Study of the roughness effect on the normal spectral emissivity of GH3044

Abstract

The normal spectral emissivity is a significant parameter characterizing the radiative capacity of the object's surface. However, the normal spectral emissivity of superalloys varies with the rough state of the surface, causing unacceptable errors in radiation thermometry and heat transfer calculation for aero-engines and gas turbines. A computational method for estimating the effect of roughness on the normal spectral emissivity of superalloys was established based on constructing randomly rough surfaces. Through this method, the effect of roughness on four emissivity models commonly used in multispectral radiometric thermometry (MRT) was computationally evaluated, and the relationship between roughness and spectral emissivity was quantitatively analyzed. In addition, the normal spectral emissivity of GH3044 superalloy with different rough surfaces at 300 K and high temperatures was experimentally measured and compared with the result calculated by this computational method. Their maximum relative error was close to ± 5 % for the rough surface without emissivity oscillation. This study promotes understanding the mechanism of normal spectral emissivity varying with roughness.