http://yetl.yabesh.ir/yetl1/handle/yetl/19061 2026-08-23T23:42:36Z http://yetl.yabesh.ir/yetl1/handle/yetl/4316945 Experimental Investigation of Mach Number Effect on Overall Cooling Effectiveness for a Transonic Vane Krull, Matthew R.; Lynch, Stephen P. Abstract. To keep metal temperature at allowable levels in modern gas turbine engines, both internal and external (film) cooling is necessary, which is represented by an overall cooling effectiveness. Previous studies measured overall cooling effectiveness for first-stage vanes in low-speed experiments, where it is appropriate to use the mainstream gas temperature as the hot fluid reference temperature. For better application to gas turbine operating conditions, the recovery temperature is applied. This arises due to the viscous dissipation within the boundary layer and accounts for local Mach number variation and the boundary layer state. To understand the influence of Mach number on overall effectiveness, a two-cavity fed metallic film-cooled vane with cylindrical showerhead, pressure side, and suction side film cooling rows was experimentally tested in a high-speed linear cascade at exit Mach numbers ranging from 0.7 to 1.1 and varying blowing ratios. Vane surface temperature measurements were obtained with infrared thermography. In addition to studies with both cavities flowing, a study of the superposition of overall cooling was performed for individual cavities. This study showed that cooling effectiveness did not significantly change with Mach number and that the principle of superposition for overall effectiveness can be applied to transonic film-cooled vanes. Additionally, the appropriate reference temperature for overall effectiveness was explored. While utilizing the recovery temperature as the reference temperature resulted in the collapse of overall effectiveness at subsonic Mach number, the inlet total temperature is a better reference temperature in cases where shocks are present. 2026-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4316941 Aerodynamic Interaction Between Main Annulus Flow and Injected Secondary Air in Transonic High-Pressure Turbine Stage Okita, Yoji; Kazawa, Junichi; Yamane, Takashi; Tanaka, Nozomi; Fuchigami, Kazutaka; Sato, Hiroki; Hamabe, Masaaki; Tanimitsu, Haruyuki Abstract. This study explored the effects of secondary air blowing on the main annulus flow field and the performance of a transonic high-pressure turbine (HPT) experimentally and numerically. The test section featured a single-stage, unshrouded turbine with a blading consistent with modern low aspect ratio HPTs. The full annular, rotating, continuous turbine test rig was used for the whole testing campaign. This resulted in the most accurate and unparalleled matching of the similarity parameters to reality for both the primary and secondary air streams. An elaborate secondary air system built into the hardware enabled it to simulate all the critical coolant/purge air streams typically found in advanced hot sections. Detailed three-dimensional flow field and efficiency measurements for various secondary air flowrates were conducted. A complete set of numerical simulations was conducted in parallel with testing to assess how effectively they capture the flow physics, particularly the interaction between the mainflow and ejected secondary air streams. The rotor exit survey in the experiment suggests that film-coolant ejection from stator vanes intensifies passage vortices in the cascade, especially at the hub. Rotor blade film-cooling and rotor forward purge air appear to have the same enhancing effect on rotor-induced passage vortices. However, the vortex intensity in the region of stator–rotor vortex interaction is not enhanced further or even suppressed. Blade coolant also appears to enhance tip leakage flow, which then reduces work extraction. The enhanced tip leakage discharges into the mainstream, boosting the tip clearance vortices. Coolant blown from the over-tip casing also appears to enhance the passage vortices at the tip; however, it also has a positive effect, diminishing the tip leakage vortices. 2026-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4316934 The Impact of Multiscale Ceramic Matrix Composite Roughness on Heat Transfer and Boundary Layer Behavior Wilkins, Peter H.; Lynch, Stephen P.; Thole, Karen A. Abstract. Ceramic matrix composites (CMCs) can enable more efficient gas turbines relative to traditional nickel alloys, resulting from enabling higher turbine entry temperatures that, in turn, benefit cycle performance. One negative effect of adding CMCs to the hot section is the introduction of a unique surface roughness due to the underlying weave topology. This surface roughness is generally at a macroscale compared with traditional turbine roughness, such as deposits or erosion, which are well known to interact with the boundary layer development and increase convective heat transfer. In this study, scales representative of traditional turbine roughness in combination with macroscale weave roughness are investigated for convective heat transfer augmentation and boundary layer behavior. In addition to investigating the impact of the CMC roughness scales, 5-harness satin and twill weave patterns are studied to understand the differences between weaves. Heat transfer measurements are conducted in scaled-up wind tunnel tests using a conjugate steady-state analysis with freestream turbulence intensities of 0.5% and 24%. Boundary layer behavior is measured using particle image velocimetry to capture cross-stream and streamwise planes. Compared to the 0-deg 5-harness satin surface, the twill surface has a higher Stanton number augmentation, owing to the increased number and high density of flow-facing features that disrupt the boundary layer. Additionally, the large-scale weave roughness and traditional small-scale turbine roughness act largely independent of one another. 2026-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4316931 Electrostatic Effects on Airborne Particle Deposition in Gas Turbine Engines Sabau, Tanner J.; Frith, Kyle H.; Bons, Jeffrey P. Abstract. The effects of electrostatics on the deposition of 0–5 µm Arizona Road Dust within a gas turbine hot section were studied. These experiments focused on different cooling methods found in turbine components: impingement cooling jets and double-walled cooling circuits. Particles within a flow can experience tribocharging through collisions with their surroundings: walls of passages and other particles. For the impingement cooling jet, dust was entrained with hot air through a 6.35-mm-diameter pipe at a mean velocity of 57 m/s. The gas temperature ranged from 755 K to 1005 K to test the temperature sensitivity of any electrostatic effects. The dust-laden jet impinges on a charged plate (−12 kV to +12 kV) to form a deposit. The effect of plate charge on the morphological characteristics of the deposit formation was assessed. For the double-walled cooling circuit, a charge (−5 kV to +5 kV) was applied to both the effusion interior and impingement exterior. Dust was entrained in an 810 K flow with a pressure ratio (PR) of 1.03. No significant electrostatic effect was observed for this geometry. These findings were supported by lower-temperature gravity-drop tests through charged parallel plates and a charged cylindrical pipe. The more fundamental tests confirmed that Arizona Road Dust particles tribocharge negatively and are attracted to positive potential surfaces. This effect appears to be augmented at higher temperature. The cylindrical gravity-drop confirmed that electrostatic influence diminishes due to the absence of electric field lines within enclosed geometries. 2026-01-01T00:00:00Z