Turbine Casing Clearance Control via Impingement Cooling
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Solution Overview
Problem
Heavy-duty gas turbines face challenges in achieving uniform heat transfer coefficients across non-uniform casing surfaces, leading to high cooling air supply pressures and inefficiencies, as existing impingement cooling systems designed for small turbines are not feasible for larger, non-standard surfaces.
Innovation Solution
A system comprising an impingement cooling manifold attached to the turbine casing, a temperature sensing device, a blower, and a control system that determines and maintains a setting temperature to control clearance between turbine blades and the casing, using a controller to adjust air flow and coolant temperature for optimal cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If small impingement cooling holes are used to achieve higher heat transfer coefficients on the casing, then the heat transfer coefficient is improved, but the differential pressure drop across the holes increases resulting in high cooling air supply pressures which negatively impacts net efficiency
Solution Approach 1:
The patent applies different hole diameters in different regions of the impingement cooling manifold to match the non-uniform heat transfer requirements of the turbine casing. Larger holes are used in regions requiring lower heat transfer coefficients, while smaller holes are used in regions requiring higher coefficients, thereby achieving uniform overall cooling without excessive pressure drops.
Solution Approach 2:
The system dynamically adjusts the cooling air flow rate based on real-time temperature measurements from thermocouples positioned at multiple locations on the turbine casing. This dynamic control allows the system to maintain optimal heat transfer coefficients while minimizing the cooling air supply pressure and associated energy losses.
2Temperature
If air impingement cooling systems designed for small turbines are applied to heavy-duty gas turbines, then cooling capability is achieved, but uniform heat transfer coefficient cannot be achieved across large non-uniform non-standard casing surfaces
Solution Approach 1:
The impingement cooling manifold incorporates varying hole diameters and spacing patterns tailored to the specific geometry and thermal requirements of the heavy-duty turbine casing. This localized customization ensures uniform heat transfer coefficients across the large, non-uniform casing surfaces that cannot be adequately served by standard small-turbine designs.
Solution Approach 2:
The cooling manifold is divided into multiple zones with different hole configurations, each zone targeting a specific region of the turbine casing with its unique thermal characteristics. This segmentation allows precise control of heat transfer in each region, achieving overall uniformity across the entire casing surface.
3Temperature
If compressor extraction air is used as cooling medium in heavy-duty gas turbines, then cooling is provided, but the design heat transfer coefficients require cooler air temperatures which is not feasible
Solution Approach 1:
The system modifies the thermal parameters of the cooling air by pre-cooling it through heat exchangers or by selecting alternative air sources with lower temperatures. This parameter change enables the use of compressor extraction air or other available air sources to achieve the required heat transfer coefficients without requiring impractically low temperatures.
4Ease of operation
If clearance control is achieved by allowing higher or lower impingement cooling, then clearance control is possible, but the clearances cannot be easily measured using instrumentation in permanent installations
Solution Approach 1:
The system employs thermocouples positioned at strategic locations on the turbine casing to continuously monitor temperature. These temperature measurements provide indirect feedback about the clearance conditions, allowing the control system to adjust impingement cooling to maintain optimal clearances without requiring direct mechanical measurement instrumentation in the difficult-to-access permanent installation environment.
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 effectively controls clearance and maintains a uniform heat transfer coefficient, reducing air pressure requirements and improving efficiency by dynamically adjusting cooling based on casing temperature and operating conditions.
Implementation Method 1
Air impingement cooling has been used to manage the casing temperature of small gas turbines
Implementation Method 2
the blower forces air onto the impingement cooling manifold to cool the casing
Implementation Method 3
a temperature sensing device for determining the temperature of the turbine casing
Implementation Method 4
determining the setting temperature of the casing based on a transfer function... and modifying the temperature of the casing based on the setting temperature
Data Source
AI summary
A system for controlling the clearance between a turbine blade and the turbine casing that includes an impingement cooling manifold attached to a turbine casing, a temperature sensing device for determining the temperature of the turbine casing, a blower, a control system logic for determining the setting temperature of the casing, and a controller for controlling the blower, wherein the blower forces air onto the impingement cooling manifold to cool the casing towards the setting temperature and control the clearance.