English to Russian Tech/Engineering Petroleum Eng/Sci

Compressors are tested using air or nitrogen.
The compressor is tested per the aerodynamic similarity coefficients of inlet Mach number, inlet volume to speed ratio (Q/N) and specific speed (Ns).
The flow is varied from the maximum (choke) to the minimum (surge) to verify the off design head and efficiency characteristics.
The following compressor non-dimensional coefficients are used:
Phi (φ) = Cm/Um, Flow coefficient
Cm = gas inlet meridional velocity
Um = blade inlet meridional velocity