Pulse Detonation APU Combustor for Higher Turbine Drive Efficiency
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Solution Overview
Problem
Conventional auxiliary power units (APUs) in aircraft seek improvements in thermal, transfer, and fuel efficiencies, particularly in the operation of accessory devices and systems.
Innovation Solution
The use of pulse detonation combustion tubes (PDTs) that generate a standing pressure wave to sustain combustion, timed fuel injection, and ignition at the discharge end of the PDTs to drive a turbine, enhancing efficiency by increasing combustion rates and reducing pressure loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional continuous combustion is used in APU combustors, then stable operation is achieved, but combustion efficiency and fuel efficiency are limited
Solution Approach 1:
The patent implements periodic detonation combustion in the combustor, where fuel and air are mixed and ignited in periodic pulses rather than continuous combustion. This periodic detonation creates high-pressure waves that significantly increase combustion efficiency and energy release rate, directly addressing the contradiction between fuel efficiency and combustion rate by using timed periodic action to achieve both high energy utilization and high productivity
Solution Approach 2:
The patent changes the combustion mode from conventional continuous low-pressure combustion to high-pressure detonation combustion. By altering the pressure parameter and combustion speed parameter, the system achieves superior fuel efficiency and power output, resolving the contradiction between energy use efficiency and combustion productivity
2Power
If higher combustion rates are achieved to improve power output, then power efficiency increases, but pressure loads on engine components increase
Solution Approach 1:
The periodic detonation combustion creates controlled high-pressure waves that occur in discrete pulses rather than continuous high pressure. This allows the engine to achieve high power output through the cumulative effect of periodic pressure spikes while avoiding sustained high pressure loads on components, effectively resolving the contradiction between power efficiency and pressure stress
Solution Approach 2:
The system uses dynamic control of the detonation timing and frequency to optimize power output while managing pressure loads. By adjusting the operational parameters of the periodic detonation, the engine can adapt to different power requirements while keeping pressure loads within acceptable limits through controlled dynamic operation
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 PDTs enhance engine efficiency by increasing combustion rates and reducing pressure loads, resulting in improved power and fuel efficiency for accessory devices and systems.
Implementation Method 1
an igniter for igniting a fuel air mixture within the detonation tube near the discharge end
Implementation Method 2
Compressed air from the compressor is mixed with fuel in a combustor
Data Source
AI summary
An accessory power unit assembly includes a combustor assembly that includes a pulse detonation tube that defines a curved passage between an inlet that receives a compressed airflow and a discharge end. The detonation tube operates as a resonant cavity to sustain a standing pressure wave. Fuel injected into the pulse detonation tube is timed to coincide with movement of a standing wave toward a discharge end. The standing wave provides an increase in pressure of an output exhaust gas driving the turbine without a corresponding increase in load.