Effects of Variable Diffuser Vanes on Performance of a Centrifugal Compressor with Pressure Ratio of 8.0

Abstract

Abstract:In numerous applications, centrifugal compressors are required to provide a high pressure ratio with good efficiency while also working in a wide operating range. This is a challenge because as pressure ratio increases, efficiency and operating range inevitably decline. This paper studies the effects of a variable geometry diffuser on the performance and operating range of a centrifugal compressor with high pressure ratios of up to 8.0. The numerical method employed three-dimensional Reynolds-averaged Navier-Stokes simulations. An analysis of the matching of the vaned diffuser with the impeller for different working conditions and diffuser vane angles is presented. The results show that improved matching of the adjusted diffuser increased efficiency by 4.5%. The range extension mechanism of the variable diffuser is explained, and it is shown that adjusting the vane angle by +6 • to −6 • extended the operating range of the compressor by up to 30.0% for pressure ratios between 5.0 and 6.0. The interaction between diffuser and impeller was examined, and the independent characteristic of the impeller is illustrated. The connection between the incidence angle at the leading edge of the impeller and flow separation near the tip of the impeller is discussed.

A Revisit to Recent Developments in the Underfloor Air Distribution Systems

“…The plate's position changes in response to a signal from the controller or the thermostat in the area it serves [55]. A VA diffuser's nominal airflow is about 150 cfm at 0.05 pressure drop, or twice the flow rate of a swirl diffuser [56].…”

Experimentally Validated Extension of the Operating Range of an Electrically Driven Turbocharger for Fuel Cell Applications

“…They showed that a reduction in the leading edge angle results in a shift of the compressor operating range towards lower mass flow rates. By implementing an actuation mechanism, which allows the flexible pivoting of the diffuser vanes, the operating range of the compressor can be adjusted depending on the operating conditions [13,14]. However, gaps between end walls and diffuser vanes, which are necessary for a flexible pivoting concept, cause aerodynamic losses and thus reduce efficiency.…”