Turbine Noise Generation in Turbofan Engines
The Acoustics Discipline of the Fundamental Aeronautics Program is pursuing technologies to reduce aircraft noise with the ultimate goal of containing objectionable noise from aircraft to within the airport boundary. Aircraft noise is an amalgam of propulsion and airframe sources whose relative contributions depend on the aircraft type and operating condition. Generally speaking, the propulsion (i.e., engine) noise is a significant contributor to the total aircraft noise signature. Of the various sources of engine noise, fan and jet sources have received much attention in the past, but with the advent of ultra high bypass ratio engines (like the P&W geared turbofan), turbine noise is emerging as an important source of noise that must be mitigated in the future low-noise propulsion systems. The Turbine Noise project’s objective is to develop an understanding of how and where the noise is produced inside the turbine. From this knowledge, noise models can be formulated which will aid in the evaluation of new engine designs and in the development of turbine noise mitigation technologies.
The NASA turbomachinery aerodynamics solver TURBO is used to calculate the time varying pressure field inside the turbine. A portion of this unsteady pressure field will propagate through the turbine blade rows and will emerge as noise from the engine exhaust. Frequency, modal content and other characteristic information may be extracted from the pressure data by post-processing and used to construct reduced order models for the noise generation and propagation. To properly capture important pressure wave features inside the turbine the numerical mesh must be about ten times denser than what is typically used for aerodynamic performance calculations. Such dense meshes, required by the wave propagation physics, result in very large computational resource requirements.
Principal Investigator name: Dale Van Zante
Email: Dale.E.VanZante@nasa.gov
Phone: (216) 433-3640
Organization: NASA Glenn Research Center, Acoustics Branch
Co-investigators: Edmane Envia, NASA Glenn Research Center, Acoustics Branch
