Volume 5, Issue 1 SEP 2015

IJRAET

DESIGN AND SIMULATION OF A MARINE PROPELLER

1 T. CHITTARANJAN KUMAR REDDY, 2 K.NAGARAJA RAO

1 PG Scholar, Department of MECH, VIVEKANANDA GROUP OF INSTITUTIONS, Ranga Reddy, Telangana, India.

2 Associate Professor (HOD), Department of MECH, VIVEKANANDA GROUP OF INSTITUTIONS, Ranga Reddy,

Telangana, India.

Abstract—

A propeller is a type of fan that transmits power by

converting rotational motion into thrust. A pressure

difference is produced between the forward and rear

surfaces of the airfoil-shaped blade, and a fluid (such as air

or water) is accelerated behind the blade. Propeller

dynamics can be modelled by both Bernoulli's principle

and Newton's third law. A marine propeller is sometimes

colloquially known as a screw propeller or screw.

The present work is directed towards the study of marine

propeller working and its terminology,simulation and flow

simulation of marine propeller has been performed.The

von misses stresses ,resultant deformation ,strain and areas

below factor of safety has been displayed.

The velocity and pressure with which the propeller blades

pushes the water has been displayed in the results.

KEYWORDS: Propeller, Design, Analysis, Static, CDF

(Computational Flow Dynamics)

INTRODUCTION

INTRODUCTION TO PROPELLER:

A propeller is a type of fan that transmits power by

converting rotational motion into thrust. A pressure

difference is produced between the forward and rear

surfaces of the airfoil-shaped blade, and a fluid (such as air

or water) is accelerated behind the blade. Propeller

dynamics can be modelled by both Bernoulli's principle

and Newton's third law. A marine propeller is sometimes

colloquially known as a screw propeller or screw.

Marine propeller

HISTORY AND DEVELOPMENT:

The concept of a propulsion device resembling what is

now called the screw propeller is certainly not new. The

experience of ancients with sculling oars, coupled with the

later development of rotary engines, obviously suggested a

combination of a series of inclined plates secured to a

rotary hub. In 945 B.C., the Egyptians used a screw-like

device for irrigation purposes. Archimedes (287-212 BC),

the first scientist whose work had a lasting effect on the

history of naval architecture and ship propulsion, has been

credited with the invention of the screw.Hecreated the

screw to pump out flooded ships.

The screw pump, designed by Archimedes for supplying

irrigation ditches, was the forerunner of the screw

propeller. Drawings done by Leonardo DA Vinci (1452-

1519) (Figure 1-1 below) contain pictures of water screws

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for pumping. However, his famous helicopter rotor more

nearly resembles a marine screw.

Despite this knowledge, application of screw propulsion to

boats and ships didn't take place until the advent of steam

power. Due to greater suitability with the slow-turning,

early steam engines, the first powered boats used paddle

wheels for a form of water propulsion. In 1661, Toogood

and Hays adopted the Archimedian screw as a ship

propeller, although their boat design appears to have

involved a type of water jet propulsion.

At the beginning of the 19th century, screw propulsion was

considered a strictly second-rate means of moving a ship

through the water. However, it was during this century that

screw propulsion development got underway. In 1802,

Colonel John Stevens built and experimented with a

single-screw, and later a twin-screw, steam-driven boat.

Unfortunately, due to a lack of interest, his ideas were not

accepted in America.

The Invention of the Screw Propeller

The credit for the invention of the screw propeller narrows

down to two men, Francis Petit Smith and John Ericsson.

In 1836, Smith and Ericsson obtained patents for screw

propellers, marking the start of modern development.

Ericsson's patent covered a contra-rotating bladed wheel,

as well as twin-screw and single-screw installations.

Ericsson's propeller design took advantage of many of the

unique benefits of the bladed wheel. With the wheel, it was

possible to obtain the increased thrust of a large number of

blades in a small diameter without cluttering up the area

adjacent to the hub.

Yet, both the inner and outer elements supplied propulsive

thrust. The wheel design was inherently strong, without

much unnecessary material to interfere with its basic

action. The outer ring also served to keep lines, ice, and

debris away from the blades. There is no clear-cut

evolution of the bladed wheel into the modern screw

propeller, although the bladed wheel possessed most of the

elements of a successful propulsive device. It seems to

have been used in the original Ericsson form and then

dropped in favor of the conventional screw.

BASIC PROPELLER PARTS :

The first step to understanding propellers and how they

work is familiarizing your-self with the basic parts of a

boat propeller.

A. Blade Tip: The maximum reach of the blade from the

center of the propeller hub. It separates the leading edge

from the trailing edge.

B. Leading Edge: The part of the blade nearest the boat,

which first cuts through the water. It extends from the hub

to the tip.

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C. Trailing Edge: The part of the blade farthest from the

boat. The edge from which the water leaves the blade. It

extends from the tip to the hub (near the diffuser ring on

through-hub exhaust propellers).

D. Cup: The small curve or lip on the trailing edge of the

blade, permitting the propeller to hold water better and

normally adding about 1/2" (12.7 mm) to 1" (25.4 mm) of

pitch.

E. Blade Face: The side of the blade facing away from the

boat, known as the positive pressure side of the blade.

F. Blade Back: The side of the blade facing the boat,

known as the negative pressure (or suction) side of the

blade.

G. Blade Root: The point where the blade attaches to the

hub.

H. Inner Hub: This contains the Flo-Torq rubber hub or

Flo-Torq II Delrin® Hub System (Figures 2-2 above and

2-3). The forward end of the inner hub is the metal surface

which generally transmits the propeller thrust through the

forward thrust hub to the propeller shaft and in turn,

eventually to the boat.

I. Outer Hub: For through-hub exhaust propellers. The

exterior surface is in direct contact with the water. The

blades are attached to the exterior surface. Its inner surface

is in contact with the exhaust passage and with the ribs

which attach the outer hub to the inner hub.

J. Ribs: For through-hub exhaust propellers. The

connections between the inner and outer hub. There are

usually three ribs, occasionally two, four, or five. The ribs

are usually either parallel to the propeller shaft ("straight"),

or parallel to the blades ("helical").

K. Shock-Absorbing Rubber Hub: Rubber molded to an

inner splined hub to protect the propeller drive system

from impact damage and to flex when shifting the engine,

to relieve the normal shift shock that occurs between the

gear and clutch mechanism - generally used with low

horsepower applications.

L. Diffuser Ring: Aids in reducing exhaust back pressure

and in preventing exhaust gas from feeding back into

propeller blades.

M. Exhaust Passage: For through-hub exhaust propellers.

The hollow area between the inner hub and the outer hub

through which engine exhaust gases are discharged into

the water. In some stern drive installations using a

through-transom exhaust system, this passage carries air.

N. Performance Vent System (PVS): PVS, is a patented

Mercury ventilation system, allows the boater to custom

tune the venting of the propeller blades for maximum

planing performance. On acceleration, exhaust is drawn

out of the vent hole located behind each blade.

When the next propeller blade strikes this aerated water,

less force is required to push through this water allowing

the engine RPM to rise more rapidly.

Water flows over the vent holes once the boat is on plan

sending exhaust through the exhaust passage. Varying the

size of the exhaust holes engine RPM can be controlled,

outboards perform better with venting and stern drives

typically require less venting if any at all.

Hub Configurations :

At the center of the propeller is the hub. If exhaust gases

are discharged into the water through the hub, the propeller

is called a through-hub exhaust (or Jet-Prop™ exhaust)

propeller.

If the exhaust gases are not discharged into the water

through a passage in the hub, but rather over the hub, the

propeller is called an over-the-hub exhaust propeller.

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through the propeller's hub. This is accomplished by

extending the drive shaft out through the very bottom of

the transom. When running properly only one blade of a

two bladed propeller is actually in the water. The surface

propeller is very efficient at minimizing or eliminating

cavitation by replacing it with ventilation. With each

stroke, the propeller blade brings a bubble of air into what

would otherwise be the vacuum cavity region.

SOLIDWORKS

Solid Works is mechanical design automation software

that takes advantage of the familiar Microsoft Windows

graphical user interface.

It is an easy-to-learn tool which makes it possible for

mechanical designers to quickly sketch ideas, experiment

with features and dimensions, and produce models and

detailed drawings.

A Solid Works model consists of parts, assemblies, and

drawings.

Typically, we begin with a sketch, create a base feature,

and then add more features to the model. (One can also

begin with an imported surface or solid geometry).

We are free to refine our design by adding, changing, or

reordering features.

Associativity between parts, assemblies, and drawings

assures that changes made to one view are automatically

made to all other views.

We can generate drawings or assemblies at any time in

the design process.

The SolidWorks software lets us customize functionality

to suit our needs.

MODELLING OF MARINE PROPELLER

Modeling of marine propeller :

First sketching the outer hub on right plane as shown

below:

Figure : sketch of outer hub

Then by using revolve option outer hub is generated as

shown

Figure : revolve of outer hub

Now blade profile is sketched on reference plane which is

taken by 30 deg angle to right plane .

sketching of blade profile

Then blade extrusion of 5mm is performed as shown

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Extrusion of blade

By using flex operation bending of blade is generated as

shown

Figure : Bending of blade

Next extrusion of inner hub is performed as shown below

Extrusion of inner hub

Now blades are circularly patterned on the outer hub

.here we are generating three blade propeller as shown

circular pattern of blades

Now Ribs are extruded as shown

Extrusion of ribs

Necessary filleting and chamfering is done and the final

marine propeller is as follows:

Marine propeller

Four different views of marine propeller as shown below :

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Different views of marine propeller

FINITE ELEMENT MODELLING

INTRODUCTION TO FEM

Many problems in engineering and applied science are

governed by differential or integral equations. The

solutions to these equations would provide an exact, closed

form solution to the particular problem being studied.

However, complexities in the geometry, properties and in

the boundary conditions that are seen in most real world

problems usually means that an exact solution cannot be

obtained in a reasonable amount of time. They are content

to obtain approximate solutions that can be readily

obtained in a reasonable time frame and with reasonable

effort. The FEM is one such approximate solution

technique.

The FEM is a numerical procedure for obtaining

approximate solutions to many of the problems

encountered in engineering analysis. In the FEM, a

complex region defining a continuum is discretised into

simple geometric shapes called elements. The properties

and the governing relationships are assumed over these

elements and expressed mathematically in terms of

unknown values at specific points in the elements called

nodes. An assembly process is used to link the individual

elements to the linked system. When the effects of loads

and boundary conditions are considered, a set of linear or

nonlinear algebraic equations is usually obtained. Solution

of these equations gives the approximate behaviour of the

continuum or system. The continuum has an infinite

number of degrees of freedom (DOF), while the discretised

model has a finite number of DOF. This is the origin of the

name, finite element method.

SIMULATION OF MARINE PROPELLERThe static

analysis is performed on marine propeller .When the ice

block of 2000N hits the marine propeller the effects have

been observed .

Naming the static analysis as marine propeller simulation

Marine propeller simulation

ADDITION OF MATERIAL TO PROPELLER:

Adding 6061 alloy material to the propeller as shown

below.

Figure : Addition of alloy steel to propeller

FIXING OF GEOMETRY :

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Shaft diameter is kept fixed in propeller becase it connects

the propeller and engine.

Figure : fixing of geometry

APPLICATION OF LOAD :Loads are applied to the

blades ,outerhub,inner hub and ribs of the propeller.

Figure : Application of load of 2000N

MESHING:

Fine Meshing of size 6mm is performed on the propeller

then the meshing modelled is shown below:

Fine meshing of size 6mm

SOLVE :

Then running the simulation of propeller to see the von

misses stresses,resultant displacement and areas below

Factor of safety.

running the simulation

RESULTS :

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von misses stresses for fine meshing

The yield strength for the material is 620.4MPa and the

maximum stress obtained is 699.4(Mesh size 6mm) MPa.

It means that if the stress is greater than the yield stress

the material will not break but will deform plastically.

Deflection for fine meshing of size 6mm

Figure : strain produced on propeller

areas below factor of safety

A factor of safety less than 1 at a location indicates that the

material at that location has failed.A factor of safety of 1 at

a location indicates that the material at that location has

just started to fail. A factor of safety greater than 1 at a

location indicates that the material at that location is safe.

COMPARISION OF RESULTS:

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Figure :comparision of results

FLOW SIMULATION

SOLIDWORKS FLOWSIMULATION

INTRODUCTION :

SolidWorks Flow Simulation 2010 is a fluid flow analysis

add-in package that is available forSolidWorks in order to

obtain solutions to the full Navier-Stokes equations that

govem the motion of fluids. Other packages that can be

added to SolidWorks include SolidWorks Motion and

SolidWorks Simulation. A fluid flow analysis using Flow

Simulation involves a number of basic steps that are shown

in the following flowchart in figure.

Flowchart for fluid flow analysis using Solidworks Flow

Simulation

INSERTING BOUNDARV CONDITIONS: boundary

conditions are required for both the inflow and outflow

faces of internal flow regions with the exception of

enclosures subjected to natural convection. Visualization

of boundary conditions can be shown with anows of

different colors indicating the type and direction of the

boundary condition. The boundary conditions are divided

in three different types: flow openings, pressure openings

and walls.

List of available boundary conditions in Solid Works Flow

Simulation

Each boundary condition has a number of parameters

related to it that can be set to different values. The

available parameters for each boundary condition are

shown in table below:

List of available parameters for different boundary

conditions in Solid Works Flow Simulation

The flow parameter depends on the boundary condition but

includes velocity, Mach number and mass and volume

flow rate. The direction of the flow vector can be specified

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as normal to the face, as s'wirl or as a 3D vector. The

thermodynamic parameters include temperature and

pressure. For the turbulence parameters you can choose

between speci[ing the turbulence intensity and length or

the turbulence energy and dissipation (k-e turbulence

model). The boundary layer is set to either laminar or

turbulent. You can also specify velocity and thermal

boundary layer thickness for the inlet velocity boundary

condition as well as speciry the core velocity and

temperature. For the real wall boundary condition you can

speciry the wall roughness together with wall temperature

and heat transfer coefficient. The real wall

also has an option for motion in the form of translational or

angular velocity.

CHOOSING GOALS:

Goals are criteria used to stop the iterative solution

process. The goals are chosen from the physical

parameters of interest to the user of Flow Simulation. The

use of goals minimizes errors in the calculated parameters

and shortens the total solution time for the solver. There

are five different types of goals:

Global goals, point goals, surface goals, volume goals and

equation goals. The global goal is based on parameter

values determined everywhere in the flow field whereas a

point goal is related to a specific point inside the

computational domain. Surface goals are determined on

specific surfaces and volume goals are determined within a

specific subset of the computational domain as specified

by the user. Finally, equation goals are defined by

mathematical expressions. Table is showing 48 different

parameters that can be chosen by the different types of

goals.

Figure : List of available parameters for different goals in

SolidWorks Flow Simulation

VIEWING RESULTS

Results can be visualized in a number of different ways as

indicated by table :

List of available results in SolidWorks Flow Simulation

ADVANTAGES OF FLOW SIMULATION :

Low Cost:

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The most important advantage of computational prediction

is its low cost. In most applications, the cost of a computer

run is many orders of magnitude lower than the cost of

corresponding experimentation. This can reduce or even

eliminate the need for expensive or large-scale physical

test facilities. This factor assumes increasing importance

as the physical situation to be studied becomes larger and

more complicated. Further whereas the prices of most

items are increasing, computing cost is likely to be even

lower in the future.

Speed:

A computational investigation can be performed with

remarkable speed. A designer can study the implication of

hundreds of different configurations in less than a day and

choose the optimum design process; rapid evaluation of

design alternatives can be made. On the other hand, a

corresponding experimental investigating would take a

long time.

Complete information:

A computer solution of problem gives detailed and

complete information. It can provide the values of all

relevant variables (such as velocity, pressure, temperature,

concentration, turbulence intensity) throughout the domain

interest. This provides a better understanding of the flow

phenomenon and the product performance. For this

reason, even when an experiment is performed, there is

great value in obtaining a companion computer solution to

supplement the experimental information.

Ability to stimulate Realistic Conditions:

In theoretical calculation, realistic conditions can be easily

stimulated. There is no need to resort to small scale or

cold models. Through a computer program, there is little

difficulty in having a very large or very small dimension,

in treating very low or very high temperatures, in handling

toxic or flammable substances, or in following very fast or

very slow processes.

Ability to stimulate Ideal Conditions: A prediction

method is sometimes used to study a basic phenomenon,

rather than a complex engineering application. In the

study of phenomenon, one wants to focus attention on a

few essential parameters and eliminates all irrelevant

features. Thus many idealizations are desirable for

example: two dimensionally constant densities an adiabatic

surface of an infinite reaction rate. In a computation

approach, such conditions can be setup with case and

precision, whereas even careful experimental can barely

approximate the idealization.

Reduction of Failure risks: CFD can also be used to

investigate configurations that may be too large to test or

which pose a significant safety risk including pollutant

spread and nuclear accident scenarios. This can often

provide confidence in operation, reduce or eliminate the

cost of problem solving during installations, reduce

product liability risks.

APPLICATIONS OF FLOW SIMULATION :

Automobile and Engine Applications:

To improve performance means environmental quality,

fuel economy of modern trucks and cars. It is study of the

external flow over the body of a vehicle, or the internal

flow through the internal combustion engines.

Industrial Manufacturing Applications:

A mould being filed with liquid modular cast iron is a

good example. The liquid flow fields are calculated as a

function of time. Another example is manufacture of

ceramics.

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Civil engineering Applications:

Problems involving the theology of rivers, lakes etc are

also subject of investigations using CFD. Example is

filling of mud from an underwater mud capture reservoir.

Environmental Engineering Applications:

The discipline of heating, air conditioning and general air

circulation through buildings are some of the examples of

the application situations. The example is fluid burning in

furnaces.

Product design:

The ultimate functionality of a product depends on its cost,

efficiency, robustness, and acceptance in the commercial

market. In products that are developed to improve the

environment through energy conservation; fluid-flow, heat

and mass transfer plays an important role. CFD now with

its multitude capabilities serves as an essential tool for

modeling these phenomena in the design of such products.

Product improvement:

Many of the current industrial products have been

developed in pre-CFD periods. As we become more

energy efficient conscious, we find that the products

involving thermal-fluid systems can be redesigned to

reduce their energy consumption. Successfully redesigned

products not only can lower the operating cost but remain

competitive in the market place. In addition they may be

introduced as new lines of products to stimulate the growth

of the business.

Bio medical engineering:

Flow modeling with computational fluid dynamics (CFD)

software lets you visualize and predict physical

phenomena related to the flow of any substance. It is

widely used in medical, pharmaceutical, and biomedical

applications.

FLOW SIMULATION OF MARINE PROPELLER

The purpose of the flow simulation is to see the flow

trajectories of the fluid that is moved by propeller .In this

flow simulation no velocity and pressure conditions are

given but aim is to calculate them.

First rotating region has to be extruded around the

propeller that is the volume that will be rotated,

Figure : Extrusion of rotating region

On solidworks flow simulation menu creating new study

name “Marine propeller flow simulation” as shown.

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creating study name

Then selecting SI units , external analysis and rotation

region as shown.

Setting external analysis and rotation region

Adding water as a project fluid from the liquids

water as project fluid

By using default wall conditions and default initial

conditions and setting result resolution as shown.

setting result resolution

Then flow simulation tree will appear on left side of the

screen. The computational domain

is adjusted as shown by editing it.

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editing of computational domain

Then adding rotational region by selecting the boss extrude

of marine propeller’s rotational region and the speed is

2000 rpm.

Addition of rotational region of speed 2000 rpm.

Then running the flow simulation

running of flow simulation

RESULTS :On the results tree flow trajectories has been

inserted by selecting the surfaces which are in contact

with the fluid i.e, water.

inserting flow trajectories

flow trajectories of water [velocity]

The water velocity has been displayed on the above figure.

The water leaves with 14m/s velocity from the marine

propeller blades as shown above.

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flow trajectories of water [ pressure]

The pressure increases with in the rotating region and then

decreases as shown

CONCLUSIONS

The marine propeller working and terminology

has been studied.

The marine propeller with 3 blades has been

modeled in solidworks 2014.

The solidworks simulation has been studied and

the marine propeller simulation has been

performed.

The maximum induced stresses i.e, 699.4Mpa in

propeller is greater than the material yield

strength 620.4Mpa.This means that if the stress is

greater than the yield stress the material will not

break but will deform plastically.

The resultant deformation, strain and areas below

factor of safety has been displayed.

The solidworks flow simulation has been studied

and the velocity and pressure with the blades of

the propeller has been calculated.

The flow trajectories for velocity and pressure

have been displayed.

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