Impingement Cooling Flow Diverters for Gas Turbine Ducts
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Solution Overview
Problem
Current impingement cooling methods for hot gas ducts in gas turbines face challenges in maintaining efficient heat transfer due to increasing cross-flow velocities and non-homogeneous heat loads, which divert impingement jets away from the duct wall, reducing cooling effectiveness and leading to hot spots.
Innovation Solution
The proposed impingement cooling arrangement incorporates flow diverters strategically placed within the cooling flow path to divert cross-flow away from apertures, maintaining consistent impingement density and heat transfer coefficients by managing flow velocity and area, using a combination of rib-like structures and angled or shaped diverters to optimize cooling air impingement on the duct wall.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of impingement rows is increased towards the end of the duct, then the cooling coverage is improved, but the cross flow in the cooling channel builds up and diverts impingement jets away from the duct wall, reducing heat transfer coefficients
Solution Approach 1:
The cooling channel is segmented into multiple sections with individual flow diverters placed at strategic locations. Each flow diverter creates a localized wake region that redirects cross-flow away from specific aperture rows, allowing impingement jets to maintain effectiveness throughout the duct length without being diverted by cumulative cross-flow effects
Solution Approach 2:
Flow diverters act as intermediary structures between the cross-flow and the impingement apertures. These diverters intercept the cross-flow and redirect it through wake regions, preventing the cross-flow from directly diverting the impingement jets away from the duct wall while still allowing the cross-flow to provide cooling
2Productivity
If the height of the cooling channel is increased to limit cross flow velocity, then the cross flow velocity is reduced, but the speed of the impingement jet reaching the duct wall is reduced, lowering cooling effectiveness
Solution Approach 1:
Flow diverters are placed at specific locations where cross-flow velocity becomes problematic, rather than uniformly throughout the entire duct. The diverters create localized wake regions that redirect flow only where needed, maintaining high impingement jet speeds in critical cooling zones while managing cross-flow velocity in specific problem areas
3Duration of action of stationary object
If cooling is increased at locations with higher heat load (hot spots), then the lifespan of duct components is extended, but the cross flow diverts impingement jets away from these critical areas, reducing cooling effectiveness where it is most needed
Solution Approach 1:
Flow diverters are positioned upstream of critical hot spot areas to preemptively redirect cross-flow away from aperture rows that would otherwise be affected. This preliminary redirection ensures that impingement jets reach hot spot locations with full effectiveness before cross-flow can divert them away
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 arrangement enhances heat transfer coefficients and maintains efficient cooling across the duct wall, reducing the impact of cross-flow velocities and ensuring consistent cooling, even in areas with higher thermal loads, thereby extending the lifespan of duct components.
Implementation Method 1
The impingement sleeve contains an array of holes through which compressed cooling gas discharge to generate an array of air jets which impinge on and cool the outer surface of the duct
Implementation Method 2
the injected air flows as cross flow towards one end of the duct
Implementation Method 3
at least one flow diverter is arranged in the cooling flow path to divert the cross flow away from at least one aperture
Data Source
AI summary
The present disclosure refers to an impingement cooling arrangement for cooling a duct wall of a duct guiding a hot gas flow. The impingement cooling arrangement includes an impingement sleeve which is at least partly disposed in a compressed air plenum, and spaced at a distance to the duct wall to form a cooling flow path between the duct wall and the impingement sleeve such that cooling air injected from the compressed air plenum through apertures in the sleeve impinges on the duct wall. At least one flow diverter is arranged in the cooling flow path to divert the cross flow away from at least one aperture. Besides the impingement cooling arrangement a gas turbine with such an arrangement as well as a method for cooling a duct wall are provided.