Numerical and Experimental Investigations of Steady and Unsteady Characteristics of a Counter Rotating Fan Model With Thickened Blades of Working Wheel

Abstract

Under VITAL Project funded by the European Community, Snecma as a project leader developed a counter rotating low-speed fan concept for a high bypass ratio engine [1–4]. At first, a counter rotating fan model (hereinafter referred to as CRTF1) with solid titanium blades was designed, manufactured and tested in CIAM’s C-3A anechoic chamber. The CRTF1 fan model had blades with a conventional thickness distribution in order to provide optimal mechanical properties and weight characteristics [1, 2]. To simulate blades made of composite materials, CRTF2a [3] and CRTF2b [4] counter-rotating fan models were designed with thickened blades (by 20–40%) as compared with the CRTF1 fan model to ensure mechanical properties. The CRTF2a counter-rotating fan model with thickened blades to simulate blades made of a composite material was tested in CIAM’s C-3A anechoic chamber. Fan local and integral performances within rotational speeds from ncor = 40% to ncor = 100% were measured. The numerical investigations were based on 3DFS software package developed for RANS and URANS solutions. The solution procedure is based on a modified S.K. Godunov’s scheme of implicit finite-difference second-order approximation [5]. The numerical investigations were subdivided into three stages corresponding to various problem definitions. Numerical investigations at the first stage and second stages were carried out without flow nonuniformity at the CRTF inlet. The first stage meets the requirements of the stationary problem definition. CRTF performances at this stage were calculated in the “mixing plane” approximation and compared with test data. Numerical investigations at the second stage were completed for non-stationary problem definition without flow nonuniformity at the inlet (the same as at the first stage). Calculations at this stage were carried out for the problem definition with a common period corresponding to calculations covering 5 blade channels in Rotor 1 (R1) and 7 blade channels in Rotor 2 (R2). Results of non-stationary calculations at the second stage were in good agreement with computed data at the first stage (the stationary calculation). The third stage of numerical investigations was in line with the numerical simulation of CRTF operation with total pressure nonuniformity at the inlet. At this stage the numerical investigations were carried out for non-stationary problem definition for all blade channels in Rotor 1 and Rotor 2 (10 and 14, respectively). The computed data were in good agreement with test results for CRTF integral characteristics as well as for local flow characteristics at the CRTF outlet (instantaneous and averaged by time values of flow parameters distributed in radial and circumferential directions).

Effect of inlet distortion on the performance of axial transonic contra-rotating compressor

“…No changes were reported in the total pressure ratio at the same rotational speed for uniform and nonuniform flow at the inlet but an increase in the total pressure rise and adiabatic efficiency was observed when operating under a nonuniform inflow. After that, Mileshin et al 21 found that the capacity of antidistortion of contra-rotating fan is excellent than that of the traditional rotor/stator compressor. Recently, Mistry and Pradeep 22 conducted a systemic experimental study on the low-speed contra-rotating fan.…”