The Simplification of Impeller 3D Modeling Based on Pro/E

The Simplification of Impeller 3D Modeling Based on Pro/E Li Qiang1, Cai Wanfeng2*, Li Yue3 Hefei University of Technology Research Institute of Chemical Machinery, Hefei‐china 230009 hfliqiang@163.com; 2*Cai_Wanfeng@163.com; 3Liyue@163.com

1

Abstract The centrifugal pump impeller 3D accurate models were great amount of data, tedious of data acquisition and entry, large energy‐consuming, etc. This paper writes a AutoLISP program with AutoCAD secondary development technique, and extract point coordinates of impeller two‐dimensional figure. The program simplifies the data measure in AutoCAD and the data input one by one in Pro/E, then, automatically creates impeller modeling in Pro/E with the method of recording MapKey macro. Finally, this paper carries a modelling time analysis, curve curvature analysis, surface curvature analysis and surface reflection analysis of two blades which draw by different methods in Pro / E. The results show that this method of impeller 3D modelling innovates a two‐dimensional coordinates extraction method of impeller diagram. In terms of guidance design correction, it has a good practicability. It also plays a significant effect on reducing the data processing cumbersome and increasing the quality modeling. Keywords Twisted Blades; 3D Modeling; Pro/E; AutoLISP; Data Processing

Introduction Centrifugal pump is a kind of pump which uses the centrifugal force of water generated by the rotating impeller. In order to achieve the purpose of conveying the liquid, the high speed rotation of the impeller drives liquid for rotation movement and throws the liquid. The impellers are core components of the centrifugal pump and the quality of them directly affects the performance of the centrifugal pump (Guan Xingfan, 2011; Guo Pengcheng et al, 2005).

of so large amount of data need imputing, tedious of data acquisition and the complicated inputting process etc. In addition, the process of coordinate measuring and inputting inevitably exist errors (Wei Xiuting et al, 2010; Gang Li et al, 2011). In order to figure out the problems, the author finds a method to realize the automatic impeller modeling. The Method of Blade Data Extraction The manufacture of the impeller is adopting the method of casting or 3D printing by providing impeller hydraulic drawing. The 3D modelling can be used for conducting a mold preliminary examination before production and CFD analyzing. The Traditional Method of Blade Data Extraction In Figure 1, the intersection points between wood pattern line and 0 to 6 six vertical axis should be measured. The number of the points is very huge. In addition, these points still need to be put in the Pro/E one by one. It is complicated by this method. Blade Extraction Method Based Autolisp 1)

The Brief Introduction of Autolisp

AutoLISP is a programming language designed for the secondary development of AutoCAD, which originates in LISP language and embeds in the interior of AutoCAD. It is the organic combination of the LISP language and the AutoCAD (Zhou Lelai et al, 2008).

The impeller is comprised of multiple blades which have complex curved surfaces. In order to ensure the quality of the impeller design and manufacturing, the geometric modelling of blades has to be very accurately (Lai Xide, 2008).

Engineers can conduct a variety of engineering analysis and calculations, draw complex graphics automatically, define new AutoCAD commands, drive the dialog boxes, and the control menus by using AutoLISP language (Sun Yanhang et al, 1999).

Blades include cylindrical blades and twisted blades. Because the shape of twisted blade is complicated, its 3D accurate modelling processing has the problem that

2)

Autolisp Program Design

(Li Xuezhi, 2006; Jiang Chaojun et al, 2004; Wang

The Simplification of Impeller 3D Modeling Based on Pro/E 23

Zhengxia, 2007) Program code: (defun c:zbtq () (setq filename (getstring ʺ Please enter file nameʺ)) (if (> (strlen filename) 0) (setq file (open (strcat ʺd:/ʺ filename ʺ.txtʺ) ʺwʺ)) (setq file (open (strcat ʺd:/ʺ ʺImpeller coordinates file.txtʺ) ʺwʺ))) (write‐lineʺ! CYLINDRICAL coordinates: \n! r theta Z\n!ʺ file ) (setq m (getreal ʺ Please select impeller type: zero represents a centrifugal pump impeller and non‐zero on behalf of the axial flow pump impeller ʺ ) ) (if (= m 0)(progn (setq n (getint ʺ Please put curve number ʺ)) (repeat n (progn (setq ent_b (entget (ssname (ssget) 0))) (setq jd (getreal ʺ Please enter impeller angleʺ)) (setq ent_pb (assoc 10 ent_b)) (setq p1 (getpoint ʺ Please select a coordinate reference pointʺ)) (setq x (car p1) y (cadr p1)) (while (/= ent_pb nil) (progn (setq px (nth 1 ent_pb)) (setq py (nth 2 ent_pb)) (setq px (‐ px x)) (setq pzz (rtos (* px (cos 180)) 2 2)) (setq pjd (rtos jd 2 2)) (setq py (‐ py y)) (setq prr (rtos py 2 2)) (setq data (strcat prr ʺ ʺ pjd ʺ ʺ pzz)) (write‐line data file) (setq newlt (list px py)) (setq ent_b (subst (cons 1 newlt) (assoc 10 ent_b) ent_b)) (setq ent_pb (assoc 10 ent_b))))))) (progn (setq n (getint ʺ Please put curve number ʺ)) (repeat n (progn (setq ent_b (entget (ssname (ssget) 0)))(setq r (getreal ʺ Please enter impeller cutting radius valueʺ)) (setq ent_pb (assoc 10 ent_b)) (setq p1

(getpoint ʺ Please select a coordinate reference pointʺ)) (setq x (car p1) y (cadr p1)) (while (/= ent_pb nil) (progn (setq px (nth 1 ent_pb)) (setq py (nth 2 ent_pb)) (setq px (‐ px x)) (setq px (/ px r)) (setq px (* px 57.3)) (setq py (‐ py y)) (setq prr (rtos r 2 2)) (setq pjd (rtos px 2 2)) (setq pzz (rtos py 2 2)) (setq data (strcat prr ʺ ʺ pjd ʺ ʺ pzz)) (write‐line data file) (setq newlt (list px py)) (setq ent_b (subst (cons 1 newlt) (assoc 10 ent_b) ent_b)) (setq ent_pb (assoc 10 ent_b)))))))) (close file) (princ)) The format of point coordinate data obtained from AutoLISP program running in AutoCAD is txt, the Txt format need to be converted into pts format which can be accepted for Pro/E. The designed program has taken it into account, and the txt suffix can be changed into pts suffix. In this paper, point coordinate data can be imported by “offsetting the coordinate system reference point” tool, which adapts to the design of both centrifugal pump impellers and axial flow pump impellers. The operation process of the program is shown in figure 1, and the operation results are shown in figure 2(a). PTS file format is as follows: ! DATUM POINT ARRAY DATA FILE !CYLINDRICAL coordinates: ! r theta z Among them: r refers to radius (R) in cylindrical coordinate system; theta refers to angle(θ)in cylindrical coordinate system; Z refers to z Coordinate in cylindrical coordinate system.

(a) The dialog box of file name

(b) The dialog box of curve number

(c) The dialog box of impeller cutting radius value

(d) The dialog box of coordinate reference point

FIGURE 1. THE OPERATION PROCESS OF AUTOLISP PROGRAM.

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Li Qiang, Cai Wanfeng, Li Yue

(a) The point coordinate data

(b) The point coordinates of blade pressure surface

(c) Blade side boundary figure

FIGURE 2. THE POINTS AND BLADE SIDE BOUNDARY FIGURE

recorded by ʺToolsʺ ‐ ʺMapping keyʺ. F1 key is selected as the impeller mapping key in this paper.

Impeller Automatic Modeling In this paper, the idea of impeller modeling is as follows: First record the mapping key macro of impeller modeling process, then execute the point coordinates created by AutoLISP program, and last press impeller mapping key to execute automatic modeling of the impeller. The Recording of Mapping Key Macro (Dai Yuzhu et al, 2004; Zhang Renhui et al, 2009; Hou Weihua et al, 2006; Qi Xueyi, 2008) Mapping keys are keyboard macros which map a sequence of commands to specific keyboard keys or key combinations. Mapping keys are stored in the configuration file named mapkey, and each macro starts with a new line. The keyboard macro of impeller mapping key is

(1) Blade point coordinates are imported into Pro/E by ʺoffsetting the coordinate system reference pointʺ tool. (2) The points are imported into Pro/E are curved by ʺcurve toolʺ. (3) After the creation of the pressure surface and suction surface using the ʺboundary mixing toolʺ, the extra four surfaces of the blade can also be created with the ʺboundary mixing toolʺ. And then the six surfaces are merged and solidified. We can obtain the three‐dimensional model of a single blade after cutting the solidified blade with the shaft cross‐section diagram. (4) As the 3D model of single blade has been built, the work can be finished easily and the macro of impeller mapping keys has been created.

(a) The curve figure of blade pressure surface

(b)The blade pressure surface

(c)The blade 3D model

(d) Impeller water body figure

FIGURE 3. THE OPERATION PROCESS OF IMPELLER 3D MODELING.

The Simplification of Impeller 3D Modeling Based on Pro/E 25

Impeller Automatic Modeling

Curve Analysis

Open Pro/E after creating the macro and executing mapping key F1, then the impeller would be automatically created according to the tips, as shown in Figure 2(b) and Figure 3.

Two red curves in figure 2(c) are conducted to curve analysis by ʺAnalysisʺ ‐ ʺGeometryʺ ‐ ʺCurvature ʺ tools. The analysis results as shown in Figure 4(a). As can be seen from Figure 4(a), the change of the blade edge curvature has been stably improved a lot than before. It is indicating that the surface is more smoothness than it is before, so that the quality of the blades has increased.

Comparative Analysis The Comparison of Modeling Time The comparison experiment has been conducted on a set of people selected randomly. The results are shown in Table 1.

Surface Analysis (Yang Bin, 2005; Meng Junqiang, 2007) The impeller pressure surfaces obtained by the two methods are conducted to reflecting and coloring analysis by ʺAnalysisʺ ‐ ʺGeometryʺ ‐ ʺReflectionʺ tools. The analysis results are shown in Figure 4(b) and Figure 4(c). The smoothness of the surface can be measured on the basis of the degree of uniformity ʺreflectionʺ stripes. From Figure 4(b), can be found that the uniform of reflective stripes on the blade is better than it of before.

As shown in Table 1, the modelling time of new method gets great reduction, and modeling takes most of the time on data extraction and input of the blades. AutoLISP program is used to extract the impeller hydraulic drawing data, and create three‐dimensional modeling. It not only reduces the tedious of modeling and data processing time but improves modeling quality. The quality plays an important role in both finite element analysis and the performance of the hydraulic model.

The coloring curvature comparison of two blades is shown in Figure 4(c). The red zone represents a small curvature, while the green zone represents a larger curvature. It can be seen from the figure that the new method can effectively improve the quality of impeller model.

Measures of the impeller quality criteria are: smoothness and continuity of the blade curves and surfaces, which is reflected in the curvature of the curve and surface curvature.

TABLE 1 THE COMPARISON OF MODELING TIME.

Serial number

Blade modeling time of old method (min)

Blade modeling time of new method (min)

1 2 3 4 5

95 87 100 72 96

3 2 3 2 3

Impeller water body modeling time of old method (min) 113 102 125 90 118

(b) The reflection comparison figure of blade

(c) The colouring curvature comparison figure of blade

(a) The curvature comparison figure of blade side boundary

Impeller water body modeling time of new method (min) 10 8 12 6 8

FIGURE 4. THE RESULTS OF THE ANALYSIS.

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Li Qiang, Cai Wanfeng, Li Yue

Conclusions

and Irrigation Machinery Engineering, 2006, 24(1):14‐16,

(1) This article discusses the impeller modeling methods. Noticing the weaknesses of traditional modeling approach, so a new method is provided. By using AutoLISP, the author writes a program to simplify and extract data from drawing. By mapping key macros, the automatic modeling of impeller is achieved. (2) The new modeling approach improves the model quality. On the one hand, it uses much more data from the drawing; On the other hand, the automatic acquisition for coordinates minimizes the error of measurement and input. (3) This method can be used to obtain accurate 3D model of the impeller, which is the key point of researching high‐efficiency pumps. Completing the three‐dimensional model builds the foundation for subsequent meshing and finite element analysis.

26. Jiang Chaojun, Fan Ziyan. The point coordinates picking methods in AutoCAD drawing [J].Railway Investigation and Surveying, 2004, 30(6): 30‐32. Li Xuezhi. Visual LISP programming (AutoCAD2006)[M]. Beijing: TSINGHUA Uinversity Press, 2006: 251‐305. Lai Xide. Digital Design and Manufacturing of vane fluid machinery [M]. Chengdu: Sichuan Uinversity Press, 2008:2. Meng Junqiang. NURBS modeling technology research based on turbine blades [D]. Nanjing: Nanjing University of Aeronautics and Astronautics, 2007. Qi Xueyi,Zhang Jing,Hou Weihua. 3D design of double channel impeller. [J].Journal of Drainage and Irrigation Machinery Engineering, 2008, 26(2): 15‐18. Sun Yanhang, Wan Chuan, Li yongxuan.ObjectARX Practical Guide

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