Design of Monoblock Centrifugal Pump Impeller

Transcription

1 Design of Monoblock Centrifugal Pump Impeller Authors Mr. Chetan Kallappa Tambake 1, Prof. P. V. Salunke 1 Department of Mechanical Engineering, Walchand Institute of Technology, Ashok Chowk, Solapur , Maharashtra, India chetantambake@gmail.com, Contact No: Associate Professor, Department of Mechanical Engineering Walchand Institute of Technology, Ashok Chowk, Solapur , Maharashtra, India ABSTRACT This paper deals with design of monoblock centrifugal pump. The different parameters of pump impeller are impeller inlet and outlet diameter, blade angles and blade numbers but one of the most critical parameter is Impeller blade angles. In the present work, the conventional design of pump is carried out using empirical equations and then the model of closed impeller was generated using CATIA V5 software. The project work consists of to design and fabricate different impellers with keeping inlet angle constant and varying outlet blade angles and blade numbers too. Keywords- impeller design, CATIA V5, vane profile 1. INTRODUCTION A pump is a hydraulic machine which converts mechanical energy into hydraulic energy Or pressure energy. If the mechanical energy is converted into pressure energy by means of centrifugal forces acting on the fluid then the hydraulic machine is called as centrifugal pump. The centrifugal pump was developed in Europe in the late 1600 s and was seen in the United States in the early 1800 s. Centrifugal pumps are widely used in variety of applications such as water supply, irrigation, stream power plants, sewage, oil refineries, chemical plants, hydraulic power service etc. It is also used for transportation of solids and liquids over short to medium distance through the pipelines. Mostly, centrifugal pumps are designed to handle liquids normally single stage. The design of centrifugal pump involves large number of interdependent variables. The main components of centrifugal pump are Impeller and Casing. Fig. 1 shows the schematic diagram of centrifugal pump with parts. Impeller is the main rotating part that provides the centrifugal acceleration to the fluids; it is attached to drive shaft and driven by a motor. The material used for impeller is bronze, polycarbonate, cast iron, stainless steel. Casing houses the whole assembly and protects from harm. It directs the water of the impeller. It is Mr. Chetan Kallappa Tambake et al IJMEIT Volume 3 Issue 3 March 015 Page 1074

2 an air tight chamber surrounding the impeller. The shape of the casing is designed in such a way that the kinetic energy of the impeller is gradually changed to potential energy. This is achieved by gradually increasing the area of cross section in the direction of flow. Nowadays, for flow analysis Computational Fluid Dynamics tool is being widely used. Computational Fluid Dynamics (CFD) is branch of fluid dynamics, which uses numerical methods and algorithms to solve and analyze problems that involve fluid flows and used to simulate various design alternatives, identify flow problems, develop solutions and evaluate operating strategies.. OBJECTIVES To perform design, modelling, testing and analysis of the closed impeller by using software with modification in inlet and outlet blade angles of the impeller and optimization of number of vanes of the impeller to investigate the changes in head as well as efficiencies. 3. LITERATURE REVIEW A detailed review of the literature on the improvement in design of an impeller is presented as follows. Most of the researchers has kept outlet angle as constant by varying inlet blade angle for design and analysis purspose. Khin Cho Thin et al. 4 [008] explained the design & performance analysis of centrifugal pump. The design of centrifugal pump is done by taking input parameters like head, discharge, power, and speed. After completion of design, the performance analysis is carried out. Performance analysis of centrifugal pump includes shock losses, impeller friction losses, volute friction losses, disk friction losses, recirculation losses, actual head and graphs are drawn for each loss. For determining characteristic curves of centrifugal pump values of theoretical head, slip, shock losses, recirculation losses, etc. are calculated by varying volume flow rate. Amit Bhuptani et al. 1 [013] had undergone performance analysis of centrifugal pump by using conventional design method. The important parameters like impeller inlet and outlet diameter, inlet and outlet blade angle, inlet width, number of vanes are calculated by using conventional design method. The modeling is done by using Solid Works 009 software and meshing is done by using ANSYS 13.0 workbench. The simulation tool used is Fluid Flow (CFX). For boundary conditions, K- turbulence model is selected. He examined that, modified impeller having maximum pressure as compared to existing impeller which ultimately increases head then existing impeller. Ashish J. Patel et al. [014] had undergone design and analysis of centrifugal pump impeller. Conventional design method is used for determining values of different parameters. CFD methodology is used for analysis purpose and K- turbulence model is used as turbulence model. Shardul Sunil Kulkarni 6 [014] explained about design of a centrifugal pump and performance is analyzed by Computational Fluid Dynamic (CFD). The design is carried out by the input parameter provided by customer. Depending upon the calculated parameters modeling of pump component is done on PTC Creo.0 and meshing is done in ICEM tool which is used for CFD software and performance curves are drawn. Shyam Karanth et al. 7 [014] had undergone design and analysis of a submersible pump for improvement in the pump efficiency. The different parameters are calculated and used for modeling of submersible pump impeller. The author had done design in such a way that, the overall efficiency of new pump model is increased by 7% as compared to existing model. 4. DESIGN OF MONOBLOCK PUMP IMPELLER The selected pump is three horse power motor drive single stage monoblock centrifugal pumps. Impeller is designed on the basis of design flow rate, pump head and pump speed. For design calculations, the design parameters of Laxmi 3AM60 Pump are taken as follows: Flow rate, Q = 650 LPM Mr. Chetan Kallappa Tambake et al IJMEIT Volume 3 Issue 3 March 015 Page 1075

3 Power = 3 HP Head, H = 1 m Pump Speed, n = 880 rpm Gravitational Acceleration, g = 9.81 m/s Density of water, 1000 kg/m 3 Pipe Size = mm Type of Impeller = Closed Impeller Now, Flow rate, Q = 650 LPM = Flow rate, Q = m 3 /s Power = 3 HP Since, 1 HP = 746 W = kw Power = 3 HP = =.38 kw Power = 3 HP =.38 kw Specific Speed (n s ): n s = (1) n s = n s = RPM Table no.1 Selection of Centrifugal Pump Sr. No. Specific Speed (rpm) Type of Centrifugal Pump Slow speed pump with radial flow at outlet Medium speed pump with radial flow at outlet High speed pump with radial flow at outlet High speed pump with mixed flow at outlet High speed pump with axial flow at outlet Overall Efficiency ( ) = ( 100 Overall Efficiency ( ) = 56.9 % Hydraulic Efficiency (η Hy ): η Hy = () η Hy = η Hy = = 76.15% Eye Diameter of Impeller (D 0 ): D 0 = k 0 (3) Where, K 0 = constant parameter which value is chosen as 4.5 D 0 = 4.5 D 0 = m = mm Inlet Diameter of Impeller (D 1 ): D 1 = (1.1~1.15) k 0 (4) D 1 =1.14 D 1 = m = mm Assumptions for Velocity Diagram of pump impeller; [5] 1. Liquid enters the impeller eye in radial direction.. No energy losses in impeller due to friction and eddy formation. 3. Liquid enters without shock. 4. Uniform velocity distribution in the passage between two adjacent vanes. According to above table no. 1 and value of specific speed it is found that, the type of pump is Medium speed pump with radial flow at outlet. Overall efficiency is calculated as; Overall Efficiency ( ) = 100 Where, Pump output = Pump output = 1.74 kw Here, Q = 650 lpm Pump input = 3 HP =.38 kw = Fig. : Velocity Diagram From inlet velocity diagram; Mr. Chetan Kallappa Tambake et al IJMEIT Volume 3 Issue 3 March 015 Page 1076

4 Inlet Tangential Velocity (U 1 ): U 1 = (5) U 1 = U 1 = m/s Now, Absolute Velocity of liquid at inlet (V 1 ); Mass flow rate, Q = D 1 V 1 /4 V 1 = 4 Q/ D 1 (6) V 1 = V 1 =.1675 m/s = V f1 Inlet blade angle of impeller (β 1 ): tanβ 1 = tanβ 1 = (7) tanβ 1 = tanβ 1 = β 1 = tan 1 (0.180) β 1 = From right angle triangle, Relative velocity at inlet (Vr 1 ): Vr 1 = V 1 + U 1 Vr 1 = Vr 1 = Vr 1 = 1.1 m/s = Vr Or Relative velocity at inlet, (8) Vr = (9) Vr 1 = Vr 1 = 1.80 m/s Relative velocity at inlet, Vr 1 = 1.80 m/s Outlet diameter of impeller (D ): Now, Head coefficient (ψ) is given by; Ψ = Ψ = g H /η U Generally, Ψ = 0.5 to 0.6 The value taken for Ψ is 0.58 U = U = (10) U = m/s Tangential velocity at outlet, U = m/s Outlet diameter of impeller (D ): U = (11) D = D = D = m = 15.1 mm From outlet velocity triangle, Flow coefficient ( ) is given by; = = (1) Generally, = 0.1 to 0. The flow coefficient is taken as Flow velocity at outlet (V f ) is; V f = U V f = V f = m/s Flow velocity at outlet, V f = m/s Velocity of whirl at outlet (V w ) is; Vr = V f + (U - V w ) (13) (1.1) = (3.3033) + ( V w ) = ( V w ) V w = m/s Velocity of whirl at outlet, V w = m/s Absolute velocity of liquid at outlet (V ); V = (14) V = V = m/s Outlet blade angle (β ) is; tanβ = (15) tanβ = tanβ = tanβ = β = tan -1 (0.807) β = = Outlet blade angle, β = = Relative velocity at outlet, Vr = (16) Vr = Vr = m/s Relative velocity at outlet, Vr = m/s Radius of the Impeller Eye (R 0 ): Mr. Chetan Kallappa Tambake et al IJMEIT Volume 3 Issue 3 March 015 Page 1077

5 R 0 = (17) R 0 = R 0 = m R 0 = 34.88mm Blade Number (Z): Blade Number, 6 Slip Value (σ): β β (18) σ = (19) σ = σ = σ = Slip Value, σ = Pressure Head (H m ): H m = (0) H m = H m = m Radius of circular arc (R): R = (1) Where, R = radius of outlet diameter = 6.55 mm R 1 = radius of inlet diameter = mm β 1 = Inlet blade angle β = outlet blade angle R = 5. Number of vanes, Z=6 6. Inlet vane angle, β 1 =10.1 o 7. Outlet vane angle, β = Tangential velocity at inlet, U 1 =1.075 m/s 9. Tangential velocity at outlet, U = m/s 10. Flow velocity at inlet, V f1 =.1675m/s 11. Flow velocity at outlet, V f1 =.8550 m/s 1. Relative velocity at inlet, V r1 =1.1 m/s 13. Relative velocity at outlet, V r =1.1m/s 14. Hydraulic efficiency, η Hy =76.15% 15. Overall efficiency, η overall = 56.96% 5. MODELING OF IMPELLER USING CATIA Fig. 3 shows the model of closed type impeller is created using CATIA V5 software. The impeller has six vanes enclosed between two shrouds. Fig. 4 shows the vanes of impeller. The impeller inlet angle is and outlet angle is There are total six vanes and thickness of each vane is 4 mm. Two holes of diameter 3. mm are drawn at 60 mm. R = R = mm The calculated parameters are as below; 1. Specific Speed, N s =46.48 RPM. Impeller Eye Diameter, D 0 =69.97mm 3. Impeller inlet Diameter, D 1 =79.77mm 4. Impeller Outlet Diameter, D =15.1mm Fig.3: Model of Impeller using CATIA Mr. Chetan Kallappa Tambake et al IJMEIT Volume 3 Issue 3 March 015 Page 1078

6 6. CONCLUSIONS Fig. 4 Vanes of Impeller To design a centrifugal pump impeller a procedure is proposed. The design and modelling is done by using theoretical and software method. To make vanes of impeller, it is important to draw the curves accurately as per dimensions. In vane profile, if number of circles increases then curve becomes smooth in nature. Technology, Vol.-, , PP Mehul P. Mehta, Performance Analysis of Mixed Flow Pump Impeller using CFD, International Journal of Emerging Trends and Development, Vol.1, Jan 013, PP: Shardul Sunil Kulkarni, Parametric Study of Centrifugal Pump and its Performance Analysis using CFD, International Journal of Emerging Technology and Advanced Engineering, Vol. 4, July 014, PP: Shyam Karanth, V. K. Havanur, Design, Modeling & Analysis of a Submersible Pump and to improve the Pump Efficiency, International Journal of Latest Trends in Engineering and Technology (IJLTET), Vol. 4, July 014, PP Prof. V. M. Patil, Prof. D. M. Patil, Prof. V. K. Otari, Prof. U. N. Jawale, Fluid Power Nirali Publication, Third Edition, Pp. No REFERENCES 1. Amit Bhuptani, Prof. Ravi K. Patel, K. M. Bhuptani, Design and Analysis of Centrifugal Pump, Journal of Information, Knowledge and Research in Mechanical Engineering, Vol.-, Nov. 1-13, PP: Ashish J. Patel, Bhaumik B. Patel, A Survey of CFD Analysis of Centrifugal Pump Impeller, IJSRD, Vol.-, 014, PP Gundale V.A., Joshi G.R., A Simplified 3d Model Approach in Constructing the Plain Vane Profile of A Radial Type Submersible Pump Impeller, Research Journal of Engineering Sciences, Vol. 4, July 013, PP Khin Cho Thin, Mya Mya Khaing and Khin Moung Aye, Design and Performance Analysis of Centrifugal Pump, World Academy of Science, Engineering and Mr. Chetan Kallappa Tambake et al IJMEIT Volume 3 Issue 3 March 015 Page 1079