Browsing by Subject "Rib turbulators"
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Item Experimental measurements of conjugate heat transfer on a scaled-up gas turbine airfoil with realistic cooling configuration(2010-05) Dees, Jason Edward; Bogard, David G.; Clemens, Noel T.; da Silva, Alexandre K.; Ezekoye, Ofodike A.; Moser, Robert D.This study performed detailed measurements on and around scaled up conducting and adiabatic airfoils with and without film cooling. The conducting vane was a matched Bi airfoil, which accurately scaled the convective heat transfer and conduction through the solid, in order to produce non-dimensional surface temperatures and thermal boundary layers that were representative of an actual engine. Measurements made on all vane models included surface temperature measurements and thermal profiles above the walls. Separate measurements on non-film cooled and film cooled conducting models allowed for the individual contributions of the internal convective cooling and external film cooling to the overall cooling scheme to be quantified. Surface temperature and thermal field measurements above the wall were also performed on a film cooled adiabatic model. For the conducting model with internal cooling only, strong streamwise temperature variations were seen. The surface temperature variations were highly dependent on the local external and internal heat transfer coefficients. Spanwise temperature variations also existed, but were modest in comparison to streamwise variations. Comparing the thermal fields above the film cooled adiabatic and conducting walls allowed for the assumption that the conducting wall would not significantly affect the thermal field in the film cooling jet to be tested. Near the edge of the film cooling jet the developing thermal boundary layer had a clear effect on the overlying gas temperature, suggesting that the common assumption that the adiabatic wall temperature is the appropriate driving temperature for heat transfer to a film cooled wall was invalid. On the jet centerline thermal boundary layer effects were less influential, due to the development of a new, thin boundary layer. This suggested that the adiabatic wall temperature as driving temperature for heat transfer was a reasonable assumption on the jet centerline for most cases tested. As film cooling momentum flux ratio increase, thermal boundary layer effects became more influential on the jet centerline. Additionally, the high resolution surface temperature measurements and thermal field measurements above the wall presented in the current study represent a significant improvement in the data available for validation of computational simulations of conducting turbine airfoils.Item Heat Transfer Enhancement in Rectangular Channel with Compound Cooling Techniques(2013-11-27) Krad, BelalVarious compound internal cooling techniques were investigated in this experiment to see which combinations can offer the greatest heat transfer. Combinations of rib turbulators as well as pin0fins were used in different configurations in order to analyze heat transfer and pressure loss characteristics to determine which configuration had the overall best performance. Two different flow configurations were considered, a uniform channel flow setup as well as a jet impingement setup. There were a total of sixteen cases performed for the experiment, eight for the channel flow and eight for the jet impingement. The types of cases that were performed were: a smooth surface case, two cases of only copper rib turbulators (P/e ratios of 5 and 10), two cases of only copper pin0fins (P/e ratios of 5 and 10), and three cases of a combinations of copper rib turbulators and pin0fins (P/e ratios of 2.5, 5, and 10). All of the cases were performed at four different Reynolds numbers to explore the effect of Reynolds number on the heat transfer. In terms of the channel flow experiment, the results indicate that the all ribs case with a P/e ratio of 5 had the highest heat transfer coefficients but also produced the highest friction factor. If the total area is considered and not just the projected area, than the case of all pins P/e ratio of 10 is the best candidate due to its extensively low pressure drop and moderate heat transfer. In terms of the jet impingement experiment, none of the cases significantly enhanced heat transfer and many of them had results lower than the smooth case. The case of all pins P/e ratio of 5 performed the best out of all the rough cases but the case of all pins P/e ratio of 10 perform the best when taking into account the total surface area. Cross0flow contributed to the jet impingement results, lowering the local Nusselt number due to the bending of the jet beams in the low x/d regions but started increasing the local Nusselt number at further x/d due to the cross flow heat transfer.