Aviation Fuel System Pump Switching and Vibration Control
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Solution Overview
Problem
The fuel system incorporating both centrifugal and constant-volume pumps experiences pressure mismatches and vibrations when switching between modes, due to the different mechanisms and proportional rotational speed dependencies of these pumps, leading to inefficient energy transfer and potential system instability.
Innovation Solution
A fuel system configuration that includes a speed changer connecting the engine to the centrifugal pump, allowing adjustable speed ratio, and a shut-off and switching mechanism to control the flow passageways, enabling seamless switching between centrifugal and constant-volume pump modes, thereby matching discharge pressures and minimizing vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a centrifugal pump is used to increase fuel pressure, then energy efficiency is improved and system size is reduced, but discharge pressure becomes insufficient when engine rotational speed is low
Solution Approach 1:
The patent combines a centrifugal pump and a constant-volume pump into a single fuel system. The centrifugal pump handles high-speed operation efficiently, while the constant-volume pump supplements pressure at low speeds. Both pumps can operate simultaneously or independently based on engine conditions, merging their advantages to resolve the contradiction between energy efficiency and sufficient discharge pressure across all operating ranges.
Solution Approach 2:
The patent dynamically switches between centrifugal pump-only mode, constant-volume pump-only mode, and combined mode based on engine rotational speed and fuel pressure requirements. This dynamic operation allows the system to optimize energy efficiency at high speeds while ensuring sufficient pressure at low speeds, resolving the contradiction adaptively across different operating conditions.
2Stress or pressure
If both centrifugal pump and constant-volume pump are provided in the fuel system, then sufficient discharge pressure is achieved at low engine speeds, but pressure mismatch and vibrations occur when switching between pump modes
Solution Approach 1:
The patent introduces a pressure equalization chamber that pre-adjusts the discharge pressure from the constant-volume pump before it enters the common fuel line. This preliminary pressure adjustment ensures that when switching between pump modes, the pressures are already matched, preventing vibrations and instability during transitions while maintaining sufficient pressure at low engine speeds.
3Stress or pressure
If a constant-volume pump is added to compensate for low-speed pressure deficiency, then discharge pressure is sufficient at low engine speeds, but the fuel system becomes more complicated and energy efficiency deteriorates
Solution Approach 1:
The patent merges the constant-volume pump and centrifugal pump into an integrated fuel system with shared components such as the pressure equalization chamber and common discharge line. This merging approach, while adding a pump, consolidates other system elements and uses the constant-volume pump only when necessary, thereby limiting overall complexity while ensuring sufficient pressure.
Solution Approach 2:
The patent employs the constant-volume pump only partially - specifically when engine rotational speed is low and centrifugal pump pressure is insufficient. During high-speed operation, only the centrifugal pump operates. This partial use of the constant-volume pump minimizes its impact on system complexity and energy consumption while providing necessary pressure supplementation only when required.
4Loss of energy
If the centrifugal pump is directly connected to the engine, then energy efficiency is improved by eliminating electric power conversion, but the discharge pressure varies significantly with engine rotational speed
Solution Approach 1:
The patent dynamically adjusts the fuel pressure by switching between centrifugal pump operation, constant-volume pump operation, and combined operation based on real-time engine rotational speed and pressure requirements. This dynamic adaptability allows the system to maintain appropriate pressure across the full engine speed range while keeping the centrifugal pump directly connected to the engine for high energy efficiency.
Solution Approach 2:
The patent introduces a pressure equalization chamber as an intermediary between the pumps and the fuel line. This intermediary component buffers and equalizes pressure fluctuations from both pump types, allowing the centrifugal pump to remain directly connected to the engine for efficient power transfer while the intermediary chamber ensures pressure adaptability across varying engine speeds.
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
The system effectively matches discharge pressures between the centrifugal and constant-volume pumps, reducing vibrations and ensuring stable fuel pressure delivery across varying engine rotational speeds, enhancing energy efficiency and system stability.
Implementation Method 1
a centrifugal pump (2a) which increases the pressure of fuel
Implementation Method 2
a constant-volume pump (2i) which increases the pressure of fuel
Data Source
Figure 1
Figure 2
AI summary
A fuel system (1A) includes: a constant-volume pump (2i) and a centrifugal pump (2a) increasing the pressure of fuel (N) to be supplied to an engine (E) for aviation and discharging the fuel; an operation controller (4) configured to select in accordance with the operation state of the engine, one of a constant-volume pump-using mode of increasing the pressure of fuel using the constant-volume pump and a centrifugal pump-using mode of increasing it using the centrifugal pump; and a speed changer (2c) connecting the engine and the centrifugal pump, changing the rotational speed of rotational power output from the engine and transmitting the rotational power to the centrifugal pump, and being capable of adjusting the speed-changing ratio of the rotational speed.