Calculation of heat transfer and thermal deformations in roots-type machines

The paper presents a numerical simulation methodology for heat transfer and thermal deformations in Roots-type rotary machines. The key design challenge for oil-free vacuum pumps is considered, namely the determination of optimal operating clearances that ensure a balance between high efficiency and prevention of rotor jamming due to thermal expansion. A review of calculation methods is performed, ranging from analytical one-dimensional models to three-dimensional simulation using conjugate heat transfer and the finite element method. The developed model enables detailed analysis of temperature distribution in the rotor and housing. Validation of the numerical simulation results against experimental data shows a discrepancy not exceeding 11%. Based on this model, an analysis of thermal deformations is carried out, and the variation of rotor-housing clearances under different operating conditions is determined. It is established that an increase in inlet pressure leads to a significant rise in axial deformations (from 0.057 mm to 0.38 mm). The proposed methodology allows prediction of Roots-type machine performance at the design stage and minimization of the jamming risk.
EDN: BRPHCZ, https://elibrary/brphcz

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