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ABSTRACT
Modern gas turbines operate at high inlet temperatures to improve thermal efficiency; therefore, it is necessary to cool the turbine blades. Various techniques are used for heat transfer enhancements, such as ribs, protrusions, pin fin, dimples, etc.; the present study focused on compound and rib alone channel. W-shaped, semicircular and multi-semicircular shaped ribs with dimples are studied experimentally to find the optimum configuration for blade cooling. The experiment was carried out at Reynolds numbers 12,600 to 35,000; the ratio of pitch (P) to height (e) of the rib was 8 to 10, the ratio of rib height to channel hydraulic diameter (Dh) was 0.156 and the ratio of dimple depth (δ) to dimple diameter was 0.2. It was observed that the combination of rib and dimple channel (compound channel) performance was higher than the rib channel. The W-shaped rib compound channel shows the highest thermal performance over semicircular and multi-semicircular rib compound channels, and also sees a small rise in friction loss in compound channel. Realizable k–ɛ turbulence model was used for analysis and observed less difference between experimental and CFD results. In the rib channel, semicircular rib performed better than other tested ribs.
Nomenclature
| Symbol | = | Description |
| A | = | Area of rectangular duct |
| AR | = | Channel aspect ratio (W/H) |
| Dh | = | hydraulic diameter of duct |
| W | = | Width of duct |
| H | = | height of duct |
| L | = | Test section length |
| p | = | Rib pitch |
| m˙ | = | air mass flow rate |
| Qnet | = | Net heat input |
| h | = | Convective heat transfer coefficient |
| Pin | = | Inlet pressure at test section |
| Pout | = | outlet pressure at test section |
| k | = | thermal conductivity of air |
| Dimensionless number | = | |
| Nu | = | Nusselt number |
| Nuo | = | Nusselt number for smooth circular duct |
| f | = | Friction factor |
| fo | = | Friction factor for smooth circular duct |
| Re | = | Reynolds number |
| Greek symbol | = | |
| δ | = | dimple depth |
Acknowledgments
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Data availability statement
The authors confirm that the data supporting the findings of this study are created by authors own study by doing experimental work and the data that support the findings of this study are available within article and its supplementary materials.
Reserved DOI: doi:10.17632/gz695yywsw.1
Disclosure statement
No potential conflict of interest was reported by the authors.
Additional information
Notes on contributors
Prakash Santosh Patil
Prakash S. Patil is a research scholar in the Department of Mechanical Engineering at Rajarshi shahu college of Engineering, Pune, India.His research interest includes thermal heat power, turbo machines etc.
K. K. Dhande
Dr. Kishor K. Dhande is currently working as a Head & Professor in the Department of Mechanical Engineering at D.Y. Patil Institute of technology, Pune, India. His research interest includes design, Vibration , Mechatronics etc.
S. L. Borse
Dr. Sachin L. Borse worked as a Professor in the Department of Mechanical Engineering at Rajarshi shahu college of Engineering, Pune, India. His research interest includes thermal heat power, CFD etc.