Twin Air Source Ejector for Gas Turbine Pressurizing Stability
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Solution Overview
Problem
Gas turbine engine pressurizing air systems experience fluctuations in bleed air temperature and pressure, causing transient thermal stresses and rubbing issues in engine components and seals due to varying engine operating conditions.
Innovation Solution
A twin-air source pressurizing air system is implemented, utilizing a low-pressure and high-pressure air source with an ejector or calibrated hole to mix air flows, ensuring a stable intermediate temperature and pressure by varying the energy distribution ratio, thereby reducing temperature variations in the mixed air supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If bleed air is extracted from a single compressor stage, then the system structure is simple, but the temperature and pressure of the bleed air fluctuate significantly under varying engine operating conditions
Solution Approach 1:
The patent divides the single bleed air source into multiple compressor stages (e.g., intermediate pressure stage and high pressure stage), each providing bleed air at different temperature and pressure levels. This segmentation allows the system to select or combine air from different stages to maintain stable output conditions despite varying engine operating conditions.
Solution Approach 2:
The patent changes the parameters (temperature and pressure) of the bleed air by extracting from different compressor stages. By selecting air from stages with different pressure ratios and temperatures, the system can compensate for fluctuations and maintain stable bleed air properties under varying engine conditions.
2Quantity of substance
If bleed air demand increases from a particular compressor stage, then more air is available for pressurizing purposes, but the air pressure and temperature delivered from that stage decrease
Solution Approach 1:
The patent merges bleed air from multiple compressor stages into a common pressurizing air system. When demand increases from one stage causing pressure and temperature drops, the system combines this with air from other stages to maintain overall pressure and temperature levels while satisfying the increased quantity demand.
3Power
If the engine operates at full power level, then more power is available, but the temperature and pressure of bleed air at compressor stages increase causing transient thermal stresses
Solution Approach 1:
The patent utilizes parameter changes by selecting bleed air from different compressor stages depending on engine operating conditions. At full power levels where thermal stress is a concern, the system can select air from stages with more favorable temperature characteristics or combine stages to achieve the required pressure while managing temperature effects.
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 provides relatively stable bleed airflows, reducing transient thermal stresses and rubbing in engine components and seals by maintaining consistent air supply conditions across varying engine operations.
Implementation Method 1
An ejector is located in a cavity in fluid communication with the high pressure source of air. The ejector has a motive flow inlet thereof in fluid communication with the cavity, a secondary flow inlet thereof connected to the low pressure source of air and an outlet thereof connected to a pressurized area of the engine for delivery of a mixed air flow from the high and low pressure sources of air thereto.
Implementation Method 2
The ejector has a motive flow inlet thereof in fluid communication with the cavity, a secondary flow inlet thereof connected to the low pressure source of air
Data Source
AI summary
A passive pressurizing air system for a gas turbine engine includes a flow path for directing an air flow having a low temperature and low pressure, extending through a cavity to a pressurized area of the engine. The cavity contains pressurized air having a high temperature and high pressure. An air flow mixing apparatus is provided for adding the pressurized air from the cavity into the flow path to provide a mixed air flow having an intermediate temperature and intermediate pressure.