Browsing by Author "Tepe, AU"
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Web of Science Effects of Extended Jet Holes to Heat Transfer and Flow Characteristics of the Jet Impingement Cooling(2019.01.01) Tepe, AU; Arslan, K; Yetisken, Y; Uysal, UWeb of Science Experimental and numerical investigation of jet impingement cooling using extended jet holes(2020.01.01) Tepe, AU; Yetisken, Y; Uysal, U; Arslan, KWeb of Science Publication Improvement of film cooling effectiveness on a flat surface subjected to streamwise pressure gradient by using ramp(2021-05-01) Tepe A.Ü.; Tepe, AUIn this study, a numerical study was performed to elucidate the influence of triangular with concave edge shaped (TCES) ramp on film cooling effectiveness (FCE) and flow characteristics. Since the turbine airfoil subjects to the streamwise pressure gradient (SPG) in real operating conditions, the influence of various SPG in which acceleration parameters (K) are −1.20 × 10−6, 0, 0.45 × 10−6, 0.8 × 10−6, 1.50 × 10−6 and 2.13 × 10−6 on FCE were investigated comprehensively. Numerical computations were carried out with various blowing ratio (M) including 0.40, 0.85, 1.00 and 1.25 to explore the performance of TCES on FCE under different blowing ratio. On the other hand, three different ramp locations on the surface were investigated to evince the optimum design parameter of the TCES ramp. Results were compared with the baseline case. Air was used as the hot gas flow for the turbine airfoil and CO2 was assumed to be the coolant flow to simulate the real operation condition of the turbine. Therefore, corresponding density ratio of the fluids is DR = 1.50. Numerical simulations were performed using SST k-ω with low-Re correction turbulence model. Flow characteristics and area-averaged, laterally-averaged, longitudinally-averaged FCE were investigated quantitatively. Results showed that mounting TCES ramp on the surface has a great potential for the enhancement of FCE by forming a pair of anti-CRV on the flow that counteracts the detrimental effect of CRV on FCE. Hereby, area-averaged FCE enhanced 435.15% using upstream TCES ramp (Case2) at K = 0.45 × 10−6 and M = 1.25 compared to the baseline case. On the other hand, the favorable pressure gradient (FPG) contributed to the enhancement of FCE by tilting jet stream towards the wall. Consequently, upstream TCES ramp was the best design for laterally spreading the coolant and showed the best performance for thermal protection of turbine airfoil from the hot working fluid compared to other cases.Web of Science Jet impingement cooling on a rib-roughened surface using extended jet holes(2020.01.01) Tepe, AU; Uysal, U; Yetisken, Y; Arslan, KPublication Numerical investigation of a novel jet hole design for staggered array jet impingement cooling on a semicircular concave surface(2021-04-01) Tepe A.Ü.; Tepe, AUStaggered array jet impingement cooling (JIC) on a semi-circular concave surface has investigated numerically. The main objective of this work is to examine elongated jet holes on heat transfer and flow characteristics of the staggered array JIC and to elucidate its applicability on cooling of a turbine blade. Jet holes were elongated to the target surface by the nozzles. Numerical computations were performed with different jet Reynolds numbers (5000≤Re≤25000), normalized confinement plate-to-target plate distances (1.0≤H/d≤8.0) and jet nozzle-to-target plate gap (0.5≤G/d≤6.0). Average Nusselt (Nu) number, local Nu number distributions on the surface, flow characteristics and Thermal Performance Factor (TPF) were comprehensively investigated. Numerical results were compared with the normal staggered array JIC. Results showed that local Nu number and average Nu number increases with decreasing G/d. The highest enhancement of heat transfer using elongated jet hole is obtained as 20.16% by decreasing G/d to 0.5 at H/d = 8.0. However, highest TPF is estimated as 1.11 at H/d = 8.0 by G/d = 2.0 for Re = 25,000. Decreasing of G/d provides more uniform heat transfer on the surface of interest in comparison with normal staggered array JIC. Consequently, elongating jet hole is a feasible heat transfer enhancement design for the staggered array JIC on a semicircular concave surface.