Chen Zeng (201375033)

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1. Department of Naval Architecture, Ocean & Marine Engineering Project Report NM982 - Research Project - SOT Title: Parametric Design & Optimization of…
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  • 1. Department of Naval Architecture, Ocean & Marine Engineering Project Report NM982 - Research Project - SOT Title: Parametric Design & Optimization of Propellers-Linking Grasshopper with VB & Python Author: Chen Zeng (201375033) Supervisor: Prof. Evangelos Boulougouris Date: 13.08.2014
  • 2. Contents i Contents 1 Introduction 1 1.1 Background and context . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Scope and objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.3 Introduction to Grasshopper . . . . . . . . . . . . . . . . . . . . . . . 1 2 Literature review of the topic area 3 2.1 Ship propellers and propulsion . . . . . . . . . . . . . . . . . . . . . . 3 2.2 OpenProp: An open-source parametric design and analysis tool for propellers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.3 Further computer-analysed data of the Wageningen B-screw series . . 6 3 Preliminary analysis 7 3.1 Fundamental parameters . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2 Characteristics of Wageningen B-screw series . . . . . . . . . . . . . . 8 3.2.1 Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2.2 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4 Realization of parametric propeller design with Grasshopper 15 4.1 general parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.2 Geometry of the propeller . . . . . . . . . . . . . . . . . . . . . . . . 17 4.3 Analysis of the propeller . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.4 Automatic optimisation . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.5 The test of the programme . . . . . . . . . . . . . . . . . . . . . . . . 21 5 Conclusions and further discussion 22 5.1 Achievement of the programme . . . . . . . . . . . . . . . . . . . . . 22 5.2 The shortages of this programme . . . . . . . . . . . . . . . . . . . . 22 5.3 Further discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Bibliography 23
  • 3. List of Figures ii List of Figures 1.1 The Example of the usage of Grasshopper . . . . . . . . . . . . . . . 2 2.1 The phases of propeller design[1] . . . . . . . . . . . . . . . . . . . . 4 2.2 OpenProp information flow chart[2] . . . . . . . . . . . . . . . . . . . 5 3.1 Definition of pitch .[1] . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2 Outline definition.[1] . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.3 The Geometry of B5-screw series[1] . . . . . . . . . . . . . . . . . . . 8 3.4 The sketch diagram of the profile of B5-screw series[4] . . . . . . . . . 10 4.1 The finished in Grasshopper . . . . . . . . . . . . . . . . . . . . . . . 15 4.2 The part of general parameters . . . . . . . . . . . . . . . . . . . . . 16 4.4 Calculated parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.5 The part of geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.6 The outside and inside aspects of the Cluster of geometry building. . 18 4.7 The procedures to position points . . . . . . . . . . . . . . . . . . . . 19 4.8 The geometry of single blade . . . . . . . . . . . . . . . . . . . . . . . 19 4.9 The part of analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.10 The tool of Genome . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.11 Data dam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.12 The usage of the programme . . . . . . . . . . . . . . . . . . . . . . . 21 4.13 The running of the optimisation . . . . . . . . . . . . . . . . . . . . . 21
  • 4. List of Tables iii List of Tables 3.1 Geometry of the Wageningen B-screw series[4]. . . . . . . . . . . . . . 9 3.2 Values of V 1 for use in the equations.[4] . . . . . . . . . . . . . . . . 11 3.3 Values of V 2 for use in the equations.[4] . . . . . . . . . . . . . . . . 11 3.4 Coefficients for the KT and KQ polynomials representing the Wa- geningen B-screen series for a Reynolds number of 2 × 106 .[4] . . . . . 14 4.1 Extent of the Wageningen B-screw series[1]. . . . . . . . . . . . . . . 17
  • 5. 1 Introduction 1 1 Introduction 1.1 Background and context Being developed for more than one hundred years, propellers have been equipped by most vessels all over the world as the major propulsion system because of its relatively high efficiency and simple driving structure. However, due to the highly twisted geometry and numerous variable parameters, it is hard to operate the de- sign and optimization loops manually, which is time consuming. Additionally, the traditional two-dimensional drawing, like figure: 3.3, cannot demonstrate the real geometry of the propellers. Thus, traditional design method can hardly cooperate with some advanced manufactural technology, for example 3-D printing. A new Computer Aided Design (CAD) method called parametric design has be- come a strong trend in contemporary architecture design practise. As its name implies, such term means that to digitally model a series of design vari- ants ,through one or several mathematical connections,whose relationships to each other are defined. Then, numerous related but distinct structures can be formed.[2] 1.2 Scope and objectives The main objective of the project is to investigate the feasibility of introducing parametric design into the design and optimization procedures of propeller. The project will focus on one propeller series of B-screw which is one of the most widely used propeller series. The propeller model is build with the utilization of the software Grasshopper, which can be projected and changed by just modifying its parameters. Moreover, the characteristics can be calculated with these parameters and some other coefficients from the propeller model. Finally the optimization loops can be set just by using the repeating function. 1.3 Introduction to Grasshopper Rhinoceros is quite popular among architecture designers, especially those with a focus on formal design considerations which is used in multiple design industries due to its ease of use and processing speed. The Grasshopper is a graphical algorithm editor as a plug-in for Rhinoceros. With- out formal scripting experience, designers can quickly generate parametric forms with the plug-in ([2]). As shown in figure 1.1, the functions of Rhinoceros repre-
  • 6. 1.3 Introduction to Grasshopper 2 sented by a number of nodes within Grasshopper, and the relationships of parameters the connecting lines. Figure 1.1: The Example of the usage of Grasshopper Additionally, as several coding languages, such as Visual Basic and Visual C#, can be used inside Grasshoppers working panel, not only the parametric geometry design, but also the analysis can be implemented. Eventually, since the propellers’ structural factors and performance characteristics depend on several parameters. So, it is suitable to operate design and optimization with the utilization of Grasshopper, which can dramatically shorten the working time of designing loop and improve the efficiency.
  • 7. 2 Literature review of the topic area 3 2 Literature review of the topic area 2.1 Ship propellers and propulsion Paper citation: Carlton, J.S.(2007). Marine propellers and propulsion. – 2nd ed. Elsevier Ltd. All, 2007. This book demonstrates almost all aspects of propeller. In it, Carlton(2007) attempt to balance theoretical and practical considerations in each chapter of the book. Therefore, the material presented will be valuable for the practitioner in marine science. For innovative studies, particularly of a theoretical nature, the data presented here will act as a starting point for further research. There are twenty-five chapters included by this book. The first two chapters are the introduction of the subject, chapter three the geometry and the fourth and fifth the working environment of the propeller and the wake field. Chapters six to fifteen deal with propulsion hydrodynamics, and the chapters from the seventeenth to the twentieth deal with the mechanical aspects of propellers. The final five chapters discuss various practical aspects of propeller technology, starting with design, then continuing to operational problems, service performance and, finally, to propeller inspection, repair and maintenance. This thesis focuses on the third, sixth and twenty-second chapters from the whole book. The following is the brief introduction and some comments of these chapters. Chapter three is the beginning of the main component of this book, which con- siders propeller geometry. Additionally, the part is the foundation of the rest of the book on which the rest of the book. Without a thorough knowledge of propeller ge- ometry, the subject will not be fully understood. From which, I acquired a detailed knowledge about how a propeller model is structure. However, only the traditional two dimensional cartography is recorded here, which may not suitable for digital design, consequently it should be modified to attain the requirement of parametric design. Chapter six has the name of propeller performance characteristics, which is the basic knowledge of the propulsion hydrodynamics. To discuss the performance char- acteristics of a propeller, Carlon(2007) divided the topic into open water and behind- hull properties. As the open water characteristics is the description of the forces and moments acting on the propeller when operating in a uniform fluid stream, these are steady loadings by definition. But, the behind-hull characteristics are those gen- erated by the propeller when operating in a mixed wake field behind a body, hence these have both a steady and unsteady part by the very nature of the environment in which the propeller operates. The author treated both types of characteristics
  • 8. 2.2 OpenProp: An open-source parametric design and analysis tool for propellers4 separately in this chapter, especially for some propeller series. After thoroughly read this chapter, the propeller of Wageningen B-screw series is chosen as the objec- tive propeller. The information of such propeller in this book is not detailed, more specific data should be found. Each of chapters except this one in this book has considered different aspects of the propeller in detail. But, in chapter twenty-two, Carlon(2007) attempts to provide a basis for drawing together the various threads of the subject, so that the propeller and its design process can be considered as an integrated entity. The real propeller design is the loop that contains different phases of design and optimization, which can be seen from the figure below (fig: 2.1). Actually, the whole propeller design procedures should comprise information from vessels that is not derived. So, the project only includes part of the design loop. Figure 2.1: The phases of propeller design[1] 2.2 OpenProp: An open-source parametric design and analysis tool for propellers Epps, B., Chalfant, J., Kimball, R., Techet, A., Flood, K., & Chryssostomidis, C. (2009). OpenProp: An open-source parametric design and analysis tool for pro- pellers. In Proceedings of the 2009 Grand Challenges in Modeling & Simulation Conference (pp. 104-111). Society for Modeling & Simulation International. OpenProp is a suite of open-source propeller and turbine design codes written in the MATLAB programming language[2]. The methodology of these codes is the
  • 9. 2.2 OpenProp: An open-source parametric design and analysis tool for propellers5 same as what utilized by the US Navy for parametric design of marine propellers. Being a GUI-based user-friendly tool, OpenProp can be used by both propeller design professionals as well as beginners to it. Started from 2001, a team of researchers at MIT, Marine Maritime Academy and Univeresity of Marine have contributed to the OpenProp code. In OpenProp, the input parameters, design, geometry, and operating states of a propeller are collected with the usage of data structures. iIn the figure 2.2, the data flow is illuminated. From this figure, it can be seen that after the data (diameter, rotation rate) is inputted and optimised, the procedures go into two parts. In the one part (the right part) the consequential propeller design is analysed at off-design conditions in the analyser to determine off-design operating states. The other part, the crafter than draw the three dimensional geometry and prepare rapid prototyping files for producing the propeller. The total design loop of the recent project is based on such data flow structure. But, the methodology of this is a little bit not suitable for the usage of the propeller of Wageningen B-screw series. Figure 2.2: OpenProp information flow chart[2]
  • 10. 2.3 Further computer-analysed data of the Wageningen B-screw series 6 2.3 Further computer-analysed data of the Wageningen B-screw series Oosurveld, M.W.C., & Van Oossanen, P. (1975). Further computer-analysed data of the Wageningen B-screw series. This paper illustrates the detailed polynomials that give the open-water character- istics of the Wageningen B-series propellers. With the help of a multiple regression analysis of the original open-water test data of the 120 propeller models comprising the B-series, these polynomials were derived. Than, all test data was corrected for Reynolds effects via an equivalent profile method developed by Lerbs. The open-water characteristics of such propeller series can be derived by polyno- mials, which can be easily employed by coding software. Because loads of propeller characteristics can only be derived with graphs that may be hard to be applied digitally. Furthermore, dislike the description of the characteristics of Wageningen B-series propellers from the book ’Marine propellers and propulsion’, the information of it here is detailed, for example, each of the parameters appears in the polynomials are explained specifically.
  • 11. 3 Preliminary analysis 7 3 Preliminary analysis 3.1 Fundamental parameters A number of parameters should be utilized when designing a propeller. The following paragraphs define the fundamental parameters can be utilized in either geometry or optimization. VA is the advance velocity, D the diameter of propellers and Z the blade number. N is the rotation ratio per minute with the unit of round/min, which usually transferred to the rotation ratio per second n = N/60. Pitch ratio is P/D, where D is the diameter of the propeller and P is the pitch. Here the meaning of pitch is shown by the figure 3.1. Assume a point P locating on the surface of a cylinder of radius r being at some initial point P0.Then it moves towards the direction of the blade profile as the figure shows which forms a helix over the cylinder surface and the points P1,P2,...,Pn illustrates the helical track. Then, pitch is the axial distance of two nearby points which have the same circumferential position on the cylinder surface, such as the distance of the points P0,P12 from the picture 3.1. Figure 3.1: Definition of pitch .[1] Blade area ratio (AE/AO or BAR) is the ratio of expanded area (AE) to the area of the roundness(AO) with the diameter which equals to the propeller diameter D. From the fig:3.2, the expanded area is the area surrounded by the expanded outline which is the outline of the blade profiles on the plane.
  • 12. 3.2 Characteristics of Wageningen B-screw series 8 Figure 3.2: Outline definition.[1] The thrust coefficient, torque coefficient, advance coefficient are illustrated in following equations:KT = T ρn2D4 , KQ = Q ρn2D5 and J = VA n·D , where T and Q are the propeller thrust and torque. And all the other coefficients in those equations have already be shown in the previous paragraphs. 3.2 Characteristics of Wageningen B-screw series Wageningen B-screw series is perhaps the most extensive and widely used propeller series which is a comprehensive fixed pitch, non-ducted propeller series with general purposes. 3.2.1 Geometry The fig3.3 shows the geometry of the B-screw propeller series with five blades. From the figure, it can be identified that the propeller geometry is built by using expanded profiles which are the surfaces of a blade cut by the cylinder surface with different radius. The rake here is fifteen degrees. Figure 3.3: The Geometry of B5-screw series[1] The following texts inside the section illustrate the geometry factors of blade sections from 0.2R to 1.0R (R is the radial of the propeller). The table below (3.1) gives the general dimensions, such as the chords and maximum thickness of each sections.
  • 13. 3.2 Characteristics of Wageningen B-screw series 9 Table 3.1: Geometry of the Wageningen B-screw series[4]. Dimensions of four-, five-, six- and seven-bladed seven-bladed B-screw series. r/R c D · Z AE/AO a/c b/c t/D = Ar − Br · Z Ar Br 0.2 1.662 0.617 0.350 0.0526 0.0040 0.3 1.882 0.613 0.350 0.0464 0.0035 0.4 2.050 0.601 0.351 0.0402 0.0030 0.5 2.152 0.586 0.355 0.0340 0.0025 0.6 2.187 0.561 0.389 0.0278 0.0020 0.7 2.144 0.524 0.443 0.0216 0.0015 0.8 1.970 0.463 0.479 0.0154 0.0010 0.9 1.582 0.351 0.500 0.0092 0.0005 1.0 0.000 0.000 0.000 0.0030 0.0000 Dimensions of three-bladed propellers. r/R c D · Z AE/AO a/c b/c t/D = Ar − Br · Z Ar Br 0.2 1.633 0.616 0.350 0.0526 0.0040 0.3 1.832 0.611 0.350 0.0464 0.0035 0.4 2.000 0.599 0.350 0.0402 0.0030 0.5 2.120 0.583 0.355 0.0340 0.0025 0.6 2.186 0.558 0.389 0.0278 0.0020 0.7 2.168 0.526 0.442 0.0216 0.0015 0.8 2.127 0.481 0.478 0.0154 0.0010 0.9 1.657 0.400 0.500 0.0092 0.0005 1.0 0.000 0.000 0.000 0.0030 0.0000 Ar, Br = constants in equation for t/D. a = distance between leading edge and generator line at r. b = distance between leading edge and location of maximum thickness. c = chord length of blade section ar radius r. t = maximum blade section thickness at radius r. The diagram (2.1) shows a typical blade section. By it, the detailed meaning of each of the parameters recorded in this section is illustrated. Then, by combing the equations of 3.1 and 3.1 with the data of V1 and V2 which are kept in the table 3.2 and 3.3 respectively, the Y-coordinates of the face and back line of a profile are derived. Finally, the plane sections of a propeller blade can be gained by linking it with the coefficients.
  • 14. 3.2 Characteristics of Wageningen B-screw series 10 Figure 3.4: The sketch diagram of the profile of B5-screw series[4] Yface = V1(tmax − tt.e.) Yback = (V1 + V2)(tmax − tt.e.) + tt.e. for P ≤ 0. (3.1) Yface = V1(tmax − tl.e.) Yback = (V1 + V2)(tmax − tl.e.) + tl.e. for P ≥ 0. (3.2) Referring to the diagram 3.4, notice the following: Yface, Yback are vertical ordinate of a point on a blade section on the face and on the back with respect to the pitch line. tmax is the maximum thickness of blade section. tt.e., tl.e. are extrapolated blade section thickness at the trailing and leading edges. V1, V2 are tabulated functions dependent on r/R and P. P is non-dimensional coordinate along pitch line from position of maximum thickness to leading edge (where P = 1), and from position of maximum thickness to trailing edge (where P = −1).
  • 15. 3.2 Characteristics of Wageningen B-screw series 11 Table 3.2: Values of V 1 for use in the equations.[4] r/R P −1.0 −0.95 −0.9 −0.8 −0.7 −0.6 −0.5 −0.4 −0.2 0 0.7-1.0 0 0 0 0 0 0 0 0 0 0 0.6 0 0 0 0 0 0 0 0 0 0 0.5 0.0522 0.0420 0.0330 0.0190 0.0100 0.0040 0.0012 0 0 0 0.4 0.1467 0.1200 0.0972 0.0630 0.0395 0.0214 0.0116 0.0044 0 0 0.3 0.2306 0.2040 0.1790 0.1333 0.0943 0.0623 0.0376 0.0202 0.0033 0 0.25 0.2598 0.2372 0.2115 0.1651 0.1246 0.0899 0.0579 0.0350 0.0084 0 0.2 0.2826 0.2630 0.2400 0.1967 0.1570 0.1207 0.0880 0.0592 0.0172 0 0.15 0.3000 0.2824 0.2650 0.2300 0.1950 0.1610 0.1280 0.0955 0.0365 0 r/R P +1.0 +0.95 +0.9 +0.85 +0.8 +0.7 +0.6 +0.5 +0.4 +0.2 0 0.7-1.0 0 0 0 0 0 0 0 0 0 0 0 0.6 0.0382 0.0169 0.0067 0.0022 0.0006 0 0 0 0 0 0 0.5 0.1278 0.0778 0.0500 0.0328 0.0211 0.0085 0.0034 0.0008 0 0 0 0.4 0.2181 0.1467 0.1088 0.0833 0
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