At large pre-swirl,the flow loss induced by the inlet guide vane(IGV)usually degrades the economy of the regulation scheme.Aiming at reducing flow loss at large pre-swirl,the sweep angle at the leading edge of the IGV is changed in forward direction relative to the shroud line.The traditional shape of the shroud of the inlet pipe connecting with the IGV is modified to the cone.The secondary flow initiated within the improved design overcomes the considerable hub flow separation caused by the centrifugal for...