Proceedings Volume Cover
THE SOCIETY OF NA~AL ARCHITECTS AND MARINE ENGINEE  
601 Pavoma Avenue, Jersey City NJ 01  
,
RS  
306  
Paper to ~e presented at the Propellers , Symposium  
88  
Virginia Beach, Virginia, September 2 •  
,
'
0
21 1988  
Hyd~odynamic Aspects of Propeller/Stator  
D
No. 3  
es1gn  
J. E. Kerwin A  
· t M  
Massa h  
'
sso?,a e ember, W. B. Coney, Student Member and C-Y Hsin Visitm  
c usetts Institute of Technology, Cambridge, MA  
'
'
A bstract  
A
theoretical meth d - .  
od ,ror etermmmg opt1mum circula-  
.
.
.
_
t
ion d1srib t·  
r
f
d
u ions ,or propeller/stato combinations and  
r
or etermin ng the t'  
i
r
I • , •  
.
1rcum1eren 1a variation m c1rcula-  
t
10n for no  
·
·
.
n-ax1symmetr1c stators is presented. Com-  
parisons of th • •  
t·  
I
eore 1ca pred1ct10ns and water tunnel  
measurement ·  
r
·
b
h"  
s are given ,or a given propeller operating  
e ind an ax·  
·
Th  
.
i
symmetric and a non-axismmetric stator.  
eoret1cal  
·
.
comparisons are made between a hypothet-  
designed to operate without stator, and  
°Ptimum propeller/stator design. This comparison  
~cna  
l
pr~pelle  
r
a
1
Inc udes  
d"  
1
·
.
.
pre  
ct1ons of efficiency, uns teady loading and  
cav1tat1on.  
1
I
ntro duction  
lt is  
II  
we known that the employment of stators up-  
Figure 1: Computer depiction of a pre-swirl sta•  
st  
r
eam  
o
d
.
.
fi  
r
ownstream of a propeller, as illustrated Ill  
gure 1, can esult in a reduction of rotational energy  
~s~es, and therefore higher propulsive efficiency. In ad-  
tor/propeller system.  
r
1
d
1t1on  
a
.
.
th . '  
non-ax1symmetnc upstream stato  
e inflow to downstream propeller in such a way that  
eady forces and cavitation is reduced. Both these  
r can alter  
There are two distinct steps in this process. The  
first is to determine the optimum radial distribution of  
circulation on the propeller and stator blades, and to  
determine the circumferential variation in stator circu•  
lation distribution to achieve a particular induced wake  
field in the plane of the propeller. The second step is  
a
t
S
un  
c;  
n
cepts are far from new, and an interesting account  
0
.
many of the past patent disclosures in this field is  
g~ven by Larimer, et al /13]. Yet, in spite of this knowl•  
ge, the emp ~yment of stators in ship propulsion is  
e
l
to determine the geometry of the propeller and stator  
blades such that the desired circulation distribution is  
rare. This is in contrast to the field of turbomachinery,  
Where multiple stages of fixed and rotating blade rows  
are generally employed.  
achieved.  
The first step can be treated within the framework of  
.
If  
induced losses are small to begin with, which  
lifting-line theory, and a procedure for optimizing multi•  
component propulsors was given by the present authors  
in 1986 [6). This theory is extended in the present paper  
to include an approximate representation of the hub and  
is true for li  
g
htly and moderately oaded marine pro•  
l
Pellers, the potential gain which can be achieved by  
c'.11ploying stators is also small. In that case, it is not ob•  
vious whether or not the viscous losses of the stator can  
its associated pressure drag, and the circumferentiall  
varying velocity field induced by non-axisymmetricall  
y
y
~e overcom  
e
by the reduction in induced drag. In fact,  
is probably safe to say that unless the prop ller/stato  
comb nation is properly designed, the answer will be no.  
While the ability of non-axisymrnetric stator to  
It  
.
e
r
loaded stators.  
A vortex lattice lifting-surface code for the analysis  
of non-axisymmetric stators was developed by Hsin, and  
i
a
a lter circumferential variations in the propeller inflow  
has been understood for a long time, theoretical design  
methods for achieving this goal have not been available.  
the  
f
undamentals of this procedure are presented here.  
This work, in combination  
w
ith existing propeller design  
J-1