The impeller chamber includes a variable area wherein {HEAD ~ a first cross sectional area} is defined between the radially outer surface and the first portion, and a second cross sectional area is defined downstream from {TAIL ~ the first cross sectional area} 
The impeller chamber includes a variable area wherein { HEAD ~ a first cross sectional area } is defined between the radially outer surface and the first portion , and a second cross sectional area is defined downstream from { TAIL ~ the first cross sectional area }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL