Self-limiting Regenerative Pump Start Stage for Centrifugal Engine Fuel Systems
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Solution Overview
Problem
High-speed centrifugal pumps in aircraft engine fuel systems fail to provide sufficient flow and pressure during engine starting at low drive speeds, leading to the need for additional pumps that increase system weight and cost, and pose risks of over-pressurization due to regenerative stages remaining engaged.
Innovation Solution
A fuel system incorporating a regenerative type pump, an ejector pump, and a series of valves that selectively control the start process with the high-speed centrifugal pump, using a regulator valve to monitor pressure and flow signals to ensure adequate start-up conditions without over-pressurization, and a method to transition from the regenerative start stage to the centrifugal pump once requirements are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a high-speed centrifugal pump is used to minimize weight and cost, then weight and manufacturing cost are reduced, but the pump cannot provide sufficient flow and pressure during engine starting at low drive speeds
Solution Approach 1:
The patent combines a regenerative pump element and a centrifugal pump element into a single integrated pump assembly that shares a common drive shaft. The regenerative element provides high pressure at low speeds during engine starting, while the centrifugal element takes over at high speeds during normal operation, allowing the system to achieve both start-up capability and weight reduction without requiring a separate start pump
Solution Approach 2:
The system dynamically switches between the regenerative pump element and the centrifugal pump element based on operating conditions. A regulator valve responds to pressure signals to selectively direct flow through either the regenerative element or the centrifugal element, enabling the pump to adapt its characteristics to match the varying demands of engine starting versus normal operation
2Productivity
If a second start pump is added to provide sufficient flow and pressure at low speed, then start-up performance is improved, but system weight and cost increase
Solution Approach 1:
Instead of adding a separate start pump, the patent merges the start function into the main pump assembly by incorporating a regenerative pump element that can operate at low speeds to provide starting flow and pressure. This eliminates the need for a second pump while maintaining start-up capability
Solution Approach 2:
The regenerative pump element serves multiple functions: it acts as the primary pump during engine starting at low speeds, and can be selectively engaged during normal operation to provide additional pressure if needed. This multi-functionality eliminates the need for dedicated start-up equipment
3Productivity
If a regenerative start stage is used to provide start-up flow, then sufficient pressure is achieved at low speed, but the system risks over-pressurization if the stage remains engaged
Solution Approach 1:
The regulator valve incorporates a feedback mechanism that monitors pressure signals from both the regenerative start stage outlet and the centrifugal pump outlet. Based on these pressure signals, the valve automatically adjusts flow distribution to ensure the regenerative stage disengages when the centrifugal pump provides sufficient pressure, preventing over-pressurization
Solution Approach 2:
The system dynamically transitions between the regenerative start stage and the centrifugal pump based on real-time pressure conditions. The regulator valve responds to pressure signals to selectively direct flow, enabling automatic disengagement of the regenerative stage when no longer needed and preventing harmful over-pressurization
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 minimizes weight and cost while ensuring sufficient flow and pressure during engine starting, effectively decoupling the start-up pump stage and preventing over-pressurization by self-limiting pressure production.
Implementation Method 1
An ejector is in selective fluid communication with the pump and the regenerative start stage. The ejector is configured to recirculate fluid from the pump outlet to the pump inlet.
Implementation Method 2
a rotary kinetic pumping element for imparting energy to an associated fluid
Data Source
AI summary
An engine fuel or pump system includes a centrifugal pump having an impeller for imparting energy to an associated fluid for an associated downstream engine fuel system. A regenerative start stage is in selective fluid communication with the pump. And ejector includes an inlet that communicates with the pump outlet and an outlet that communicates with the pump inlet. Further, a regulator valve is interposed between the pump outlet and the regenerative start stage that selectively regulates associated flow from the regenerative start stage. The associated method include directing flow from the centrifugal pump to a regenerative start stage in order to supply an associated downstream flow circuit. During low speed starting, a portion of the flow from the regenerative start stage is provided to an ejector that recirculates to an inlet of the centrifugal pump. Once the centrifugal pump provides a predetermined level of at least one of the flow and pressure requirements of the associated flow circuit, the method includes terminating flow from the regenerative start stage.