Variable Displacement Pump Control for High Turn-Down Fuel Flow
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Solution Overview
Problem
Variable displacement pumps (VDPs) face inefficiencies due to high turn-down ratios, particularly in fuel delivery systems for gas turbine engines, where minimum pump pressure flows are higher than the lowest flow requirements, leading to suboptimal performance.
Innovation Solution
A system incorporating a variable displacement pump with an electromechanical actuator, bypass valve, minimum pressure shutoff valve, and flow sensing valve, controlled by a controller to manage flow and pressure, allowing recirculation and direct electrical actuation to maintain efficient operation across varying flow conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable displacement pump is designed with high turn-down ratio capability, then the pump can function across a wider flow range, but pump efficiency deteriorates throughout the operating range
Solution Approach 1:
The pump system is segmented into multiple functional zones using bypass valves and flow control mechanisms. The pump operation is divided into high-flow mode (where bypass valve is closed) and low-flow mode (where bypass valve is open), allowing each segment to operate at optimal efficiency points while covering a wide turn-down ratio range
Solution Approach 2:
A bypass valve acts as an intermediary element that diverts excess flow away from the pump outlet when operating at high displacement settings. This mediator allows the pump to maintain high efficiency by operating at a fixed optimal point while the bypass valve handles the variable flow requirements, resolving the contradiction between adaptability and efficiency
2Temperature
If minimum pump pressure flow is increased to support VDP cooling, then cooling capability is improved, but the lowest flow for fuel burners cannot be met
Solution Approach 1:
The bypass valve is dynamically controlled based on real-time flow demands. During high-demand periods, the bypass valve closes to maximize fuel flow to burners. During low-demand periods, the bypass valve opens to provide sufficient flow for VDP cooling, creating a dynamic system that adapts to changing operational requirements and resolves the contradiction between cooling needs and fuel delivery
3Ease of operation
If conventional valve systems are used for flow control, then flow management is achieved, but system weight and complexity increase
Solution Approach 1:
Multiple valve functions are merged into integrated valve assemblies. The bypass valve incorporates both flow control and cooling functions, while the BOPV combines bypass and shutoff capabilities in a single integrated component. This merging reduces the total number of separate valves and associated hardware, thereby reducing system weight while maintaining comprehensive flow control capability
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 enhances pump efficiency by reducing valve count, minimizing horsepower extraction, and decreasing system weight and heat rejection, enabling better fuel management and performance in aircraft engines.
Implementation Method 1
An electromechanical actuator (EMA) is operatively connected to actuate the variable displacement mechanism
Implementation Method 2
A bypass valve (BPV) can includes 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
The MPSOV can be connected in fluid communication with the outlet line, configured to block flow through the outlet line for shutoff
Implementation Method 4
A flow sensing valve (FSV) can be connected in the outlet line, wherein the FSV includes a sensor configured to generate sensor data indicative of flow out of the outlet line
Implementation Method 5
A first electrohydraulic servo valve (EHSV) can be connected in fluid communication with the BPV by a first control line
Data Source
AI summary
A system includes a variable displacement pump (VDP) in fluid communication with an inlet line and with an outlet line. The VDP includes a variable displacement mechanism configured to vary pressure to the outlet line. An electromechanical actuator (EMA) is operatively connected to actuate the variable displacement mechanism for direct electromechanical control of the VDP.