Aircraft Start Pump Generator for Lighter Fuel Pump Sizing
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Solution Overview
Problem
Aircraft fuel systems are burdened with unnecessary weight due to oversized main fuel pumps designed for engine start-up, which are inefficient during cruise conditions, leading to increased fuel burn and heat production.
Innovation Solution
Incorporating an electric motor-driven start pump that operates in a forward direction during start-up to assist the main fuel pump and reversely generates electrical power during cruise, reducing the size and power requirements of the main fuel pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the main fuel pump is sized to accomplish engine start-up, then the engine can be reliably started, but the main fuel pump adds unnecessary weight to the aircraft during cruise conditions
Solution Approach 1:
The fuel pumping function is segmented into two separate pumps: a main fuel pump sized for cruise conditions and a start pump sized for start-up conditions. This allows each pump to be optimally sized for its specific function, eliminating the need for an oversized main fuel pump during cruise.
Solution Approach 2:
The start pump is designed with multi-functionality to serve dual purposes: it provides fuel during engine start-up and then converts to a generator during cruise conditions to produce electrical power. This universal design justifies its inclusion by providing multiple benefits rather than being purely additional weight.
2Quantity of substance
If the main fuel pump is oversized for start-up conditions, then sufficient fuel flow is provided during start-up, but the pump consumes excessive power during cruise conditions
Solution Approach 1:
The fuel delivery system is divided into two separate pumping systems with different capacities. The start pump handles high flow rate requirements during start-up, while the main fuel pump handles lower flow rate requirements during cruise, optimizing power consumption for each operating condition.
Solution Approach 2:
The start pump serves itself by converting to generator mode during cruise conditions. The fuel flow that would otherwise be wasted is used to drive the start pump in reverse, generating electrical power that benefits the aircraft system.
3Weight of moving object
If a separate start pump is added to assist during start-up, then the main fuel pump can be smaller, but the device complexity increases
Solution Approach 1:
The start pump is designed as a multi-functional component that serves as a fuel pump during start-up and as a generator during cruise conditions. This dual functionality offsets the added complexity by providing multiple benefits from a single additional component.
Solution Approach 2:
The start pump combines multiple functions into one component: fuel pumping capability and generator capability. By merging these functions into a single component rather than adding separate systems, the overall complexity is minimized.
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 solution reduces fuel consumption and weight by allowing the main fuel pump to be smaller, while generating additional electrical power for aircraft systems, thus optimizing fuel efficiency and power availability.
Implementation Method 1
an electric motor driven start pump fluidly connected to the check valve and the selector valve... During a cruise condition, the fuel system is configured to permit the fuel to flow from a high-pressure fuel source and through the electric motor driven start pump to drive the electric motor driven start pump to generate electrical energy
Data Source
AI summary
A fuel system for an aircraft includes a main fuel pump, a metering valve fluidly connected to the main fuel pump, a selector valve fluidly connected to the metering valve, a check valve fluidly connected to the metering valve, and an electric motor driven start pump fluidly connected to the check valve and the selector valve. During a start-up condition, the fuel system is configured to permit a fuel to flow through the electric motor driven start pump and through the selector valve to an engine. During a cruise condition, the fuel system is configured to permit the fuel to flow from a high-pressure fuel source and through the electric motor driven start pump start pump to drive the electric motor driven start pump to generate electrical energy.