Auxiliary Compressor Cooling Air System for Gas Turbine Efficiency
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Solution Overview
Problem
Current gas turbine engines face efficiency losses due to the tapping of cooling air from the compressor section, which reduces overall engine performance and requires additional energy to pressurize the air for the turbine section, especially when air is tapped closer to the exit, where pressures and temperatures are higher.
Innovation Solution
An inter-stage cooled cooling air system that includes an auxiliary compressor driven by an electric motor, with heat exchangers to condition the air before delivery to the turbine section, allowing independent operation of the compressor speed and tailored airflow characteristics based on flight profiles and engine conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling air is tapped from the compressor section to supply the turbine section, then the turbine components are cooled to maintain operating temperatures, but the overall engine efficiency is reduced due to the loss of compressed air and additional energy required for pressurization
Solution Approach 1:
The cooling air system is segmented into multiple stages with separate control. Cooling air is tapped at different compressor stages (low pressure and high pressure compressors) and delivered to different turbine sections independently. This allows optimization of cooling air extraction points to minimize efficiency loss while ensuring adequate cooling of specific turbine components.
Solution Approach 2:
Heat exchangers are introduced as intermediary components between the compressor section and turbine section. These heat exchangers pre-cool the cooling air before it enters the turbine, reducing the thermal load on turbine components and allowing for more efficient cooling air management. The heat exchangers act as mediators that transfer heat from the cooling air to the bypass flow, improving overall system efficiency.
2Stress or pressure
If air is tapped closer to the compressor exit to provide cooling air, then the pressure and temperature of the cooling air are increased, but more energy is required to pressurize the air and overall engine efficiency is reduced
Solution Approach 1:
The compressor section is divided into low pressure and high pressure compressors with separate cooling air extraction points. This segmentation allows cooling air to be tapped at optimal pressure stages for different turbine sections, avoiding the need to compress all cooling air to maximum pressure and thereby reducing the energy required for pressurization.
Solution Approach 2:
The system changes the pressure parameters of cooling air by tapping at different compressor stages. Cooling air for the low pressure turbine is extracted at lower pressure points, while cooling air for the high pressure turbine is extracted at higher pressure points. This parameter optimization reduces the work required by the auxiliary compressor while maintaining adequate cooling air pressure at each turbine section.
3Device complexity
If the auxiliary compressor is driven mechanically from the compressor section, then the system is simpler, but the compressor speed cannot be independently controlled and airflow characteristics cannot be tailored to specific flight profiles
Solution Approach 1:
The mechanical drive system connecting the auxiliary compressor to the main compressor is replaced with an electric motor drive system. This substitution allows the auxiliary compressor to be controlled independently of the main compressor speed through electrical control, enabling tailored airflow characteristics for different flight profiles while maintaining reasonable system complexity through the use of electric motors and controllers.
Solution Approach 2:
The auxiliary compressor is designed with dynamic control capabilities through electric motor drive. The compressor speed and airflow can be dynamically adjusted based on flight conditions, engine operating parameters, and cooling requirements. This dynamic control allows the system to adapt to varying flight profiles and optimize cooling air delivery under different operating conditions.
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
This system enhances engine efficiency by optimizing cooling air pressure and temperature delivery to the turbine section, reducing energy losses and improving thermal and propulsive efficiencies by decoupling the auxiliary compressor speed from the main compressor speeds.
Implementation Method 1
a first heat exchanger within an inlet passage between the air tap and the inlet to the auxiliary compressor
Implementation Method 2
A second heat exchanger is disposed within an outlet passage between the outlet of the auxiliary compressor and the turbine section
Implementation Method 3
an auxiliary compressor configured to receive air from the air tap and discharge air to the turbine section
Data Source
Figure 1
Figure 2
AI summary
A gas turbine engine (20) includes a compressor section (24) including an aft most exit (66), an air tap (64) configured to draw air from a point upstream of the aft most exit (66), an auxiliary compressor (72) configured to receive air from the air tap (64) and discharge air to a turbine section (28), an electric motor (82) configured to drive the auxiliary compressor (72), a first heat exchanger (70) within an inlet passage (68) between the air tap (64) and an inlet (74) to the auxiliary compressor (72), and a second heat exchanger (80) disposed within an outlet passage (78) between an outlet (76) of the auxiliary compressor (72) and the turbine section (28).