Large-Scale Simulations for Turbine Engine Core Noise

Abstract

As turbofan engine bypass ratios continue to increase, the contribution of the turbine to the engine and aircraft noise signature is receiving more attention. Understanding the relative importance of the various turbine noise generation mechanisms and the characteristics of the turbine acoustic transmission loss are essential ingredients in developing robust reduced-order models for predicting the turbine noise signature. A computationally based investigation has been undertaken to help guide the development of a turbine noise prediction capability that does not rely on empiricism. Under the auspices of the Fundamental Aeronautics Program, NASA is currently funding core noise research focused on the generation and propagation mechanisms of combustor and turbine noise in the combustor-turbine-nozzle system. Highly detailed numerical simulations of the unsteady flow field inside the first stage of a modern high-pressure turbine were carried out using TURBO. Spectral and modal analysis of the unsteady pressure data from the numerical simulation of the turbine stage show a circumferential modal distribution that is consistent with the Tyler-Sofrin rule, which gives confidence in the approach. Additionally, initial steps have been taken in determining the source strength hierarchy.