Single Motor Fuel Pump System with Boost and Relief Valve
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Solution Overview
Problem
In fuel systems for aircraft or jet engines, the existing technologies face challenges in boosting fuel pressure without direct power from a jet engine and maintaining efficient operation, particularly in preventing cavitation, while also minimizing weight and power consumption.
Innovation Solution
A fuel system design featuring a constant-volume fuel pump and a boost pump, both driven by a single electric motor, with a return flow channel and relief valve to stabilize pressure, allowing the boost pump to discharge more fuel per unit revolution than the fuel pump, and switching mechanisms to adjust flow rates as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If a single electric motor drives both the fuel pump and centrifugal pump, then the number of motors is reduced and weight is decreased, but the centrifugal pump cannot provide sufficient boosting pressure at low fuel flow rates
Solution Approach 1:
The fuel pump is divided into two separate units: a centrifugal pump for generating high pressure and a constant-volume pump for precise flow control. This segmentation allows each pump to be optimized for its specific function, enabling the centrifugal pump to provide sufficient boosting pressure even when operated at lower speeds by a single electric motor.
Solution Approach 2:
The system dynamically switches between different pump configurations based on fuel flow rate requirements. At low fuel flow rates, only the centrifugal pump operates to provide necessary pressure boosting. At higher fuel flow rates, the constant-volume pump is engaged to supplement the flow while maintaining pressure, thus adapting the system's performance to varying operational conditions.
2Power
If the fuel pump is driven by the jet engine, then power is available for pumping, but the pump speed cannot be optimized for varying fuel flow rate requirements, causing extra fuel circulation and power consumption
Solution Approach 1:
The mechanical drive system connected to the jet engine is replaced with an electric motor drive system. This substitution enables independent control of the fuel pump speed, allowing the pump to operate at optimal speeds for varying fuel flow rate requirements without being coupled to the jet engine's rotation speed, thereby eliminating extra fuel circulation and reducing power consumption.
Solution Approach 2:
The electric motor enables dynamic adjustment of the fuel pump speed according to actual fuel flow rate requirements. The control system can optimize the pump speed in real-time, ensuring that the pump only delivers the necessary fuel flow without excess, thus preventing the energy losses associated with circulating extra fuel.
3Reliability
If a centrifugal pump is used to boost fuel pressure, then cavitation in the fuel pump is prevented, but the discharge pressure is proportional to the square of speed, making it difficult to maintain adequate pressure at low speeds
Solution Approach 1:
The fuel pumping function is segmented into two specialized pumps: the centrifugal pump dedicated to pressure boosting and cavitation prevention, and the constant-volume pump dedicated to maintaining precise flow control. This segmentation allows the centrifugal pump to be optimized for its pressure-generating function without compromise, while the constant-volume pump ensures adequate flow even when the centrifugal pump operates at lower speeds.
Solution Approach 2:
The system dynamically engages the constant-volume pump when additional flow is needed at lower speeds. The control system monitors fuel flow rate requirements and activates the constant-volume pump in conjunction with the centrifugal pump to maintain both adequate pressure (from the centrifugal pump) and sufficient flow (supplemented by the constant-volume pump), overcoming the limitation of centrifugal pump pressure-speed relationship.
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 design effectively boosts fuel pressure to prevent cavitation and maintain constant supply to the fuel pump without direct jet engine power and without increasing the number of electric motors, enhancing efficiency and reducing weight.
Implementation Method 1
a centrifugal pump that boosts a pressure of fuel, which is supplied to the fuel pump, to an extent to which cavitation does not occur in the fuel pump
Implementation Method 2
a constant-volume fuel pump that boosts the pressure of fuel to a pressure suitable for the jet engine
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A fuel system includes a fuel pump (3) formed of a constant-volume pump for changing a discharge flow rate in conjunction with a variation in a speed of revolution of a drive shaft, a boost pump (4) disposed upstream from the fuel pump (3) and formed of a constant-volume pump of which a discharge flow rate per unit of revolution of a drive shaft is greater than that of the fuel pump (3), a single electric motor (5) rotationally driving the drive shaft of the fuel pump (3) and the drive shaft of the boost pump (4) in a state in which the speeds of revolution thereof are equal to each other, a return flow channel (7) connecting an upstream side and a downstream side of the boost pump (4), and a relief valve (8) disposed in the return flow channel (7) and opened when an internal pressure of the return flow channel (7) is greater than a reference pressure.