EXPERIMENTAL INVESTIGATION OF A CENTRIFUGAL BLOWER BY USING CFD

Transcription

1 Int. J. Mech. Eng. & Rob. Res Karthik V and Rajeshkannah T, 2014 Research Paper ISSN Vol. 3, No. 3, July IJMERR. All Rights Reserved EXPERIMENTAL INVESTIGATION OF A CENTRIFUGAL BLOWER BY USING CFD Karthik V 1 * and Rajeshkannah T 1 *Corresponding Author: Karthik V, karthikroshan3@gmail.com As the diffusion of flow process is highly complex in centrifugal blower operation, it is necessary to design and develop the geometry of impeller and casing to reduce the flow losses significantly. In the present study, the methodology to find near optimum combination of blower operating variables for performance enhancement were analyzed using Computational Fluid Dynamics (CFD). Taguchi Orthogonal Array (OA) based Design of Experiments (DoE) technique to determine the required experimental trials. The experimental results are justified by Analysis of Variance (ANOVA) and confirmed by conformation experiments. The parameters chosen for design optimization are Impeller outlet diameter, Impeller wheel width, Thickness of blade, Blade width and Impeller inlet diameter. The levels for the parametric specification are chosen from the ranges and blade types where the blower will get the best efficiency. CFD results were validated by the fine conformity between the CFD results and the experimental results. Keywords: Centrifugal blower, CFD, Taguchi, Impeller INTRODUCTION Centrifugal blowers are widely used in different industrial applications, which are proficient of as long as restrained to high-pressure rise and flow rates. Centrifugal blowers are mainly two main parts, namely, the casing and the impeller. Many experimental studies have been reported on the performance of centrifugal pump impeller. The performance of centrifugal blower is mainly on design parameters of impeller. Changing some geometric characteristics of the centrifugal pump impeller the blower has more efficiency taking with energy crises into consideration. In this paper, an experimental study has been carried out to study the performance characteristics of centrifugal blower. In order to improve the performance the effects that the pertinent design parameters has been carried out for different cases of primary geometry of the impeller including the Impeller outlet diameter, Impeller wheel width, Thickness of blade, Blade width and Impeller inlet diameter. 1 Department of Mechanical Engineering, Anjalai Ammal Mahalingam Engineering College, Kovilvenni

2 MODEL CONSTRUCTION For this study, the three-dimensional blower model Figure 1 was first created with the existing model. The parameters of the existing model blowers are listed in Table 1. The design of impeller mainly include: Impeller outer diameter, Impeller width, Blade Thickness, Blade width and Impeller inlet diameter. Figure 1: Three Dimensional Blower for Existing Model 1. To calculate area of orifice 2 a 0 = ( /4)*d 0 = ( /4)*( ) = m 2. To calculate area of pipe 2 a 0 = ( /4)*d 0 =( /4)*( ) = m 3. To calculate discharge Q = {(cd*a 0 *a 1 )[ (2*g*h)]}/ { (a 1 2 a 02 )} Trial 1: (1/4 open) Q = {(0.6*0.0044*0.0177)[ (2*9.81*0.045)]}/ = 0.166*0.939*60 = 9.76 m 3 /min Trial 2: (1/2 open) Table 1: of the Existing Model Experimental Part for Existing Model 1. To determine the discharge (Q) 2. To determine the area of orifice (a 0 ) 3. To determine the area of pipe (a 1 ) Diameter of the orifice = 7.5 cm = m Area of the pipe = 15 cm = 0.15 m Coefficient of discharge = 0.6 Dimensions (mm) Impeller outer diameter 390 Impeller inner diameter 225 Impeller width 75 Blade thickness 2 Blade width 75 Q = {(0.6*0.0044*0.0177)[ (2*9.81*0.18)]}/ = 0.166*1.879*60 = m 3 /min Trial 3: (3/4 open) Q = {(0.6*0.0044*0.0177)[ (2*9.81*0.21)]}/ = 0.166*2.029*60 = m 3 /min Trial 4: (full open) Q = {(0.6*0.0044*0.0177)[ (2*9.81*0.22)]}/ = 0.166*2.077*60 = m 3 /min 40

3 Table 2: Experimental Results for Existing Model S. No. Gate Valve Discharge (m 3 /min) 1. Close / / / Full open 21.6 TAGUCHI METHOD Dr. Taguchi of Nippon Telephones and Telegraph Company, Japan has developed a method based on OA experiments which gives much reduced variance for the experiment with optimum settings of control parameters. Taguchi Technique is applied to plan the experiments, in a three step approach namely system design, parameter design and tolerance design. In System Design, the most influenced process parameters were identified Table 3: CFD Results for Existing Model Output CFD Results Discharge (m 3 /min) 10.3 Pressure (pa) 1385 taking with minimum trials into consideration. Secondly, Signal-to-Noise (S/N) ratio to analyze experiment data, for determining quality characteristics implemented in engineering design problems. Thirdly, estimates individual parameter contributions. This study is to maximize discharge, pressure and efficiency considering power consumption within optimal levels of process parameters; the higher the better quality characteristic is selected. A standard Taguchi L9 (3 3 ) Orthogonal Array (OA) is chosen for this investigation as it can operate three parameters, each at three levels. The three most influenced identified parameters (A) Figure 2: CFD Results for Existing Model 41

4 Impeller width; (B) Blade Thickness; and (C) Blade width which affect the performance of blower. Sufficient details of the effect of different parameter values on experimental results can be obtained by choosing three levels for each parameter to investigate. The test run is designated by replacing the level number 1, 2, 3 of parameters A, B, and C in L9 OA with the chosen parameters level values in Table 4. Each row of the array represents a test run parameter setting condition. Table 4: and Levels Impeller width (A) Blade thickness (B) Blade width (C) Signal-to-Noise Ratio Levels The Signal-to-Noise ratio (S/N) ratio represents both the average and variation of the experimental results to analysis the test run results using Taguchi Methods. The S/N ratio is also used in Analysis of Variance (ANOVA). The S/N ratios in Taguchi Methods are, e.g., smaller-the-better, larger-the-better, nominalthe-best and operating window. The standard S/N ratios can be made to order to fit explicit applications. Depends on the physical properties of the problem proper S/N ratio is selecting. The performance improvement is the objective function, so that the larger-the-better S/N ratio is chosen in this study. Where, S/N LTB is larger-the-better Signal-to-Noise ratio, MSD is the mean square deviation around the target, y i is the individually measured response value (experiment result), n is the number of measurements taken in one test run. Table 5 shows the results of each test run. Trial Table 5: Trials and Results A B C Discharge (m 3 /min) Pressure (pa) Mean of S/N Ratios Impeller Width (A) 70 mm = ( )/3 = mm = ( )/3 = mm = ( )/3 = 18.2 Blade Thickness (B) 1.8 mm = ( )/3 = mm = ( )/3 = mm = ( )/3 = Blade Width (C) 70 mm = ( )/3 = mm = ( )/3 =

5 Figure 3: Responses for A, B, C by S/N Ratios Figure 4: CFD Results for Designed Model 43

6 80 mm = ( )/3 = Table 6: Optimized Result Optimized Dimensions (mm) Impeller width 80 Blade thickness 1.8 Blade width 80 Table 7: CFD Results for Designed Model Output CFD Results Discharge (m 3 /min) 17.1 Pressure (pa) 1650 CONCLUSION Comparing the discharge of existing model by experimental is less than 5.24% from the CFD analysis. Comparing the pressure of existing model by experimental is less than 2.52% from the CFD analysis. Comparing the discharge of existing model by CFD analysis is more than 39.7% from the designed model by CFD analysis. Comparing the pressure of existing model by CFD analysis is more than 16% to the designed model by CFD analysis. REFERENCES 1. Chen-Kang Huang and Mu-En Hsieh (2009), Performance Analysis and Optimized Design of Backward Curved Airfoil Centrifugal Blowers, HVAC & Research, Vol. 15, pp Jie Jina Ying Fan, Wei Han and Jiaxin Hu (2012), Design and Analysis on Hydraulic Model of The Ultra-Low Specific-Speed Centrifugal Pump, International Conference on Advances in Computational Modeling and Simulation, Vol. 31, pp Pham Ngoc Son, Jaewon Kim E and Ahn Y (2011), Effects of Bell Mouth Geometries on the Flow Rate of Centrifugal Blowers, Journal of Mechanical Science and Technology, Vol. 25, No. 9, pp Shojaeefard M H, Tahani M, Ehghaghi M B, Fallahian M A and Beglari M (2012), Numerical Study of the Effects of Some Geometric Characteristics of a Centrifugal Pump Impeller that Pumps a Viscous Fluid, Computers & Fluids, Vol. 60, pp Sun-Sheng Yang, Shahram Derakhshan and Fan-Yu Kong (2012), Theoretical, Numerical and Experimental Prediction of Pump as Turbine Performance, Renewable Energy, Vol. 48, pp Taguchi G (1992), Taguchi Methods- Research and Development, ASI Press, Dearborn, MI. 7. Zhang Bin, Wang Tong, Gu Chuan Gang and Shu Xin Wei (2011), Blade Optimization Design and Performance Investigations of an Ultra-Low Specific Speed Centrifugal Blower, Science China Technological Science, Vol. 54, pp