Numerical investigation of heat transfer in generic gas turbine blade with impingement cooling under high crossflow effect

Abstract

Gas turbines have been among the most transformative thermal machines since the mid-20th century, playing a central role in aviation, power generation, and industrial energy systems. Following the rapid technological progress after World War II, gas turbines became indispensable due to their high power-to-weight ratio, continuous-flow operation, operational reliability, and compact structural design. Over time, advancements in aerodynamic design, materials science, and combustion technology have enabled these systems to operate at increasingly demanding conditions. Today, gas turbines are widely utilized in Aerospace Engineering and energy production sectors, where continuous improvements in efficiency and performance remain primary objectives. A key parameter governing gas turbine performance is the turbine inlet temperature. Increasing this temperature directly enhances thermodynamic cycle efficiency and specific power output. However, this improvement comes at the expense of significantly elevated thermal loads on turbine components, particularly rotor blades and stator vanes. These components are subjected to extreme temperature gradients, high thermal stresses, and aggressive environmental conditions, which may lead to degradation mechanisms such as thermal fatigue, oxidation, corrosion, and creep. Consequently, the development of advanced cooling strategies, along with high-temperature-resistant materials and thermal barrier coatings, has become essential for ensuring component durability and operational safety. In addition to thermal considerations, modern gas turbine systems must also meet stringent requirements related to aerodynamic efficiency, fuel consumption, and emission reduction. These multi-objective design constraints necessitate a highly integrated approach, where thermal management, structural integrity, and aerodynamic performance are simultaneously optimized. As gas turbine technology continues to evolve toward higher operating temperatures and more compact configurations, the importance of efficient and reliable cooling techniques becomes increasingly pronounced. Among various internal cooling techniques, jet impingement cooling has gained significant attention due to its ability to produce very high local heat transfer coefficients, particularly in stagnation regions where the cooling jet directly impacts the surface. This characteristic makes it especially suitable for critical regions such as the leading edge of turbine blades, where heat fluxes are highest and geometric constraints limit the use of alternative cooling approaches. The effectiveness of impingement cooling is primarily attributed to strong jet momentum, intense turbulence generation, and thin thermal boundary layers formed at the impingement zone. Nevertheless, in realistic gas turbine environments, impinging jets are rarely isolated. Instead, they interact with a crossflow that develops within the cooling passage as the coolant progresses downstream. This crossflow introduces significant complexity into the flow field by deflecting the jet trajectory, weakening the stagnation region, and altering the overall heat transfer distribution. Furthermore, the interaction between the jet and crossflow leads to the formation of shear layers, vortical structures, and enhanced turbulence in the wall-jet region. These effects collectively result in a substantial deviation from classical impingement behavior, making the prediction of heat transfer characteristics considerably more challenging. Therefore, a detailed understanding of jet–crossflow interaction mechanisms is essential for the accurate design and optimization of turbine blade cooling systems. The present study provides a comprehensive numerical investigation of internal heat transfer characteristics in a generic gas turbine blade passage cooled by jet impingement under high crossflow conditions. A three-dimensional computational fluid dynamics (CFD) model was developed using a Reynolds-Averaged Navier–Stokes (RANS) framework, incorporating a suitable turbulence model capable of resolving complex flow features such as jet deflection, flow separation, reattachment, and turbulence generation. Particular attention was given to accurately capturing near-wall flow behavior and its influence on convective heat transfer. To ensure the reliability of the numerical approach, the model was validated against experimental data available in the literature. Comparisons of local Nusselt number distributions and area-averaged values demonstrated strong agreement, confirming that the simulation framework is capable of accurately representing both the flow physics and thermal characteristics of the system. A detailed parametric study was conducted to evaluate the influence of key governing parameters, including jet Reynolds number (ReD), jet-to-surface distance (H/D), and jet-to-jet spacing (P/D). Simulations were performed under a high crossflow intensity of approximately 60%, representative of realistic operating conditions in gas turbine cooling passages. The investigated parameter ranges include ReD = 10,000–40,000, H/D = 1.4–5.3, and P/D = 2–8. This wide parameter space allows for a systematic assessment of both momentum-driven and geometric effects on heat transfer performance. Using the numerical dataset, an empirical correlation was developed to predict the Nusselt number as a function of ReD, H/D, and P/D. The proposed correlation exhibits high predictive accuracy, with a Mean Absolute Percentage Error (MAPE) of 3.72%, indicating excellent agreement with the simulation results. The power-law form of the correlation highlights the dominant role of jet Reynolds number, while also capturing the secondary influence of geometric parameters. The results clearly demonstrate that the jet Reynolds number is the primary parameter controlling heat transfer enhancement. Increasing ReD leads to stronger jet penetration, higher turbulence intensity, and more effective disruption of the thermal boundary layer, thereby significantly increasing the Nusselt number. Conversely, increasing the jet-to-surface distance (H/D) reduces the jet's momentum before reaching the surface, weakening the stagnation region and decreasing heat transfer performance. Similarly, increasing the jet spacing (P/D) reduces jet interaction and results in a less uniform and generally lower heat transfer distribution. Although both H/D and P/D have notable effects, their influence remains secondary compared to that of ReD. In conclusion, this study provides a detailed numerical framework and a robust empirical correlation for analyzing jet impingement cooling under high crossflow conditions. The findings offer valuable insights into the complex interaction mechanisms governing heat transfer in turbine blade cooling passages. The proposed correlation serves as a practical engineering tool for rapid performance estimation during preliminary design stages, while the numerical methodology establishes a strong foundation for further advanced investigations. Overall, this work contributes to the development of more efficient and reliable cooling strategies for next-generation gas turbine systems.