Gas Turbine Cooling Air Control via Heat Exchanger
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Solution Overview
Problem
Gas turbine engines face challenges in efficiently delivering high-pressure cooling air to turbine blades, particularly due to increased pressures and temperatures resulting from gear reduction systems, which can lead to overheating and reduced turbine blade lifespan if cooling air is insufficiently pressurized or cooled.
Innovation Solution
A gas turbine engine design that includes a tangential on-board injector (TOBI) to deliver cooled air to turbine blades, with sensors measuring air pressure and temperature characteristics to control the cooling air flow through a heat exchanger and valve adjustments, ensuring adequate cooling before entering a low power mode if thresholds are exceeded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling air is tapped from high pressure location and passed through heat exchanger, then cooling effectiveness is improved, but system complexity and energy loss increase
Solution Approach 1:
The system performs preliminary cooling of the compression air before it enters the turbine section by passing it through a heat exchanger that utilizes cold air from the fan inlet. This advance cooling ensures that the air is already at an optimal temperature for turbine blade cooling, eliminating the need for additional cooling energy downstream and thereby reducing overall energy loss.
Solution Approach 2:
The patent introduces an intermediary heat exchanger system that mediates between the hot compression air and the cold fan inlet air. This intermediary device transfers thermal energy from the compression air to the cold air, effectively cooling the compression air without direct contact between the two air streams, thus achieving temperature reduction while managing energy transfer efficiently.
2Speed
If gear reduction is added between fan drive turbine and fan rotor, then fan speed control is improved, but pressures and temperatures in turbine sections increase
Solution Approach 1:
The system applies preliminary cooling to the compression air before it enters the high-temperature turbine section. By pre-cooling the air using the heat exchanger with cold fan inlet air, the overall temperature level in the turbine section is reduced, compensating for the temperature increase caused by the gear reduction system.
Solution Approach 2:
The patent changes the temperature parameter of the compression air by passing it through a heat exchanger where it is cooled by cold air from the fan inlet. This parameter change (temperature reduction) occurs before the air enters the turbine section, effectively managing the temperature increase that results from the gear reduction system.
3Stress or pressure
If sensor monitoring and valve adjustment are implemented, then cooling air pressure control is improved, but device complexity increases
Solution Approach 1:
The system implements a feedback control mechanism where a sensor continuously monitors the pressure of the cooled air after it leaves the heat exchanger. This pressure information is fed back to a controller that automatically adjusts the position of a valve to maintain the cooling air pressure within desired parameters, ensuring optimal cooling effectiveness while compensating for varying operating conditions.
Solution Approach 2:
The control system operates autonomously to maintain cooling air pressure without requiring external intervention. The sensor detects pressure deviations and the controller automatically adjusts the valve position to correct these deviations, enabling the system to self-regulate and maintain optimal cooling air pressure throughout varying 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 solution effectively maintains optimal cooling of turbine blades by adjusting cooling air flow based on measured characteristics, preventing overheating and extending blade lifespan by ensuring sufficient cooling air pressure and temperature are maintained.
Implementation Method 1
heat is removed from compressed air bled from the compressor section, for purposes of cooling in the turbine section, using a first heat exchanger to transfer heat from the cooling air to an intermediate fluid
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A gas turbine engine (20) includes a compressor section (24), a combustor (56), and a turbine section (28) having a high pressure turbine (54) comprising a plurality of turbine blades (130). The gas turbine engine (20) includes a tap (104) for tapping air that is compressed by the compressor section (24), to be passed through a heat exchanger (108) to cool the air, the cooled air to be passed to the plurality of turbine blades (130). A sensor (140) is located downstream of a leading edge of the combustor (56), and is configured to measure a characteristic of the cooled air. A controller (150) is configured to compare the measured characteristic to a threshold and control an operating condition of the gas turbine engine (20) based on the comparison.