Modeling and optimization of the milling process of compressor rotors

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The efficiency of rotary screw air compressors is highly dependent on the clearance between their paired screw rotors. Insufficient clearance leads to interference between the paired rotors in operation, and excessive clearance leads to backlash and loss of efficiency. Although rotor clearance is carefully designed to avoid such problems, the actual rotor clearance can deviate from its nominal design due to various factors, and manufacturing errors are among the major contributors to this deviation. The current practice to determine the contribution of manufacturing errors to rotor profile deviations, and compensating for them in the design stage, involves numerous costly trial and errors which may not result in the optimum design of the rotor and its manufacturing process. Alternatively, substituting physical trials with modeling and simulation of the manufacturing process can lead to substantial cost savings and improving compressor efficiency. The objective of this project is to identify and minimize the deviation of the rotor profile due to manufacturing errors by developing physics-based simulations of rotor milling processes. The developed simulations will use the kinematic models of the process to predict the shape of the machined rotor profile based on the tool profile and machining parameters. In addition, forces and vibrations that arise during the process will be simulated using a Virtual Machining System (VMS). Process simulations will then be used to determine optimum machining parameters that would lead to minimum deviations in the shape of the machined profile without compromising productivity. The current rotor profiles at VMAC will be used as case studies to verify the effectiveness of the developed simulations in reducing manufacturing errors in rotor milling processes.