Combustor Effusion Holes for Dilution Zone Cooling
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Solution Overview
Problem
The local wake area of dilution openings in aircraft engine combustors becomes oxidized due to a lack of cooling and the presence of hot recirculating gas flow, reducing the durability of heat shields.
Innovation Solution
The combustor design incorporates effusion holes oriented to direct cooling air into the wake area of dilution jets, creating a cooling film on the hot side of heat shield panels, with some effusion holes extending through the inner skin at angles normal or opposite to the flow direction of combustion gases to counteract recirculating hot flows and prevent oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If effusion openings are positioned downstream of dilution openings to cool combustor components, then cooling efficiency is improved, but the wake area of dilution openings becomes oxidized due to lack of cooling
Solution Approach 1:
The effusion openings are divided into multiple rows: a first row positioned downstream of dilution openings for general cooling, and a second row positioned immediately downstream of dilution openings to specifically cool the wake area. This segmentation allows different regions to receive targeted cooling, preventing oxidation in the wake area while maintaining overall cooling efficiency.
Solution Approach 2:
Different rows of effusion openings provide different cooling characteristics to different regions. The second row of effusion openings provides enhanced cooling specifically to the wake area that is prone to oxidation, while the first row provides general cooling to the combustor components. This local differentiation ensures that the wake area receives adequate cooling protection.
2Quantity of substance
If dilution openings provide significant mass flow to dilute fuel-rich gas flow, then combustion control is improved, but the wake area becomes prone to oxidation due to hot recirculating gas flow
Solution Approach 1:
The hot recirculating gas flow that causes oxidation is counteracted by introducing cooling air through effusion openings positioned to directly cool the wake area. The cooling air creates a protective cooling film that converts the harmful hot recirculating flow into a cooled, less oxidizing environment, allowing the dilution openings to maintain their mass flow function without causing oxidation.
3Temperature
If effusion openings extend through outer or inner skins at shallow angles to cool components, then cooling efficiency is improved, but the design becomes more complex
Solution Approach 1:
The effusion openings are segmented into multiple rows with different orientations: the first row extends at shallow angles for efficient cooling, while the second row extends at angles normal to or opposite to the flow direction to specifically address the wake area. This segmentation allows each row to be optimized for its specific cooling function, maintaining overall cooling efficiency while managing design complexity through systematic arrangement.
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 effectively increases the lifespan of heat shields by providing localized cooling to areas prone to oxidation, enhancing the durability of combustor components.
Implementation Method 1
effusion openings may be used to direct air to cool combustor components such as combustor liners, domes and heat shields
Implementation Method 2
direct cooling air into the wake area of dilution jets, creating a cooling film on the hot side of heat shield panels
Implementation Method 3
The local wake area of the dilution openings downstream of these dilution openings may become oxidized due to a lack of cooling and the presence of a hot recirculating gas flow
Data Source
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AI summary
A combustor (16) of an aircraft engine comprises a liner (20) defining a primary and a dilution zone (32, 34) having a hot surface (26a, 26b) exposed to a flow of combustion gases traveling from the primary zone (32) downstream to the dilution zone (34) and a cold surface (26c, 26d). Dilution holes (36) extending through the liner (20) from the cold surface (26c, 26d) to the hot surface (26a, 26b) delimit the primary zone (32) from the dilution zone (34). Effusion holes (42) extending through the liner (20) from the cold surface (26c, 26d) to the hot surface (26a, 26b) direct cooling air (E) into the dilution zone (34). Two or more rows of effusion holes (42) positioned within three dilution hole diameters downstream of the dilution holes (36) are oriented relative to the liner (20) to direct the cooling air (E) in a cooling direction that is at least one of normal to the direction of the flow (D) of gases passing adjacent the effusion holes (42), and against the direction of the flow (D) of gases passing adjacent the effusion holes (42).