Jet Engine Combustor Ramp Angle for Stable Flame
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Solution Overview
Problem
In supersonic jet engines, maintaining a stable flame is challenging due to the short residence time of fuel in the combustor, leading to potential boundary layer delamination and unstart conditions when the ramp angle exceeds 13.5 degrees, which restricts fuel-air mixing and combustion efficiency.
Innovation Solution
A jet engine design with a ramp angle of the ramped surface equal to or more than 13.5 degrees, combined with a specific height and configuration of the ramp section, promotes fuel-air mixing and maintains a stable flame by preventing subsonic flow and unstart states, while using a flame stabilizer and multiple ramp sections to enhance combustion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ramp angle is increased to promote fuel-air mixing, then combustion efficiency is improved, but boundary layer delamination occurs leading to unstart conditions
Solution Approach 1:
The patent applies local quality by providing a cooling hole only at the upstream end of the ramp section, creating a localized cooling effect where it is most needed to prevent boundary layer delamination at the critical leading edge, while allowing the rest of the ramp to maintain its high angle for effective fuel-air mixing
Solution Approach 2:
The patent introduces cooling air as an intermediary substance that flows through the cooling hole to interact with the boundary layer at the ramp's upstream end, preventing delamination and maintaining stable flow conditions that allow the high ramp angle to function effectively
2Productivity
If the ramp angle is increased to enhance fuel-air mixing, then combustion efficiency is improved, but subsonic flow occurs causing unstart conditions
Solution Approach 1:
The patent applies local quality by providing a cooling hole only at the upstream end of the ramp section, creating a localized cooling effect where it is most needed to prevent boundary layer delamination at the critical leading edge, while allowing the rest of the ramp to maintain its high angle for effective fuel-air mixing
Solution Approach 2:
The patent introduces cooling air as an intermediary substance that flows through the cooling hole to interact with the boundary layer at the ramp's upstream end, preventing delamination and maintaining stable flow conditions that allow the high ramp angle to function effectively
3Reliability
If the combustor length is increased to extend fuel residence time, then flame stability is improved, but fuselage size increases
Solution Approach 1:
The patent changes the flow conditions parameters by introducing cooling air at a specific location and ratio (1-10% of total air flow), which modifies the boundary layer characteristics to prevent delamination, thereby maintaining stable combustion in a more compact configuration
Solution Approach 2:
The patent segments the cooling function from the overall combustor structure by providing a dedicated cooling hole at the upstream end of the ramp section, separating the cooling function from the main combustor volume and enabling compact design while maintaining stability
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 configuration effectively maintains stable combustion and prevents unstart conditions, promoting fuel-air mixing and combustion efficiency even at supersonic speeds, overcoming traditional limitations on ramp angle and ensuring efficient propulsion.
Implementation Method 1
a cooling hole is provided for the upstream end of the ramp section. Cooling air is introduced into the upstream end of the ramp section through the cooling hole
Implementation Method 2
When a ramp is arranged in a supersonic flow, the relation of Mach number (inlet Mach number) of fluid flowing on the upstream side than the ramp and delamination Mach number when the fluid flowing on the ramped surface of the ramp delaminates from the ramped surface is possible to be acquired
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
A jet engine is provided with an inlet 11 and a combustor 12 having a fuel injection port 30a. The combustor 12 has a wall part 16 that defines an air flow path FA. The wall part 16 has a ramp part 60, which has an inclined face 62, and a first wall face 17 extending to the front-side end of the inclined face 62. The fuel injection port 30a is positioned at the ramp part 60. The inclination angle θ relative to the first wall face 17 of the inclined face 62 is at least 13.5 degrees. The height by which the ramp part 60 protrudes from the first wall face 17 does not exceed one fifth of the height of the inlet of the combustor 12. Thus provided are a jet engine and a flying object in which the inclination angle of the inclined face of a ramp is made larger so as to promote the mixing of fuel and air and to allow for stable flame holding at the rear of the ramp.