Split Lubrication System for Gas Turbine Engine Parasitic Loss Reduction
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Solution Overview
Problem
Gas turbine engine oil pump systems typically experience excessive oil flow due to being sized for maximum conditions, leading to engine parasitic losses from churning and pumping, and existing solutions like variable displacement pumps are costly and heavy.
Innovation Solution
A two-pump lubrication system where one pump is driven by a low-speed shaft and another by a high-speed shaft, with optimized capacities to minimize lubricant supply based on respective speeds, and optionally controlled by a system monitoring mechanical speed and loads to match lubrication requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single oil supply pump is sized to meet maximum flow conditions, then sufficient lubricant is provided at all operating points, but excessive oil flow occurs at off-design conditions causing parasitic losses
Solution Approach 1:
The single pump system is segmented into two separate pumps: a low-speed pump driven by the N1 shaft and a high-speed pump driven by the N2 shaft. Each pump is sized to meet lubrication requirements at specific operating ranges, eliminating the need for one oversized pump to handle all conditions. This segmentation allows optimal pump sizing for each operating regime, reducing parasitic losses while maintaining reliable lubrication.
2Loss of energy
If valves are used to divert excess oil flow back to the supply tank, then parasitic losses are reduced, but system complexity increases
Solution Approach 1:
Instead of using static valves to divert excess flow, the system employs dynamic control through two independently variable-speed pumps. The pumps' rotational speeds can be adjusted in real-time to match lubrication demands, dynamically optimizing flow delivery without requiring complex valve mechanisms or flow diversion systems.
3Loss of energy
If a variable displacement oil pump is used, then lubricant flow is optimized for different operating conditions, but cost and weight increase
Solution Approach 1:
The variable displacement pump functionality is achieved through segmentation into two separate fixed-displacement pumps with variable speeds. Rather than one complex variable displacement unit, the system uses two simpler fixed-displacement pumps whose combined output is controlled by varying their rotational speeds independently, reducing weight while maintaining optimization capability.
Solution Approach 2:
The two-pump system provides multi-functionality by covering the full range of lubrication requirements that a single variable displacement pump would provide. The low-speed pump handles baseline and low-demand conditions while the high-speed pump addresses peak and high-demand conditions, together achieving universal coverage across all operating points.
Data Source
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AI summary
A lubrication system for use in a gas turbine engine is comprised of a first pump driven by a first shaft at a first speed and a second pump driven by a second shaft at a second speed that is faster than the first speed. The first and second pumps provide lubricant to an engine operating system. The pumps are optimized based on differential speed changes between the two drive speeds for the respective shafts to provide an optimized oil flow for the engine as a whole. A gas turbine engine and a method of operating a gas turbine engine are also disclosed.