Navier-Stokes and Potential Calculations of Axial Spacing Effect on Vortical and Potential Disturbances and Gust Response in an Axial Compressor

Abstract

The effect of blade row axial spacing on vortical and potential disturbances and gust response is studied for a compressor stator/rotor configuration near design and at high loadings using 2D incompressible Navier-Stokes and potential codes, both written for multistage calculations. First, vortical and potential disturbances downstream of the isolated stator in the moving frame are defined; these disturbances exclude blade row interaction effects. Then, vortical and potential disturbances for the stator/rotor configuration are calculated for axial gaps of 10%, 20%, and 30% chord. Results show that the potential disturbance is uncoupled; the potential disturbance calculated from the isolated stator configuration is a good approximation for that from the stator/rotor configuration for all three axial gaps. The vortical disturbance depends strongly on blade row interactions. Low order modes of vortical disturbance are of substantial magnitude and decay much more slowly downstream than do those of potential disturbance. Vortical disturbance decays linearly with increasing mode except very close to the stator trailing edge. For a small axial gap, lower order modes of both vortical and potential disturbances must be included to determine the rotor gust response.

Wake Vorticity Decay and Blade Response in an Axial Compressor With Varying Axial Gap

“…To verify grid independence, two grid sizes were computed -172x78 cells per row with 108 cells per blade surface and 258x114 cells per row with 160 cells per blade surface. The former grid is found to be satisfactory (Chung, 1995) and is adopted in this work. A slip interface is located at the mid-gap between the two blade rows, which separates two grid systems fixed with respect to each blade.…”

“…A slip interface is located at the mid-gap between the two blade rows, which separates two grid systems fixed with respect to each blade. Numerics are passed through the interface as provided in detail in Chung and Wo (1997) and Chung (1995).…”

“…Manwaring and Wisler (1993) provided extensive comparison between the state-of-the-an analysis methods and data on forced response. Chung and Wo (1997) used both Navier-Stokes and panel codes to split the disturbances between blade rows into vortical and potential contributions and Wo et al (1997) provided details on decomposition of forced response. Hsu and Wo (1998) recently showed that if the blades are clocked properly the potential disturbance from the second rotor row can substantially reduced the upstream stator response caused by wakes from the first rotor blades.…”

Experimental and Numerical Study of Gust and Gust Response in a Rotor/Stator Axial Compressor

“…This section briefly describes the calculation methods. More details can be found in Chung (1995), and Chung and Wo (1995).…”

“…Verdon (1993) also reviewed unsteady aerodynamic methods for turbomachinery aeroelastic and aeroacottstic applications. Numerous excellent calculations of unsteady blade force for rotor/stator or wake/blade configuration include Rai (1987), Lewis and Delaney (1987), Giles (1988Giles ( , 1990, Rai and Madavan (1990), Korakianitis (1993a, I 993b), Chung and Wo (1995), Valkov and Tan (1995), and others. The work of Valkov and Tan provided exceptional physical insight into the cause of unsteady blade loading due to moving wakes.…”