ABSTRACT\r\nThe combination of variable speed control and adjustable\r\ndiffuser vanes offers an attractive design option for centrifugal\r\ncompressors applied in industrial applications where a wide\r\noperating range at high efficiency level and a favorable surge\r\nline is required. However, the knowledge about the impact on\r\ncompressor performance of a diffuser vane clearance between\r\nvane and diffuser wall which is mandatory since the diffuser\r\ngeometry adjustment has to take place during operation, is still\r\nnot satisfying.\r\nThe results of characteristic line and probe measurements\r\npresented in Part I [18] of this two-part paper showed that an\r\none-sided diffuser clearance not necessarily need to lead to a\r\nnegative impact on compressor operating behavior but is able to\r\ncontribute to an increase in flow range, stall margin, pressure\r\nratio and efficiency, as long as the diffuser passage is broad\r\nenough with respect to the clearance height.\r\nIn order to reveal the relevant flow phenomena, in Part II\r\nthe results of detailed measurements of the pressure distribution\r\nat diffuser exit and Particle Image Velocimetry (PIV)\r\nmeasurements inside the diffuser channel performed at three\r\nclearance configurations and three diffuser angles at a fixed\r\nradial gap are discussed. It was found, that for defined diffuser\r\nconfigurations the clearance flow amplifies the diffuser throat\r\nvortex capable to reduce the loading of the highly loaded vane\r\npressure side and to support a more homogenous diffuser flow.\r\nIt turned out that the coaction of the geometry parameter\r\ndiffuser vane angle and diffuser clearance height is of particular\r\nimportance.\r\nThe experimental results are published as an open CFD\r\ntestcase “Radiver 2” [17], extending the experimental data base\r\nof the testcase "Radiver" published in 2003 by Ziegler [24].    «

ABSTRACT\r\nThe combination of variable speed control and adjustable\r\ndiffuser vanes offers an attractive design option for centrifugal\r\ncompressors applied in industrial applications where a wide\r\noperating range at high efficiency level and a favorable surge\r\nline is required. However, the knowledge about the impact on\r\ncompressor performance of a diffuser vane clearance between\r\nvane and diffuser wall which is mandatory since the diffuser\r\ngeometry adjustment has to take place d...    »