Gas Turbine Combustor Spool Thrust Reduction Via Cavity Venting
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Solution Overview
Problem
Gas turbine engines face a risk of bearing failure due to rapid temperature rise during a postulated loss of oil event, which reduces heat dissipation and leads to increased axial loads on the spool.
Innovation Solution
A spool thrust reduction system that includes a depressurizing seal assembly and a controller to form a continuous axial seal within the impeller inner cavity, venting gases to reduce pressure and maintain the seal, thereby reducing axial loads on the shaft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a loss of oil event occurs during operation, then heat dissipation in the thrust bearing assembly is significantly reduced, but this results in rapid rise in bearing temperature and potential bearing failure
Solution Approach 1:
The system applies preliminary anti-action by detecting the loss of oil event and immediately actuating the depressurizing seal assembly to form a continuous axial seal before the bearing temperature can rise to critical levels. This preventive measure isolates the impeller inner cavity, vents gases to reduce pressure, and thereby reduces axial loads on the bearing, preventing temperature rise rather than addressing it after occurrence.
Solution Approach 2:
The depressurizing seal assembly serves as an intermediary mechanism between the loss of oil event and the thrust bearing assembly. By forming a seal and venting gases, it mediates the reduction of axial loads on the bearing, which in turn reduces heat generation and prevents temperature rise, thus protecting the bearing without requiring direct cooling intervention.
2Force
If the depressurizing seal assembly forms a continuous axial seal about the impeller inner cavity, then axial loads on the shaft are reduced, but this requires actuation of the seal assembly to move the seal land
Solution Approach 1:
The depressurizing seal assembly is designed to be self-actuating through the loss of oil detection system. When oil loss is detected, the controller automatically actuates the seal assembly to move the seal land toward the downstream face of the impeller, forming the continuous axial seal. This self-service mechanism eliminates the need for manual intervention or complex external actuation systems.
3Stress or pressure
If the seal land forms a continuous axial seal about the impeller inner cavity, then gases are vented to decrease gas pressure, but this must be maintained while the gas turbine engine is operating
Solution Approach 1:
The system ensures continuity of useful action by maintaining the continuous axial seal formed by the depressurizing seal assembly throughout the duration of the loss of oil event. The controller continues to actuate the seal assembly to keep the seal land positioned against the downstream face of the impeller, ensuring uninterrupted gas pressure reduction and axial load mitigation for as long as the oil loss condition persists.
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 system extends the operating life of the thrust bearing assembly by minimizing temperature increase and thrust loads, allowing safe operation and potential safe landing of aircraft in case of a loss of oil event.
Implementation Method 1
vent gases from the impeller inner cavity to decrease a gas pressure in the impeller inner cavity
Implementation Method 2
thrust bearing assemblies are configured to mitigate axial loads on the spool(s)
Data Source
AI summary
Gas turbine engines and methods for reducing spool thrust in a combustor section thereof are provided. The engines include an impeller, a shaft coupled to the impeller, an inner cavity downstream of the impeller, a thrust bearing assembly mechanically coupled to the shaft, a seal assembly having a seal land, and a controller. The controller is configured to detect a loss of oil event to the thrust bearing assembly and, in response, actuate the seal assembly to move the seal land toward a downstream face of the impeller to form a continuous axial seal about the inner cavity, vent gases from the inner cavity to decrease pressure therein to an extent less than an operating gas pressure thereof, and maintain the axial seal and the pressure within the inner cavity and thereby reduce the axial loads on the shaft.