Study of Combustion Noise Generation in a Realistic Turbine Stage Configuration

Abstract

Generation of combustion noise is here studied in a realistic turbine stage configuration, where the temperature fluctuations generated by an aeronautical burner (responsible of the direct combustion noise generation, often neglected in most of the studies) are modelled using a cylindrical fluctuating energy source term placed upstream of the inlet guide vanes. This modelling not only better accounts for the actual physical combustion noise generation phenomena, but also for the actual stratification of temperature at the combustor exit and covers a broader range of exciting frequencies as in actual engines. The temperature fluctuations generated by this realistic fluctuating energy source term are then convected through the turbine stage and the resulting noise is analyzed and compared with previous LES results with ideal monochromatic entropy forcing and analytical compact methods. New physical insight on the various noise generation mechanisms and mode conversion is also provided.

Effect of Film Cooling on Entropy Noise Generation in a Stator Blade Row

“…This showed that the increase is partially due to the entropy generation of a shock wave and the wake. However, the magnitude of the generated entropy wave is of three magnitudes smaller [18] in comparison to the forced entropy wave in Fig. 9.…”

“…9. An increase in axial entropy wave amplitude in the wake has been highlighted by Beceril et al [18]. This showed that the increase is partially due to the entropy generation of a shock wave and the wake.…”

“…[18] investigated localized entropy wave streaks. These localized waves are less sensitive to shear dispersion and act like a passive scalar advected along the streamlines [18].…”

Turbomachinery Noise Predictions: Present and Future

“…Yet, the additional entropy source placed in front of the stator leading edge triggers a significant increase of the gradient of density on the suction side of the stator, and consequently the boundary layer flow with earlier transition, thicker and more unsteady vortex shedding impacting the rotor blades. Several outstanding findings have been made by Becerril et al [92], which are summarized by the entropy transmission coefficients shown in Figure 16. In both plots CHORUS (thick black line) stands for the 2-D stage predictions at midspan as presented by Papadogiannis et al [88], and studied in detail by Bauerheim et al [91].…”

“…The former result suggested that the actual reflection at the turbine inlet was less prone to instabilities, and the latter suggested that the 2-D approximation of CHORUS through the turbine stages could be satisfactory. More recently a more realistic cylindrical source term mimicking the actual temperature stratification and hot streaks at the exit of the combustion chamber in an actual aero-engine has been injected at the inlet in front of the stator leading edge [92]. The flow topology of both cases with and without entropy volumic spot are shown in Figure 15 for the latter case.…”