Turbine Disc Cooling Air Control for Radial Clearance
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Solution Overview
Problem
Existing cooling methods in turbomachines reduce the absolute temperature level of turbine discs, leading to increased radial clearance and reduced performance, while also failing to maintain optimal thermal protection.
Innovation Solution
A turbine design with alternating annular rows of moving and fixed blades and an internal radially formed annular cavity, featuring a cooling air supply circuit with controlled airflow through internal and external orifices, allowing air to be directed into different zones based on operating conditions to balance cooling and performance requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling air is injected into the cavity to cool the turbine discs, then thermal protection of the discs is improved, but radial clearance at the blade tip increases and performance decreases
Solution Approach 1:
The cooling system is segmented into multiple independent air supply circuits, each with its own control means. The first circuit supplies cooling air to a first zone of the cavity, while the second circuit supplies cooling air to a second zone of the cavity. This segmentation allows independent control of cooling in different regions, enabling optimization of both thermal protection and performance by directing cooling air precisely where needed without excessive radial clearance increase.
2Reliability
If cooling air is drawn from the high-pressure compressor and routed to the turbine, then the risk of overheating is reduced, but the absolute temperature level and thermal expansion of the disc decrease leading to increased radial clearance
Solution Approach 1:
Different zones of the cavity receive cooling air with different characteristics. The first zone receives cooling air that provides thermal protection, while the second zone receives cooling air that maintains optimal temperature for minimizing radial clearance. This local differentiation of cooling quality allows simultaneous improvement of reliability and control of radial clearance by matching cooling intensity and temperature to the specific requirements of each zone.
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 actively regulates airflow to prioritize either cooling or performance, optimizing thermal protection and reducing radial clearance, thereby maintaining turbomachine efficiency.
Implementation Method 1
a cooling air supply circuit for the internal annular cavity, the downstream end of the supply circuit comprising an internal annular row of orifices and an external annular row of orifices opening into the internal radially formed annular cavity
Implementation Method 2
These control means thus achieve an acceptable compromise between cooling requirements and turbomachine performance requirements. The control systems inject cooling air that directly or indirectly impacts the discs. Air directly impacting the discs will be cooler than air indirectly impacting them, due to the heat the discs receive from contact with the cavity components through the recirculation loops.
Data Source
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AI summary
A turbine (1) for a turbomachine of longitudinal axis (X), comprising: an alternating arrangement of annular rows of movable blades (64) and of fixed blades (65) and a radially inner annular cavity (68) formed radially inside the movable and fixed blades (64, 65), and a supply circuit (32) for supplying cooling air to the inner annular cavity (68), the downstream end of the supply circuit (32) comprising an inner annular row of orifices (81) and an outer annular row of orifices (82) opening into the radially inner annular cavity (68), the turbine further comprising means (85) for controlling the flow rate of supply air to the orifices of the inner and outer annular rows of orifices (81, 82).