge pump operatively connected the turbine gearbox to drive scavenge flow of the first lubricant/coolant from the compressor to the sump tank;

a second scavenge passage from the turbine to the sump tank including a second scavenge pump operatively connected the turbine gearbox to drive scavenge flow of the first lubricant/coolant from the turbine to the sump tank; and

a third scavenge passage from the heat engine to the sump tank including a third scavenge pump operatively connected to the turbine gearbox to drive scavenge flow of the first lubricant/coolant from the heat engine to the sump tank.

14. The system as recited in claim 13 , wherein the sump tank includes a partition for consolidating scavenge flows from the heat engine into the third scavenge passage, and separating the scavenge flows from the heat engine from a main sump volume fed by the first, second, and third scavenge pumps, and further comprising a chip sensor in the third scavenge line.

15. A hybrid propulsion system comprising:

a heat engine configured to drive a heat engine shaft;

an electric motor configured to drive a motor shaft;

a transmission system connected to receive rotational input power from each of the heat engine shaft and the motor shaft and to convert the rotation input power to output power;

a first lubrication/coolant system connected for circulating a first lubricant/coolant fluid through the heat engine;

a second lubricant/coolant system in fluid isolation from the first lubrication/coolant system, wherein the second lubricant/coolant system is connected for circulating a second lubricant/coolant fluid through the electric motor;

a combining gearbox connected to the heat engine and to the electric motor for combining power from the heat engine and electric motor to provide output power; and

a pressure pump operatively connected to be powered by the combining gear box, wherein the pressure pump is connected in a coolant line of the second lubricant/coolant system between a sump tank and the electric motor for driving flow of the second lubricant/coolant from the sump tank to the electric motor.

16. The system as recited in claim 15 , wherein the coolant line includes a cooler for cooling the second lubricant/coolant with ambient air, and wherein the coolant line branches to supply the second lubricant/coolant to the combining gearbox and to the electric motor.

17. The system as recited in claim 16 , further comprising a scavenge passage operatively connecting between a sump tank of the second lubricant/coolant system and the electric motor and the combining gearbox, wherein a scavenge pump is included in the scavenge passage.

18. The system as recited in claim 17 , further comprising:

a reduction gearbox operatively connected to receive power output from the combining gearbox, wherein the coolant line includes a branch for supplying the second lubricant/coolant to the reduction gearbox;

a scavenge passage branch connecting between the reduction gearbox and the scavenge passage; and

a second scavenge pump in the scavenge passage branch for driving flow from the reduction gearbox to the sump tank.

19. The system as recited in claim 1 , further comprising a third coolant system connected for circulating a third coolant fluid through the heat engine.

20. The system as recited in claim 19 , further comprising a compressor connected through an air line to supply boost air to the heat engine, wherein the air line includes an intercooler for cooling the compressed air, wherein the third coolant system is connected to the intercooler for heat exchange between the third coolant and the compressed air.

21. The system as recited in claim 1 , wherein the heat engine shaft and the motor shaft are combined as a single common shaft connected to the transmission system.