TY - CONF

T1 - The loss behaviour of milled turbine blades

AU - Schreyer, Bastian

AU - Seume, Joerg R.

PY - 2005

Y1 - 2005

N2 - The manufacturing cost of milled turbine blades increase with the required surface quality. Turbine surfaces manufactured with reduced milling time are characterized by a rougher surface texture generated by the milling tool. Profile losses of 12 different industrially manufactured turbine blade cascades (qualities) were investigated in a linear cascade wind tunnel in order to generate information about the roughness effect of the milled surface structure. The ratios of surface roughness to chord length for the tested blade surfaces are in the range of Ra/c=8.8 × 10-7 ⋯ 5.6 × 10-5 and Ra = 0.1 ⋯ 4.4 μm. The Reynolds number was varied from 0.74 × 106 ⋯ 1.14 × 106 and the inflow angle from 50° to 120°. The profile loss was determined by wake traverse measurements at the mid span. Parameters of the turbulent boundary layer were evaluated from hot-wire anemometry measurements. Measuring roughness and blade shape by the contact stylus technique and multi coordinate measurement, respectively, provided the data for correlating profile losses and blade geometry. Trailing edge thickness, varied due to manufacturing uncertainties, significantly contributes to the profile loss. To separate trailing edge losses from losses due to the surface roughness, an experimental correlation of trailing edge loss and thickness was established. For this purpose, turbine blades with deterministically varied trailing edge thickness were used. No negative impact on the profile loss was observed for the use in typical industrial application, even when rough milling structures were tested, as long as the micro-roughness is within certain limits.

AB - The manufacturing cost of milled turbine blades increase with the required surface quality. Turbine surfaces manufactured with reduced milling time are characterized by a rougher surface texture generated by the milling tool. Profile losses of 12 different industrially manufactured turbine blade cascades (qualities) were investigated in a linear cascade wind tunnel in order to generate information about the roughness effect of the milled surface structure. The ratios of surface roughness to chord length for the tested blade surfaces are in the range of Ra/c=8.8 × 10-7 ⋯ 5.6 × 10-5 and Ra = 0.1 ⋯ 4.4 μm. The Reynolds number was varied from 0.74 × 106 ⋯ 1.14 × 106 and the inflow angle from 50° to 120°. The profile loss was determined by wake traverse measurements at the mid span. Parameters of the turbulent boundary layer were evaluated from hot-wire anemometry measurements. Measuring roughness and blade shape by the contact stylus technique and multi coordinate measurement, respectively, provided the data for correlating profile losses and blade geometry. Trailing edge thickness, varied due to manufacturing uncertainties, significantly contributes to the profile loss. To separate trailing edge losses from losses due to the surface roughness, an experimental correlation of trailing edge loss and thickness was established. For this purpose, turbine blades with deterministically varied trailing edge thickness were used. No negative impact on the profile loss was observed for the use in typical industrial application, even when rough milling structures were tested, as long as the micro-roughness is within certain limits.

UR - http://www.scopus.com/inward/record.url?scp=84925436452&partnerID=8YFLogxK

M3 - Paper

T2 - 6th Conference on Turbomachinery: Fluid Dynamics and Thermodynamics, ETC 2005

Y2 - 7 March 2005 through 11 March 2005

ER -