Conjugate heat transfer analysis of the effects of impingement channel height for a turbine blade endwall

Abstract

Advancements in cooling for applications such as gas turbines components require improved understanding of the complex heat transfer mechanisms and the interactions between those mechanisms. Critical cooling applications often rely on multiple thermal protection techniques, including internal cooling and external film cooling in gas turbine airfoils, to efficiently cool components and limit the use of coolant. Most research to quantify the effectiveness of such cooling technologies for gas turbine applications has isolated internal and external cooling in separate experiments. The research presented in this paper uses a conjugate heat transfer approach to account for the combined effects of both internal and external cooling. The geometry used for this study is a turbine blade endwall that includes impingement and film cooling as well as the relevant conduction through the endwall. Appropriate geometric and flow parameters were scaled to ensure engine relevant dimensionless temperatures were obtained. Using the conjugate heat transfer approach, the effect of varying the height of the impingement channel was examined using spatially resolved external wall temperatures obtained from both experiments and simulations. A one-dimensional heat transfer analysis was used to derive the average internal heat transfer coefficients from the experimental results. Both experiments and simulations showed good agreement between area averaged cooling effectiveness and impingement heat transfer coefficients. The cooling effectiveness and heat transfer coefficients peaked for an impingement channel height of around three impingement hole diameters. However, the heat transfer coefficients were more sensitive than the overall effectiveness to the changes in height of the impingement channel.

Thermomechanical Analysis of Purging Plugs by Applying Fluid–Solid Conjugate Heat Transfer Modeling

“…A dimensionless instant temperature change Θ was calculated according to Equation to better visualize the instant temperature gradients in the purging plug every second.where t is the integer time in second and T is the temperature.…”

“…Therefore, conventional methods for defining heat transfer coefficients combined with constant environment temperatures at the macroscale are not applicable . Instead, the fluid–solid conjugate heat transfer method has the potential to provide instantaneous heat transfer coefficients along the interface for further thermal and thermomechanical modeling of solid parts . Lee investigated the thermal behavior in single‐phase flow through rectangular microchannels ranging in width from 194 to 534 μm for Reynolds numbers from 300 to 3500 .…”

“…[15,16] Instead, the fluid-solid conjugate heat transfer method has the potential to provide instantaneous heat transfer coefficients along the interface for further thermal and thermomechanical modeling of solid parts. [17][18][19][20][21] Lee investigated the thermal behavior in single-phase flow through rectangular microchannels ranging in width from 194 to 534 μm for Reynolds numbers from 300 to 3500. [22] He revealed that conjugate heat transfer modeling shows satisfactory agreement with experimental data, especially for 534 μm wide microchannels.…”

Modelling of heat transfer and fluid flow in the hot section of gas turbines used in power generation: A comprehensive survey

“…The majority of previous works related to conjugate heat transfer (CHT) models (eg, Starke et al, Montenay et al, Ni et al, Heselhaus, and Sun et al) has assumed steady flow conditions to study heat transfer and flow field characteristics. However, actual flow conditions inside turbines are often variable and unsteady.…”

“…In the loosely coupled method, different solvers are used for the fluid and solid regions. The heat flux at the blade and the fluid‐solid interface is established through an iterative exchange of the solution variables . Currently, both methods are used to simulate heat transfer within turbine components …”