Gear pump
A gear pump has first and second meshing gears for pumping a fluid. The gear pump further has a first electrical motor having a first rotor, a first stator and first coil windings. The gear pump further has a second electrical motor having a second rotor, a second stator and second coil windings. The first rotor is operatively connected to the first gear and the second rotor is operatively connected to the second gear such that each gear is rotated by its respective rotor. The first and second coil windings are energized by respective and separate first and second electrical power circuits such that the first and second meshing gears can be driven independently of each other.
1. A fuel pumping unit for an aero-engine, the fuel pumping unit having a low pressure pump and a high pressure pump, the low pressure pump supplying fuel at a raised pressure to the high pressure pump for onward supply to a fuel metering unit of the aero-engine, the high pressure pump having:
first and second meshing gears for pumping a fuel;
a first electrical motor having a first rotor, a first stator and first coil windings; and
a second electrical motor having a second rotor, a second stator and second coil windings;
wherein the first rotor is operatively connected to the first gear and the second rotor is operatively connected to the second gear such that each gear is rotated by its respective rotor;
wherein the first and second coil windings are energised by respective and separate first and second electrical power circuits such that the first and second meshing gears can be driven independently of each other;
wherein the first rotor and the first gear are mounted, axially spaced from each other, on a first gear shaft, and the second rotor and the second gear are mounted, axially spaced from each other, on a second gear shaft; and
wherein the pump is configured such that the electrical motors are cooled by a cooling flow formed from a flow of the pumped fuel and the electrical motors are fully immersed in the fuel.
2. The fuel pumping unit according to claim 1 , wherein the first and second electrical power circuits each include a respective variable frequency motor drive.
3. The fuel pumping unit according to claim 1 , further having a control unit which controls the power provided by the first and second electrical power circuits to run the pump at different speeds.
4. The fuel pumping unit according to claim 3 , wherein the control unit further varies the relative amounts of power provided by the circuits so that varying amounts of mechanical power can be transferred between the gears.
5. The fuel pumping unit according to claim 3 , wherein the control unit further compares the power provided by the circuits with a reference power characteristic to monitor the health of the pump.
6. The aero-engine having the fuel pumping unit according to claim 1 .