Affiliation:
1. Department of Mechanical Engineering, Northeastern University, Boston, MA 02115
2. General Electric—Aircraft Engines, Lynn, MA 01910
Abstract
Trailing edge cooling cavities in modern gas turbine blades often have trapezoidal cross-sectional areas of relatively low aspect ratio. To enhance cooling effectiveness in these passages, they are roughened with tapered turbulators. Furthermore, to provide additional cooling for the trailing edge, the cooling air may be ejected through trailing edge slots as it moves radially along the cooling passage. The tapered turbulators, in conjunction with the presence of these slots along the smaller base of the trapezoidal cavity, create both spanwise and longitudinal variations in heat transfer coefficient on the turbulated walls. Moreover, the continuous variation of cooling air velocity along these passages causes a continuous change in static pressure, which also requires investigation. Liquid crystals are used in this experimental investigation to study the effects of tapered turbulators on heat transfer coefficients in trailing edge passages with and without bleed holes. The tapered turbulators are configured on two opposite walls of the trapezoidal test section in a staggered arrangement with an angle of attack to the mainstream flow, α, of 90 deg. Nine different test geometries consisting of two passage aspect ratios, AR, were tested over a range of turbulator aspect ratios, ARt, blockage ratios, emax/Dh, pitch-to-height ratios, S/emax, and Reynolds numbers. Channel pressure losses were also measured and both heat transfer and friction factor results for several geometries are compared. It is concluded that (a) there exists a large spanwise variation in heat transfer coefficient in test sections with no bleed holes, (b) adding bleed holes to the smaller base of the trapezoidal cavity gives a spanwise velocity component to the mainstream flow and reduces this variation, and (c) Nusselt numbers measured in the test sections with bleed holes correlate well with local Reynolds number.
Reference29 articles.
1. Abuaf, N., Gibbs, R., and Baum, R., 1986, “Pressure Drop and Heat Transfer Coefficient Distributions in Serpentine Passages With and Without Turbulence Promoters,” The Eighth International Heat Transfer Conference, C. L. Tien, V. P. Carey and J. K. Ferrel, eds., pp. 2837–2845.
2. Burggraf, F., 1970, “Experimental Heat Transfer and Pressure Drop With Two Dimensional Turbulence Promoters Applied to Two Opposite Walls of a Square Tube,” Augmentation of Connective Heat and Mass Transfer, A. E. Bergles and R. L. Webb, eds., ASME, pp. 70–79.
3. Chandra
P. R.
, 1988, “Effect of Rib Angle on Local Heat/Mass Transfer Distribution in a Two Pass Rib-Roughened Channel,” ASME JOURNAL OF TURBOMACHINERY, Vol. 110, pp. 233–241.
4. Chandra
P. R.
, and HanJ. C., 1989, “Pressure Drop and Mass Transfer in Two-Pass Ribbed Channels,” AIAA J. Thermophysics, Vol. 3, No. 3, pp. 315–319.
5. Dittus, F. W., and Boelter, L. M. K., 1930, “Publications in Engineering, Vol. 2, University of California, Berkeley, CA, p. 443.
Cited by
49 articles.
订阅此论文施引文献
订阅此论文施引文献，注册后可以免费订阅5篇论文的施引文献，订阅后可以查看论文全部施引文献