Variable Fuel Injection for Ramjet Flame Stabilization
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Solution Overview
Problem
Dual-mode ramjet engines face challenges in maintaining flame stabilization and maximizing thrust force due to limitations in fuel injection technologies, particularly with wall fuel injection methods that either reduce fuel flow into the cavity-type flame holder or decrease combustion efficiency when adjusting fuel and air mixing ratios based on flight speed.
Innovation Solution
A variable fuel injection device with a sliding injector and mixer that adjusts fuel distribution and penetration within the combustor and flame holder, utilizing a controller to optimize fuel injection and mixing according to flight conditions, enhancing combustion stability and thrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the amount of fuel injected from the wall is increased to increase penetration distance and mixing ratio in the combustor, then thrust force increases, but the amount of fuel flowing into the cavity-type flame holder is reduced, adversely affecting flame stabilization
Solution Approach 1:
The fuel injection system is divided into two independent parts: wall fuel injection holes for thrust generation and cavity-type flame holder fuel injection holes for flame stabilization. This segmentation allows each part to be optimized independently - the wall injection holes can inject fuel to maximize penetration and thrust, while the cavity injection holes maintain sufficient fuel flow for flame stabilization regardless of the wall injection rate.
Solution Approach 2:
The cavity-type flame holder acts as an intermediary structure that receives fuel from both the wall injection holes and the cavity injection holes. It serves as a buffer zone that ensures sufficient fuel reaches the flame holder even when wall injection is maximized, thereby maintaining flame stabilization while allowing high thrust generation through wall injection.
2Reliability
If the amount of fuel injected from the wall is decreased to increase fuel flow into the cavity-type flame holder for flame stabilization, then flame stabilization improves, but the penetration distance of fuel decreases and mixing ratio in the combustor is reduced, weakening combustion reaction and thrust force
Solution Approach 1:
The fuel injection system is divided into two independent parts: wall fuel injection holes for thrust generation and cavity-type flame holder fuel injection holes for flame stabilization. This segmentation allows each part to be optimized independently - the wall injection holes can inject fuel to maximize penetration and thrust, while the cavity injection holes maintain sufficient fuel flow for flame stabilization regardless of the wall injection rate.
Solution Approach 2:
The system changes the injection parameters by providing two separate injection locations with potentially different injection rates and angles. The wall injection holes can operate at high rates for maximum thrust, while the cavity injection holes provide a steady baseline flow for flame stabilization, allowing independent optimization of both thrust and flame stability parameters.
3Reliability
If fuel is injected directly into the cavity-type flame holder, then flame stabilization may improve, but unvaporized fuel absorbs latent heat during phase change, decreasing flame temperature and adversely affecting flame stabilization
Solution Approach 1:
Fuel is pre-vaporized in the wall injection holes before reaching the cavity-type flame holder. By injecting fuel through the wall at a controlled rate and allowing it to vaporize in the hot combustor environment, the fuel is transformed from liquid to vapor phase before entering the cavity, preventing latent heat absorption that would otherwise cool the flame and destabilize it.
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 variable fuel injection device improves combustion efficiency, maintains flame stability, and increases thrust force by adjusting fuel distribution and promoting turbulent flow, optimizing fuel mixture and reducing internal drag across varying flight conditions.
Implementation Method 1
a sliding injector configured to perform a sliding operation from an upper surface of the combustor along a height direction perpendicular to an air flow direction
Implementation Method 2
a plurality of fuel injection holes formed on both sides and configured to inject fuel
Implementation Method 3
a fuel injection passage passing through the inside along the height direction to be opened downward, and configured to inject fuel
Implementation Method 4
air flowing in from the front passes through the combustor
Implementation Method 5
vaporized fuel and air may need to be mixed in a desirable ratio inside the flame holder
Implementation Method 6
a cavity-type flame holder formed behind the sliding injector on the upper surface of the combustor and having a cavity that is concavely recessed
Data Source
AI summary
Disclosed is a dual-mode ramjet engine including: a combustor through which air flowing in from the front passes; a sliding injector configured to perform a sliding operation from an upper surface of the combustor along a height direction perpendicular to an air flow direction; and a cavity-type flame holder formed behind the sliding injector on the upper surface of the combustor and having a cavity that is concavely recessed, wherein the sliding injector includes: a plurality of fuel injection holes formed on both sides and configured to inject fuel; a fuel injection passage passing through the inside along the height direction to be opened downward, and configured to inject fuel; and a first sliding drive unit configured to drive the sliding injector to perform the sliding operation.