Effect of Coolant Injection on Heat Transfer for a Simulated Turbine Airfoil Leading Edge

Abstract

This paper presents an experimental study of the heat transfer on the leading edge of a simulated film cooled turbine airfoil. Previous studies have shown that use of film cooling on the leading edge of an airfoil can significantly increase the heat transfer coefficients around the leading edge which counter-acts the benefits of the adiabatic effectiveness provided by the coolant film. These heat transfer results complement our earlier study of the adiabatic effectiveness for this leading edge and film cooling hole geometry. Heat transfer and adiabatic effectiveness results were combined to determine the overall performance of the film cooling in terms of the net heat flux reduction. Heat transfer coefficients were found to be significantly increased by the film cooling flow in a narrow region which followed the path of the coolant flow. However, heat transfer coefficients were maximum to one side of the coolant jet, consistent with a streamwise vortex flow which is believed to be generated by the interaction of the mainstream with the coolant jet. Overall performance in terms of the net heat flux reduction was found to be unaffected by the large heat transfer coefficients in the vicinity of the holes, but was significantly diminished farther downstream.

CFD Predictions of Heat Transfer Coefficient Augmentation on a Simulated Film Cooled Turbine Blade Leading Edge

“…Two separate regions of high heat transfer coefficient were predicted computationally downstream of the off-stagnation holes whereas only one large region of elevated heat transfer coefficients is observed experimentally. Moreover the numerical prediction of the laterally averaged heat transfer coefficient augmentation exhibited good agreement for low blowing ratios with experimental data from Yuki et al (1998).…”

“…Since one of the purposes of the present study was to compare the computational prediction of heat transfer coefficients with experimental data, the geometry of the leading edge used in these simulations was identical to the computational study carried out by Dobrowolski et al (2009) and as close as possible to the physical model employed by Yuki et al (1998) and Johnston et al (1999). However it should be pointed out that these studies had a quarter circle model with a suction slot on the bottom whereas the present study used a half cylinder model.…”

“…The coolant mass flow was varied to match the average blowing ratio M desired. Finally the Reynolds number in these simulations (Re = 48,500) was somewhat different from the Reynolds number at which Yuki et al (1998) and Johnston et al A constant heat flux of was applied on the external surface of the leading edge. The local heat transfer coefficient was then computed using its definition:…”

“…In this section, computational predictions of the heat transfer coefficient augmentation were compared with experimental data from Yuki et al (1998) and Johnston et al (1999) because these studies are the only experimental data that had the same commonly used round hole configuration. However it should be acknowledged that their model was not a full leading edge thus this was not a perfect comparison.…”

“…York and Leylek (2002) conducted realizable k-ε heat transfer coefficient simulations on a leading edge model identical to the one used by Yuki et al (1998) and Johnston et al (1999), i.e. a quartercylinder with a flat afterbody.…”