Isothermal Boundary Condition at Casing Applied to the Rotor 37 Transonic Axial Flow Compressor

Computational fluid dynamics (CFD) simulations are presented with an isothermal boundary condition at the casing for running NASA Rotor 37. The casing temperature is set to the inlet total temperature. Relative to the adiabatic simulations, the comparison to experimental efficiency is much improved for the 100% speed line. The efficiency difference between the isothermal and adiabatic solutions is about 1%, and matches the low-flow test condition. The profiles of total temperature with the isothermal boundary condition match the data near the casing. The adiabatic simulation has a total temperature overshoot that has been consistently part of any data comparison of CFD with this data set, and is typical of most compressor calculations. The efficiency profile has a similar improvement in matching the data because of its relationship to temperature. The real rig is not isothermal at the casing and may require more complex simulations such as a conjugate heat transfer approach to truly match the physics. However, the isothermal boundary condition is more accurate and more realistic than the adiabatic boundary condition.