Turbine Exhaust Case Plenum Cooling and Pressurization
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Solution Overview
Problem
Gas turbine engine exhaust system components, particularly the forward outer diameter ring and its plenum, face adverse pressure gradients and high temperatures leading to stress, wear, and short lifespans due to inadequate cooling and pressurization, resulting in undesirable hot gas inflow and thermal gradients.
Innovation Solution
A cooled turbine exhaust case assembly is introduced, featuring a forward outer diameter ring plenum that receives cooling gas through defined openings or a bent cooling sleeve assembly, with cooling air exiting through film cooling holes to provide film cooling and pressurize the plenum, reducing hot gas inflow and thermal gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the FODR plenum is not adequately pressurized, then the structure is simpler, but hot gas inflow increases causing thermal damage and component degradation
Solution Approach 1:
The patent employs pneumatic principles by introducing cooling gas through the turbine case into the FODR plenum to create positive pressure. This pressurization prevents hot gas inflow by maintaining a pressure differential that blocks reverse flow, solving the harmful effect without requiring complex mechanical barriers or seals.
Solution Approach 2:
The patent changes the pressure parameter within the FODR plenum by introducing cooling gas. This parameter change from atmospheric or negative pressure to positive pressure effectively prevents hot gas inflow. Additionally, the cooling gas temperature parameter is controlled to provide thermal protection while managing the thermal environment within the plenum.
2Temperature
If cooling gas is introduced to the FODR plenum, then thermal protection is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent utilizes film cooling holes that create a porous-like cooling effect. These holes allow cooling gas to escape and form a protective film along the FODR inner surface, providing thermal protection. The porous approach distributes cooling across multiple small openings rather than requiring large complex cooling structures, simplifying manufacturing.
Solution Approach 2:
The cooling gas acts as an intermediary substance between the hot gas flowpath and the FODR plenum. It absorbs thermal energy and carries it away, protecting the plenum and FODR from excessive temperatures. This intermediary approach avoids direct thermal contact and the need for complex thermal barriers or insulation systems.
3Productivity
If cooling openings are defined in the turbine case, then cooling efficiency is improved, but structural strength and pressure containment are compromised
Solution Approach 1:
The patent segments the cooling function from the primary structural function by locating cooling openings in the turbine case that feed into a dedicated FODR plenum. This segmentation allows the turbine case to maintain its structural integrity for pressure containment while the plenum serves as the cooling distribution system, eliminating the conflict between openings and structural strength.
Solution Approach 2:
The patent extracts the cooling gas distribution function from the turbine case structure by introducing cooling gas through the case wall into a separate FODR plenum. This extraction allows the turbine case to focus on its primary structural role while the plenum handles cooling distribution, resolving the contradiction between structural strength and cooling efficiency.
4Temperature
If the cooling gas flow path is optimized, then thermal protection is enhanced, but pressure cyclic oscillations increase
Solution Approach 1:
The patent incorporates feedback by using a slider seal plate that responds to pressure differential changes. When hot gas attempts to flow backward into the plenum, the negative pressure differential causes the slider to move and seal the gap, preventing hot gas intrusion. This feedback mechanism maintains thermal protection while dampening pressure oscillations through active response to pressure changes.
Solution Approach 2:
The patent employs dynamic elements including the movable slider seal plate and adjustable cooling gas flow. The slider dynamically adjusts its position based on pressure conditions, and the cooling gas flow rate can be modulated to optimize thermal protection while managing pressure oscillations. This dynamic approach allows the system to adapt to varying operating conditions rather than being fixed.
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
The solution effectively reduces hot gas inflow, attenuates pressure cyclic oscillations, and limits thermal gradients, thereby extending the lifespan of engine components and reducing maintenance costs by providing comprehensive cooling and pressurization of the turbine exhaust case assembly.
Implementation Method 1
a cooling gas flow is introduced to a forward outer diameter ring (FODR) plenum
Implementation Method 2
cooling gas can be introduced to the FODR plenum through one or more cooling openings defined in a turbine case
Implementation Method 3
one or more cooling holes can be defined in a forward region of the FODR for allowing cooling air to exit the FODR plenum to a hot gas flowpath of the engine in order to provide film cooling
Implementation Method 4
Adequate pressurization of a FODR plenum at the hot gas flowpath can prevent undesirable inflow of hot gases into the FODR plenum
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
A cooled turbine exhaust case assembly (14) includes a plenum (24) defined at least in part by a forward outer diameter flowpath ring (16) and a turbine case (12), a probe (26) positioned at a probe opening (28) formed in the forward outer diameter flowpath ring, and an inlet opening (40) in the turbine case (12) for introducing cooling air to the plenum (24).