Flow-Sensed Bypass Recirculation for Variable Displacement Pumps
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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 a bypass valve and flow sensing mechanism controlled by a controller to manage recirculation flow based on sensor data, maintaining baseline flow and adjusting as needed to meet downstream demands, using electrohydraulic servo valves for precise actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the pump is designed for high turn-down ratio operation, then the pump can meet varying flow demands from minimum cooling flow to maximum fuel flow, but the pump efficiency becomes suboptimal across the operating range
Solution Approach 1:
The system employs a flow sensor to continuously monitor the actual flow rate and feeds this information back to the controller. The controller adjusts the bypass valve position based on the feedback signal to maintain optimal pump efficiency across varying flow conditions, resolving the contradiction between high adaptability and energy efficiency.
Solution Approach 2:
The bypass valve is dynamically adjusted based on real-time flow conditions rather than being fixed. The controller modulates the bypass valve opening to optimize pump efficiency at different operating points, allowing the system to adapt dynamically between high turn-down ratio operation and efficient pumping.
2Reliability
If the minimum pump pressure flow is increased to support VDP cooling, then the VDP cooling is ensured, but the flow available for fuel burners exceeds the lowest flow requirement
Solution Approach 1:
The excess flow that exceeds the minimum burner requirement is extracted from the main flow path and redirected through the bypass valve back to the pump inlet. This allows the pump to maintain higher minimum flow for cooling while the bypass mechanism removes the surplus flow that would otherwise be unavailable for precise fuel metering.
Solution Approach 2:
The bypass valve acts as an intermediary flow path that reconciles the conflict between cooling requirements and fuel delivery requirements. It provides a controlled recirculation path that allows the pump to operate at higher flows for cooling while delivering precise lower flows to the burners.
3Adaptability or versatility
If a bypass valve is added to enable high turn-down ratio operation, then the flow flexibility is improved, but the system complexity increases
Solution Approach 1:
The bypass valve is designed to perform multiple functions: it enables high turn-down ratio operation, maintains pump efficiency, ensures minimum cooling flow, and works with the flow sensor and controller to provide adaptive flow control. This multi-functionality justifies the addition of the valve by consolidating several control objectives into a single component.
4Device complexity
If conventional pump control is used, then the system is simple, but it cannot maintain optimal pump efficiency across high turn-down ratios
Solution Approach 1:
The flow sensor provides continuous feedback on actual flow conditions to the controller, which adjusts the bypass valve to maintain optimal pump efficiency. This closed-loop feedback control system resolves the contradiction by using relatively simple sensing and control components to achieve significant energy efficiency improvements across the pump's operating range.
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
Enhances pump efficiency by allowing high turn-down ratios while maintaining optimal flow, reducing valve count, and eliminating the need for metering valves, suitable for fuel supply in aircraft engines.
Implementation Method 1
A flow sensing valve (FSV) is connected in the outlet line. The FSV includes a sensor configured to generate sensor data indicative of flow out of the outlet line.
Implementation Method 2
A bypass valve (BPV) includes a BPV inlet in fluid communication with the outlet line, and a BPV outlet in fluid communication with a bypass line that feeds into the inlet line upstream of the VDP.
Implementation Method 3
A first electrohydraulic servo valve (EHSV) can be connected in fluid communication with the BPV by a first control line. The first EHSV can be operatively connected to the controller for active control of the first EHSV to actuate the BPV.
Data Source
AI summary
A system includes a variable displacement pump (VDP) in fluid communication with an inlet line and with an outlet line. A bypass valve (BPV) includes a BPV inlet in fluid communication with the outlet line, and a BPV outlet in fluid communication with a bypass line that feeds into the inlet line upstream of the VDP. An actuator is operatively connected to control the BPV to vary flow from the BPV inlet to the bypass line. A flow sensing valve (FSV) 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 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.