Dimensionless numbers and experimental considerations in correlating freestream vorticity and stagnation region heat transfer
Effect of free-stream turbulence on stagnation region heat transfer is important in a number of engineering applications, especially in gas turbines where the temperature of combustion gases exceeds the allowable temperature limit of turbine blade materials. Accurate prediction of heat transfer to the stagnation region of blades and vanes is still a major challenge in designing the blade cooling system of a gas turbine. A complete understanding of turbine blade heat transfer may be difficult because of the complexity of gas turbine flows. However, a fundamental understanding of the isolated influence of each of the free-stream turbulence characteristics on gas turbine blade heat transfer would allow them to be incorporated more effectively into cooling system designs. While there have been several studies on the effect of different free-stream turbulence characteristics on stagnation region heat transfer, studies on the effect of vorticity on stagnation region heat transfer is limited. The primary reason for this is the difficulty and uncertainty in measuring the vorticity field. However, vorticity measurement techniques have improved over the last few years, and it is rational to study the effect of free-stream vorticity. Vorticity is the underlying characteristic of turbulence, and knowledge of the effect of vorticity on stagnation region heat transfer should provide some additional insight into the physics of the problem. Furthermore, the inclusion of freestream vorticity should improve previous correlation models, and lead to more accurate models to predict stagnation region heat transfer. Because of the large number of variables involved, it is desirable to perform a dimensional analysis of the system prior to the design of the experiment. The purpose of this paper is to formulate the appropriate dimensionless numbers for an experimental study on the effect of free stream vorticity on stagnation region heat transfer and to discuss the experimental considerations of the proposed study. The variables of interest for the system are selected, and the dimensionless numbers are formulated by the matrix method. The formulated dimensionless parameters are compounded to obtain a number of physically more interpretable dimensionless numbers based on the theory of convection heat transfer and turbulent flow characteristics. From the compounded dimensionless numbers, the parameters to be varied in the experiment are identified, the parameters to be varied in the experiment are identified, and the possibilities of varying these parameters and discussion on the heat transfer model are presented. Finally, the proper method of presenting the experimental results under the guidance of dimensional analysis is discussed.
- Research Organization:
- Memorial Univ. of Newfoundland, St. John's, Newfoundland (CA)
- OSTI ID:
- 20026772
- Resource Relation:
- Conference: 5th ASME/JSME Thermal Engineering Joint Conference, San Diego, CA (US), 03/14/1999--03/19/1999; Other Information: 1 CD-ROM. Operating system required: Windows i386(tm), i486(tm), Pentium (R) or Pentium Pro, MS Windows 3.1, 95, or NT 3.51, 8 MB RAM, MacIntosh and Power MacIntosh with a 68020 or greater processor, System software version 7.1, 3.5 MB RAM (5 MB for PowerMac) 6 MB available hard-disk space, Unix; PBD: 1999; Related Information: In: Proceedings of the 5th ASME/JSME thermal engineering joint conference, [3600] pages.
- Country of Publication:
- United States
- Language:
- English
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