Bearing Chamber Seal Ejector Switching During Engine Starting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
During gas turbine engine starting, the lower air pressure from the compressor bleed can reverse the pressure differential across bearing chamber seals, leading to oil leakage from the chamber.
Innovation Solution
A sealing air system that switches the motive fluid supply to the ejector from the starter air system during starting, ensuring a higher pressure is maintained across the bearing chamber seal, using a switching mechanism to connect the starter air system with the ejector and compressor, and optionally includes an air/oil separator to minimize oil entrainment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If compressor bleed air is used to supply sealing air during engine starting, then the sealing air system is simple, but the air pressure may be lower than chamber pressure causing oil leakage
Solution Approach 1:
The ejector is designed to accept motive fluid from multiple sources (starter air system during starting, compressor bleed air during normal operation). This multi-functionality allows the same sealing mechanism to operate reliably across different engine conditions without requiring completely separate systems for each operating phase.
Solution Approach 2:
The ejector acts as an intermediary device that converts motive fluid pressure into a vacuum effect to maintain positive pressure differential across the seal. By using the ejector as a mediator, the system can effectively utilize lower pressure starter air during starting while still achieving reliable sealing, and then transition to direct compressor bleed air usage during normal operation.
2Reliability
If ejector is used to pump sealing air during starting, then positive pressure drop is maintained, but device complexity increases
Solution Approach 1:
The ejector serves multiple functions: during starting it creates vacuum to maintain seal pressure differential, and during normal operation it can be bypassed or used in a different configuration. This multi-functionality justifies the added complexity by providing reliable sealing across all operating conditions with a single component.
Solution Approach 2:
The system changes operational parameters by switching the source of motive fluid based on engine operating conditions. During starting, high-pressure starter air is used as motive fluid; during normal operation, lower-pressure compressor bleed air suffices. This parameter change allows the ejector to be effective during critical starting phases while maintaining simplicity during routine operation.
3Productivity
If air vent duct allows oil to escape, then sealing air can be vented, but oil loss occurs
Solution Approach 1:
The air/oil separator is positioned specifically in the air vent duct where oil-contaminated sealing air needs to be removed. This localized quality improvement targets only the vented air stream, allowing efficient oil removal from the vent path while maintaining proper lubrication in the bearing chamber. The separator creates a local purification zone without affecting the overall sealing function.
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
Maintains a positive pressure drop across the bearing chamber seal at all engine conditions, including during starting and cranking, reducing oil leakage and the amount of lubricant required, while ensuring clean air exhaust.
Implementation Method 1
an ejector located within the air vent duct to pump sealing air from the bearing chamber seal and through the air vent duct
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A gas turbine engine sealing air system comprising a bearing chamber seal to prevent lubricant fluid loss from a fluid chamber, the sealing effected by ingress of sealing air. The system comprises an air vent duct coupled to the bearing chamber seal. An ejector is located within the air vent duct to pump sealing air from the bearing chamber seal and through the air vent duct. A first duct is coupled between a starter air system of the gas turbine engine and the ejector to provide motive fluid to the ejector during gas turbine engine starting.