Degradation of Film Cooling Performance on a Turbine Vane Suction Side Due to Surface Roughness

Rutledge, James L.; Robertson, David; Bogard, David G.

doi:10.1115/gt2005-69045

Cited by 12 publications

(11 citation statements)

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“…Roughness effects on the suction side of a simulated vane were investigated by Bogard et al 56 and Rutledge et al 57 Roughness upstream and downstream of a row of cylindrical holes was investigated independently, using an array of conical elements 0.25d in height. This roughness configuration was estimated to have an equivalent sand grain roughness Reynolds number of Re k ≈ 50 based on the boundary-layer flow approaching the coolant holes.…”

Section: H Surface Roughnessmentioning

confidence: 99%

Gas Turbine Film Cooling

Bogard

Thole

2006

Journal of Propulsion and Power

684

179

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The durability of gas turbine engines is strongly dependent on the component temperatures. For the combustor and turbine airfoils and endwalls, film cooling is used extensively to reduce component temperatures. Film cooling is a cooling method used in virtually all of today's aircraft turbine engines and in many power-generation turbine engines and yet has very difficult phenomena to predict. The interaction of jets-in-crossflow, which is representative of film cooling, results in a shear layer that leads to mixing and a decay in the cooling performance along a surface. This interaction is highly dependent on the jet-to-crossflow mass and momentum flux ratios. Film-cooling performance is difficult to predict because of the inherent complex flowfields along the airfoil component surfaces in turbine engines. Film cooling is applied to nearly all of the external surfaces associated with the airfoils that are exposed to the hot combustion gasses such as the leading edges, main bodies, blade tips, and endwalls. In a review of the literature, it was found that there are strong effects of freestream turbulence, surface curvature, and hole shape on the performance of film cooling. Film cooling is reviewed through a discussion of the analyses methodologies, a physical description, and the various influences on film-cooling performance. Dr. David Bogard is a Professor of Mechanical Engineering at the University of Texas at Austin, and holds the John E. Kasch Fellow in Engineering. He received his B.S. and M.S. degrees in mechanical engineering from Oklahoma State University, and his Ph.D. from Purdue University. He has served on the faculty at the University of Texas since 1982. Dr. Bogard has been active in gas turbine cooling research since 1986, and has published over 100 peer-reviewed papers. He was awarded the ASME Heat Transfer Committee Best Paper Award in 1990 and 2003, and is a fellow of the ASME. Dr. Karen Thole holds the William S. Cross Professorship of Mechanical Engineering at Virginia Polytechnic Institute and State University. She received her B.S. and M.S. degrees in mechanical engineering from the University of Illinois, and a Ph.D. from the University of Texas at Austin. She spent two years as a postdoctoral researcher at the Institute for Thermal Turbomachinery at the University of Karslruhe in Germany and in 1994 she accepted a faculty position at the University of Wisconsin-Madison. In 1999, she became a faculty member in the Mechanical Engineering Department at Virginia Polytechnic Institute and State University where she was promoted to professor in 2003. She received the National Science Foundation CAREER Award in 1996, which was directed at developing a better understanding of gas turbine heat transfer. Dr. Thole's areas of expertise are heat transfer and fluid mechanics specializing in turbulent boundary layers, convective heat transfer, and high freestream turbulence effects. She has published more than 80 peer-reviewed papers and has advised over 30 graduate theses.

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Section: H Surface Roughnessmentioning

confidence: 99%

Gas Turbine Film Cooling

Bogard

Thole

2006

Journal of Propulsion and Power

684

179

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“…This is because of the erosion, spallation and deposition as illustrated in Figure 22. Previous works on surface roughness done by Bogard et al [47] and Rutledge et al [48], though limited to their narrow set of test conditions, revealed that a rougher airfoil surface will lead to early boundary layer transition making it thicker which results in turbulent mixing in the boundary layer. Shown in Figure 24 it can be seen that the rougher configuration (gray) have lower effectiveness values at BR's of 0.3 and 0.7.…”

Section: The Effect Of Surface Roughness On Film Cooling Effectivenessmentioning

confidence: 98%

Dependence of Film Cooling Effectiveness on 3D Printed Cooling Holes

Aghasi

Gutmark

Munday

2016

Volume 5C: Heat Transfer

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Film Cooling Effectiveness is closely dependent on the geometry of the hole emitting the cooling film. These holes are sometimes quite expensive to machine by traditional methods so 3D printed test pieces have the potential to greatly reduce the cost of film cooling experiments. What is unknown is the degree to which parameters like layer resolution and the choice among 3D printing technologies influence the results of a film cooling test. A new flat-plate film cooling facility employing oxygen sensitive paint (OSP) verified by gas sampling and the mass transfer analogy and measurements both by gas sampling and OSP is verified by comparing measurements by both gas sampling and OSP. The same facility is then used to characterize the film cooling effectiveness of a diffuser shaped film cooling hole geometry. These diffuser holes are then produced by a variety of additive manufacturing technologies with different build layer thicknesses. Technologies used include Fused Deposition Modeling (FDM), Stereo Lithography Apparatus (SLA) and PolyJet with build layer thicknesses ranging from 0.001D (25 μm) to 0.12D (300 μm). These are compared with an aluminum coupon manufactured by traditional machining methods. The objective is to determine if cheaper manufacturing techniques afford usable and reliable results. Tests are carried out at mainstream flow Mach number of 0.30 and blowing ratios (BRs) from 1.0 to 3.5. The coolant gas used is CO2 yielding a density ratio of 1.5. Surface quality is characterized by an Optical Microscope that measures surface roughness. Test coupons with rougher surface topology generally showed delayed blow off and higher film cooling effectiveness at high blowing ratios compared to the geometries with lower measured surface roughness. At the present scale, none of the additively manufactured parts consistently matched the traditionally machined part, indicating that caution should be exercised in employing additively manufactured test pieces in film cooling work.

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“…The occurrence of these structures depends on local details of the geometry and flow conditions. Rutledge et al (2005) investigated the influence of surface roughness on the heat transfer. Upstream roughness enlarges the boundary layer thickness by a factor of three.…”

Section: Introductionmentioning

confidence: 99%