Fluid-structure interaction and vibration analysis of the fuel system of a turbofan engine with optimal dimensions

This paper investigates the main problem of combustion instability in turbofan engines which is usually the unbalanced fuel pump causing turbulences in the fuel flow as well as vibrations in the fuel pipes of the system.At first, the equations of frequencies are derived analytically in the direct and knee joint pipes to verify the results of the Abaqus software. The results show an acceptable accuracy of the Abaqus software to solve the problem of the fluid coupling structure. The results show that the vibration frequency of this part of the fuel transfer system (2.5 to 18 Hz in different modes) is very low compared to the entire engine operational frequency (around 140 Hz). The maximum transverse displacement (range) is relatively significant (up to 16 mm), which is noticeable with respect to the overall dimensions of the system. However, this amplitude would decrease by two clamped-ended with two fastened belts. In the following part, optimization of the system parameters was done using the Design-expert Software and NSGA II code. The basic parameters studied in this paper are radius, thickness, and length of the pipe with different spans, as well as the turbulence inflow. Optimal mode is achieved with laminar velocity contours. In conclusion, the outflow disturbance has been decreased, which consequently reduces the turbulence of the fuel that can improve combustion stability