Dual Pump Fuel Supply System for Gas Turbine Engine
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Solution Overview
Problem
Conventional fuel supply systems for gas turbine engines face arduous operating conditions for pump bearings, particularly at high pressure cruise, due to increased bearing loads and waste heat rejection, leading to reduced bearing life and potential design changes.
Innovation Solution
A dual positive displacement pump system with a switching valve that allows for series or parallel operation modes, where the first pump has a higher capacity than the second, and a pressure split regulating valve maintains pressure ratios across both pumps, reducing heat rejection and bearing loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single positive displacement pump is used in a conventional fuel supply system, then the system structure is simple, but the bearing loads and heat rejection increase significantly at high pressure cruise conditions, reducing bearing life
Solution Approach 1:
The single pump is divided into two separate positive displacement pumps with different displacement volumes. The first pump has a larger displacement volume while the second pump has a smaller displacement volume. This segmentation allows the system to distribute the pumping workload between two units, reducing the bearing loads and heat rejection on any single pump during high pressure cruise operations, thereby improving bearing life without significantly increasing overall system complexity
Solution Approach 2:
A switching valve is introduced to dynamically change the connection mode between the two pumps from series to parallel based on operating conditions. During high pressure cruise, the pumps operate in parallel to reduce individual bearing loads. During other operating conditions, the pumps can operate in series to maintain system efficiency. This dynamic reconfiguration allows the system to optimize performance across different operating regimes while protecting bearing life during critical high pressure cruise
2Productivity
If a single positive displacement pump operates at high pressure cruise, then the pump delivers required fuel flow, but waste heat rejection to the fuel increases significantly due to high spill flow and high pressures
Solution Approach 1:
The pump system is segmented into two pumps with different displacement volumes. During high pressure cruise, the larger first pump operates in parallel with the smaller second pump, allowing the system to maintain required fuel flow delivery while reducing the spill flow through each individual pump. This segmentation reduces waste heat rejection to the fuel, preventing excessive temperature rise during high pressure cruise operations
Solution Approach 2:
The system changes the operating parameters by switching between series and parallel connection modes of the two pumps. During high pressure cruise, parallel operation reduces the pressure rise across each pump and increases spill flow capacity, thereby reducing waste heat rejection. During other operating conditions, series operation maintains higher pressure rise and reduces spill flow, optimizing fuel temperature management. This parameter change allows the system to balance fuel flow delivery with temperature control
3Productivity
If the pump size is calculated for maximum fuel flow with a safety margin, then the pump can handle peak demands, but at idle conditions the output exceeds demand and causes excessive waste heat rejection
Solution Approach 1:
The switching valve enables dynamic reconfiguration of the pump system between series and parallel modes based on fuel flow demand. At idle conditions, the system can switch to series operation where the smaller second pump handles the low flow demand, while the larger first pump is unloaded or operates at very low flow. This dynamic adaptation prevents excessive waste heat rejection at idle by matching pump output to actual fuel demand, while maintaining the capability to deliver maximum fuel flow when required
Data Source
AI summary
A fuel supply system for a gas turbine engine comprises a first positive displacement pump (16), a second positive displacement pump (27), said first and second positive displacement pumps (16, 27) being operable simultaneously for the supply of fuel from a low pressure source, and switching valve means (14) downstream of said first positive displacement pump (16) for changing a connection mode between said first and second positive displacement pumps (16, 27) between a series mode and a parallel mode.