Reprint ISSN 0974-1518 I J O ENGINEERING RESEARCH AND INDUSTRIAL APPLICATIONS NTERNATIONAL OURNAL F (IJERIA) @ ASCENT PUBLICATION ASCENT PUNE, INDIA www.ascent-journals.com
International J. of Engg. Research & Indu. Appls. (IJERIA). ISSN 0974-1518, Vol.5, No. II (May 2012), pp 99-108 IMPROVEMENT IN THE DESIGN OF A RADIAL TYPE VERTICAL SUBMERSIBLE OPEN WELL PUMP IMPELLER USING CFD VIRAJIT A. GUNDALE AND S. A. PATIL Abstract The usual practice of the Pump manufacturers in the small scale sector is to reverse engineer an existing design of an Impeller. Initially it seems an easy task to copy the overall dimensions of an impeller. But, it is a risk in copying the vane profile of existing impeller as it can have serious implications on the performance of the pump. This paper presents the improvements done in the vane profile for some candidate industry s Vertical Submersible Open well pump using one of the published design procedures available and known to the Industry. The improved Impeller model is then analyzed using turbo machinery geometry modeling and flow simulation system. The purpose of the analysis is to verify the performance at duty point or BEP (Best Efficiency Point). The paper also discusses the step by step procedure of both modeling for CFD as well as the entire CFD Process using a commercial CFD Software. ----------------------------------------- Keywords: Impeller, Vertical Submersible Open Well pump, turbomachinery geometry modeling, flow simulation, duty point, BEP, CFD http: //www.ascent-journals.com
100 VIRAJIT A. GUNDALE AND S. A. PATIL 1. INTRODUCTION CFD and its application is a rapidly developing discipline due to the continuous development in the capabilities of commercial software and the growth of computer power. CFD is already widely used in industry and its application is set to spread. CFD suffers from one big drawback - accuracy. In reality, most problems are far too complex to be solved accurately. For many applications however, such as building design, the level of accuracy required is very low and CFD results are more than adequate. Also, CFD usually gets the qualitative picture correct, which is useful in helping people understand what is happening within a flow. As a result of the accuracy of CFD being relatively poor, highly dependent on mesh quality and the models used, effective use of CFD relies heavily on experienced users. Before performing any CFD calculation, one should think about the information needed and how it will be extracted. To display the results of a CFD calculation most systems come with a post-processing and visualization package. These are often based on commercial packages. This paper discusses and presents the results of the application of CFD for the analysis and redesign of an existing Vertical Submersible Open Well pump. The subject Impeller of this paper is from a Radial Type Submersible Pump commercially available in the Indian Market. Such type of pumps are installed in Open Wells, Rivers or Lakes which are extensively used nowadays for Agricultural Irrigation use. The existing designs were developed by various companies in Ahmedabad and Coimbatore at the time where Computer Simulation was not available. Within the redesign steps process, two steps were undertaken in order to improve the existing Impeller at BEP : 1. Constructing 3D CAD Model copying all the existing geometry of the Impeller excluding the Vane Profile. The Vanes will be constructed based upon published design procedure available and known to the Industry. 2. Conducting CFD Analysis and verify the BEP of the new design and compare it with the existing one. The results presented in this paper are limited to the BEP operation, at which existing impeller was analyzed, and which the proposed new impeller was developed.
IMPROVEMENT IN THE DESIGN OF A RADIAL 101 2. CONSTRUCTION OF THE 3D CAD MODEL The vane angles β 1 and β 2 and diameters D 1 and D 2 are determined using various published procedures by Val S. Lobanoff and Robert R. Ross, Stepanoff, A. J., as well as by John Tuzson. The next step is to construct the vane shape. There are several methods to construct the vane shapes. The vane profile is constructed using the method suggested by G.K. Sahu in his book Pumps. The one used in practice consists of tangent circular arc. The radius of the Circular arc contained between the rings D 1 and D 2 is given by, R = Where R 2 and R 1 are the radius of Inner and Outer diameters of the impeller. Using these formulae we will design a Radial flow impeller for a Vertical Submersible Monoset for the following specifications : Q= 730 LPM at H = 13.5 Meters. This is a popular Impeller model available in the commercial market. CFD Analysis will be conducted on this design. Figures 1.1, 1.0 and 1.1 shows the construction of this impeller model. Figure 1.0 : Vane Generation
102 VIRAJIT A. GUNDALE AND S. A. PATIL The diffuser is a model which is the exact copy of the existing Vertical Submersible Open Well Pump. Fig 1.2 and 1.3 represent the 3D CAD Model of the Diffuser. A great portion of the energy imparted to the fluid by pumps consists of a velocity head:, whereas the energy is usually desired in the form of pressure. Consequently, an important component of pumps is a diffuser, which transforms the velocity head leaving the pump impeller into a pressure head by slowing the velocity head leaving the pump impeller into a pressure head by slowing down the flow gradually. Figure 1.1 : Vane Profile Figure 1.2 : Diffuser Model
IMPROVEMENT IN THE DESIGN OF A RADIAL 103 Figure 1.3 : Diffuser Vanes 3. ASSEMBLY FOR CFD ANALYSIS The next task is creating an Assembly representing the arrangement of the Impeller, Diffuser and Bowl. It must replicate the exact orientation of the actual pump. Fig 1.4 represents the assembly. The stationary parts here are the Bowl and the Diffuser. Figure 1.4 : Assembly for CFD Analysis
104 VIRAJIT A. GUNDALE AND S. A. PATIL The impeller has to be given a rotation of 2800 rpm or 292 rad/s. To facilitate this we have to include a part called Cover into the assembly as shown below in figure 1.5 The Rotation of the Impeller should be Anti- clockwise. This cover is disabled from the component control option as it will not take part in the CFD Analysis. Figure 1.5 : Impeller with Cover 4. BOUNDARY CONDITIONS The manufacturer of the existing 5.6 Kw/ 2 Stage Vertical Submersible Monoset pump has declared the performance at BEP as follows : Discharge Q= 0.01216 m 3 /sec (730 LPM) at 13.7 Meters of head. These are the inputs to be given as the Boundary Condition for our CFD Analysis. The initial boundary conditions are given as shown in above figure which are 1. An Inlet pressure of 101325 Pa which is the Environment pressure. 2. We have to set a pressure head of 13.5 m or 132355.88 Pa at the outlet. 3. It is then necessary to assign stationary walls condition to the guide vanes as shown below in figure 1.6
IMPROVEMENT IN THE DESIGN OF A RADIAL 105 Figure 1.6 : Boundary Conditions Aim of the Analysis: We have set the rotation to 2800 rpm and set a pressure head of 13.5 m which is the operating condition for this impeller. We will check the discharge of this impeller which is supposed to be 730 lpm. We will measure this value at the Impellers Outlet side. This will verify the design of the Vertical Submersible Open Well pump Impeller. Figures 1.7 shows the CFD Analysis in progress whereas figures 1.8 and 1.9 represent the output of this analysis Figure 1.7 : CFD Analysis
106 VIRAJIT A. GUNDALE AND S. A. PATIL Figure 1.8 : Cut Plot Figure 1.9 : Flow Trajectories
IMPROVEMENT IN THE DESIGN OF A RADIAL 107 6. RESULTS AND DISCUSSION Table 1.0 clearly suggests that there is a substantial improvement in the discharge of this design from 730 lpm to 793 lpm. If 90% accuracy of this result is considered still it will be worth trying to develop his impeller. In the past some successful designs are already developed using this same modeling and CFD approach. Table 1 : Results of the CFD Analysis Name Unit Value Progress Use in convergence Delta Criteria SG Volume Flow Rate 1 m^3/s 0.0132132 100 On 0.0001266 0.00014916 Equation Goal 1 lpm 792.794 100 On 7.5970860 8.94969838 CONCLUSION The results were conveyed to leading manufacturers in Maharashtra and Gujarat namely M/s VIRA PUMPS, Kolhapur Maharashtra, INDIA and UPAJ Engineering Pvt. Ltd, Ahmedabad, Gujarat, INDIA. Both of them have accepted and approved this design and will implement the same very shortly. The analysis of the existing impeller and the redesign effort for improved impeller demonstrated the potential for an improvement of the existing pump impeller using the integrated modeling and flow simulation approach. This can thus justify how such type of analysis can radically reduce the development time as well as the development costs. The analysis can be effortlessly repeated by making adjustments or modifications of the models till the desired result is not achieved. ACKNOWLEDGEMENTS We are heartily thankful to VIRA PUMPS, Kolhapur, Maharashtra, INDIA and UPAG Engineering Pvt. Ltd, Ahmedabad, Gujrat, INDIA for sharing us valuable information for this paper and providing necessary resources and setup for performing necessary experiments & trials.
108 VIRAJIT A. GUNDALE AND S. A. PATIL REFERENCES [1] Tuzson John, Centrifugal Pump Design, John Wiley & Sons, INC.,2000, ISBN 0-471-36100-3. [2] Lobanoff Val S., Ross Robert R., Centrifugal Pumps Designs & Applications, Jaico Publishing House, 2003, ISBN 81-7224-418-5. [3] Stepanoff A.J., Centrifugal and axial flowpumps, 1993, Krieger Pub. Co. in Malabar, Fla. [4] Elder R.L., Advances of CFD in Fluid Machinery Design, 2002, John Wiley & Sons Inc, ISBN 13: 9781860583537 [5] Sahu G.K., Pumps, New Age International (P) Ltd., 2005, ISBN 81-224-1224-6 [6] Versteeg, H.K. and Malalasekera, W., 2007, An introduction to Computational Fluid Dynamics: the Finite-Volume Method (2nd edition), Pearson. [7] Cooper, P.(1999): Perspective: The new face of R&D- A Case Study of the Pump Industry, ASME Journal of Fluids Engineering, December, pp. 654-664 Also Chemical Engineering, February, pp. 84-88. [8] Virajit Avinash Gundale, 2010, A new design approach for water cooled submersible motor and radial flow type pump with emphasis on both Electrical and Mechanical consideration PhD Thesis, UNEM, Costa Rica. Virajit A. Gundale Professor, Department of Mechanical Engineering, Sharad Institute of Technology College of Engineering, Yadrav Dist. Kolhapur, India. S. A. Patil Professor and Head, Department of Mechanical Engineering, Sinhgad Institute of Technology and Science, Narhe, Pune, Maharashtra, India.