Thermal deformation of radial leakage gaps in roots blower using coupled solvers and dynamic mesh

Conjugate heat transfer (CHT) with Finite Element Modelling has proven to be a highly effective numerical tool for predicting the physical interaction between fluid and solid with heat transfer. In rotary positive displacement machines, high temperatures cause thermal expansion, consequently changing clearance gaps and influencing both performance and reliability. To enhance the machine’s efficiency and reliability, researchers have conducted experimental and numerical studies to measure heat transfer and gap variation caused by the expansion of the solids. However, real-time calculation of gap changes remains underexplored. Due to practical constraints, experimental investigation is usually not feasible; therefore, this study focuses on developing a numerical model to assess interaction of leakage gap variations driven by heat transfer. The results include surface temperature of the rotor tip, mass flow rate, power output, and outlet gas temperature, and were validated on Roots blower using infrared thermography data. A coupled fluid-solid solver to analyse flow, deformation and gap variation was used in this research. Findings show that the choice of the boundary data exchange frequency between solvers significantly influences the results of the transient heat transfer simulation, as demonstrated by the temperature distribution on the rotor’s tip surface. At a timescale of 2000 and with data exchanged at every time step, the model exhibits a good accuracy, which was within 8% of the test values across the range of operating conditions. This study concluded that, due to thermal expansion, the radial gap size increases, resulting in the increased leakage flow.