Effects of hot geometry changes on the off-design performance of a transonic fan rotor

Abstract

Hot-to-cold transformation is essential to achieve the desired aerodynamic performance in highly loaded fan rotors. However, due to the hot geometry changes resulting from variations in blade loads, the aerodynamic performance during operation will still deviate from that of the baseline geometry under off-design conditions. This paper proposes a method for calculating the aerodynamic performance of rotors while considering hot geometry changes. By performing thermal-fluid-structure interaction calculations for the cold geometry of a transonic fan rotor, the aerodynamic performance differences between the hot and baseline geometries are analyzed. Numerical calculations indicate that the deformation of hot geometry decreases with the reduction of total pressure ratio, rotational speed, and inlet total temperature and total pressure, leading to insufficient blade untwist and an increase in the tip clearance. Changes in rotational speed have the most obvious impact on the deformation of hot geometry. The maximum deformation at 40% speed decreased by 81.1%, resulting in a 1.5% reduction in choked mass flow rate. However, peak efficiency is not sensitive to changes in hot geometry, with the maximum deviation in peak efficiency for off-design conditions being only 0.12%. The changes in axial velocity density indicate that the decrease in flow capacity is primarily due to insufficient blade untwist rather than the increase in tip clearance. By considering hot geometry changes, high-fidelity data results can be obtained, providing better guidance for experimental data analysis while improving adaptability to off-design conditions.