Geared gas turbine engine with oil deaerator and air removal

A method of designing a gas turbine engine comprising:

• providing a fan drive turbine for driving a gear reduction, said gear reduction for driving a fan rotor;
• and
• providing a lubrication system for supplying oil to said gear reduction, with an oil tank, the lubrication system including a lubricant pump;
• and
• supplying an air/oil mixture to an inlet of a deaerator, said deaerator including a separator for:
• separating oil and air,
• delivering separated air to an air outlet, and
• delivering separated oil back into an oil tank,
• wherein said separated oil is first delivered into a pipe outwardly of the oil tank, and then into a location beneath a minimum oil level in the oil tank, the pipe having a pipe inlet, a pipe outlet, and a pipe midportion located therebetween, the pipe midportion is spaced apart and outwardly from the oil tank,
• wherein air within the oil tank moves outwardly through an air exit into the deaerator, and an exit velocity from the deaerator of the separated air is less than or equal to 14 feet/second, and an inlet velocity of the air/oil mixture to the deaerator is less than or equal to 14 feet/second.

A gas turbine engine comprising:

• a fan drive turbine driving a gear reduction, said gear reduction driving a fan rotor;
• and a lubrication system supplying oil to said gear reduction, the lubrication system including a lubricant pump supplying an air/oil mixture to an inlet of a deaerator, said deaerator including a separator for:
• separating oil and air,
• delivering separated air to an air outlet, and
• delivering separated oil back into an oil tank,
• wherein said separated oil is first delivered into a pipe outwardly of the oil tank, and then into a location beneath a minimum desired oil level in the oil tank, the pipe having a pipe inlet, a pipe outlet, and a pipe midportion located therebetween, the pipe midportion is spaced apart and outwardly from the oil tank,
• wherein air within the oil tank moves outwardly through an air exit into the deaerator;
• an exit velocity from the deaerator of the separated air is less than or equal to 14 feet/second;
• and
• wherein a dwell time of oil in the oil tank as removed by said oil pump, on average, is five seconds or less.