Compliant mechanical stop for limiting split ring diffuser travel

In a centrifugal compressor having a casing and an impeller rotatably mounted therein for bringing a working fluid from an inlet to the entrance of an annular radially disposed split ring diffuser, said diffuser including an inner ring, said inner ring having a plurality of first channel sections formed therein, an outer ring, said outer ring having a plurality of second channel sections formed therein, each second channel section having a complementary first channel section;

• said compressor including a drive positioning mechanism for rotating said inner ring circumferentially within said outer ring between a first, fully open position wherein said complementary first and second channel sections are aligned to allow a maximum flow of fluid through said complementary channel sections, and a second, partially closed position, wherein said first and second complementary flow guide channels are misaligned to restrict flow of fluid through said complementary channel sections, the drive positioning mechanism comprising:
• an actuator;
• a pinion axle rotationally driven by said actuator at a first end of said pinion axle;
• a pinion gear mounted to a second end of said pinion axle;
• a rack gear fixedly mounted to said inner ring extending radially outwardly from said inner ring and adapted to engage in meshing arrangement with said pinion gear;
• first and second limit stops in said actuator for limiting travel of said inner ring between said first position and said second position;
• and
• a compliant mechanical stop on a side of said rack gear which touches an outer ring stop on said outer ring when said inner ring is in said first position, so as to prevent actuator stall.