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Open water diagram Efficiency, Propeller-hull interaction, Quality
indexS i ll i Systematic propellers series
Propeller design through series◦ Choice of Propeller D n Ae/A0 Z◦ Choice of Propeller D, n, Ae/A0, Z
Practise Exam◦ Wo 5 okt 7e uur Zaal E vraag 1 Weerstands◦ Wo 5 okt, 7e uur Zaal E, vraag 1 – Weerstands
berekening◦ Wo 12 okt, 7e uur Zaal E, vraag 2 – Schroef
b kberekening
Lift
Angle of
attack
LiftL
ThrustT
Resultingforce
Rattack
vAAdvance velocity
T
pitch angle
velocitywatercircumferential speed
of bladevt=0 7 n D
DragD
Torque forceQ/r
pitch angle
vt 0.7 n DD
From lecture mt219 Marine Engineering – Peter de Vos
RVP2
SED
D
RVPP Qn
1 12 1
At T Vw Qn
2 5
2 4
1 11 2
AVt T n Dw nD n D Q
2T
OQ
K JK
1 2H
T QJ K K
w nD n D Q
R
K
,
, , ,
, Thrust Identity2 2
Q OT TO
Q B Q B Q O
KK KJ JK K K
, , Torque Identity
R
T B T OT K KK J J
, ,
, Torque Identity2 2
R
OQ B T O QK K K
Definition of Quality Index
OQI
Ideal efficiency comes from Actuator Disk consideration on axial energy losses
I
consideration on axial energy losses2
I 1 1I
TC
Wageningen B series Kaplan Series (M)AU Series
Large BAR/Pitch/Blade number range
Max efficiency and opt. P/D can be read directly once Bp is known!
Independent variables KT and KQIndependent variables KT and KQ
• Use KQ/J3 when power is knownUse KQ/J when power is known to determine operating point J
• Use KT/Jx when thrust is known to determine operating point J
• Any 2 of 3 variables in J should be known to determine third from
di i l ki i tnon dimensional working point
Operating point???
2 22 2 2
2 2 4 2 2 2T
TA A
K T n D TK J J JJ n D V D V
Constant en bekend
Max Diameter fixed by afterbody
D i i f i ll diDetermination of optimum propeller diameter
O ti d d i d l it Optimum depends on required velocity, thrust and rpm
Optimum rarely lies on the top of an open Optimum rarely lies on the top of an open water curve
Optimum can be as low as 35-40% for Opt u ca be as o as 35 0% ocertain choices of propulsion
