APU Emergency Power via Independent Hydrogen Fuel Circuit
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Solution Overview
Problem
Aircraft auxiliary power units (APU) and ram air turbines (RAT) impose unnecessary in-flight loads and suffer from severe maintenance constraints, limiting their effectiveness as power sources during standard flight conditions and emergency situations.
Innovation Solution
The APU is repurposed to provide emergency power by using a specific, independent fuel supply of hydrogen, which is stored in a stable form and can be instantaneously converted for combustion, eliminating the need for the RAT and reducing maintenance burdens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the APU is used as a non-propulsive energy source during flight, then additional power is provided to aircraft systems, but the APU represents an unnecessary in-flight load
Solution Approach 1:
The APU is designed to perform multiple functions: it serves as both a source of non-propulsive power during normal flight operations and as an emergency power source for vital systems. This multi-functionality allows the APU to provide power benefits while being integrated into the aircraft's existing power architecture, reducing the need for separate dedicated emergency power equipment.
2Reliability
If the RAT is installed to meet emergency power requirements, then emergency power is provided to vital systems, but the equipment imposes severe maintenance constraints
Solution Approach 1:
The emergency power function is merged with the APU system rather than using a separate RAT. The APU's existing fuel supply infrastructure is utilized for emergency power, and the same APU unit that provides non-propulsive power also serves as the emergency power source. This integration eliminates the need for a separate RAT and its associated maintenance requirements.
Solution Approach 2:
The RAT is extracted from the aircraft system entirely. Instead of installing and maintaining a separate RAT, the patent extracts the emergency power function and assigns it to the APU, which already has the necessary infrastructure. This removes the maintenance burden of the RAT while preserving emergency power capability.
3Device complexity
If the APU uses common fuel supply from aircraft engines, then fuel infrastructure is simplified, but the APU is vulnerable to fuel contamination affecting reliability
Solution Approach 1:
The fuel supply system is segmented into a common fuel supply for normal APU operation and a separate emergency fuel supply for emergency power mode. The common supply uses the aircraft's existing fuel infrastructure, while the emergency supply includes dedicated fuel tanks and circulation systems that are isolated from contamination sources. This segmentation allows simplified overall architecture while ensuring reliability through isolated emergency fuel paths.
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 reduces unnecessary loads and maintenance costs by allowing the APU to efficiently supply emergency power to vital systems without contaminating the main fuel system, enhancing aircraft operational reliability and safety.
Implementation Method 1
Hydrogen is either directly stored in a solid, liquid or gaseous state in the specific source, or produced by appropriate refining of kerosene stored in that specific source. Advantageously, the storage of hydrogen is carried out in a solid form, which is particularly stable and which allows an almost instantaneous change of state in liquid or gaseous form by a pyrotechnic ignition.
Implementation Method 2
the storage of hydrogen is carried out in a solid form, which is particularly stable and which allows an almost instantaneous change of state in liquid or gaseous form by a pyrotechnic ignition.
Data Source
Figure 1~2
Figure 3
AI summary
The invention aims to eliminate the need for a backup turbine or RAT in an aircraft by proposing to dedicate an auxiliary power unit (APU) to providing emergency power. To this end, the APU is protected from the main common cause of failure with engines—namely, fuel contamination—by implementing an independent fuel supply. An auxiliary power supply architecture comprises an APU (2; 23 to 27) and a basic fuel supply circuit (3) (4), including a fuel storage tank (31), a primary circulation line (32), and secondary lines (33, 34) for injecting this fuel into the combustion chambers (21) of the APU (2) via suitable injectors (22).This architecture (1) also includes another independent circuit (5) for supplying the APU group (2), comprising an emergency tank (51), in particular of hydrogen, a specific primary conduit (52) for circulating the emergency fuel (6) and secondary conduits (53, 54) for injecting the emergency fuel (6) into the combustion chambers (21) by appropriate injectors (28).