Variable Displacement Pump Bypass Control for High Turn-Down Flow
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Solution Overview
Problem
Conventional variable displacement pumps face inefficiencies due to high turn-down ratios, particularly in fuel delivery systems for gas turbine engines, where minimum pump pressure flows exceed the lowest flow requirements, leading to suboptimal performance.
Innovation Solution
A system with feedback mechanisms using position and pressure sensors to control a bypass valve and variable displacement mechanism, allowing for active control of recirculation flow based on downstream demands, reducing valve count and eliminating the need for a metering valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the pump is designed with a high turn-down ratio to meet varying flow demands, then the pump can supply both high flow for cooling and low flow for fuel burners, but the pump efficiency deteriorates across the operating range
Solution Approach 1:
The pump system is segmented into two independent control pathways: a bypass line with its own electrohydraulic servo valve for high-flow cooling demands, and a main fuel line with a separate electrohydraulic servo valve for precise low-flow fuel delivery. This segmentation allows each subsystem to operate independently at optimal efficiency points, resolving the contradiction between high adaptability and energy loss.
2Reliability
If the minimum pump pressure flow is increased to support VDP cooling, then the VDP cooling requirement is met, but the flow available for fuel burners exceeds the lowest flow requirement
Solution Approach 1:
The system incorporates feedback control through electrohydraulic servo valves that receive commands from a controller based on actual flow and pressure conditions. The bypass valve is controlled to maintain a minimum baseline flow for VDP cooling, while the fuel metering valve precisely regulates the remaining flow to match actual fuel burner demands, eliminating excess flow and improving fuel delivery efficiency.
3Ease of manufacture
If conventional control techniques are used for VDPs, then the system is simpler to implement, but the system cannot achieve high turn-down ratios with optimal efficiency
Solution Approach 1:
The patent replaces conventional mechanical control mechanisms with electrohydraulic servo valves that provide precise electronic control. This substitution enables the system to achieve high turn-down ratios with optimal efficiency by allowing dynamic, programmable control of both the bypass and fuel metering functions, overcoming the limitations of simpler mechanical control systems.
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
Enables high turn-down ratios with improved efficiency and reduced valve count, enhancing performance in fuel delivery systems, especially for gas turbine engines.
Implementation Method 1
A first electrohydraulic servo valve can be connected in fluid communication with the bypass valve by a first control line for control of the bypass valve
Implementation Method 2
A second electrohydraulic servo valve can be connected in fluid communication with the variable displacement mechanism by a second control line for control of the flow through the variable displacement pump
Implementation Method 3
A flow sensing valve (FSV) can be in the outlet line with a sensor configured to generate sensor data indicative of flow through the VDP
Data Source
Figure 1
AI summary
A system includes a variable displacement pump (VDP) (102) in fluid communication with an inlet line (104) and with an outlet line (106). A bypass valve (BPV) (110) includes a BPV inlet (112) in fluid communication with the outlet line, and a BPV outlet (114) in fluid communication with a bypass line that feeds into the inlet line upstream of the VDP. An actuator (118) is operatively connected to control the BPV to vary flow from the BPV inlet to the bypass line. A flow sensing valve (FSV) (148) is connected in the outlet line. The FSV includes a sensor configured to generate sensor data indicative of flow out of the outlet line. A controller (150) operatively connected to the actuator to control recirculation flow passed through the BPV based on the sensor data and based on a predetermined low threshold of flow through the VDP.