Date of Defense
28-10-2025 11:00 AM
Location
Room 1043, F1 Building
Document Type
Dissertation Defense
Degree Name
Doctor of Philosophy in Mechanical & Aerospace Engineering
College
College of Engineering
Department
Mechanical and Aerospace Engineering
First Advisor
Dr. Mahmoud Elgendi
Keywords
Turbine Blade; Leading Edge Cooling; Jet Impingement; Inlet Geometry; impingement Jet Diameter; Swirl Cooling; Inline and Staggered Multiple Outlets
Abstract
Gas turbine blades operate in extreme environments, exposed directly to high-temperature combustion gases that cause severe thermal stresses, weaken material integrity, and may lead to structural failure. Proper cooling is crucial to lower blade temperatures, reduce thermal stresses, prevent failure, and improve overall engine efficiency. This work presents a detailed numerical study of various cooling configurations by applying two advanced leading-edge cooling methods, jet impingement and swirl cooling, across different inlet mass flow rates and jet Reynolds numbers (Rej) ranging from 1,000 to 20,000 to evaluate their cooling performance.
Several advanced leading-edge cooling configurations are proposed and compared with the conventional single-outlet design. A multiple outlets impingement configuration with a return channel addresses the limitations of the single outlet approach by reducing jet interference, improving flow distribution, and enhancing both heat transfer and overall cooling effectiveness. The maximum surface temperature decreases from 345 K and 460 K (single outlet) to 338 K and 425 K (multiple outlets) at Rej = 10.47×10³ and 1.047×10³, respectively. At Rej = 10.47×10³, the maximum Nusselt number (Nu) on the surface with multiple outlets exceeds that of the single outlet case by 56% near the center of the leading edge, 44% in the mid-downstream region, and 28% near the top region.
To address practical installation considerations, the investigation also examines how inlet adapters in leading-edge configurations impact cooling performance. Two inlet designs, one with a rectangular entrance without an adapter and the other similar one with an adapter, are evaluated under identical conditions. The circular adapter, while beneficial for alignment and sealing, causes uneven local heat transfer and broadens the distribution of Nu, whereas the rectangular inlet provides more uniform cooling. With the adapter, only 4–5% of the total mass flow enters the first jet at the start of the leading edge, while 12–13% enters the next jet at both Rej. Additionally, at Rej = 1.047×10⁴, the adapter increases the maximum surface temperature by 7% (from 339.5 K to 364 K) and decreases the maximum and average Nu by 1.6% and 1%, respectively. The inlet adapter study further examines how tapered and straight impingement jet geometries affect mass flow distribution, heat transfer, and internal flow behavior. The findings show that tapering has a more substantial impact at lower Rej, where it improves upstream jet utilization and local heat transfer by enhancing flow attachment. At Rej = 5×10³, the tapered configuration allowed 6.4% and 15% of the total mass flow through the first two jets, compared to 5.9% and 13.5% in the straight configuration, and achieved a 6.5% higher peak Nu for the tapered jet. These differences decrease at Rej = 10 × 10³, where both geometries demonstrate nearly identical results, indicating that tapering's effect is less significant at higher flow momentum. The results highlight the importance of optimizing adapter configurations, with recommended angles between 10° and 20°, for effective momentum diffusion and uniform flow distribution. This novel target-based optimization concept, analogous to a targeted therapy approach, is introduced to enhance leading-edge cooling by adaptively modifying only the geometrically affected regions identified through flow and heat transfer analysis.
Building on these findings, the study demonstrates the advantages of multiple outlets with swirl cooling and evaluates their thermal performance. The research further extends the concept of multiple outlets to three swirl jet configurations: inline, staggered, and inline with separation walls. Results show that the first outlet is highly sensitive to geometry, with the staggered configuration reducing flow by up to 35.8% compared to the inline configuration. In contrast, the walled configuration increases flow by up to 50% relative to the inline configuration without walls. Meanwhile, the last outlet experiences almost no change in the staggered case but decreases by 16.4% in the walled case at Rej = 5×10³. At Rej = 20×10³, the increase is significant (23.71% in staggered, 4% in walled). These patterns suggest that staggered jets redistribute coolant toward the far downstream outlet, while the walls redirect the flow to maintain balance across the outlets.
These findings provide clear design guidelines for next-generation turbine blade leading-edge cooling, highlighting the benefits of multiple outlets configurations and optimized inlet geometries for enhanced durability and fuel efficiency in high-performance gas turbines.
Included in
JET IMPINGEMENT AND VORTEX/SWIRL COOLING OF DIFFERENT INLET AND OUTLET GEOMETRICAL CONFIGURATIONS FOR TURBINE BLADE LEADING EDGE COOLING
Room 1043, F1 Building
Gas turbine blades operate in extreme environments, exposed directly to high-temperature combustion gases that cause severe thermal stresses, weaken material integrity, and may lead to structural failure. Proper cooling is crucial to lower blade temperatures, reduce thermal stresses, prevent failure, and improve overall engine efficiency. This work presents a detailed numerical study of various cooling configurations by applying two advanced leading-edge cooling methods, jet impingement and swirl cooling, across different inlet mass flow rates and jet Reynolds numbers (Rej) ranging from 1,000 to 20,000 to evaluate their cooling performance.
Several advanced leading-edge cooling configurations are proposed and compared with the conventional single-outlet design. A multiple outlets impingement configuration with a return channel addresses the limitations of the single outlet approach by reducing jet interference, improving flow distribution, and enhancing both heat transfer and overall cooling effectiveness. The maximum surface temperature decreases from 345 K and 460 K (single outlet) to 338 K and 425 K (multiple outlets) at Rej = 10.47×10³ and 1.047×10³, respectively. At Rej = 10.47×10³, the maximum Nusselt number (Nu) on the surface with multiple outlets exceeds that of the single outlet case by 56% near the center of the leading edge, 44% in the mid-downstream region, and 28% near the top region.
To address practical installation considerations, the investigation also examines how inlet adapters in leading-edge configurations impact cooling performance. Two inlet designs, one with a rectangular entrance without an adapter and the other similar one with an adapter, are evaluated under identical conditions. The circular adapter, while beneficial for alignment and sealing, causes uneven local heat transfer and broadens the distribution of Nu, whereas the rectangular inlet provides more uniform cooling. With the adapter, only 4–5% of the total mass flow enters the first jet at the start of the leading edge, while 12–13% enters the next jet at both Rej. Additionally, at Rej = 1.047×10⁴, the adapter increases the maximum surface temperature by 7% (from 339.5 K to 364 K) and decreases the maximum and average Nu by 1.6% and 1%, respectively. The inlet adapter study further examines how tapered and straight impingement jet geometries affect mass flow distribution, heat transfer, and internal flow behavior. The findings show that tapering has a more substantial impact at lower Rej, where it improves upstream jet utilization and local heat transfer by enhancing flow attachment. At Rej = 5×10³, the tapered configuration allowed 6.4% and 15% of the total mass flow through the first two jets, compared to 5.9% and 13.5% in the straight configuration, and achieved a 6.5% higher peak Nu for the tapered jet. These differences decrease at Rej = 10 × 10³, where both geometries demonstrate nearly identical results, indicating that tapering's effect is less significant at higher flow momentum. The results highlight the importance of optimizing adapter configurations, with recommended angles between 10° and 20°, for effective momentum diffusion and uniform flow distribution. This novel target-based optimization concept, analogous to a targeted therapy approach, is introduced to enhance leading-edge cooling by adaptively modifying only the geometrically affected regions identified through flow and heat transfer analysis.
Building on these findings, the study demonstrates the advantages of multiple outlets with swirl cooling and evaluates their thermal performance. The research further extends the concept of multiple outlets to three swirl jet configurations: inline, staggered, and inline with separation walls. Results show that the first outlet is highly sensitive to geometry, with the staggered configuration reducing flow by up to 35.8% compared to the inline configuration. In contrast, the walled configuration increases flow by up to 50% relative to the inline configuration without walls. Meanwhile, the last outlet experiences almost no change in the staggered case but decreases by 16.4% in the walled case at Rej = 5×10³. At Rej = 20×10³, the increase is significant (23.71% in staggered, 4% in walled). These patterns suggest that staggered jets redistribute coolant toward the far downstream outlet, while the walls redirect the flow to maintain balance across the outlets.
These findings provide clear design guidelines for next-generation turbine blade leading-edge cooling, highlighting the benefits of multiple outlets configurations and optimized inlet geometries for enhanced durability and fuel efficiency in high-performance gas turbines.