Afterburner Ignition Zone Primary Flow Diversion
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Solution Overview
Problem
After-burner devices in bypass turbojets face insufficient ignition performance under low-pressure flying conditions, which is not compatible with operational requirements.
Innovation Solution
A method that involves diverting a fraction of the primary flow into the after-burner ignition zone to increase the temperature, enhancing ignition performance by modifying the aerodynamic characteristics and fuel mixture temperature, without requiring additional cooling means for the ignitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ignition occurs in the secondary flow, then the ignitor member does not require additional cooling means, but ignition performance becomes insufficient under low-pressure conditions
Solution Approach 1:
The patent applies local quality by creating a localized hot zone within the ignition zone. A fraction of the hot primary flow is directed specifically into the ignition zone where the ignitor is located, while the rest of the secondary flow continues to cool the ignitor. This localized heating improves ignition performance without requiring complete temperature increase of the entire flow field.
Solution Approach 2:
The patent uses the primary flow as an intermediary substance to transfer thermal energy to the ignition zone. The hot primary flow acts as a mediator that delivers heat to the fuel-air mixture in the ignition zone, enabling effective ignition without directly heating the entire secondary flow or requiring complex cooling systems for the ignitor.
2Reliability
If the speed of flow surrounding the ignition zone decreases, then transit time of fuel mixture increases improving ignition performance, but control of local speed becomes extremely complex and expensive
Solution Approach 1:
The patent changes the temperature parameter of the flow in the ignition zone by introducing hot primary flow. This temperature change naturally affects the density and speed of the fuel-air mixture, extending transit time and improving ignition performance without requiring complex active control systems to manipulate flow speed directly.
3Reliability
If pressure in the ignition zone is increased, then ignition performance improves, but pressure cannot be increased beyond compressor limits without compromising pumping margin
Solution Approach 1:
The patent creates a localized pressure and temperature enhancement in the ignition zone by directing a fraction of the primary flow into this specific region. The pressure and temperature are elevated locally where needed for ignition, while the overall system pressure remains within compressor operating limits.
Solution Approach 2:
The patent applies partial action by using only a fraction of the primary flow (not the entire flow) to heat and pressurize the ignition zone. This partial application of the hot flow provides sufficient ignition conditions while avoiding excessive pressure increases that would compromise the compressor's pumping margin.
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 method ensures consistent ignition performance across all flight stages by raising the fuel mixture temperature, compensating for low-pressure conditions and maintaining ignitor longevity.
Implementation Method 1
a fraction of the primary flow is taken and brought locally into the after-burner ignition zone in order to raise the temperature in this zone to a value that is higher than the temperature of the secondary flow so as to encourage after-burner ignition
Data Source
AI summary
The after-burner device receives a “hot” central primary flow from the turbine of the turbojet and a “cold” peripheral secondary flow, and it has an after-burner ignition zone situated in the secondary flow that reaches the after-burner device. A fraction of the primary flow is brought into the after-burner ignition zone in order to raise the temperature in said zone to a value that is higher than that of the secondary flow so as to encourage after-burner ignition.