Circulatory Flow Characteristics in Side Channel Blowers

Abstract

Side channel blowers generate their pressure rise by a complex inner flow field. Despite being subject to scientific investigations since the 1940s, the mechanism behind the generation of high-pressure coefficients, i.e. around 20, are still not fully known. In literature, two main theories try to explain the inner workings and the momentum transfer from theimpeller to the fluid. One approach sees the momentum being transferred by shear stresses between the impeller and the slower fluid in the channel. The other approach sees the circulatory flow, generated by the centrifugal force acting on the circumferentially moving fluid, as the key mechanism to energy transfer from the impeller to the fluid. A review of both mechanisms is necessary to allow for further improvements in the efficiency. In the current work, a numerical analysis of a straight side channel model is presented. The model holds the possibility to omit the influence of the centrifugal force and thus prevent the generation of a circulatory flow. Hence, only shear stresses between fluid and impeller contribute to the momentum transfer. The results show that the circulatory flow is essential to a proper energy transfer and thus high pressure coefficients.

Influence of different design parameters on side channel compressor performance

“…This leads to several internal compression cycles during one rotation and thus a high pressure ratio. This flow pattern is typical for any type of side channel machine and highly turbulent [20].…”

“…The stripper between inlet and outlet interrupts the side channel and prevents significant backflow from outlet to inlet. Flow and energy transfer in impeller and side channel can be described by the circulation theory, first introduced by Wilson [27] in 1955 and since confirmed multiple times [15,20,23,24,26,28]. According to this theory, the fluid has a helical trajectory from the outer radius of the impeller into the side channel and back into Fig.…”

Design of Experiment on the influence of channel design onto regenerative compressor performance

“…The high pressure ratio is based on this internal multistaging. This flow pattern is characteristic for any type of regenerative machine and highly turbulent (Münsterjohann et al, 2017). The circulating flow strongly influences the performance of the regenerative compressor and depends on different design parameters.…”

Wall Pressure and Blade Surface Pressure in a Side Channel Blower

“…A comparison of both theories has been performed in [20]. The results show that the circulatory flow theory is superior to the mixing or turbulence theory in the explanation of the pressure generation in side channel blowers.…”