Dual-Pump Fuel System for Gas Turbine Windmill Restart
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Solution Overview
Problem
Gas turbine engines face challenges in reliably restarting during windmilling conditions due to inadequate fuel supply from standard fuel pumps, leading to increased weight and heat generation from oversized pumps.
Innovation Solution
A dual-pump fuel system comprising a main fuel pump and an auxiliary fuel pump, where the main pump provides fuel at varying rates based on shaft speed and the auxiliary pump supplements the fuel supply during windmilling, ensuring adequate fuel for reliable restarts without the need for oversized pumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large fuel pump is used to ensure adequate fuel supply during windmill starts, then the reliability of engine restart is improved, but the weight of the fuel system increases
Solution Approach 1:
The fuel pump system is divided into two separate pumps: a main fuel pump for normal operation and an auxiliary fuel pump specifically for windmill start conditions. This segmentation allows each pump to be optimized for its specific function, with the auxiliary pump providing the additional fuel flow needed during low-speed restarts without requiring the main pump to be oversized.
Solution Approach 2:
The auxiliary fuel pump serves multiple functions: it provides fuel during windmill starts, can supplement the main pump during normal operation if needed, and ensures reliable engine restart across all operating conditions. This multi-functionality allows a single auxiliary component to address various fuel supply scenarios.
2Reliability
If a large fuel pump is used to ensure adequate fuel supply during windmill starts, then the reliability of engine restart is improved, but the heat generation increases
Solution Approach 1:
By segmenting the fuel pump function into main and auxiliary pumps, the system avoids concentrating all fuel delivery demands on a single large pump. The auxiliary pump handles the additional fuel flow requirement during windmill starts, distributing the workload and reducing the heat generation burden on any single pump component.
3Reliability
If a large fuel pump is used to ensure adequate fuel supply during windmill starts, then the fuel supply capability is improved, but the device complexity increases
Solution Approach 1:
The fuel system is segmented into main and auxiliary pump components, each with dedicated functions. This segmentation, while adding a component, actually simplifies the control logic compared to a single complex pump system, as each pump can operate independently based on simple operational criteria.
Solution Approach 2:
The auxiliary fuel pump acts as an intermediary component that bridges the gap between the main fuel pump's limited output during windmill conditions and the engine's required fuel flow. This intermediary pump provides the supplemental fuel flow needed without requiring complex modifications to the main pump or engine fuel system.
Data Source
AI summary
A fuel system (10) for a gas turbine engine (18) having a shaft (30) and requiring fuel to be supplied at a first rate for engine start up, the fuel system (10) including: a main fuel pump (14) for providing fuel to the gas turbine engine (18), the main fuel pump (14) having an output varying with shaft speed, the output being at a windmilling rate when the engine (18) is windmilling, the windmilling rate being less than the first rate; and an auxiliary fuel pump (40) for providing fuel to the gas turbine engine (18) and having an auxiliary output rate greater than or equal to the difference between the first rate and the windmilling rate. A method of operating such a fuel system (10) is also disclosed.