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Propeller engine problem:
Experts in marine propellers and ship propulsion explain that cavitation erosion is caused by the traveling
of bubbles around the surface of blade aerofoil. When these bubbles collapse, they generate pressures that
are harmful to the surface of the blades and at the same time these bubble turn into smaller bullets
usually called microjets whose speed is very very high. When the microjets hit or travel along the surface
of the propeller blades in very high pressure, they cause erosion on the blade surface. Continuous
microjets impacts (or also called (bombardment) of the bubbles on the surface of the blades of the
propellers is the cause of fatique failure of the blade surface that triggers the beginning of propeller
erosion.
Marine air pollution why so bad?
It is an indisputable fact that marine diesel engines contribute significantly to airpollution that damages the environment as well as harms public health. The mainreason for marine engines propagating significant air pollution is because they burn thelowest grade of diesel fuel. Diesel engines are used widely as power sources primarilydue to their high thermal efficiency, high fuel economy, and durable performance.However, in the process they emit large quantity of toxic gases and solid substanceswhich significantly pollute air.
Image Credits : Cargo Ship polluting the airfrom cleantechlawandbusiness (http://cleantechlawandbusiness.com/cleanbeta/wp-
content/uploads/2009/12/large-cargo-ship-pollution-smoke-photo4.jpg)
What are these toxic solids and harmful gases?
The marine diesel engine's toxic emissions mainly consists of the following components
y Smogy Particulate matter
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y Global warming gases
Smog forming emissions
Nitrogen oxide (NOx)
NOx is formed when nitrogen combines with oxygen inside the extremely hot and highlypressurized chambers of marine diesel engines. This NOx combines with hydro carbonsin the atmosphere forming ozone which produces smog. Ozone is good when it is highin the stratosphere, where it protects earth from the ultraviolet rays of the sun, but whenozone is dangerously low in the atmosphere it traps heat and badly affects humanhealth.
Sulfur dioxide (SOx)
SOx is formed when unburned fuel in diesel engines produces small particles of sulfur
and carbon, which together contribute to smog. SOx is directly related to the sulfurcontent in fuel, which when combined with water vapor, results in acid rain.
Chloroflorocarbons (CFCs)
Emissions of CFCs from the global shipping fleet is estimated at 3,000-6,000 tons orapproximately 1 to 3 percent of yearly global emissions. CFCs are also extremelypoisonous as far as air pollution is concerned.
Particulate matter
Particulate matter consists of tiny solid particles and liquid droplets which consist ofsoot, dust, salt, acid, and metals that are invisible to the human eye but that appear as acloud or fog. These particles are less than 10 microns in diameter and one seventh thethickness of human hair. Diesel contains 60 to 200 times more small particles thanthose in gasoline engine exhaust.
Global Warming gases
Gobal warming gases includes methane, nitrogen oxide and the cruelest culprit - carbondioxide. All these are produced from the burning of fossil fuels. These gases when inatmosphere trap heat and cause global warming and climate change. It has been
predicted that global warming will lead to dilapidated environmental concerns in thenear future if adequate steps to reduce emission of toxic gases is not taken.
To find out about the regulations and steps that needs to be taken in order to reduceemissions from marine diesel engines read cold ironing techniques.
References
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Marine diesel engines and air pollution : Blue water networks
www.nescaum.org
www.earthscape.org
Read more: http://www.brighthub.com/engineering/marine/articles/24522.aspx#ixzz1EJOfRc I7
y Propeller Induced VibrationPropeller induced vibration can be caused by inaccuracies in pitch, camber andsection shape. Prop Scan allows us to see and remove these inaccuracies. Thisresults in a smoother, more efficient and often faster propeller. Bring in your
propellers for a free examination, we will need information from your vesselperformance form.
y Tip ErosionAbrasives present in the surroundings often cause tip erosion. Tip erosion reducesthe overall diameter and performance of your propeller. Come and visit us, bringyour propeller and your vessels performance form with you and we will show youhow we will restore your propeller to better than new.
y Propeller CavitationPropeller cavitation causes vibration, noise and serious damage to your propeller.Can it be avoided? Cavitation problems must be split into two categories. 1 Propellerinduced cavitation. 2 Vessel induced cavitation i.e. cavitation caused by appendages,hull shape and application.If the cavitation is propeller induced then we can measure your propeller using theProp Scan inspection system and show you the cause of it. What do we need? Weneed your propeller and your vessel performance form to complete your freepropeller assessment.
y Singing PropellerSome propellers produce a high pitched noise at certain points between idle speedand full RPM. At the best of times this can be annoying, if this point lies spot in themiddle of your cruising RPM it will be intolerable. Help is at hand.We will need your propeller and your vessel performance form, with this informationwe will be able to remove the noise from your propeller.
y Propeller induced engine overloadIf you are the proud owner of a beautiful yacht but you are a little embarrassedabout the black smoke that is emerging from its transom, then it's time to dosomething about it. Overloading your engine will vastly reduce the overall life of thisengine and the black smoke can seriously affect your boating pleasure.You dont have to put up with it anymore. Bring in your propellers along with yourvessel performance form and we will tell you, with no obligation to you, what needsto be done to overcome your problem.
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y Propeller not loading the engineWhen an engine revs higher than its recommended maximum RPM, it does notdevelop its maximum Horsepower. In other words you are not using your engine atits utmost capabilities. Most of the time this means there is additional speed to begained. How much can we gain? Let us provide you with a free assessment. We willneed your propeller and your vessel performance form to complete your inspection.
y Propellers not synchronizedMany twin screw vessels have badly synchronized propellers in other words the portand starboard engine are not loaded equally at equal RPM. This is caused by pitch,camber and section shape differences between the two propellers. Can it beresolved? You can bring in your propellers and we will show you what the differenceis between the port and the starboard propeller. At the same time we will advise you,at no cost to you, what it takes to resolve your propeller problem. We also require acompleted vessel performance form to complete your propeller analysis.
y Reversing problemsReversing qualities are influenced by the position of your propeller and the section
shape on the suction side of your propeller. If there is a suction section shapeproblem, Prop Scan will locate it! Let us scan your propeller, free of charge, andshow you how we propose to resolve your problem.
y Excessive Fuel Consumption
Does your boat consume more fuel than the recommended amount?
The reason for greater fuel consumption is having a low classedpropeller. On average, an ISO Class I propeller uses between 5-10%
less fuel than a Class III propeller!
y Poor propeller performancePoor propeller performance can be caused by MANY different reasons. Incorrect
propeller selection, poor propeller accuracy etc. etc.. What ever it is we will help youfind it. Complete the vessel performance form, take your propeller and come andvisit the closest Prop Scan shop to you. We will assess your propeller at no charge toyou and give you our professional opinion on how his problem can be resolved.
y Other ProblemsThere are many more propeller problems that we could address on this site, if yousuffer a problem not mentioned on this page, contact your nearest Prop Scan shop.
Fuel Consumption
For safety reasons, learn how far a tank will take you
The only way you can estimate how far a tank of fuel will take you is if you know the fuel-consumption figures foryour engine. Following are some general rules:A marine diesel engine consumes about 1 gallon per hour (GPH) forevery 18 hp generated (a 27 hp engine running at two-thirds capacity will generate 18 hp).Another way tocalculate the amount of diesel fuel used in 1 hour is to multiply the horsepower being used by 0.055.Four-strokeinboard gasoline engines need about 1 GPH for every 10 hp generated. Alternatively, you can estimate the numberof gallons consumed in 1 hour by multiplying horsepower used by 0.1.Gasoline outboard motors vary so much in theduties they are required to perform that no one formula is accurate for all; however, all outboards use moregasoline per mile than inboards. Furthermore, two-stroke out-boards have a much greater thirst than four-strokes.Individual fuel-consumption figures must be arrived at by careful measurement of fuel used over a measureddistance, preferably on a there-and-back run to cancel out the effects of current.It is fairly safe to assume,however, that an older two-stroke gasoline outboard will be 10 to 50 percent thirstier than an inboard gasoline
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engine of the same horsepower. Newer fuel-injected two-stroke outboards show a considerable improvement infuel-consumption figures, however.The few diesel outboard engines available are mainly used by professionalinshore fishermen. Amateur sailors tend to avoid them because of their weight, vibration, and high initial expense,but their miserly fuel consumption gives small boats a long range and their heavy engineering ensures long life andreliability.Most marine engines, gasoline or diesel, are designed to run continuously at about 70 to 80 percent oftheir maximum output. Diesels, in particular, thrive on hard work and tend more toward the top of the range.Therule of thumb about fuel reserves is that you should plan on using one third of your total capacity to get where
youre going and one third to get back; the other third is your emergency reserve.See also Fuel Economy; FuelCapacity; Fuel Weight; Wasted Fuel.
Read more: http://www.answers.com/topic/fuel-consumption-1#ixzz1EJTXzPec
Ajetboat is a boat propelled by a jet of water ejected from the back of
the craft. Unlike a powerboat ormotorboat that uses apropellerin the
water below or behind the boat, a jetboat draws the water from under the
boat into a pump inside the boat, then expels it through a nozzle at
the stern.
Jetboats were originally designed by Sir William Hamilton(who
developed a waterjet in 1954) for operation in the fast-flowing and
shallow rivers ofNew Zealand, specifically to overcome the problem of
propellers striking rocks in such waters.
Previous attempts at waterjet propulsion had very short lifetimes,
generally due to the inefficient design of the units and the fact that theyoffered few advantages over conventional propellers. Unlike these
previous waterjet developments, such asCampini's and the Hanley
Hydrojet, Hamilton had a specific need for a propulsion system to
operate in very shallow water, and the waterjet proved to be the ideal
solution. From this the popularity of the jet unit and jetboat increased
rapidly, and through further developments it was found the waterjet
offered several other advantages over propellers for a wide range of
vessel types, and as such waterjets are used widely today for many high
speed vessels including passenger ferries, rescue craft, patrol boats andoffshore supply vessels.
Jet boats are highly maneuverable, and many can, from full speed, be
reversed and brought to a stop within little more than their own length, in
a maneuver known as a "crash stop". The well known Hamilton turn or
"jet spin" is a high speed manoevre where the boat's engine throttle is
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cut, the steering is turned sharply and the throttle opened again causing
the boat to spin quickly around with a large spray of water.
There is no engineering limit to the size of jet boats, though the validity
of their use depends a lot on the type of application. Classic prop-drives
are generally more efficient and economical at low speeds (up to about
20 knots) but as boat speed increases beyond this the extra hull
resistance generated by struts, rudders, shafts, etc., means waterjets
are more efficient in the 20-50 knot range. Also, in situations with very
large propellers turning at slow speeds (such as tug boats), the
equivalent size waterjet would be too big to be practical. For these
reasons the vast majority of waterjet units are installed in high-speed
vessels and in particular situations where shallow draught,
maneuverability, and load flexibility are main concerns.The biggest jet-driven vessels are found in military use or the high speed
passenger/car ferry industry. South Africa's Valour class
frigates(approximately 120m long) are the biggest jet-propelled vessels
so far. Even these German-built vessels are capable of performing
"crash stops".
Contents
[hide]
1 Function
2 Applications
3 Drawbacks
4 Notes
5 See also
6 External links
[edit]Function
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Jetboat on the Rogue River by Grants Pass, Oregon.
A conventional screw propeller works within the body of water below a
boat hull, effectively "screwing" through the water to drive a vessel
forward by generating a difference in pressure between the forward and
rear surfaces of the propeller blades and by accelerating a mass ofwater rearward. By contrast a waterjet unit delivers a high pressure
"push" out the stern of a vessel by accelerating a volume of water as it
passes through a specialised pump mounted above the waterline inside
the boat hull. Both methods yield thrust due to Newton's third law
every action has an equal and opposite reaction.
In a jetboat, the waterjet draws water from beneath the hull where it
passes through a series of impellers and stators - known as stages -
which increase the velocity of the waterflow. Most modern jets are singlestage while older waterjets may have as many as three stages. The tail
section of the waterjet unit extends out through the transom of the hull
above the waterline. This jetstream exits the unit through a small nozzle
at high velocity to push the boat forward. Steering is accomplished by
moving this nozzle to either side, or less commonly, by small gates on
either side that direct the jetstream. Because the jet boat relies on the
flow of water through the nozzle for control, it is not possible to steer a
conventional jet boat without the engine running.
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A jetboat on Shotover Canyon in New Zealand, the country for which jetboats were originally invented.
Unlike conventional propeller systems where the rotation of the propeller
is reversed to provide astern movement, a waterjet will continue to pump
normally while a deflector is lowered into the jetstream after it leaves the
outlet nozzle. This deflector redirects thrust forces forward to provide
reverse thrust. Most highly developed reverse deflectors redirect the
jetstream down and to each side to prevent recirculation of the water
through the jet again - which may cause aeration problems - andincrease reverse thrust. Steering is still available with the reverse
deflector lowered so the vessel will have full maneuverability. With the
deflector lowered about halfway into the jetstream, forward and reverse
thrust are equal so the boat maintains a fixed position, but steering is still
available to allow the vessel to turn on the spot - something which is
impossible with a conventional single propeller.
Unlike hydrofoils, which use underwaterwings or struts to lift the vessel
clear of the water, standard jetboats use a conventional planing hull to
ride across the water surface, with only the rear portion of the hull
displacing any water. With the majority of the hull clear of the water,
there is reduced drag, greatly enhancing speed and maneuverability, so
jetboats are normally operated at planing speed. At slower speeds with
less water pumping through the jet unit, the jetboat will lose some
steering control and maneuverability and will quickly slow down as the
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hull comes off its planing state and hull resistance is increased.
However, loss of steering control at low speeds can be negated by
lowering the reverse deflector slightly and increasing throttle - so you
increase thrust and thus control without increasing boat speed itself. A
conventional river-going jet boat will have a shallow-angled (but not flat-bottomed) hull to improve its high speed cornering control and stability
while also allowing it to traverse very shallow water. At speed, jetboats
can be safely operated in less than 3 inches (7.5 cm) of water.
One of the most significant breakthroughs in the development of the
waterjet was to change the design so it expelled the jetstream above the
water line, contrary to many people's intuition. Hamilton discovered early
on that this greatly improved performance, compared to expelling below
the waterline, while also providing a "clean" hull bottom (i.e.: nothingprotruding below the hull line) to allow the boat to skim through very
shallow water. It makes no difference to the amount of thrust generated
whether the outlet is above or below the waterline, but being above the
waterline reduces hull resistance and draught. Hamilton's first waterjet
design had the outlet below the hull and actually in front of the inlet. This
probably meant that disturbed water was entering the jet unit and
reducing its performance, and the main reason why the change to above
the waterline made such a difference.
Queenstown, New Zealand, where jetboats are used extensively
foradventure tourism, claims to be the jetboat capital of the world, and
jetboats are very common for many coastal and riverine tourism
activities in the country, such as the Excitorin the Bay ofIslands.
[edit]Applications
USMC Expeditionary Fighting Vehicle. Note the bow, which is extended intohydroplaning position.
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Applications for jetboats include most activities where conventional
propellers are also used, but in particular passenger ferry services,
coastguard and police patrol, navy and military, adventure tourism
(which is becoming increasingly popular around the globe), pilot boat
operations, surf rescue, farming, fishing, exploration, pleasure boating,and other water activities where motor boats are used. Jetboats can also
be raced for sport, both on rivers and on specially designed racecourses.
Recently there has been increasing use of jetboats in the form ofrigid-
hulled inflatable boats and as luxury yacht tenders. Many jetboats are
small enough to be carried on a trailer and towed by car. Jetboating
Australia (http://www.jetboatingaustralia.com/) is a group of people with
jetboats, most of which can be towed on a trailer.
One very important feature of the jetboat is the fact that it has noexternal rotating parts; it is thus safer for swimmers and marine life,
though these can still be struck by the hull. The safety benefit itself can
sometimes be reason enough to use this type of propulsion.
In 1977 SirEdmund Hillary led a jetboat expedition, titled "Ocean to
Sky", from the mouth of the Ganges River to its source. One of the
jetboats was sunk by a friend of Hillary.[1]
[edit]Drawbacks
The fuel efficiency and performance of a jet boat can be affected by
anything that effects the smooth flow of water through the jet unit. For
example a plastic bag sucked onto the jetunit's intake grill can have quite
an adverse effect.
Another disadvantage of jetboats appears to be that they are more
sensitive to engine / jetunit mismatch compared to engine / propeller
mismatch in propeller driven craft. If the jetpropulsion unit is not well
matched to the engine performance, inefficient fuel consumption and
poor performance can result.
However, a jet propulsion unit that is well matched to the engine is more
fuel efficient that a propeller because it does not waste power by
throwing water radially. Normally, the engine in a jetboat is directly
coupled to the pump shaft eliminating the need for a gearbox and
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therefore eliminating any gearbox losses. Most propeller driven vessels
have gearboxes in which power is lost resulting in increased fuel
consumption and/or reduced performance. In my experience, a jet boat
will normally use about half the fuel that a boat of the same size does
which is propelled by an outboard motor at the same speed. The mainreason commercial ferries use jets is to reduce fuel consumption.
[edit]
Pump-jet
From Wikipedia, the free encyclopedia
This article includes a list of references, related reading or external links, but its
sources remain unclear because it lacks inline citations. Please improve this article byintroducing more precise citations where appropriate. (February 2008)
Typical 'jet ski' pump jet
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Rear view of pump-jet on a Mark 50 torpedo
A pump-jet, hydrojet, orwater jet, is a marine system that creates a jet ofwaterforpropulsion. The
mechanical arrangement may be aducted propellerwith nozzle, or a centrifugal pump and nozzle. The first
functioning man-made pump-jet engine was created by New ZealandinventorSir William Hamilton in 1954.
In the Ordovician period the first known cephalopods swam by a natural built-in reciprocating hydrojet.citation
needed
Contents
[hide]
1 Advantages
2 Disadvantages
3 Sources
4 See also
Advantages
Pump jets have some advantages over bare propellers for certain applications, usually relate to requirements
for high-speed or shallow-draftoperations. These include:
Increasing the speed before the onset ofcavitation, because of the raised internal dynamic pressure
High power density (with respect to volume) of both the propulsor and the prime mover(because a smaller,
higher-speed unit can be used)
Protection of the rotating element, making operation safer around swimmers and aquatic life
Improved shallow-water operations, because only the inlet needs to be submerged
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Increased maneuverability, by adding a steerable nozzle to create vectored thrust
Noise reduction, resulting in a low sonarsignature; this particular system has little in common with other
pump-jet propulsors and is also known as "shrouded propeller configuration"[1]
; applications:
submarines, for example the Royal NavyTrafalgar-class andAstute-class, the US NavySeawolf-class,
the French NavyTriomphantclass, and the Russian NavyBoreiclass.
modern torpedoes, such as the Spearfish, the Mk 48 and Mk 50 weapons.
Disadvantages
Can be less efficient than a propeller at low speed
More expensive
Higher weight in the boat because of entrained water
Will not perform well if the boat is heavier than the jet is sized to propel
Can suffer more easily from cavitation than a conventional propeller
Can become clogged with debris; e.g., seaweed[2
The Analysis of Intelligent Water-jet Propulsion System Optimization on Self-service
Gliding-hydrofoil Craft
WangGuo
Jiangsu University of Science and Technology
Zhenjiang, Jiangsu, China
E-mail:[email protected]
YangSonglin
Jiangsu University of Science and Technology
Zhenjiang, Jiangsu, China
E-mail:[email protected]
ChenPeng
Jiangsu University of Science and Technology
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Zhenjiang, Jiangsu, China
E-mail:[email protected]
AbstractIn this paper, the auther establish a model of
water-jet propulsion system for self-service gliding-hydrofoil
craft. A fuzzy logic controller is designed based on MATLAB
and SIMULINK. And simulation experiment is performed.
Experiment results show that the fuzzy logic controller is
useful and is affected by interference. And the less the
interference, the more balanced the effect is.
Keywords-self-service gliding-hydrofoil craft; water-jet
propulsio; fuzzy controlling; simulation
I. INTRODUCTION
In order to achieve unmanned control on modern ship an
excellent control system is much necessary, and only with it
the voyage performance can be insured and the task can be
managed. At present time, intelligent control thory has been
widely applied in every profession, for example, pilotless
aircraft, pilotless automobile and automatic generating line
and so on. But the application in modern ship isnt enough.
In this paper, the target is the fuzzy controller applied in the
intelligent propulsion system of self-service
gliding-hydrofoil.
Propulsion system of self-service gliding-hydrofoil
complicated enough needs repeated measuring and
amending in the design and in this process needs much effort
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of human being. The application of modern technology of
simulation can replace many actual tests. Modern
technology of simulation also can simulate some actual tests
which cant be done because of various reasons and
condition limits. Therefore its application improves the
efficiency greatly and reduces cost. Propulsion system and
self-service controlling simulation is a great important
application in the vessel dynamical system design.
Propulsion system of self-service gliding-hydrofoil is a
complex non-linear system and couldnt be analysed by
linearized theory. Now the technology of simulation could
reduces the test cycle and the costs and drops the experiment
condition and has good repetitiveness, therefore the
application of the technology of simulation is necessary.
The research on optimization design is divided into
on-line and off-line form. Off-line optimization is aimed at
an optimization problem: in the natural course of event
definiting the design variable and objective function and
limited condition and programing composition then
performing the program to get the optimizing results.
On-line optimization uses terrace optimization: through the
efficient optimizeation method and deploying optimization
parameter to achieve the on-line optimization-computat and
then to obtain the optimum relation. We can get the most
right answer in a short time with the optimized algorithm. In
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this paper, the writer will use the chaos optimized mothed to
obtain the most great controlling parameter of propulsion
system of self-service gliding-hydrofoil.
II. THE DESIGN OF THE VELOCITY CONTROLLING MODEL
FOR SELF-SERVICE GLIDING-HYDROFOIL
In this paper, the two-dimensional fuzzy controller is
used to control the velocity. At first, the senors collect the
real time velocity. Second, the real-time velocity is
compared with the target speed and then the speed variation
E and the varation rate EC are evaluated. Third, the CPU
computes the rotate speed controlled quantity and sends the
quantity to the propulsion system to achieve to control the
self-service propulsion system of gliding-hydrofoil at real
time.
With the above-mentioned introduction, we fix the E and
EC as the input variable and the pump speed n as the output
variable.
The formulas is as follow:
Input variable:
s
E = v0
v (1)
EC dv dt
s
= (2)
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Output variable: U = n and P (3)
In the formuals, v0 is the target speed and vs
is the
real-time speed and their unit is kn/s; n and P are the
propellers rotate speed and pitch and their units are r/s and
m.
The fuzzy control system builded by the fuzzy logic
toolbox in MATLAB is in Fig. 1:
2009 Second International Symposium on Computational Intelligence and Design
978-0-7695-3865-5/09 $26.00 2009 IEEE
DOI 10.1109/ISCID.2009.209
250Figure 1.The fuzzy controller based on the fuzzy logic toolbox.
In Fig. 1, Es basic field is [-1.2, 1.2] and the
unit is kn and the word set is {NB, NM, NS, O,
PS, PM, PB} standing for {negative big, negative
middle, negative small, zero, positive small,
positive middle, positive big}; ECs basic field is
[-1.2, 1.2] and the unit is kn/s and the word set is
{NB, NM, NS, O, PS, PM, PB}; Us basic field
is [-12, 12] and the unit is r/s and the word set is
{NBB, NBS, NMB, NMS, NSB, NSS, O, PSS,
PSB, PMS, PMB, PBS, PBB}. The membership
grade function of linguistic value is triangular
form membership function. The principle is
Mamdani principle. And the principle based on
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the experts experiencr in the TABLE
TABLE . THE PRINCIPLE OF FUZZY CONTROLLING OF PROPULSION SYSTEM.
NB NM NS O PS PM PB
NB PBB PBS PMB PMS PSB PSS O
NM PBS PMB PMS PSB PSS O NSS
NS PMB PMS PSB PSS O NSS NSB
O PMS PSB PSS O NSS NSB NMS
PS PSB PSS O NSS NSB NMS NMB
PM PSS O NSS NSB NMS NMB NBS
PB O NSS NSB NMS NMB NBS NBB
III. BUILDING THE PROPULSION SYSTEM
A. Building the simulation model for
propulsion system
The intelligent propulsion system of
self-service gliding-hydrofoil uses the fuzzy
controller to compare the target speed and the
real-time speed then provide the controlled
quantity rotate speed. Then main engine
regulates the rotate speed based on the speed
fuzzy controller gaven to achieve to turn the
pump and then achieving the control on
self-service propulsion system of
gliding-hydrofoil and pushing the self-service
gliding-hydrofoil at real time. The propulsion
system of sel-service gliding-hydrofoil is in the
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Fig. 2:
Figure 2.The propulsion system of sel-service gliding-hydrofoil.
Clock
Time Display
2
1
kec
ke
ku
Saturation
Fuzzy
Logic
Controller
Target speed
Actual speed
Memory1
Memory
Saturation 1
1
Deltan
Target speed
Y
Fuzzy controller
Md&Mp
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v0&vs
Engine
hydro-jet
propulsion system
target
speed
n
current
speed
MP n
n0 Md
vs
Y
YV
P
M
n
s
v
Rotate speed n
Input variable
EC U
E
251B. Building the mathematical model for
propulsion system
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1) The mathematical model for self-service
gilding-hydrofoil propulsion system
Sloving the problem mainly based on the
translation and rotation function:
Translation function:
s P t
mdv dt = T R (4)
Rotation function:
d P f
2 I dn dt = M M M (5)
In the function: m as the quality of ship; vs
as
the real-time speed; TP as the thrust force
produced by pump; Md as the torque producted
by main engine; MP as the torque absorption by
propeller; Mf
as the friction torque; Rt
as the
overall drag, divided into hydrofoil resistance and
hull resistance. Hull resistance can be divided
into friction drag and residual resistance and the
friction drag can be calculated by equivalent
plank theory and the residual resistance can be
calculated by similarity theory. The same to the
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hydrofoil resistance.
2) The mathematical model for the water jet
propulsion
The thrust force and the torque producted by
water-jet propulsion based on the water jet
propulsion theory is as follow:
Thrust force ( ) P a s
T = Q v v (6)
Torque M P
= PD
2n (7)
In the formuals: TP as the effective thrust; MP
as the torque absorption; as the water density;
va
as the spout speed; vs
as the real-time speed;
as the wake coefficient; ve
as the inducer speed
(ve=*vs
); n as the pump rotate speed.
Flow quantity
3
Q P
Q = K nD (8)
Actual speed = 2 + 1 + ( )
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2
s e
v gH v (9)
Pump head
22
H P
H = K n D (10)
Pump required power D P
P = QH / (11)
In the formuals: Q as the pump flow quantity;
DP as the pump diameter; KQ as the flow quantity
dimensionless coefficient; H as the pump head;
KH as the head coefficient; as the water head
loss coefficient and equalled to 0.2 in this paper;
PD as the power pump needed; as the water unit
weight; as the pump efficiency and generally
equalled to 0.8~0.85 and 0.85 is choosen in this
paper.
IV. THE SIMULATION RESULTS AND ANALYSIS
A. The interface of the simulation and
optimization system software
This software was built based on the
MATLAB program. It has fuzzy control system
and various kind of mathematical motheds. All
kind of high-speed unpiloted ships are loaded in
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the software, for example, gliding-hydrofoil craft
Mono-Hull HSC and wave piercing catamaran
etc simulation models. Its interface is simple and
convenient and commucates convenient. As
shown in Fig. 3:
Figure 3. High-speed ship intelligent propulsion system
simulation interface.
B. Optimization and simulation experiment
1) The ship form
In this paper, the ship form is a
gliding-hydrofoil in the optimization and
simulation process. Its parameters are as follow:
displacement is 84T; the WL is 26.458m; the
beam is 4.788; the draft weight is 1.386T. In
order to meet the needs of experiment model the
gliding-hydrofoil uses the water jet propulsion.
2) The experiment results and analysis
The simulation experiment results are in the
Fig.4 and Fig.5. In Fig.4, the initial speed is 49kn
and target speed is 47kn and its a downward
process. Though in Fig.5, the initial speed is 45kn
and the target speed is 47kn and its a upward
process.
There are four experiment results photo in the
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Fig.4 and Fig.5 and that separately stand for the
control efficient of20%, 15%, 10%, 0%
disturbance. In the Fig.4 process we can see the
control process gradually to stability and the
stable time approximately is 120s with no
disturbance. With the increasing degree of
disturbance, overshoots and stable time also
increases. In the Fig.5 process we can easily see
the control process also gradually to stability and
without disturbance the stable time is 120s and
the overshoots and the stable time changing with
the disturbance is the same as the Fig. 4.
Because of the fuzzy controller the control
effect is like above-mentioned. The intelligent
control of propulsion system is achieved through
the fuzzification and fuzzy reasoning and
fuzzification again process.
(a)20% disturbance
252(b)15% disturbance
(c)10% disturbance
(d)0% disturbance
Figure 4. Simulation experiment results(1).
(a)20% disturbance
(b)15% disturbance
(c)10% disturbance
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[1] Sheng Zhenbang and Liu Yingzhong, Ship Principle,
ShangHai: Shanghai JiaoTong University Press, the
first edition, May.2004,vol 1 and vol 2.
[2] Yang Songlin, The Methods and Application of
Engineering Fuzzy Theory, Bei Jing:National Defence
Industry Press, 1996.
[3] Gibbs and Cox Inc, Marine Design Mutual For
FiberglasR Reinforced Plarticr,1960, pp. 213302.
[4] Shen Fenghai, Liang Zhongde, Zhou Yihong and Gu
Hong, [Dissertation], The Design of High Speed
Water-jet Planing Boat, in Development and
Experimental, pp. 4064
[5] Dong Liang, Optimum Design of High-Speed Ships
Propulsive Performance and Simulation and
Optimization of Its Rapidity, in Shipbuilding of
China, vol,49, NO.3 Sep.2008, pp. 31950.
[6] KENNEDY J.EBERHART R.C. Particle Swarm
Optimization, [A], Proceedings Of The 1955 IEEE
Intema-tional Conference On Neural Networks [C]. Los
Angeles. USA: IEEE. 1995: 1942~1948.
[7] Middha, B.; Raj, V.; Gangwar, A.; Kumar, A.;
Balakrishnan, M.; Ienne, P. A Trimaran based
framework for exploring the design space of VLIW
ASIPs with coarse grain functional unitsA Trimaran
based framework for exploring the design space of
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VLIW ASIPs with coarse grain functional units . Dept.
of Comput. Sci. & Eng., Indian Inst. of Technol., Delhi,
India . 2-4 Oct. 2002
[8] Wang Lixiang, Water-jet and Water-jet Pump, in the
General Machinery, NO. 10, 2007, pp, 1215.
[9] Li Yan, Yang Songlin and Chen Shuling, The
Optimization of the Intelligent Water-jet Propulison
System of Wave Piercing Vessel, in Marine
Technology, NO. 1, 2006, pp. 1415.
[10] Wu Xiaoping and Xi Wei, Simulation on intemgent
propulsion system of gliding-hydrofoil craft, in
Ship Science and Technology, vol, 26, NO. 4 ,Aug.
2004, pp.1922.
[11] Yang Songlin, Research on the Tntegrated
Optimization Method of the Tntelligent Propulsion
System s Optimal Controls Parameters Combination of
Hydrofoil Craft with Controllable Pitch Propeller,
Zhenjiang. Jiangsu. China, Jiangsu University of
Science and Technology.2004
253
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Why consider jet propulsion for your boat? Just as the technology of cell phones, televisions, and clockradios are undergoing a transition from analog to digital, marine propulsion technology appears to bemoving quickly to offer alternatives to the venerable propeller. Just as today's digital technology isexpanding the potential of the entire electronics scene, jet propulsion is providing many new advantages inthe marine industry, from pleasure craft to offshore work boats.
What is marine jet propulsion? Basically, it is a function of differences in themass-flow of water. Water enters and exits a jet drive at differing velocities,power is converted to thrust via an impeller, and the thrust propels theboat. Steering right and left is accomplished by directing the system's exit
flow in one direction or the other, much like directing the thrust of asubmerged propeller-driven system. Forward and reverse motion isinfinitely controllable through a reverse deflector that simply diverts thethrust fore or aft.
Today's jet-drive technology provides recreational and commercial boaters with many practical benefits thatare not present with propeller-driven units. What are some of these benefits?Safety - Water skiers, swimmers, recreational and commercial divers are safe from the threat of injury (orworse) from turning propellers. There is minimal potential for damage to jet-driven boats from hittingfloating debris, and there are no propellers to foul on stray ropes or fishing lines. Jet-propelled boats simplyride over floats and lines attached to lobster and crab pots. Jet driven boats have expanded access toshallower waters, particularly in tidal areas. The potential for major drive damage from running aground, aswith submerged propellers, is eliminated.
Maneuverability - Jet-driven boats have excellent maneuverability, even at low speeds, because of vectored(directed) thrust. Whatever a situation requires, the needed amount of thrust can be directed fore or aft,port or starboard. Thrust is applied smoothly by control of the reverse deflector, an integral component ofthe unit. This vectored thrust affords jet-driven boats very responsive steering, ideal for control in narrowwaterways and avoiding other vessels. There is infinite control of fore and aft movement, even in severewind and sea conditions.
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Economy - Jet drives are easy on engines and transmissions. A jet drive, well matched to an engine and
hull, allows the engine to operate at optimum cruise throttle settings, thus providing better fuel economy. Instart-and -stop situations, (for example, water taxis, lobster and crab fishing boats), the engine is set atoptimum throttle, the transmission is left in forward, and all stopping, holding and accelerating is smoothlycontrolled with the reserving deflector. Basic maintenance consists of monitoring bearing oil levels andchecking for anode depletion. If service is required, many external parts can be owner-serviced in the water,
without hauling the boat (such work can often be done on a beach or rack which is exposed at low tide).This is especially beneficial if inspection or service is needed miles from a full service marina. If operated inrelatively clean water, many years of service may be expected from the encased impeller. End result: loweroperating costs.
Comfort - Compared to propeller-driven systems, jet drives greatly reduce on-board noise and vibrationlevels. Jet drives rotate at higher speeds than propellers, and the impellers are encased in precision-craftedhousings. Thus, vibration levels are much lower than with propeller-driven units. Considering that thrust isdeveloped within the jet itself and is transmitted directly to the hull, engines may be fitted with flexibleengine mounts to further reduce engine-generated.
Environment - Vessels with jet drives have much lower underwater noise signatures than vessels withpropellers. In addition to being a relevant consideration for military applications, this in an especiallysignificant factor where marine life and other environmental matters are concerned. Propeller-driven boatsare restricted in several areas of Florida because of potential harm to fragile coral. Along with being safer for
swimmers, the jet drive is also safer for marine life. The endangered West Indian manatee is a goodexample. Since 1976, more that 43% of manatee deaths were attributed to humans, most of them inboating related incidents, primarily from impact with underwater propellers. Manatees, if struck by jet-driven boats, are much less likely to be injured.
Other Applications - Jet driven vessels are ideal for use in towing or recovery operations because maximumthrust for any throttle setting is available, at even the lowest boat speed. Jet-driven boats are often able toget closer to the a grounded vessel to assist in the recovery. Jet drives have no equal in their ability to stopa planing boat. Approximately 50% of forward thrust may be util ized when the reversing deflector isdeployed (it is essential to warn and prepare passengers and crew before performing an emergency stop).While jet-driven watercraft are definitely the "wave" of the future, they may not be suitable for all
applications. Propeller drives still have their place!
Jet drives should best be considered as alternatives to propellers, not necessarily as replacements. Jet
drives have unique advantages for vessels operating in certain roles. Propeller-driven vessels have otherattributes. Matching their attributes to the particular vessel's configuration and mission is advised.
Indeed, much is happening in the marine propulsion arena these days. The trend toward jets is real,
primarily because of the various benefits over propeller drives as noted in this article. So, to
summarize....Jet driven boats give you more maneuverability, tend to be more efficient, more economical,
quieter, safer and more environmentally sound. You'll be seeing more Jet drives on the waves in the future!
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Ship Propulsion
The primary function of any marine engineering plant is to convert the chemical energy of fuelinto useful work and to use that work in the propulsion of the ship. A propulsion unit consists ofthe machinery, equipment and controls that are mechanically, electrically, or hydraulically
connected to a propulsion shaft. After reading this chapter, you will have a basic understanding ofhow a ship's propulsion unit works. You will learn about the three main types of propulsion unitsused in the Navy. You will also learn how power is transmitted from the propulsion unit to theship's propeller through the use of gears, shafts, and clutches.
PRINCIPLES OF SHIP PROPULSION
A ship moves through the water through propelling devices , such as paddle wheels or propellers.These devices impart velocity to a column of water and move s it in the opposite direction inwhich it is desired to move the ship. A force, called reactive force because it reacts to the forceof the column of water, is developed against the velocity-imparting device. This force, also calledthrust, is transmitted to the ship and causes the ship to move through the water.
The screw-type propeller is the propulsion device used in almost all naval ships . The thrustdeveloped on the propeller is transmitted to the ship's structure by the main shaft through thethrust bearing (fig.). The main shaft extends from the main reduction gear shaft of the reductiongear to the propeller. It is supported and held in alignment by the spring bearings, the stern tubebearings, and the strut bearing. The thrust, acting on the propulsion shaft as a result of thepushing effect of the propeller, is transmitted to the ship's structure by the main thrust bearing.In most ships, the main thrust bearing is located at the forward end of the main shaft within themain reduction gear casing. In some very large ships, however, the main shaft thrust bearing islocated farther aft in a machinery space or a shaft alley.
The main reduction gear connects the prime mover (engine) to the shaft. The function of the mainreduction gear is to reduce the high rotational speeds of the engine and allow the propeller to
operate at lower rotation speeds. In this way, both the engine and the propeller shaft rotate attheir most efficient speeds.