Arrays of staggered pin fins are a typical geometry found in the trailing edge region of modern airfoils. If coolant is supplied by bleeding from the mid-section of the airfoil instead of provided through the root, the channel length is not long enough to reach a fully developed flow which is commonly found from the fifth row downstream.  This present study focuses on the developing section (four rows) of a staggered array with a height to diameter ratio of 2 and a spanwise and streamwise spacing of 2.5 respectively. Measurements are conducted at two Reynolds numbers of 10,000 and 30,000 based on the maximum velocity and pin diameter. Stereoscopic PIV is used to describe the flow field and turbulence characteristics in the wake of the first and third row pin. It is found that the dominating vortical structures depend highly on the Reynolds number. A transient thermochromic liquid crystal technique is used to obtain local heat transfer coefficients on the endwall which are then discussed in the context with the vortical structures. It is well known that RANS simulations fail to accurately predict the turbulence production and destruction in such pin fin arrays. A large eddy simulation is validated through the experimental results and directly compared to the RANS results. Through the local comparison of turbulence production, destruction, turbulent kinetic energy, velocity profiles in the wake and in between the pins conclusions are made on the physical shortcomings of the RANS results and recommendations for mitigation are made. LES simulations are too expensive for design iterations in industry so that RANS is still used. The findings in this study help design engineers to make better physics-based design decisions.


Investigation of Endwall Heat Transfer in Staggered Pin Fin Arrays

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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