Gas Turbine Blade Cooling
Jet Impingement Cooling
New cooling concepts, e.g., mesh cooling and double-wall cooling, allow coolant to be closer to hot gas, leading to higher heat transfer efficiency. In new cooling technologies, impingement cooling is an attractive method for the removal of heat loads because impingement jet cooling has relatively high effectiveness and can effectively adjust the amount of cooling air. We comprehensively illustrate the effect of Reynolds number, hole spacing, jet-to-target distance, hole inclination, and target wall thickness on the convective and conjugate heat transfer performance of a narrow impinging jet array.
Related publications:
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W. Li, L. Yang, X. Li, J. Ren, H. Jiang, and P. M. Ligrani, 2017, “Effect of Reynolds Number, Hole Patterns, and Hole Inclination on Cooling Performance of an Impinging Jet Array, Part I: Convective Heat Transfer Results and Optimization,” ASME Transactions-Journal of Turbomachinery, 139(4), p. 041002.
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W. Li, L. Yang, X. Li, J. Ren, H. Jiang, 2017, “Effect of Reynolds Number, Hole Patterns, Target Plate Thickness on Cooling Performance of an Impinging Jet Array, Part II: Conjugate Heat Transfer Results and Optimization,” ASME Transactions-Journal of Turbomachinery, 139(10), p.101001.
Film Cooling
Film cooling is a major component of the overall cooling of turbine airfoils. Holes placed in the body of the airfoil to allow coolant to pass from the internal cavity to the external surface. The ejection of coolant gas through holes in the airfoil body results in a layer or “film” of coolant gas flowing along the external surface of the airfoil. Since this coolant gas is at a lower temperature than the mainstream, the heat transfer into the airfoil is reduced. The adiabatic film effectiveness has a predominant effect in the design of the overall airfoil cooling. We revealed the significant film cooling degradation in thin-walled airfoil experimentally and numerically. We proposed a new geometrical method to design novel fan-shaped holes with short hole length-to-diameter ratios for achieving high film cooling effectiveness.
Related publications:
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W. Li, X. Li, J. Ren, H. Jiang, 2018, “A Novel Method for Designing Fan-Shaped Holes with Short Length-To-Diameter Ratio in Producing High Film Cooling Performance for Thin-Wall Turbine Airfoil,” ASME Transactions-Journal of Turbomachinery, 140(9), p. 091004.
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W. Li, W. Shi, X. Li, J. Ren, H. Jiang, 2017, “On the Flow Structures and Adiabatic Film Effectiveness for Simple and Compound Angle Hole with Varied Length-to-Diameter Ratio by Large Eddy Simulation and Pressure Sensitive Paint Techniques”, ASME Transactions-Journal of Heat Transfer, 139 (12), p.122201.
Double-walled Effusion System
The double-wall, effusion cooling system represents one potential advancement in gas turbine cooling that may permit a further elevation in turbine core temperatures. Such
systems demonstrate higher overall cooling effectiveness and convective efficiency. Effusion-type systems also display superior film cooling performance due in part to the more regular, closely packed array of film holes on the outer surface as well as the low blowing ratios effusion systems typically operate at. We envisioned the potential of reducing the turbine airfoil thickness to promote cooling efficiency, thereby generating thin-walled effusion cooling airfoils. We quantify the cooling contributions of impingement cooling, effusion cooling, internal pin-fin array, and conjugate units, and verify the cooling enhancement by utilizing the thin-walled airfoil designs.
Related publications:
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W. Li, X. Lu, X. Li, J. Ren, H. Jiang, 2019, “On Improving Full-Coverage Effusion Cooling Efficiency by Varying Cooling Arrangements and Wall Thickness in Double Wall Cooling Application,” ASME Transactions-Journal of Heat Transfer, 141(4), p. 042201.
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W. Li, X. Lu, X. Li, J. Ren, H. Jiang, 2019, “Wall Thickness and Injection Direction Effects on Flat Plate Full-Coverage Film Cooling Arrays: Adiabatic Film Effectiveness and Heat Transfer Coefficient”, International Journal of Thermal Sciences, 136, pp. 172-181.
Bioinspired Heat Exchangers
Hypersonic engine cooling
Supercritical CO2 cycle
Turbine for supercritical CO2 cycle
The supercritical carbon dioxide (sCO2) based Brayton cycle is a proposed alternative to replace conventional Rankine cycles in terms of high cycle efficiency, compact turbomachinery and heat exchangers. In the sCO2 cycle, however, the existing heat exchangers have been challenged by a large portion of heat transfer (approximately 60–70% of total cycle heat transfer) and high cycle efficiency required. We design novel heat exchangers by utilizing triply periodic minimal surface (TPMS) structures, which are a class of structures composed of two distinct inter-penetrating volume domains separated by an area-minimizing wall to enhance heat transfer and improve cycle efficiency.
Related publications:
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W. Li, G. Yu, Z. Yu, 2020, “Bioinspired heat exchangers based on triply periodic minimal surfaces for supercritical CO2 cycles”, Applied Thermal Engineering, 179, 115686.