Bearing-Chamber Pressure System for Gas Turbine Oil Leakage Control
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Solution Overview
Problem
In gas-turbine bearing chambers, pressure reversal during speed reduction or shutdown leads to oil leakage due to the inability of existing seals to manage negative pressure profiles, resulting in oil exiting through the seal, which is not effectively mitigated by current solutions relying on enhanced scavenging and reduced seal air pressure.
Innovation Solution
An additional vent valve is introduced in the bearing chamber to rapidly compensate for pressure differences, connected to a vent line, oil separator, or bypass duct, ensuring the internal pressure remains close to or below the seal air pressure, preventing flow reversal and oil leakage by opening when the pressure difference exceeds a certain value during speed reduction or shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If enhanced oil scavenging is implemented (larger scavenge pumps, improved collection devices), then oil removal capacity is improved, but device complexity and response speed during pressure reversal are insufficient
Solution Approach 1:
The vent valve is pre-configured with a pressure differential setting that automatically activates it during speed reduction or shutdown conditions. This preliminary setup allows the system to respond immediately when pressure reversal occurs, preventing oil leakage without requiring complex active control systems or larger scavenge pumps.
Solution Approach 2:
The vent valve acts as an intermediary component between the bearing chamber and the external environment (or oil separator). It mediates the pressure balance by opening to equalize pressure when reversal occurs, simplifying the overall system by replacing the need for enhanced scavenge pump capacity while still preventing oil leakage.
2Loss of substance
If seal air pressure is reduced to lower bearing chamber pressure, then oil leakage during speed reduction is improved, but the ability to maintain positive pressure during normal operation is worsened
Solution Approach 1:
The vent valve dynamically adjusts the bearing chamber pressure based on operating conditions. During normal operation, it remains closed maintaining positive pressure. During speed reduction or shutdown, it automatically opens to equalize pressure, providing dynamic pressure management that adapts to changing conditions without requiring continuous pressure reduction.
Solution Approach 2:
The system changes the pressure parameter in the bearing chamber based on operational state. The vent valve is set to activate at a specific pressure differential threshold, allowing the system to maintain different pressure levels during normal operation versus shutdown conditions, optimizing performance for each state.
3Reliability
If narrow bearing gaps with carbon seals are used, then seal capacity is improved, but the seal becomes incapable of withstanding negative pressure profiles during speed reduction
Solution Approach 1:
The vent valve provides preliminary anti-action by preventing the development of negative pressure profiles across the seal. It opens before significant pressure reversal can occur, equalizing pressures and protecting the carbon seal from conditions it cannot withstand, thereby preserving seal reliability during speed reduction.
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 prevents oil leakage and reduces oil consumption by ensuring minimal flow reversal across the seal, enhancing the oil scavenge system and maintaining a stable pressure environment within the bearing chamber, even during gas turbine shutdown or speed reduction.
Implementation Method 1
the valve can also be connected to an oil separator, or venting can be accomplished through the vent valve into a bypass duct... the vent valve according to the present invention can be a simple pressure-limiting valve set such that it will open when the difference between the pressure in the bearing chamber and the seal air pressure exceeds a minimum value
Data Source
AI summary
A gas turbine has a rear bearing chamber 2 including a bearing arrangement 1. A vent valve 14 vents the bearing chamber 2 as a function of relative pressure of the bearing chamber.