Oxy-fuel Burner Bluff Bodies Flame Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing combustion burners face challenges in controlling flame length, particularly for laminar flames, which are prone to deflection and incomplete combustion due to low momentum and instability, leading to operational inefficiencies and potential damage from impinging on combustor walls.
Innovation Solution
The burner design incorporates multiple bluff bodies within the gas supply conduit at different axial positions to initiate and amplify turbulence, promoting a transition to turbulent flames at lower Reynolds numbers, thereby enhancing flame stability and control while minimizing pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple bluff bodies are added to the gas supply conduit to generate turbulence, then flame stability and turbulence are improved, but device complexity increases
Solution Approach 1:
The patent changes the flow regime parameter from laminar to turbulent by introducing bluff bodies, which fundamentally alters the flame stability characteristics. This parameter change enables stable combustion at lower velocities and prevents flame deflection, directly resolving the technical contradiction between maintaining simplicity and achieving reliability.
Solution Approach 2:
The bluff bodies act as intermediary elements that mediate between the gas supply and the flame. These intermediaries generate turbulence and prevent flame deflection without requiring complex control systems, thus improving flame stability while maintaining relatively simple device architecture.
2Loss of energy
If the burner operates in laminar flow regime, then pressure loss is minimized, but flame control and stability deteriorate
Solution Approach 1:
The patent intentionally transitions the flow regime from laminar to turbulent by introducing bluff bodies, accepting the associated pressure loss as a necessary trade-off for achieving reliable flame control. This parameter change fundamentally improves flame stability and prevents deflection, which cannot be achieved in laminar flow.
Solution Approach 2:
The patent converts the potentially harmful effect of pressure loss into a beneficial outcome by using the pressure drop across the bluff bodies to generate turbulence. This turbulence, while causing some pressure loss, ultimately improves flame stability and control, transforming the harmful pressure loss into a useful mechanism for flame stabilization.
3Length of moving object
If flame length is increased in laminar operation, then heat transfer coverage is improved, but flame deflection and incomplete combustion worsen
Solution Approach 1:
The patent changes the flow regime parameter from laminar to turbulent, which fundamentally alters the flame characteristics. In turbulent flow, the flame becomes shorter and more compact, but combustion completeness improves significantly due to enhanced mixing. This parameter change resolves the contradiction by achieving reliable combustion through a different mechanism rather than extending flame length.
Solution Approach 2:
The patent inverts the conventional approach of extending flame length to improve heat transfer coverage. Instead, it uses turbulence to create a shorter, more stable flame with better mixing, which achieves complete combustion and reliable operation. This inversion of the traditional approach resolves the technical contradiction between flame length and combustion completeness.
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 design ensures more efficient and controlled flame behavior, reducing soot formation and temperature stratification, and preventing premature failure of burner components by maintaining a turbulent flame regime, even at low firing rates, thus improving operational reliability and fuel efficiency.
Implementation Method 1
The use of multiple bluff bodies facilitates the diffusion of turbulence by initiation of eddies at multiple locations in the flow field, while the longitudinal spacing promotes amplification of turbulent effects emanating from each upstream bluff body
Implementation Method 2
Mixing in a laminar flame is governed by molecular diffusivity, a material property of the gases being mixed, while mixing in turbulent flames is driven by turbulent 'eddies.'
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A burner gas supply apparatus for increasing flame turbulence, the apparatus comprising a conduit having a characteristic width, W, defined by an inner surface having a circumferential direction and an axial direction, the axial direction terminating in a nozzle defining a nozzle exit plane and having a characteristic dimension, d, where d <= W; and three bluff bodies each with a characteristic dimension, Dbb-i, projecting a length, Li into the conduit from the inner surface, and an axial spacing Xi between adjacent bluff bodies (between the downstream bluff body and the nozzle exit plane in the case of X1) wherein 0.5 <= Li/W <= 1 and wherein Xi/Dbb-i <= 30.