When designing of rotary-screw propulsion units
of snow and swamp-going amphibious vehicles it
should be considered that:
1. The efficiency of using of input power for full-
submerged Archimedes screws of RSP in
mooring mode and in typical range of moving
modes is one-third of that of propellers with the
same diameter.
2. The maximum efficiency of RSP Archimedes
screws in travelling modes realises in the
advance ratio range 0.6β¦1.0 (the higher values
conforming to better overwater characteristics
correspond to larger helix angles). When
advance ratio is less than 0.5 Archimedes screws
have non-typical for propellers reduction of
thrust coefficient because of increasing of
resistance of massive hub during growing of
induced velocities.
3. The area of induced velocities along the
Archimedes screw (according to the result of
analysis of visualization patterns) which are 10
and more percent greater than velocity of
approaching flow has diameter equal to
1.1β¦1.2 diameters of Archimedes screw. To
reduce negative effects of interaction between
Archimedes screw and amphibia hull it is
necessary to locate Archimedes screws of RSP
at the appropriate distance from the hull.
5 CONCLUSIONS
Archimedes screws of existent RSP perform in
complex interaction with hull and appendages of
amphibia and between each other, moreover, the
semi-submerged mode is peculiar to snow and
swamp-going amphibious vehicles. The aspects
pointed require special research, nevertheless, the
performance curves of Archimedes screws in open
water received allow to determine the maximum
speed of afloat motion in the early stages of designing
when engine power and geometrical parameters of
Archimedes screws are set by land performance
conditions, and to correct these characteristics to
improve overwater performance.
ACKNOWLEDGEMENTS
The results of the given study have been obtained
with financial support of the grants of the President of
the Russian Federation β MK-336.2022.4.
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