Stator Heat Shield Cooling Units for Gas Turbines
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Solution Overview
Problem
Current stator heat shield cooling methods in gas turbines face challenges in achieving high heat transfer rates with low coolant consumption, particularly in large areas, due to limitations in convective cooling and impingement cooling systems, which result in reduced lifetime and efficiency.
Innovation Solution
The integration of impingement cooling with ribbed serpentine channels and small-scale cellular cooling units, featuring a spiral design and flow barrier elements, to enhance heat transfer while minimizing coolant consumption and pressure drops, covering the entire hot gas exposed surface of the stator heat shield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If extensive impingement cooling with cooling air discharged from side faces is used, then cooling effectiveness is improved, but coolant consumption increases significantly
Solution Approach 1:
The heat shield surface is divided into multiple discrete cooling zones, each with its own impingement cooling holes arranged in circular patterns. This segmentation allows localized cooling where most needed while reducing overall coolant consumption compared to uniform cooling of the entire surface.
Solution Approach 2:
Different regions of the heat shield receive different cooling intensities based on thermal exposure. The impingement cooling holes are strategically positioned and sized to provide higher cooling effectiveness at leading edges and other high-heat zones, while reducing coolant flow in lower-heat areas.
2Duration of action of stationary object
If cooling flow rates are increased to maintain acceptable lifetime, then heat shield lifetime is improved, but turbine and engine efficiency deteriorate
Solution Approach 1:
Cooling air is introduced through inlet openings in the inner heat shield before it contacts the hot gas-exposed outer surface. This preliminary cooling action pre-cools the air and heats the heat shield structure in advance, reducing the cooling demand during peak thermal exposure and maintaining lifetime without excessive coolant flow rates.
Solution Approach 2:
The cooling system operates continuously with cooling air flowing through inlet openings, across the cooling channels, and out through discharge openings. This continuous cooling action maintains stable heat shield temperatures and extends lifetime while operating at optimized coolant flow rates that preserve turbine efficiency.
3Temperature
If air to hot gas pressure ratio is increased by using air from higher compressor stages, then cooling effectiveness is improved, but turbine and engine efficiency deteriorate
Solution Approach 1:
The cooling system utilizes cooling air from lower compressor stages with lower pressure ratios, changing the operating parameters from conventional high-pressure-ratio cooling. This parameter change reduces the negative impact on engine efficiency while maintaining adequate cooling effectiveness through optimized impingement cooling hole geometry and arrangement.
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 configuration optimizes thermal performance, achieving uniform metal temperatures and stresses, extending the lifetime of stator heat shields while reducing coolant usage by 40% compared to traditional designs, maintaining high operation pressure ratios and heat transfer rates.
Implementation Method 1
a cooling air channel (24) formed in the outside part (21) with a first central portion (25) to receive the cooling air, and a second spiral portion (26) around the first central portion (25) to convey the cooling air outward to a cooling air outlet (27) of the second spiral portion
Implementation Method 2
the inside plate (22) comprises a plurality of inlet openings (23) formed through the inside plate to introduce the cooling air into the outside part (21), thereby impingement cooling of the outside part
Implementation Method 3
Cooling of stator heat shields, particularly of first stage is a very challenge task. Cooling effectiveness is limited to convective cooling scheme
Data Source
Figure 1~2
Figure 3~4f
Figure 5~6
AI summary
The present invention provides a stator heat shield (10) for a gas turbine, the gas turbine having a rotor defining an axis of rotation, the stator heat shield comprising a plurality of cooling units (20) disposed in array along the axis of rotation, each of the cooling units comprises an outside part (21) facing hot gas path of the gas turbine, and an inside plate (22) positioned on the outside part and exposed to cooling air, wherein the inside plate comprises a plurality of inlet openings (23) formed through the inside plate to introduce the cooling air into the outside part and thereby impingement cooling of the hot gas washed wall of the outside part , the outside part comprises a cooling air channel (24) formed therein with a first central portion (25) to receive the cooling air, and a second spiral portion (26) around the first central portion to convey the cooling air outward to a cooling air outlet of the second spiral portion.