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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.