Turbulent Heat Transfer Investigation: Turbulence Length Scales and Turbine Heat Transfer.
Abstract
This experiment was designed to study the effects of turbulent length scales on turbine blade heat transfer in a steady state cascade wind tunnel. Turbine blade heat transfer is of interest due to the beneficial effects engine performance that can arise from improvements in turbine blade cooling and design. Turbulence in this experiment was generated by means of passive grids in the upstream flow. This experiment uses a steady state liquid crystal in combination with resistance heating to measure heat transfer. The liquid crystals provide surface temperature data and the resistance heating in the blade can be computed from measured currents to determine heat transfer. When combined with flow data taken with a hot film this allows for conclusions on the effects of length scales on heat transfer to be made. This experiment showed that the turbine blade heat transfer exhibited the trends already investigated for turbulence intensity, namely an increase in heat transfer with increased turbulence, the forward movement of boundary layer transition and the elimination of pressure side spanwise variations. Comparison of the two different length scales at the same turbulence intensity showed that the length scale evidenced no affect on transition location or post-transition heat transfer. However, pre-transition heat transfer was significantly increased as the integral length scale decreased from 2.78 to 0.51. This demonstrates that smaller more compact eddies in the turbulent flow have a more significant impact on increasing heat transfer than do larger eddies of the same intensity.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 03, 1996
- Accession Number
- ADA312494
Entities
People
- Jason Sharp
- Pete Harris
Organizations
- Wright Laboratory