DESIGN AND STATIC ANALYSIS OF MARINE PROPELLER

Transcription

1 DESIGN AND STATIC ANALYSIS OF MARINE PROPELLER 1 REGALLA.LAKSHMI LAVANYA, 2 Dr.G.THRISEKHAR REDDY, 1 PG Scholar, Department of MECH, NALANDA INSTITUTE OF ENGINEERING ANDTECHNOLOGY, Kantepudi (V), Sattenapalli (M), Guntur (D), A.P, India, Pin: Mail Id: regalla.lavanya@gmail.com 2 Assistant Professor, Department of MECH, NALANDA INSTITUTE OF ENGINEERING ANDTECHNOLOGY, Kantepudi (V), Sattenapalli (M), Guntur (D), A.P, India, Pin: Mail Id: sekhar02351@gmail.com 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 modeled 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, static simulation and flow simulation of marine propeller has been performed. In static analysis the von misses stresses, resultant deformation; strain on blade area has been displayed due to applied load when the marine propeller hits the ice block In static analysis the von misses stresses, resultant deformation; strain on blade area has been displayed due to pressure created by crash of propeller on ice berg when it is under working condition by using three different materials such as one generally used titanium alloy and two advance composite materials. 60 degree and 70 degree angle marine propeller blade will be modeled by using solid works software analysis will perform by using ANSYS work bench. INTRODUCTION 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 modeled by both Bernoulli's principle and Newton's third law. A marine propeller is sometimes colloquially known as a screw propeller or screw. LITERATURE SURVEY Design and Analysis of a Marine Propeller Palnati Ramesh Babu PG scholar, Department of Mechanical Engineering, SVR Engineering College, Nandyal, JNTU Anathapur, Andhra Pradesh, India. C.Chendrudu Associate Professor, Department of Mechanical Engineering, SVR Engineering College, Nandyal, JNTU Anathapur, Andhra Pradesh, India. 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 blade pushes the water has been displayed in the results. Prediction of Propeller Blade Stress Distribution through FEA, kiam beng yeo, wai heng choong, wen hen hau The Finite Element Analysis (FEA) of marine propeller blade stress distribution due to Hydro dynamic loading is presented and discussed. The analysis provided a better insight to complex marine

2 propeller shape and interaction with hydrodynamic loadings. Stainless steel Wageningen B Series 3 blade propeller with 250 mm diameter, EAR of 0.5 and P/D ratio of 1.2 was adopted in the analysis. The propeller was subjected to the rotational speed of rpm. The pressure distribution demonstrated a positive pressure region on the face section and a negative region on the back section that produces the thrust generation. DESCRIPTION Fig. 1: Rubber-Hub 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. 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.

3 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 planning performance. On acceleration, exhaust is drawn out of the vent hole located behind each blade. HOW PROPELLER WORKS The "Push/Pull" Concept To understand this concept, let us freeze a propeller just at the point where one of the blades is projecting directly out of the page. This is a righthand rotation propeller, whose projecting blade is rotating from top to bottom and is moving from left to right. As the blade in this discussion rotates or moves downward, it pushes water down and back as is done by your hand when swimming. At the same time, water must rush in behind the blade to fill the space left by the downward moving blade. These results in a pressure differential between the two sides of the blade: a positive pressure, or pushing effect, on the underside and a negative pressure, or pulling effect, on the top side. This action, of course, occurs on all the blades around the full circle of rotation as the engine rotates the propeller. So the propeller is both pushing and being pulled through the water. marine propeller draws or pulls water in from its front end through an imaginary cylinder a little larger than the propeller diameter (Figure 4). The front end of the propeller is the end that faces the boat. As the propeller spins, water accelerates through it, creating a jet stream of higher-velocity water behind the propeller. This exiting water jet is smaller in diameter than the actual diameter of the propeller. This water jet action of pulling water in and pushing it out at a higher velocity adds momentum to the water. This change in momentum or acceleration of the water results in a force which we can call thrust. Fig. 3: Airflow through fan is similar to water flow through the propeller Fig. 4: Thrust development Fig. 2: Push and pull concept Thrust/Momentum: These pressures cause water to be drawn into the propeller from in front and accelerated out the back, just as a household fan pulls air in from behind it and blows it out towards using the figure. The FAILURES IN PROPELLER BLADE Cavitations: Occurs when the pressure on the forward face of the propeller blade becomes low enough that vapor bubbles form and the water boils. As the vapor bubbles pass over the blade face and move away from the low pressure area, they collapse. The collapsing of the vapor bubbles might seem trivial, but it is a very violent event which can result in the pitting of

4 the propeller surface. Cavitation is a major source of propeller damage, vibration, noise, and loss of performance. Cavitations can be caused by nicks in the leading edge, bent blades, too much cup or simply high boat speed. Ventilation or aeration It occurs when surface air is drawn into the propeller blades. When this happens, boat speed is lost and engine RPM climbs rapidly. This can result from a hull error, excessively tight cornering, a motor that is mounted very high on the transom, or by overtrimming the engine. Ventilation is most often confused with Cavitations. Surface-piercing This propeller is a propeller that is positioned so that when the boat is at full speed the waterline passes 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 cavitations 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. PROPELLER BLADE STATIC ANALYSIS MODEL Idealized propeller structure can be simplified as a cantilever beam pivoted at the hub axis with a single loading on the free end or uniformly loaded along the beam. However, this ideal model does not include the highly non-linear wake field or external forces or moment such as the centrifugal forces. As more parameters and flow characteristics with different condition changes, more estimation shall be necessary to improve the effectiveness of theoretical analysis. As the propeller rotates about its central hub axis, each blade suffers different inflow field effect which causes various amplitudes of cyclic resultant moments and forces. Carlton (2007) suggested the general propeller blade stress equation as: Where, σ T, σ Q, σ CBM, σ CF and σ P are the stress components due to thrust, torque, centrifugal bending, direct centrifugal force and out of plane stress components, respectively. Generally, the linear static solution through displacement method in FEA can be described by matrix equation as: Where, [K] is the structural stiffness matrix, {U} is the vector of unknown nodal displacement and {F} is load vector ({F a } and {F c } of the applied and reaction forces). For {F a }, it can be redefined to consider the loading as the mechanical {F m }, thermal {F th } and gravitational load {F gr } and subsequently as: Then, the mechanical load vector {F m } is equal to the sum of applied nodal forces and moments and pressure elements as: Where, {F nd } is the applied nodal load vector {F pr e } is the element of pressure load vector, e is the element number and nel is the number of element. Meanwhile the thermal and gravitational load vector can be solved as:

5 Where, {F nt } is the nodal temperature load vector, {F th e } is the element of thermal load vector, [M e ] is the element of mass matrix and {a} is the acceleration vector. Based on the above equations, the applied load {F a } for propeller blade stress distribution prediction without involving thermal loading through FEA method can be written as: 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. MODELING OF PROPELLER BLADE Fig.5: Sketch of the hub Where, the element of pressure load vector {F pr e } was preceded from the propeller blade pressure distribution study through CFD application. Wageningen B-Series 3 blade propeller with P/D ratio value of 1.2 was utilized to simulate the blade stress distribution due to the hydrodynamic elements. SOLID WORKS 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. Fig.6: 60 Marine propeller Fig.7: 70 Marine propeller INTRODUCTION TO ANSYS 16.0 ANSYS 16.0 delivers innovative, dramatic simulation technology advances in every major Physics discipline, along with improvements in computing speed and enhancements to enabling technologies such as geometry handling, meshing and postprocessing. These advancements alone represent a major step ahead on the path forward in Simulation Driven Product Development. ANSYS 16.0 delivers

6 innovative, dramatic simulation technology advances in every major Physics discipline, along with improvements in computing speed and enhancements to enabling technologies such as geometry handling, meshing and post-processing. These advancements alone represent a major step ahead on the path forward in Simulation Driven Product Development. FOR BLADE ANGLE 60 MATERIAL: Titanium Alloy Stress Fig. : Ansys simulation STATIC ANALYSIS OF MARINE PROPELLER Material used and properties Material Density (kg/m3) Young modulus (MPa) Poisons ratio Ti alloy E Deformation Al metal matrix Al Si Mg alloy Fixed E E Strain Load 2000N Mesh Mass

7 MATERIAL : Aluminium Metal Matix (KS1275) Stress : MATERIAL:Aluminium Silicon Magnesium Alloy Stress: Deformation : Deformation: Strain: Strain: Mass: Mass

8 FOR BLADE ANGLE 70 Applying the same boundary conditions and load Mesh MATERIAL:Titanium Alloy Mass: Stress : MATERIAL:Aluminium Metal Matrix (KS1275) Stress: Deformation Deformation Strain: Strain:

9 Mass: Mass: MATERIAL:Aluminium Silicon Magnesium Alloy Stress: RESULTS STATIC ANALYSIS 60 angle blade Materi al Stress (MPa) Deformatio n (mm) Strain Mass (kg) Deformation Titaniu m alloy Alumin ium Metal Matrix Alumin ium Silicon Magne sium Alloy angle blade Material Stres s (MP a) Deformati on (mm) Strain Mass (kg) Strain: Titanium alloy Aluminiu m Metal Matrix

10 Aluminiu m Silicon Magnesiu m Alloy CONCLUSION Brief study about marine propeller and its working is done in this project By using solid works 2016 software marine propeller of two different blade angles 60 degree, and 70 degree is done by using different commands and features in solid work software. Simulation, static analysis and flow analysis on marine propeller is performed by using ANSYS Static analysis is performed by selecting three different materials i.e. one generally used Titanium alloy and remaining two advance composite materials alloy such as Aluminium Metal matrix(ks1275) and Aluminium Silicon Magnesiun Alloy for each blade angle(60deg & 70deg) on given load condition of 2000N. Static analysis result values i.e.: stress, strain and deformation because of applied load due to impact of ice berg on blade is noted and tabulated. According to result table 60 degree angle blade is showing least stress and deformation value compare to 70 deg blade angles. Compare to material Alloy steel is showing least deformation compare to Titanium alloy but the weight ratio of Alloy steel is more than Titanium alloy and Titanium alloy showing least max stress value compare to Alloy steel. As compare to material all three materials showing nearly same stress value on same boundary condition and applied load. But composite materials are showing less weight ratio than Titanium alloy. Due to least weight to strength ratio compare to generally used Titanium alloy even which is economically high cost we can prefer such advance composite material too which has properties like good strength,least weight to strength ratio, and economically less cost too. Comparing two composite materials used in this project Aluminium silicon magnesium alloy showing least stress compare to Aluminium Metal Matrix (KS1275). REFERENCES 1) Taylor, D.w, The Speed and Power and Ships,Washington, ) J.E.Conolly, Strength Of Propellers, reads in London at a meeting of the royal intuition of naval architects on dec1.1960,pp ) Terje sonntvedt, Propeller Blade Stresses, Application Of Finite Element Methods computers and structures,vol.4,pp ) Chang-sup lee, yong-jik kim,gun-do kim and insik nho. Case Study On The Structural Failure Of Marine Propeller Blades 5) M.jourdian, visitor and J.L.Armand. Strength Of Propeller Blades-A Numerical Approach, the socity of naval architects and marine engineers, may 24-25,1978,pp ) G.H.M.Beek, visitor, lips B.V.,Drunen. Hub- Blade Interaction In Propeller Strength, the socity of naval architects and marine enginers, may 24-25,1978,pp ) George W.Stickle and John L Crigler. Propeller analysisfrom experimental data report No.712, pp ) P.Castellini, C.Santolini. Vibration Measurements On Blades Of A Naval Propeller Rotating In Water With Tracking Laser Vibromneter Dept. of mechanics,university of Ancona, pp43-54

11 9) W.J.Colclough and J.G.Russel. The Development Of A Composite Propeller Blade With A CFRP Spar aeronautical journal, Jan 1972, pp ) J.G.Russel use of reinforced plastics in a composite propeller blade plastics and polymers, Dec 1973 pp ) Bade, S.D. and A. Junglewitz, Automated strength analysis for propeller blades. Proceedings of the 10th International Conference on Computer Applications and Information Technology in the Maritime Industries, May , Berlin, Germany, pp: ) Carlton, J.S., 2007.Marine Propellers and Propulsion. 2nd Edn., ButterworthHeinemann, Oxford, UK. 13) Chau, T.B., D versus 3D stress analysis of a marine propeller blade. Zeszyty Naukowe Akademii Morskiej w Gdyni, No. 64, July ) Vidya Sagar, M., M. Venkaiah and D. Sunil, Static and dynamic analysis of composite propeller of ship using FEA. Int. J. Eng. Res.Tech., 2: ) Young, Y.L., Fluidstructure interaction analysis of flexible composite marine propellers. J. Fluids Struct., 24: ) Chang, B Application of CFD to P4119 propeller, 22ndITTC Propeller RANS/Panel Method Workshop, France. 17) Pereira J. C. F. and Sequeira, A Propellerflow predictions using turbulent vorticity confinement, V European Conference on Computational Fluid Dynamics, ECCOMAS CFD 2010, Lisbon, Portugal.