A Computational and Experimental Approach to Surge Bleed Valve Noise Reduction

A combined computational aeroacoustic (CAA) & experimental validation method was used to investigate and reduce the sources of noise in a compressor surge bleed valve used in turbofan engines. The numerical code used for computational aeroacoustics simulation was PowerFLOW from Dassault Systems which uses an unsteady Lattice Boltzmann Method (LBM) / Very Large Eddy Simulation (VLES) approach to model flow through the valve and predict downstream noise. The simulation results showed high Mach number and turbulent kinetic energy (TKE) levels in the baseline valve which had the bleed flow discharged through a single perforated plate. A novel valve design that uses a tortuous path to discharge flow was also analyzed and showed significantly lower Mach numbers & TKE levels while maintaining the same pressure ratio and mass flowrate as in the baseline valve. Acoustic pressures were monitored in the simulations for both valves at locations where microphones were placed in a hemispherical array in the test. Predicted spectral sound power levels were calculated using the data from these locations. The tortuous path valve was estimated to provide a 10dB reduction in noise levels compared to the baseline valve. Bench test measurements confirmed the simulation results.