DESIGN, ANALYSE AND MANUFACTURE PROPELLER BLADE FOR REMOTELY UNDERWATER VEHICLE ONG PUI SZE Thesis submitted in partial fulfillment of the requirements for the award of the degree of Bachelor of Manufacturing Engineering Faculty of Manufacturing Engineering UNIVERSITI MALAYSIA PAHANG JUNE 2013
vi ABSTRAK Projek ini mengandungi maklumat mengenai rekabentuk kipas untuk sebuah Kenderaan Dalam Air Kawalan Jauh (ROV). ROV adalah satu teknologi yang sering digunakan dalam ketenteraan, kejuruteraan laut dan aktiviti-aktiviti komersial seperti industri-industri cari gali minyak. Sistem propulsi memainkan peranan yang penting dalam keupayaan pergerakan ROV. Objektif tesis ini adalah untuk menjalankan simulasi untuk rekabentuk dan pembentukan kipas dan membuatkan prototaip dengan menggunakan mesin Fused Deposition Modelling. OpenProp merupakan satu program yang dibentuk oleh Massachusetts Institute of Technology yang sesuai digunakan untuk merekabentuk kipas dan dapat menganalisasikan prestasi rekabentuk. Keputusan eksperimen menunjukkan prestasi dan daya tujahan sisihan sebanyak 14% ke 19% apabila dibandingkan dengan keputusan teori. Ini disebabkan oleh kesan dinding tangki air, kekasaran permukaan dan kesan pemotongan kipas. Kesimpulannya, peningkatan harus dijalankan ke atas eksperimen untuk mendapat keputusan yang lebih tepat.
v ABSTRACT This thesis contains details on the designing a propeller for the Remotely Underwater Vehicle. Remote Operated Vehicles (ROV) is a technology which is frequently used to service the military, ocean engineering activities and also commercial activities such as oil and gas industry. Propulsion plays a significant role in the manoeuvrability of the ROV. The objective of this paper is to conduct simulation studies to design and modelling the ROV propeller blade, and then manufacture the prototype by using Fused Deposition Modeling machine. OpenProp, an open-sourced program developed at Massachusetts Institute of Technology is used to design the propeller and analyse the on-design performance of it. It is found that there is a deviation of 14% to 19% on the experimental results compared to the theoretical results. This might cause by wall effects that occurs on the tank, and surface roughness and blunt trailing edge of the blade prototype. In conclusion, improvement on the experimental setup is needed in order to obtain a much accurate results.
vii TABLE OF CONTENTS SUPERVISOR S DECLARATION STUDENT S DECLARATION ACKNOWLEDGEMENTS ABSTRACT ABSTRAK TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF SYMBOLS LIST OF ABBREVIATIONS LIST OF APPENDICES Page ii iii iv v vi vii x xi xiii xv xvi CHAPTER 1 INTRODUCTION 1.1 Background of Study 1 1.2 Problem Statement 4 1.3 Objectives 4 1.4 Scopes of Study 5 1.5 Limitation 5 CHAPTER 2 LITERATURE REVIEW 2.1 Propeller Physical 6 2.2 Propeller Mechanism 9 2.3 Motor 10 2.4 Type of Propellers 11 2.5 Propeller Material 12 2.6 Design Parameters 13 2.6.1 Blade Number 13 2.6.2 Propeller Diameter 14 2.6.3 Hub Diameter 16
viii 2.6.4 Chord to Diameter Ratio 17 2.6.5 Thrust 20 2.6.6 Drag 21 2.7 Design Considerations 25 2.7.1 Ventilation 25 2.7.2 Cavitation 26 2.8 Theory for Propeller Designing 26 2.8.1 Lifting Line Theory 26 2.8.2 Actuator Disk Theory 27 CHAPTER 3 METHODOLOGY 3.1 Flow Chart 29 3.2 Design Inputs 31 3.3 Analysis with OpenProp 31 3.3.1 Parametric Analysis 31 3.3.2 Single Propeller Design 32 3.4 Modelling of Propeller 34 3.5 Fabrication of Propeller 36 3.5.1 Rapid Prototyping 36 3.5.2 Other Manufacturing Process 37 3.6 Propeller Testing 38 CHAPTER 4 RESULTS 4.1 Simulation Results 40 4.1.1 Horizontal Propeller 40 4.1.2 Vertical Propeller 43 4.2 Stress Analysis 45 4.3 Test Rig 48 4.4 Propeller 50 4.5 Thrust and Efficiency Test 51 4.6 Discussions 51 4.6.1 Wall Effect 51 4.6.2 Blunt Trailing Edge 52 4.6.3 Surface Roughness 53 4.6.4 Limitation of Machine 53
ix CHAPTER 5 CONCLUSIONS 5.1 Conclusions 54 5.2 Recommendations 55 REFERENCES 56 APPENDICES 60
x LIST OF TABLES Table No. Title Page 2.1 The chord over diameter at each blade section 20 4.1 Simulation results of 4-, 5-, and 6-blade propellers 41 4.2 Simulation results of 4-, 5-, and 6- bladed vertical propeller 44 4.3 Thrust force and efficiency 51
xiii LIST OF SYMBOLS A d D F g I m P Q r T v V W Z θ η ρ ϕ μ ω CP CQ Total hull area that sink in the fluid Hub diameter Drag Force Gravity Current Length of the geometry Mass Power Torque Radial Thrust Speed Angular velocity Vehicle velocity Voltage Weight Number of blades Angle Efficiency (in general) Density Pitch angle Kinematics viscosity Propeller speed Area (in general) Cylindrical area of ROV Rectangular area of ROV Total area of ROV Total area where propeller swept through Drag coefficient Drag coefficient of cylindrical Drag coefficient of rectangular Thrust coefficient Propeller diameter No load current Torque coefficient Revolution per minute per volt Speed through the propeller Efficiency of the motor Efficiency of the propeller Efficiency of the propeller mechanism Efficiency of the gear box Efficiency of the actuator disk Propeller power coefficient Actuator disk torque coefficient
xiv CT KT KQ EFFY ADEFFY Js Pt Re Actuator disk thrust coefficient Propeller thrust coefficient Propeller torque coefficient Efficiency Actuator disk effiency Advance coefficient Pitch Reynolds number
xi LIST OF FIGURES Figure No. Title Page 1.1 The propulsion system of an AUV where P is the propeller, G 2 represents the gear, M for Motor, C for motor controller and B as the batteries 1.2 ROV developed that need a set of customize propeller 3 2.1 Propeller nomenclature 6 2.2 A rearward rake with angle, θ 7 2.3 The cross section of the blade 7 2.4 The blade on the left is slightly bent due to low thickness 8 2.5 Basic propeller geometry 8 2.6 The pressure face and suction back 8 2.7 Pitch and pitch angle 9 2.8 The mechanism of thrusting of the propeller 10 2.9 The comparison of efficiency and shaft torque for both 3-bladed 13 and 6-bladed propellers under a range of advance coefficient 2.10 Variation of thruster power requirements versus the propeller 15 diameter for various force and thrust density 2.11 The comparison of the efficiency of the existing model of ROV 16 for a range of diameter, where solid line represents the thrust coefficient and the dotted line is the actuator disk efficiency which is 10 times of thrust coefficient 2.12 Effect of the variation of hub diameter towards the propeller 17 efficiency 2.13 Efficiency versus advance ratio for small, medium and large BAR 18 2.14 The efficiency of the propeller is 78.73% before the chord over 19 diameter are reduced 2.15 The efficiency of the propeller is 78.83% after the chord over 19 diameter are reduced 2.16 Percentage of drag force increase in vehicle for a range of 22 diameter under different tunnel drag coefficient 2.17 Drag coefficient for common geometry 23 2.18 Drag coefficient of cylindrical bodies at different aspect ratio 24 2.19 Mean drag coefficients of rectangular cylinders with different 24 aspect ratios 2.20 Hydrodynamic model of a propeller 27 3.1 Flow chart 30 3.2 Parametric analysis by OpenProp v2.4.6 32 3.3 The GUI for single propeller design 33 3.4 The results for single ducted propeller analysis 34 3.5 Propeller drawn in Solidworks 35 3.6 Fine gaps on trailing edge of the blades 36 3.7 Propeller parts before assemble 37 3.8 Test rig for propeller efficiency and drag 38 4.1 Single design of the 6-bladed propeller 40 4.2 Lift distribution of the 6-blade design with duct 42
4.3 Cross sections of blade at different blade stations 42 4.4 3D view of the complete propeller model 43 4.5 Cross sections of blade at different blade stations 44 4.6 3D view of the complete propeller model 45 4.7 Von Mises Stress of Horizontal Propeller 46 4.8 Von Mises Stress of Vertical Propeller 46 4.9 Displacement of Horizontal Propeller 47 4.10 Displacement of Vertical Propeller 47 4.11 Test rig 48 4.12 Von Mises stress of test rig 49 4.13 Displacement of test rig due to the load 49 4.14 Horizontal propeller 50 4.15 Vertical propeller 50 A1 Top view of ROV 60 A2 Free body diagram of ROV during vertical movement 62 B1 Front view of ROV 64 B2 Free body diagram of the ROV during horizontal movement 65 C1 Free body diagram of test rig 66 D1 DC Power Supply 68 D2 Free body diagram of test rig with propeller moving 67 F1 Free body diagram of Test rig (center of gravity) 71 xii
xvi LIST OF APPENDICES Appendix Title Page A Thrust Calculation for Vertical Propeller 60 B Thrust Calculation for Horizontal Propeller 64 C Experimental Thrust Calculations 66 D Propeller s Experimental Efficiency Calculations 67 E Percentage Deviation Calculations 70 F Calculations of Additional Weight to Stabilize the Rig 71
xv LIST OF ABBREVIATIONS ABS BAR CFD CNC DAR EAR FEA FDM GUI MIT ROV RP RPM RPS UUV Acrylonitrile Butadiene Styrene Blade area ratio Computational Fluid Dynamic Computational Numerical Control Developed Area Ratio Expanded Area Ratio Finite element analysis Fused Deposition Modelling Graphical user interface Massachusetts Institute of Technology Remotely underwater vehicle Rapid Prototyping Revolution Per Minute Revolution Per Second Unmanned underwater vehicle
CHAPTER 1 INTRODUCTION 1.1 BACKGROUND OF STUDY A number of underwater vehicles are developed, where it is divided into two types which are manned underwater vehicle and unmanned underwater vehicle. The manned underwater vehicle is usually used to service the military and also gather data about the ocean. Today, there are two types of unmanned underwater vehicle (UUV) which is the remote operated vehicle (ROV) and autonomous underwater vehicle (AUV). Though ROV and AUV is both categorized as UUV, Blidberg (2001) however has proposed that the main difference between both is ROV is tethered in order to obtain power supply and transmit signals such as position while AUV has their own power and control itself to accomplish the task. Hoang and Kreuzer (2007) recommended that ROV can be equipped with different sensors. It is launched into the water from the mothership and was controlled to reach to the structure that task is needed to be conducted. ROV is used in the oil industry for almost three decades where it is useful in constructing production facilities, inspection and intervention (Liu Hsu et al., 2000). Azis et al. (2012) suggested that ROV can be utilize in inspection of cracks on the underwater section of the ship, oil and gas industry, telecommunication, geotechnical investigation and mineral exploration, which is mainly a hazardous environment for human to work. Bessa et al. (2008) suggested that the development of underwater vehicles enable tasks such as inspection and repair of offshore
2 structures, assembly and sub-sea phenomena to be completed without risking the human life by positioning and controlling the altitude of the vehicle automatically. Propeller is a device that consists of several blades that rotates to accelerate the fluid along the propeller axis, which produce thrust force in the opposite direction (Palmer, 2009). The performance of the blade can be affected by its rotational speed and the flow into the propeller (Palmer, 2009). The propulsion system consists of several components, which are the propeller, gear, motor, controller and batteries. Figure 1.1: The propulsion system of an AUV where P is the propeller, G represents the gear, M for Motor, C for motor controller and B as the batteries. Source: Palmer (2009) The performance of the propulsion system is the ratio of power output (generated thrust and resultant speed of the vehicle) to the power input supplies by the batteries (Palmer, 2009). Others include the vibrations produced by the propeller to the hull, and noise generated by the system affect the performance of the propulsion system. This paper describes the process of propeller design of a ROV developed by Professor Dr. Hj. Zahari Taha, which is shown in Figure 1.2. The goal is to design a set of propeller (two vertical propellers and three thruster propellers) for the ROV. The objective of this study is to design the ROVs propellers.
3 The design specifications are as follows: Speed, v = 1.0m/s Motor speed, ω = 85rpm (no load) Motor speed, ω = 80rpm (at cruise) Propeller hub diameter = 15% of the propeller diameter Torque, Q = 9.3256 Nm Power, P = 78.1256 W The motor speed is set at 80rpm to ensure that the motor will be operating in the safe range to prolong the motor s life cycle. Figure 1.2: ROV developed that need a set of customize propeller.
4 1.2 PROBLEM STATEMENT Recently, the development of ROV has stressed on smaller size and a more efficient energy technology. Propeller of the ROV plays a significant role in producing a more efficient horizontal and vertical movement. However, the number of research on designing and manufacturing marine propeller is less. Most of them rely on the propeller of the airplane for propulsion as off the shelf propeller is more desirable because it is cheaper and easy to replace. It is much more expensive to fabricate a customize propeller compare to buying one from the shelf. Yet the use of airplane propeller in marine vehicle is not suitable because the density of air is 1000 times less than water (D Epagnier, 2006). On the other hand, the development of new tools in propeller designing has shown a significant improvement in the design method that could enhance the process of propeller designing. However, the impact of development has yet not shown due to the designers halt at the traditional method that has gone through loads of researches and were validated, which is much more reliable and most importantly were implemented for plenty of times (Kuiper, 2010). Therefore, it is important for this research to clearly show the stages and steps of the advance method in ROV propeller development which will encourage engineers to adapt and pursue the new design and manufacturing method. 1.3 OBJECTIVES The objectives of this thesis are: i. To conduct simulation studies on ROVs propeller blade ii. To design and modeling of a ROVs propeller blade iii. To manufacture the propeller blade of ROV iv. To test the ROVs propeller blade
5 1.4 SCOPES OF STUDY This research focuses on the hydrodynamic performance of the ROV where an efficient propeller is needed to be designed and manufacture in order to produce a reliable propulsion system. The scopes of the study on ROVs propeller blade are: i. To study the design process of ROVs propellers ii. To design a propeller blade for ROVs by applying the existing method iii. To do computational simulation on the design iv. To manufacture the design by using the existing machines and equipment in the faculty v. To test the effectiveness of the design 1.5 LIMITATION The limitation in this project is the manufacturability of the machines in the Faculty of Manufacturing Engineering as these machines such as milling machine, turning machine, electrical discharge machine, and others are not suitable for machining propellers with irregular shape. The milling machine in the laboratory has only 3-axis whereas it requires a 5-axis machining in order to machine the propeller or turbines (Hurco Companies, Inc., 2012). Most of the papers suggested to use 3-D printer to manufacture the propeller as it is easier and more efficient than the other manufacturing method. Although the cost of rapid prototyping is high, the propeller will be manufactured by using rapid prototyping for better precision.
CHAPTER 2 LITERATURE REVIEW 2.1 PROPELLER PHYSICAL The radius of the propeller is the distance from the tip of the blade to the center of the hub (Duelley, 2010). The chord of the propeller is a straight line distance from the leading edge to the trailing edge at a particular blade section of the propeller (Duelley, 2010). Figure 2.1 shows the nomenclature of the propeller as described. Figure 2.1: Propeller nomenclature Source: Duelley (2010) and Schultz (2009) Rake is the angle of the propeller blade from the centerline of the hub. Figure 2.2 shows the rake angle of the propeller (Duelley, 2010). Camber of the propeller is the maximum distance between the mean line and the chord line. The maximum thickness of the blade is measured in a normal to the chord line (Ferrando, 2012). The ideal propeller would be infinitely thin so that it is more hydrodynamic (Duelley, 2010). However, this is impractical and impossible to be achieved because it is not manufacturability, durability and efficient. Low
7 thickness profile has the risk of breaking or bending when the blade is handled roughly as shown in Figure 2.3 and Figure 2.4 below (Duelley, 2010). Figure 2.2: A rearward rake with angle, θ. Source: Duelley (2010) Figure 2.3: The cross section of the blade. Source: ITTC Besides, the blade is classified into two, which is the leading edge and the trailing edge which is illustrated on the Figure 2.5 above. Leading edge is the first part that contact with water when it is rotating while trailing edge is the last part of the blade that contact with the water. From Figure 2.6 below, it can clearly be seen that the pressure face of the propeller where it has high pressure at that part. The suction back has low pressure which is the cause of the ROV to move forward.
8 Figure 2.4: The blade on the left is slightly bent due to low thickness. Source: Duelley (2010) Figure 2.5: Basic propeller geometry. Source: US Navy Figure 2.6: The pressure face and suction back Source: US Navy
9 Pitch is a measurement of the distance of propeller would move parallel to the direction of motion when it rotates at one revolution (Duelley, 2010). High pitch over diameter ratio can increase the propeller efficiency (D Epagnier, 2006). Pitch angle is the angle of the blade that is perpendicular to the water flow. It can be calculated using the Equation (2.1), where Pt is the pitch of the propeller, ϕ is the angle and r is the radial distance of any point on the blade from the center. Figure 2.7 explain about the pitch of a propeller. (2.1) Figure 2.7: Pitch and pitch angle Source: US Navy 2.2 PROPELLER MECHANISM Propeller blade and aircraft wing has similarity in the way they work where the difference is the type of fluid that flow through it. Water flow through the propeller blade and causes pressure differences on the top and bottom of the blade and therefore generate thrust force to the ROV. The velocity of the water is higher at the suction back part of the blade and cause low pressure than the pressure face. Figure 2.8 below shows that the resultant force of the ROV causes it to move forward.
10 Figure 2.8: The mechanism of thrusting of the propeller Source: US Navy 2.3 MOTOR The torque, Q of the motor is calculated by Equation (2.2) as shown in below (Duelley, 2010). ( ) (2.2) where is the torque constant (Nm per amp), I is the current drawn by the motor (amp) is the no load current (amps) and is the revolution per minute per volt. is calculated by the following Equation (2.3) (Duelley, 2010). (2.3) The electrical power, P of the motor is found to be 78.1256W by using Equation (2.4) and Equation (2.5) show below (Duelley, 2010). (2.4) (2.5)
11 The velocity of the vehicle can be calculated by substituting the power and drag to Equation (2.6) below, where T is the drag and V is the vehicle velocity. (2.6) Stanway and Stefanov-Wagner proposed that the efficiency of the propeller could be estimated by relating it with the efficiency of the motor ( ), gear box ( ), propeller mechanism ( ) and also the efficiency of the propeller ( ) which is shown in Equation (2.7) (2006). (2.7) By using the approach introduced by Duelley, it was found that the torque produced by the motor is 9.3256Nm and therefore power needed for one motor is 78.1256W. 2.4 TYPE OF PROPELLERS There are eight types of propeller, which is fixed pitch propellers, ducted propellers, podded and azimuthing propulsors, contra-rotating propellers, overlapping propellers, tandem propellers, controllable pitch propellers, and cycloidal propellers. Each propeller has its own characteristics that are suitable for certain applications. Stanway (2006) has used a ducted contra-rotating type of propellers on his ROV. Contrarotating propellers provide higher efficiency and thrust compared with single propeller because the load is supported by both propellers which therefore enable them to have higher efficiency even in low rotational speeds. Besides, counter-rotating effect of both propellers has the advantage of cancel out the losses due to the tangential velocities in the wake (Stanway and Stefanov-Wagner, 2006). However, contrarotating propeller produces some mechanical loss and a potential failure point (Stanway and Stefanov-Wagner, 2006).