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National Advisory Committee for Aeronautics, Technical Notes - Comparative Performance of a Powerplus Vane Type Supercharger and an NACA Roots Type Supercharger

This report presents the results of tests of a Power~
plus supercharger and a comparison of its performance with
the performance previously obtained with an H.A.C.A. Roots-
type supercharger. The Powerplus supercharger is a posi—
tive displacement blower of the vane type having mechanic—
ally operated vanes, the movement of which is controlled
by slots and eccentrics. The supercharger was tested at
a range of pressure differences from 0 to 15 inches of mer-
cury and at speeds from 500 to 2,500 rapom. The pressure
difference across the supercharger was obtained by throt-
tling the intake of a depression tank which was interposed
in the air duct between the supercharger and the Durley
orifice box used for measuring the air.

The results of these tests show that at low pressure
differences and at all speeds the power required by the
Powerplus supercharger to compress a definite quantity of
air per second is considerably higher than that required
by the Roots. At pressure differences from 10 to 14 inches
of mercury and at speeds over 8,000 rgp.m. the power re—
quirements of the two superchargers are practically the
same. At a pressure difference of 15 inches of mercury or
greater and at a speed of 2,500 r.p.m. or greater the per—
formance of the Powerplus supercharger is slightly better
th that of the Roots. Because the Powerplus.supercharger

afiot be operated at a speed greater than 5,000 r.p.m. as
co pared with 7,000 r.p.m. for the Roots, its capacity is L
approximately one—half that of the Roots for the same '
bulk. The Powerplus supercharger is more complicated and .
less reliable than the Roots supercharger.

The experimental work in this country on aircraft en—
gine superchargers has been confined principally to the
development of the centrifugal and the Roots—type super~
chargers. Little attention has been given -to the devel—
opment of either’the reciprocating or the vane—type super—
chargers, because of their greater weight, bulk, and com—
plicated operating mechanism.