Description
ABSTRACT
Propellerwhich isatypeoffanthattransmitspowerbyconvertingrotationalmotionintothrust was designed in this work. The design was carried out using SOLIDWORKStorecreatethegeometryofathree-dimensionalgeometry,analysiswasconducted.Thestudyiscompleted using a computational program, Ansys FLUENT, andvelocity,pressuredistribution,torqueiscomparedtoexperimental results. Reasonable results are produced such thatthe torque and efficiency trends will be in acceptable limits withrespect to experimental data. The acquired results are used asinput data to carry out stress analysis on propellers made ofthree composite materialsnamelycarboncomposite, aluminacompositeand polymercomposite.
TABLE OF CONTENTS
Cover page
Title page
Approval page
Dedication
Acknowledgement
Abstract
CHAPTER ONE
1.0 Introduction
1.1 Background of the project
- Statement of the problem
- Aim and objectives of the project
- Significance of the project
- Scope of the project
CHAPTER TWO
LITERATURE REVIEW
- Overview of the propeller
- Historical backgroundofpropeller
- Types of propeller
- Review of related studies
CHAPTER THREE
3.0 MATERIALANDMETHOD
3.1 Materials
3.2 Method
3.3 Computational fluid dynamicsanalysis
CHAPTER FOUR
4.1 FSIsimulation
4.2 results
CHAPTER FIVE
- Conclusion
- Recommendation
References
CHAPTER ONE
1.0 INTRODUCTION
Apropellerisatypeoffanthattransmitspowerbyconvertingrotationalmotionintothrust.Apressuredifferenceis produced between the forward and rear surfaces of the aerofoil-shapedblade,andafluid(suchasairorwater)isacceleratedbehindtheblade.
Propeller dynamics, like those of aircraft wings, can bemodelled by either or both Bernoulli’s principle and Newton’sthirdlaw.
A marine propeller of this type is sometimes colloquiallyknown asascrew propeller orscrew, howeverthere isadifferent class of propellers known as cycloidal propellers –theyarecharacterizedbythehigherpropulsiveefficiencyaveraging0.72comparedtothescrewpropeller’saverageof and the ability to throw thrust in any direction at any time.Theirdisadvantagesare highermechanicalcomplexityandhighercost (Kamarlouei et al., 2014).
Recent trends in the shipping industry, e.g., expanded routing in ecologically sensitive areas andemission regulations, have sharpened the perception of efficient propeller designs.Currently,propeller efficiency, estimated fuel consumption and, more often, propeller-radiated noise areparameters that steer the business Zeitgeist. However, a practical propeller design that performsreliably and sufficiently throughout the lifetime of a ship requires numerous limitations, whichare typically in conflict with the objectives. This requires judgement by experienced propellerdesigners to make decisions during the design process. To be ahead of competitors, a propellerdesigner needs to present a better design for a specific purpose, in a shorter time and at lower coststhan the adversary. The current challenge for propeller designers is to develop a propeller thatfulfilsalltherequirementsandexpectationswithinashorttimeframe (Kamarlouei et al., 2014).
The increasing interest in designing the optimal propeller shape is the motivation for this thesis,whose purpose is to further improve the state-of-the-art of the propeller design procedure bymeansofsupplementingthepropellerdesignerwithadvance design.Theartofdesigninga propeller, with the multi-disciplinary evaluation and consideration of numerous limitations,yields a systematic investigation of the design space, which is due to the generally limited time.Automatedoptimisationcanfillthedesignspacewithnumerousdesignsthatgravitate,guidedbytheoptimisationprocedure,towardsanadvancedesign.
1.1 BACKGROUND OF THE STUDY
Themarinescrewpropellerisafascinatinginvention.Ittransmitspowerintoafluidmediumbyconvertingrotationalmotionintothrust.Hydrofoilsarearrangedonashaft,whichareshapedandaligned such that a pressure difference develops between both blade sides, thereby accelerating thefluid. Today’s propeller blade shapes are highly complex free-form surfaces that require carefuldesignconsiderationsandaccuratemanufacturingengineering (Smrcka, 2015).
InspiredbytheArchimedes’screwandLeonardodaVinci’sprincipleofahelicopter,thefirstconceptsofshippropellersemergedinthe18thcenturyassuggestionstopropelships,e.g.,thoseby Robert Hooke, Daniel Bernoulli and James Watt. These earlier fan-like propellers resembletoday’s propellers in appearance. However, the first marine propellers used in applications wereArchimedean screw-type propellers, which powered a submarine developed by David Bushnell.Thedevelopmentsacceleratedatthebeginningofthe19thcentury,whentheincreasedpowerandreliability of steam engines required an improvement in propulsion for sea-going ships. Severalinventorsequippedsteam-drivenshipswithdifferenttypesandconstellationsofpropellers.JosefRessel, for instance, designed an Archimedean screw-type propeller with two blades, each of asinglerevolution,andequippedthesteamvessel’Civetta’withthispropellerin1829 (Smrcka, 2015).
In 1836, John Ericsson proposed a propulsion system of two contra-rotating propellers basedon the Bernoulli-type propeller. The propellers were mounted behind the rudder, which resulted inhindered manoeuvrability. Francis Pettit Smith tested a wooden Archimedean screw, designedwith two turns, on a 30-foot vessel in 1837.The propeller accidentally broke, and suddenly,withonlyasingleturnleft,theachievableshipspeeddoubled.Theseinventors,tonameonlya few, contributed to the development of the propeller. All of them encountered suspicion andinitial opposition from stakeholders at the time.The fact that propeller design stabilised onlytowards the end of that century highlights that the effectiveness of the propeller was not entirelyunderstood. However, screw propellers were beneficial in multiple fields, compared to typicalpaddle propulsion, and became the dominant propulsion type. Since then, many attempts havebeen made to minimise the amount of input energy to the propeller; however, the general formevolvedinthe19thcentury (Smrcka, 2015).
Propellers are still under development, and their appearance today differs from that of propellersfrom two or three decades ago.At present, modifications to the propeller design are widelymotivatedbytechnologydevelopments(e.g.,manufacturingtechnologyormaterialtechnology),regulations (e.g., DNV SILENT class notation) or costs (e.g., production andoperationcosts),whicharedrivenbythegeneraldevelopmentsofshipping.Theglobalized business world yielded an increased need for transportation, which implicitly, due to the costadvantage of size (economies of scale), resulted in an increase in ship size. During the secondhalfofthelastcentury,thecommercialfleetapproximatelytripledinnumberofships,whilethegross tonnage increased by a factor of more than six (in the world’s shipping fleet for ships of100 gross tones and more) (Burnside et al., 2019). Consequently, the installed power in the shipsincreasedandpropellersneededtotransfermoreenergytothewater;thecavitationphenomenonarose more frequently on the propeller.Cavitation has to be considered and controlled by thepropellerdesigner,andithascertainlychangedhowthepropellerbladeshapehasevolved.Inthefuture, new materials such as composites or regulations on radiated noise might initiate furtherchangestothewayinwhichwedesignpropellerblades.
Propeller design is a highly complex procedure, involving many influencing factors. Tuningthepropellergeometrytowardsefficiencyalsochangesitscharacteristicswithregardtovibration,inboard noise and cavitation behaviour, which will most likely occur when the propeller is inoperation.The propeller experiences varying inflow conditions while travelling through thecircumferential wake. This causes a varying load on the propeller blade during one revolutionand results in a local pressure drop around the blade.Depending on the operating conditions,e.g., submergence of the propeller shaft or rotational speed, the pressure sags below the vapourpressureandcavitation,i.e.,vapourpocketsintheliquid,canbeobservedatthepropeller.Whenagainenteringhigh-pressureregions,thecavitiescollapseextremelyrapidlyandmaycausenoiseand vibration, which are transferred to the ship’s hull, and cause erosion on the propeller or therudder. Cavitation and propeller-induced pressure pulses are the most evident propeller effectscontradictory to efficiency. Consequently, the only solution is to find a trade-off blade geometrythat is adapted to the flow and therefore only valid for a certain ship and the specific operatingconditions.To satisfy the ship owner’s expectations and to deliver a practical design, the designerhas to not only consider and control the cavitation but also constrain static and dynamic bladestresses,classificationrequirementsand,inthecaseofcontrollablepitchpropellers,hubstrengthandbladeclearance (Burnside et al., 2019).
Thus, propeller design is truly an art of trading performances and requirements, which isnaturallyamulti-objectiveandmulti-disciplinaryprocedureandwhichcanonlybeaccomplishedinaniterativemanner.Commonpracticeistodevelopapreliminarydesignconceptandimprovethisbysubsequentlyevaluatingallappliedobjectivesandconstraintstofindthebestcompromise.The various requirements together with seemingly countless modifications to such a free-formsurface lead to a large number of alternatives to be studied and thus place restrictions on thenumerical analysis tools.The blade geometry is, during the design synthesis, evolved by thedesigner’sexperiencetowardsthedesignphilosophyandconsideredastheoptimaldesign.Withsufficient time, a designer can efficiently analyse the design space and reach, driven by theknowledge,thebestpossibledesign.Insuchaprocedure,timeisthemostlimitingrestriction.
Thelengthoftimeavailableforaproductbeingconceiveduntilitisreadyforsaleisoneof the most important factors in a world that is changing rapidly at an accelerating pace. Thisholds for most of the engineering design tasks and in particular for the propeller design becauseeach is a unique layout for a certain ship. To be ahead of competitors, a propeller designer needsto present a better design for a specific purpose in a shorter time and at lower costs than theadversary. The current challenge for propeller designers is to develop a propeller that fulfils allrequirementsandexpectationswithintheshorttimelengthavailableinthecompetitionraces.
1.3 AIM AND OBJCTIVES OF THE STUDY
The main aim of this work is to study an advanced method of designing a marine propeller for an effective performance.
The objectives of the study are:
- To study strategies and concepts for propeller design for an effective performance of the ship.
- To study the principles and designconsiderationsofatypicalmanualdesignprocedure.
- To study differenttypesofpropeller.
- To study effect of change in material with compositematerial,inoverall efficiencyof marinepropeller.
1.4 STATEMENT OF THE PROBLEM
Apropelleristhemostcommonpropulsoronships,imparting momentum to a fluid which causes a force to act ontheship.Theidealefficiencyofanysizepropeller(free-tip)is that of an actuator disc in an ideal fluid.An actual marinepropeller is made up of sections of helicoidal surfaces whichact together ‘screwing’ through the water (hence the commonreference to marine propellers as “screws”).Three blades or four are most common in marine propellers, althoughdesigns which are intended to operate at reduced noise willhave more blades. Computational fluid dynamics (CFD) study of propeller can be used studyitsdifferentproblemlikepropellerinducedvibration,tiperosion,propellercavitation,singingpropeller,etc.Agood CFDmodelofpropeller’sworkingcanbeutilizedtostudycauseof aboveproblemsandmethodstopreventit.
1.5 SCOPE OF THE STUDY
A propeller is a rotating fan-like structure that is used to propel the ship by using the power generated and transmitted by the main engine of the ship. The propeller is an essential part of the conventional ship propulsion system. It is the rotating fan form structure that propels the ship by utilizing the power from the main engine. By converting the transmitted power to rotational motion, the propeller generates a thrust that induces momentum to the water. Hence, resulting in a force that acts on the ship and pushes it forward.This study discusses method of achieving an advanced propeller design in other to achieve an effective performance of a ship. The study was carried out UsingSOLIDWORKStorecreatethegeometryofathree-dimensionalgeometry,analysiswasconducted.Thestudyiscompleted using a computational program, Ansys FLUENT, andvelocity,pressuredistribution,torqueiscomparedtoexperimental results. Reasonable results are produced such thatthe torque and efficiency trends will be in acceptable limits withrespect to experimental data. The acquired results are used asinput data to carry out stress analysis on propellers made ofthree composite materialsnamelycarboncomposite, aluminacompositeand polymercomposite.
1.6 SIGNIFICANCE OF THE STUDY
The study shall serve a means of ensuring careful and standard design a propeller. This study will serve as a means of studying several different approaches to improve propeller design.
The study will further improve the state-of-the-art of the propeller designprocedure by supplementing the propeller designer with automated optimisation.
CHAPTER FIVE
5.1 CONCLUSION
In this work an advance propeller for effective performance was designed. Propeller generates adequate thrust to propel a vessel at some design speed with some care taken in ensuring some “reasonable” propulsive efficiency.
Considerations are made to match the engine’s power and shaft speed, as well as the size of the vessel and the ship’s operating speed, with an appropriately designed propeller.
Given that the above conditions are interdependent (ship speed depends on ship size, power required depends on desired speed, etc.)
5.2 RECOMMENDATION
- Fluid-structureinteractiondatainsaidexperiment.
- Increaseinefficiencyofmarinepropelleronreplacement with composite material by reducingitsweightwithoutcompromisingitsstrength.
- Optimizedcomponenthelpsinincreasingperformanceofmarineturbine
