Effect of pressurization on tip leakage losses in micro-scale centrifugal compressors

Turbomachinery miniaturization has been an emerging research field during the last decades and, especially, micro-scale radial compressors are becoming increasingly relevant due to development of high-speed electric motors. They can be found in a wide range applications such as micro gas turbines, aerial unmanned vehicles propulsion, fuel cells and even medical ventilators. Furthermore, use centrifugal recently proposed for heat pump using working fluids different than air which need pressurized. Since this down-scaling implies low inlet Reynolds-number, these pressurized entails beneficial effects on internal efficiency machine increase Reynolds-number within laminar-to-turbulent regime. Nevertheless, one main challenges micro-turbomachinery is large relative tip clearances assembly manufacturing tolerances. These clearance ratios lead increased leakage losses that limit drastically considered reduced-scale compressors. Besides, used aforementioned result pressure difference between suction sides blade. This precisely why goal work quantify effect The present paper proposes assessment by means both analytical numerical approaches. First, new operating conditions when calculated considering corresponding corrections Reynolds-number-dependent losses. Then, one-dimensional methods applied estimate expected reduction ratio. On other hand, model impeller-diffuser reference micro-compressor stage developed ANSYS CFX 19 order characterize complex three-dimensional interactions phenomena. Results show pressurization four selected (air, carbon dioxide, isobutane propane) desired pressures applications. A comparison presented results. While slight differences ratio found, provided not aligned However, agree fact influence all simulated.