Augmenter Pump Fuel Control for Gas Turbines
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Solution Overview
Problem
Existing fuel control systems for gas turbine engines face challenges in providing adequate fuel flow and pressure to auxiliary devices, especially at low engine speeds, while also managing heat input and bearing integrity, due to increased load demands and space constraints.
Innovation Solution
The implementation of a separate augmenter pump that runs at high pressure rise, in conjunction with a main pump, allows for controlled fuel diversion to augment fuel delivery at low engine speeds, reducing the size and heat rejection of the main pump, and ensures adequate pressure to auxiliary devices through a pressure drop control valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the minimum pump pressure rise (HP-LP) is increased to meet higher load requirements of auxiliary devices, then adequate fuel pressure to auxiliary devices is improved, but heat input to fuel increases and bearing damage risk increases
Solution Approach 1:
The fuel pump system is segmented into a main pump for bulk fuel delivery and a separate augmenter pump for providing high pressure rise to auxiliary devices. This segmentation allows each pump to be optimized for its specific function, with the augmenter pump dedicated to generating high pressure for auxiliary devices without contributing to overall heat input to the fuel system.
Solution Approach 2:
The augmenter pump acts as an intermediary device between the low pressure fuel supply and the auxiliary devices requiring high pressure. It receives fuel at low pressure from the main system and delivers it at high pressure to auxiliary devices, thereby providing the necessary pressure boost without requiring the entire fuel system to operate at high pressure rise, thus minimizing heat input.
2Power
If larger actuators and servo-valves are used to meet higher load requirements, then fuel pressure delivery capability is improved, but space constraints are violated
Solution Approach 1:
The system replaces the conventional approach of using larger mechanical actuators and servo-valves to increase power delivery capability with a hydraulic substitution approach. The augmenter pump provides the necessary pressure boost hydraulically, allowing smaller actuators and servo-valves to be used while still achieving the required power delivery to auxiliary devices.
3Weight of moving object
If the main pump size is reduced to decrease weight and heat rejection, then main pump weight and heat rejection are improved, but fuel flow adequacy at low engine speeds deteriorates
Solution Approach 1:
The fuel delivery function is segmented between the main pump and the augmenter pump. The main pump is sized for optimal weight and efficiency, while the augmenter pump supplements fuel flow specifically at low engine speeds when the main pump's output is insufficient. This segmentation allows the main pump to be smaller and lighter without compromising overall fuel flow adequacy.
Solution Approach 2:
The augmenter pump provides partial or excessive fuel flow action specifically during low engine speed conditions. It supplements the main pump's output only when needed, allowing the main pump to be sized for normal operating conditions rather than peak demand, thus reducing main pump weight and heat rejection while maintaining adequate fuel flow at all speeds.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures adequate fuel flow and pressure to auxiliary devices, reduces heat rejection and bearing wear, and maintains system efficiency by optimizing pump sizing and operation across varying engine speeds.
Implementation Method 1
a separate augmenter pump, which delivers fuel at a second high pressure (HPa) to a supply line (35)
Implementation Method 2
a pressure drop control valve (41) which senses a pressure differential (HPa-LP) across the augmenter pump (39)
Implementation Method 3
a start valve (43) connected to a delivery line (49) of the augmenter pump (39), the start valve (43) being arranged to divert a flow path from the augmenter pump (39) to the supply line (35)
Data Source
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AI summary
An engine fuel control system includes a fuel metering valve operable to control the flow of fuel between a supply line and a delivery line which delivers fuel to burners of the engine. The fuel control system further includes a fixed displacement main pump which receives fuel from a low pressure (LP) source and delivers the fuel at a first high pressure (HP) to the supply line. The fuel control system further includes an augmenter pump which receives fuel from the low pressure source and delivers the fuel at a second high pressure (HPa) to one or more fuel-pressure operated auxiliary engine devices. The fuel control system further includes a start valve which is actuated at low engine speeds to open a flow path which diverts fuel delivered by the augmenter pump away from the auxiliary engine devices to the supply line to augment the fuel delivered thereto by the main pump, the start valve being actuated at higher engine speeds to shut the flow path.