Screw Compressors- Mathematical Modelling And Performance Calculation Info

Unlike dynamic compressors (e.g., centrifugal), screw compressors trap a fixed volume of gas and reduce that volume to increase pressure. The performance of a screw compressor is dictated by the precision of its rotor profiles (male and female), the clearance between them, and the thermodynamic properties of the working fluid.

Mathematical modelling serves two primary purposes:

Assume: inlet pressure p1, inlet temperature T1, rotational speed n, rotor geometry known, discharge pressure p2 target. Use polytropic segmented model with N axial slices. Unlike dynamic compressors (e

  • Initialize slice states:

  • For each slice i from 1..N:

  • Optionally enforce polytropic step: p_i = p_i−1 (V_i−1/V_i)^n_local with n_local set by local heat transfer estimate.

  • Sum element work:

  • Compute mass flow and actual volumetric flow: Assume: inlet pressure p1, inlet temperature T1, rotational

  • Account for mechanical losses:

  • Output performance metrics:

    • The working chamber (the "lobe pocket") changes volume as the rotors turn.

    From the thermodynamic model, the following performance parameters are extracted. Initialize slice states: