Hybrid Engine Oil Circulation for Low-Spool Power Transfer
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Solution Overview
Problem
In hybrid electric engines, reducing low spool speed to transfer power can lead to oil containment issues, limiting the amount of power transfer while maintaining sufficient lubrication.
Innovation Solution
A hybrid electric propulsion system with an electric motor to control the low and high speed spools, a lubrication circuit, and a controller to manage pressure differentials in the bearing compartment, using electric power to drive the spools and lubrication pumps, independent of fuel combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If low spool speed is reduced to transfer power from low spool to high spool, then power transfer capability is improved, but oil containment in bearing compartment deteriorates
Solution Approach 1:
The patent replaces the conventional mechanically-driven oil pump system with an electrically-driven oil pump system. The electric motor-driven oil pump can maintain adequate oil pressure and flow to the bearing compartment even when the low spool speed is reduced for power transfer, thereby resolving the contradiction between power transfer capability and oil containment reliability.
Solution Approach 2:
The patent changes the operational parameters of the oil pump by decoupling it from the mechanical drive train and providing independent electrical power. This allows the oil pump to operate at optimized speeds and pressures independent of the low spool speed, maintaining oil containment reliability while enabling greater power transfer capability.
2Power
If low spool speed is reduced for power transfer, then the amount of power that can be transferred is improved, but lubrication sufficiency deteriorates
Solution Approach 1:
The electrically-driven oil pump system replaces the mechanical system, enabling the pump to maintain adequate oil supply to bearings even when low spool speed is reduced for power transfer. This independent electrical drive ensures lubrication sufficiency is maintained while maximizing power transfer capability.
Solution Approach 2:
The electric motor serves multiple functions: it enables power transfer from the low spool to the high spool, and simultaneously drives the oil pump to ensure adequate lubrication. This multi-functionality resolves the contradiction by allowing both power transfer and lubrication sufficiency to be maintained.
3Loss of energy
If electric motor is used to drive spools and pumps, then fuel consumption is reduced, but system complexity increases
Solution Approach 1:
The electric motor is designed to perform multiple functions: driving the spools for power transfer and driving the oil pump for lubrication. By consolidating these functions into a single electrically-driven system, the patent reduces overall fuel consumption while managing system complexity through functional integration rather than proliferation of separate mechanical components.
Solution Approach 2:
The patent replaces conventional mechanically-driven systems with an electrically-driven system. While this introduces electrical components, it eliminates complex mechanical linkages and reduces fuel consumption. The trade-off in complexity is offset by the benefits of electrical control flexibility and improved energy efficiency.
Data Source
AI summary
A hybrid electric propulsion system including: a gas turbine engine comprising a low speed spool, a high speed spool, and a combustor; a lubrication circuit comprising a bearing compartment, a supply pump, and a scavenger pump; an electric motor configured to augment rotational power of the low speed spool or the high speed spool; and a controller operable to: control the electric motor based upon a pressure differential between an interior of the bearing compartment and an exterior of the bearing compartment and to drive rotation of the low speed spool and/or the high speed spool via the electric motor responsive to a thrust command while fuel flow to the combustor is inhibited.