SPECIAL PROPULSION
SPECIAL PROPULSION
YACHTS & LEISURE
WHAT ARE THE OPTIONS AND WHAT ARE THE BENEFITS?
Tom van Terwisga and colleagues The quest for efficiency and comfort
or
Fighting Swirl and Vibrations
2
CONTENTS
• Do we understand all forms of propulsion?
• Which balance are we looking for?
Which balance are we looking for?
•
Efficiency, comfort, safety, wear
• The quest for efficiency
• The quest for comfort
• Where are we and where are we heading?
3
Do we understand all forms of
propulsion?
4
FORMS OF PROPULSION
• Propeller propulsion
• Bio inspired propulsion
• Flapping fins
Fl
i fi
• Pulsed jets (e.g. squid)
• Wind driven propulsion
• Sails
• Flettner rotor
Turbo sails (Cousteau foundation)
• Turbo sails (Cousteau foundation)
5
~ 1830 ‐ WHO INVENTED THE SHIP’S PROPELLER
James Watt, in 1770, wrote: "Have you ever considered a spiral oar?" Joseph Bramah, in 1785, patented the idea of a Joseph
Bramah in 1785 patented the idea of a
"screw propeller", but never tried it in practice. The Austrians have statues to Joseph Ressel, whom they claim as the inventor (see below). (
)
Various people took out patents in England and America from 1794 onwards, though nothing
America from 1794 onwards, though nothing practical was achieved. Richard Trevethick, in a 1815 patent, describes the screw propeller with considerable minuteness. ll
ith
id bl
i t
John Swan was heralded the practical inventor, after y p g
a trial boat driven by a spring, in 1824. And so on. . .
6
Gravestone of James Steadman (1790‐1865)
BIOMIMETIC FORMS OF PROPULSION
7
From Raspa et al., Universite Paris Diderot, EPL 2012
FLAPPING FIN PROPULSION
Container feeder with conventional propeller propulsion and modified hull
propeller propulsion and modified hull for flapping foil propulsion (Vermeiden et al. ONR symposium, 2012)
8
FLAPPING FIN PROPULSION
Model test set‐up in MARIN
test set‐up in MARIN’ss DWB (Vermeiden et al. ONR DWB (Vermeiden et al ONR
symposium, 2012)
9
EFFICIENCY OF FLAPPING FOIL PROPULSION
100%
η
Reference Ct value for container ship
90%
Efficiency
80%
70%
CT
1.95 < J < 4.75
0.15 < k < 0.37
60%
50%
0
0.05
0.1
0.15
0.2
0.3
J = 55.883
Jc
883
J = 44.762
Jc
762
J = 44.000
Jc
000
Ideal efficiency
Reference Ct
Benchmark
Efficiency at 3 values of JC .
AR = 5.2, Average–chord / Stroke
52 A
h d / St k = c/D
/D = 0.228 0 228
(Vermeiden et al. ONR symposium, 2012)
10
0.25
0.35
0.4
Thrust coefficient
Thrust coefficient
DESIGN OF PROPELLERS – LIMITS?
from 65 to 90 %
efficiency?
where are the
limits?
11
Which balance are we looking for?
12
Goal:l
G
• optimize propellers using genetic algorithms coupled to a panel code (PROCAL)
• multi objective and multiple conditions
Approach
• Build strategies and automate the design process
• Find the margins in your current design Find the margins in your current design
• Optimize 3D propeller geometry and sections
13
Noisse
PROPELLER OPTIMIZATION
Finding the Trade
Finding
the Trade‐off
off between efficiency and cavitation nuisance
Efficiency
THE WAGENINGEN C SERIES
C4‐40 some 5‐7% better than B‐
series?
14
The quest for efficiency
15
ENERGY LOSSES
• Axial kinetic energy losses
• Rotational or Transverse losses
• Viscous losses
Viscous losses
• Non‐uniformity losses
16
RELATIVE ENERGY LOSS TERMS FOR OPEN PROPELLERS
17
PRINCIPLE OF ENERGY BALANCE CONSIDERATIONS
Power added to wake = kinetic energy losses + pressure losses + heat
PD 

AWP
19
1
2
2
2
  uxWP
 U 02   urWP
 u2WP  uxWP rdrd    p  p0  uxWP rdrd  dissP
AWP
20
THE EFFECT OF A PRESWIRL STATOR ON HUB VORTEX
Propeller without PRE‐STATOR
21
Propeller with PRE‐STATOR
HIGH EFFICIENCY MOTORYACHT SAVANNAH
Design and built by FEADSHIP
‐
‐
‐
Larger propeller diameter (5%)
Contra rotating propellers
Total propulsive efficiency gain of some 10%
of some 10%
22
The quest for comfort
23
RELEVANCE OF PRESSURE FLUCTUATIONS
TYPICAL HULL PRESSURE AMPLITUDE SPECTRUM (FERRY)
BASICS OF PRESSURE FLUCTUATIONS
•
Risk of vibration hindrance often assessed through measurement of hull pressures
through measurement of hull pressures
•
Complicated physics of which mostly only the end result is quantified
end result is quantified
•
Dynamics of sheet cavitation and vortex cavitation governed by wakefield and cavitation governed by wakefield
and
propeller design
COMPUTATIONAL CAPABILITY
Thus far limited to sheet cavity dynamics
Acoustic diffraction code
(BEM)
Propeller flow code
(BEM
Viscous flow around
ship (RANS method)
27
PROCAL COMPUTED PRESSURE FLUCTUATIONS
28
EXAMPLES OF EROSION - PROPELLERS
Where are we?
and where are we heading?
30
SUMMARY
• A propeller is an efficient means of propulsion, but…
• The art is in finding the delicate balance between efficiency, comfort and wear
• Developments in propeller design aim to better optimize D l
t i
ll d i
i t b tt
ti i
toward the delicate balance
• Safety margins against cav. Erosion and vibrations are typically taken smaller these days
• Benefits are looming in larger propeller diameters and/or Energy saving concepts that reduce swirl losses
gy
g
p
• Alternative propulsors, such as fin propulsion and wind driven propulsion, offer ways to further reduce fuel consumption
li
ff
t f th
d
f l
ti
31
THANK YOU …
… for your attention.
We would be most grateful if you could give your comments on our development strategy
comments on our development strategy.
As only together can we keep our Leading Edge in th
the world market place!!!
ld
k t l !!!
32