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NASA
Technical
Paper
3675
A Survey
of Theoretical
and
Experimental
Coaxial
Rotor
Aerodynamic
Research
1997
Colin
P.
Coleman,
Ames
Research
Center,
Moffett
Field,
California
National
Aeronautics
and
Space
Administration
Ames
Research
Center
Moffett
Field,
California
94035-1000
Contents
Page
List
of Figures
...........................................................................................................................................................
V
Nomenclature
............................................................................................................................................................
vii
1
Summary
....................................................................................................................................................................
Introduction
...............................................................................................................................................................
1
Definitions
................................................................................................................................................................
2
2
Research
in the United
States
of
America
................................................................................................................
2
NACA
Langley
Research
Center
......................................................................................................................
4
De Lackner
Helicopters,
Inc ..............................................................................................................................
5
Sikorsky
Aircraft
...............................................................................................................................................
Research
in Russia
....................................................................................................................................................
7
13
Research
in Japan
......................................................................................................................................................
Hover
.................................................................................................................................................................
13
18
Forward
Flight
...................................................................................................................................................
19
Research
in the United
Kingdom
..............................................................................................................................
21
Research
in Germany
................................................................................................................................................
Conclusions
...............................................................................................................................................................
22
References
.................................................................................................................................................................
23
iii
List
of
Figures
Page
1
1
Henry
Bright's
1859
coaxial
design
patent
(ref.
1) ..........................................................................................
3
2
Scale
effect
on rotor
1 performance
at 327
ft/sec,
H/D
= 0.093.
Lines
drawn
through
data
(ref.
3) ...............
3
3
Effect
of solidity
on
rotor
of merit
(ref.
3) ......................................................................................................
4
Comparison
of theoretical
(solid
line)
and
experimental
static-thrust
performance
of rotor
2,
H/D
= 0.080
(ref.
3) .........................................................................................................................................
5
Experimental
results
and
equivalent
solidity
single
rotor
theory
for level
flight,
o(coaxial)
= 0.054,
_(single)
= 0.027,
H/D
= 0.093
(ref.
4) ............................................................................................................
6
Schematic
of the
advancing
blade
concept
(ref.
7) ..........................................................................................
7
Comparison
of theoretical
and
experimental
static-thrust
performance
of model
ABC
rotor,
H/D
not reported
(ref.
7)
..................................................................................................................................
8
Effect
of rotor
separation
on
ABC
performance
prediction
(ref.
8) ................................................................
9
Underestimation
of ABC
rotor
inflow
at low
speed
(ref.
11) ..........................................................................
10
Flight
test
rotor
of merit
for XH-59A
in OGE
hover
(ref.
13) ........................................................................
11
Induced
power
correction
coefficient
vs. blade
linear
twist
for various
taper
ratio
values
(ref.
26)
...............
12
Coefficients
kT and
kpr
vs.
blade
taper
ratio
(ref.
26) .....................................................................................
13
Comparison
of single
rotor
theory
(ref.
26)
with
experimental
results
(ref.
3) as reported
in
8
reference
31 ......................................................................................................................................................
10
14
Comparison
of the
coaxial
with other
helicopter
types
(ref.
31) ......................................................................
10
15
Coaxial
rotor
in a wind
tunnel
(ref.
27) ............................................................................................................
10
16
Areas
of "unsteady
flapping"
motion
for
single
and
coaxial
rotors
(ref.
34)
..................................................
11
17
Ka-32
blade
separation
distance
as a function
of advance
ratio
(ref.
34)
........................................................
11
18
Calculated
velocity
field
for the
vortex
ring
condition,
H/D
= 0.10,
v = 0.2
(ref.
28)
....................................
19
Calculated
velocity
field
for edgewise
flow
in longitudinal/vertical
plane,
H/D
= 0.10,
_
= 0.10
11
(ref.
28)
............................................................................................................................................................
12
20
3/rev
vertical
vibration
of the
Ka-25
at the
center
of gravity
(ref.
33)
............................................................
12
21
Coaxial
rotor
phasing;
(a)
ULYSS-6
solution,
(b) flight
test
solution
.............................................................
12
22
3/rev
vertical
vibration
of the Ka-50
at an unspecified
location
(ref.
33) ........................................................
12
23
Effective
increase
of coaxial
rotor
disc
area
(ref.
32) ......................................................................................
24
Experimental
results
for coaxial
and
equivalent
solidity,
single
rotors
in hover,
D = 8.2
ft (2.5
m),
12
H/D
not reported
(ref.
32)
................................................................................................................................
13
25
Comparison
of overall
helicopter
efficiencies
(ref.
32) ...................................................................................
13
26
National
Defense
Academy
experimental
apparatus
(ref.
39) .........................................................................
27
Tip
vortices
from
both
the
upper
and
lower
rotor
were
seen
to have
a faster
axial
speed
when
14
compared
to Landgrebe's
predictions,
H/D
= 0.105
(ref.
39) ..........................................................................
14
28
Effect
of mutual
interaction
on
rotor
performance
in hover,
H/D
= 0.132
(ref.
40) ........................................
15
29
System
hover
performance,
H/D
= 0.132
(ref. 40)
..........................................................................................
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