UHBR Open-test-case fan ECL5/Catana, Part 2: Mechanical and aeroelastic stability analysis

Abstract

In Part-1, the ECL5 open-test-case has been introduced. Details on design methodology, geometry, and aerodynamics of the whole stage have been presented. Part-2 focuses herein on structure dynamics and aeroelastic stability. This paper aims to provide the mechanical and aeroelastic stability characteristics of the fan stage obtained with a state-of-art industrial design process. The fan blades are composed of a laminate made of unidirectional carbon fibres and epoxy composite plies. Fibre orientations of each ply are parameters which enable to modify the mechanical behaviour with minimal impact on the aerodynamic performance. Details on the structural properties, the manufacturing process and the ply orientations are presented. First mechanical modes of the fan are described and discussed in the context of aeroelastic interactions. Their frequency distribution is validated in terms of synchronous vibration. Aeroelastic stability of the fan is evaluated at representative operating points with a systematic approach. Potential instabilities are observed far from the operating line. Therefore, they do not compromise experimental campaigns.

Experiments on Tuned UHBR Open-Test-Case Fan ECL5/CATANA: Performance and Aerodynamics

“…11% and 88% axial chord respectively). FEM calculations (as shared with the opentest-case geometry [7]) indicate a stagger angle of 60.3 • at 55% speed, slightly opening to 60 • at 100% speed.…”

“…The primary reason for deviations from design is the difference between the manufac-turing process and the used FEM model. The ACT module implemented in the commercial ANSYS Workbench 18.2 toolbox was used for all static and modal calculations and requires the assumption of layers perfectly parallel to the respective profile centerline, as described in [7]. In the fabricated geometry, layers follow the molded surfaces of the blade and meet at the centerline.…”

“…Industrial practices to minimize the risk of flutter have been applied, which is in contrast to the complementary research program CA3VIAR [5]. The detailed design process was presented in [6,7]. It resulted in a 16-bladed carbon-fibre composite configuration with a relative design tip Mach number of 1.02 at a tip speed of 288 m/s, which is significantly lower than state-of-theart industrial UHBR configurations like the direct drive LEAP or GEnx, but also compared to the only in-service geared turbofan PW1000, promising extensive potential for noise reduction and improvement of propulsive efficiency.…”

“…Radial flow migration occurs and influences the aeroelastic behaviour [21]. For the ECL5 design, predictions were ambiguous [7,8] and vary dependent on the used method. The main objective is to clearly characterize the aerodynamic flow field and instability mechanism across the whole speed range.…”

“…Structurally, the first three fan-blade eigenmodes were designed according to industrial practices by varying the carbon fibre orientations. Fan blades have been fabricated from preimpregnated layers, which are cut, oriented and stacked according to the layup described in [7] and shown in Fig. 1(a).…”