Ferrule Cascade Holes and Ribs for Turbine Combustor Flow Stability
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Solution Overview
Problem
Rich burn combustion systems in turbine engines experience instabilities in fuel and heat distribution due to swirler-induced effects, leading to high combustion hydrodynamics (P′4), exacerbated by the interaction of ferrule hole flow with primary vane air streams at high velocity.
Innovation Solution
A ferrule with a cascade of holes and ribs is employed to create low-energy vortex pairs, reducing flow instabilities by guiding airflow through channels with pins or protrusions that slow airflow velocity before it exits, minimizing interaction with primary vane airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ferrule hole flow interacts with primary vane air streams at high velocity, then mixing efficiency is improved, but flow instabilities and combustor dynamics (P′4) increase
Solution Approach 1:
The patent changes the velocity parameter of the ferrule hole flow by introducing airflow modifiers (pins or protrusions) that reduce the velocity of air exiting the ferrule holes. This parameter change allows the flow to mix with primary vane air streams more gently, reducing instabilities and combustor dynamics (P′4) while still achieving effective mixing.
Solution Approach 2:
The airflow modifiers (pins or protrusions) act as intermediaries between the ferrule hole flow and the primary vane air streams. These modifiers modify the flow characteristics by creating low-energy vortex pairs, which serve as a buffer that reduces the direct high-velocity interaction between the two air streams, thereby stabilizing the flow while maintaining mixing efficiency.
2Productivity
If high velocity airflow is used in the ferrule, then fuel-air mixing is enhanced, but interaction with primary vane air streams causes higher perturbation
Solution Approach 1:
The patent applies parameter changes by reducing the velocity of airflow exiting the ferrule holes through the use of airflow modifiers. This velocity reduction eliminates the harmful high-velocity interaction with primary vane air streams that causes flow perturbation, while still maintaining adequate fuel-air mixing through the modified flow pattern.
Solution Approach 2:
The patent converts the potentially harmful high-velocity flow into a beneficial low-velocity flow by using airflow modifiers. The modifiers transform the high-velocity stream into low-energy vortex pairs, which reduce flow perturbation and stabilizes the combustion process while still achieving effective fuel-air mixing.
3Power
If swirler induced instabilities are present, then combustion process is active, but fuel and heat distribution becomes unstable
Solution Approach 1:
The patent changes the flow velocity parameter by reducing it through airflow modifiers, which stabilizes the fuel and heat distribution in the combustion chamber. This parameter change reduces the swirler-induced instabilities while maintaining adequate combustion activity, achieving a balance between active combustion and stable distribution.
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 reduces flow instabilities within the venturi, achieving lower combustor dynamics (P′4) and improving the efficiency and durability of the fuel-air mixing system while meeting emission requirements.
Implementation Method 1
A ferrule with a cascade of holes and ribs is employed to create low-energy vortex pairs, reducing flow instabilities by guiding airflow through channels with pins or protrusions that slow airflow velocity before it exits
Data Source
AI summary
A ferrule in a fuel-air mixer assembly. The ferrule includes a body having (i) a plurality of channels having sidewalls, the plurality of channels leading to a corresponding plurality of exit openings, the plurality of channels configured to guide a first airflow therein and (ii) a plurality of cascade holes formed within the sidewalls of the plurality of channels and defining a plurality of passageways therein that are transverse to the plurality of channels. The ferrule also includes a plurality of airflow modifiers provided within the plurality of channels. The plurality airflow modifiers are configured to reduce a velocity of the first airflow when the first airflow exits through the plurality of exit openings and to generate low velocity vortex pairs to reduce interaction of the first airflow with a second airflow provided through primary vanes located downstream of the plurality of exit openings of the plurality of channels.