MODELING AND ANALYSIS OF FLAT SHAPE AND TRUNK SHAPE PISTON M. NARENDER* 1, D. BAHAR 1

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1 ISSN IJESR/July 2018/ Vol-8/Issue-7/14-20 MODELING AND ANALYSIS OF FLAT SHAPE AND TRUNK SHAPE PISTON ABSTRACT M. NARENDER* 1, D. BAHAR 1 1 Assistant Professor, Department of Mechanical Engineering., RGUKT-Basar, (T.S), India. Engine piston is one of the crucial components in internal combustion engine which endures high thermal and mechanical stress during its operation. Often Piston damages are attributed to temperature, wear, Fatigue etc. Among fatigue damages, thermal fatigue and mechanical fatigue play a prominent role. Therefore it is urgent to analyze the strength and reliability of piston. Lot of research work on piston has been proposed by researchers pertaining to new geometries, materials and manufacturing techniques. This evolution has undergone with a continuous improvement over the last decades and still paves the way for further improvements. In this communication, flat shape and trunk shape piston are designed using SOLIDWORKS software and analyzed in ANSYS software. Aluminum alloy and cast iron are considered as piston material. Results of different shape and different material for piston are compared. From the results, it is found that piston made of cast iron in trunk shape would be more suitable under static structural analysis. Keywords: Piston, flat, trunk, Aluminum, cast iron, equivalent strain, equivalent stress, Solid Works, ANSYS. 1. INTRODUCTION Function of engine is to convert energy from one form to another form. After combustion, Piston transmits the force of combustion to the crankshaft through the connecting rod and piston rings are used to seal the compression in the cylinder. In few engines, piston also functions. The piston must come to stand still at the end of each stroke before reversing its course in the combustion chamber. A schematic diagram of piston is shown in Fig. 1. Fig. 1. Schematic diagram of piston Head, skirt, ring grooves, and land are the structural components of the piston. However all pistons do not look like same but pistons can have differently shaped heads like: flat, trunk, dish etc. present study has considered *Corresponding Author 14

2 flat and trunk shaped piston. Inside combustion chamber, a very high temperature and pressure take place during combustion therefore to withstand the thermal and mechanical fatigue, a piston must be made of tough material but light in weight to maintain the power to weight ratio. In order to overcome the inertia and momentum at high speed, piston must be carefully balanced and weighted. R.C singh et. al., [1] observed that a piston should have less weight to reduce the inertia forces and rigid construction to endure thermal and mechanical distortion. Since metal expands when heated up to higher temperature therefore space must be provided for lubrication between the pistons and the cylinder walls. Clearance is also provided in the combustion chamber which depends upon the diameter of the piston as well as its material. The skirt of the bottom part of the piston runs much cooler than the top part therefore it does not require as much clearance as the head. Cast iron does not expand as fast or as much as aluminum therefore aluminum piston requires more clearance to prevent binding or seizing during overheating. Some desirable characteristics and design considerations of a piston are as follows: 1. Light weight. 2. Smooth operation and mechanically strength. 3. It should have should have required strength to withstand the high pressures and thermal distortions. 4. It should form effective oil sealing. 5. Smooth high speed reciprocation. 6. It should have minimum weight to reduce the inertia forces. By keeping aforementioned issues in consideration, cast iron and aluminum is taken as piston material. S. Ji et. al., [2] observed that AlSi alloy have been extensively used in automobile and aerospace to provide good mechanical and thermal properties with light weight structures. CH. V. Rajam et. al., [3] performed a Von misses test on a coated piston using ANSYS and examined the stresses due to the gas pressure and thermal variations. H. Zhang et. al., [4] simulated a marine diesel engine piston to analyze its temperature zones, thermal and mechanical stress by using following parameters: piston material, combustion pressure, inertial effects and temperature. S.S Chougule and V. H Khatawate [5] describes the stress distribution of the piston by using finite element method (FEM) and investigated the actual engine condition during combustion process. R. P. Georgiev and Dr. P V Roldan [6] carried out using ANSYS for optimum geometry to describe the stress distribution and thermal stresses of three different aluminum alloys piston. D. K. Sonar and M. chattopadhyay [7] studied the damage mechanisms of pistons and found that damage mechanism have different origins but mains are wear, temperature and fatigue related. From there study it was also evident that thermal stress was higher than mechanically induced stress hence thermal stresses are critical for piston design. 2. MATERIALS AND METHODS 2.1 Calculations of dimensions for piston Thickness of Piston Head ( t H ): The piston thickness of piston head calculated using the following Grashoff s formule. where P w = maximum pressure Copyright 2018 Published by IJESR. All rights reserved 15

3 D = cylinder bore/outside diameter of the piston L=Length of stroke σ t =permissible tensile stress for the material of the piston. Heat Flow through the Piston Head (H) The heat flow through the piston head is calculated using the formula. Where K= thermal conductivity of material Tc = temperature at center of piston head in C. Te = temperature at edges of piston head in C. Radial Thickness of Ring (t 1 ) Where, D = cylinder bore in mm=80 mm. P f = pressure of fuel on cylinder wall in N/mm 2. Its value is limited from to N/mm 2. Axial Thickness of Ring (t 2 ) The thickness of the rings may be taken as Number of rings (n r ) Width of the top land (b 1 ) Width of other lands (b 2 ) Maximum Thickness of Barrel at the top end(t 3 ): Radial depth of the piston ring grooves (b) is about 0.4 mm more than radial thickness of the piston rings Piston pin diameter (d 0 ) In above equations following data is considered: P w =8MPa, D=80mm, L=110mm,σ t =124.4MPa, K =174.15W/mK, (Tc-Te) =75, P f =0.042 N/mm 2 Dimensions obtained t H = 8.9mm, t 1 = 3mm, t 2 =2.1mm, n r = 4, b 1 =10.68 mm, b 2 =1.575 mm, b = 3.4 mm, t 3 =10.7 mm, d 0 =24m. Copyright 2018 Published by IJESR. All rights reserved 16

4 2.2 Materials From Ashby charts, it is concluded that aluminum alloy as well as cast iron metals have satisfied the requirement for the manufacturing of the piston and properties of these materials are presented in Table 1 respectively. Material Properties Table 1a: Properties of Aluminum Mechanical property Value Unit Density Kg/m3 Thermal Conductivity W/m/C Compressive Yield 2.07e+008 Pa Strength Tensile Yield Strength 280 MPa Tensile Ultimate GPa Strength Reference Temperature 22 C Young's Modulus 71 GPa Poisson's Ratio 0.33 Table 1b: Properties of Cast Iron Mechanical property Value Unit Density 7200 Kg/m3 Coefficient of Thermal 1.7e-005 1/C Exapansion Tensile Yield Strength 240 MPa Reference Temperature 22 O C Young's Modulus GPa Poisson's Ratio 0.28 Bulk Modulus e+005 Pa Thermal conductivity 52 W/m/C Copyright 2018 Published by IJESR. All rights reserved 17

5 3. DESIGNED MODELS OF PISTONS Two types of Pistons: flat type and trunk type pistons are designed in solid works as shown in Fig. 2a and Fig. 2b respectively. Fig. 2a: Flat type piston Fig. 2b: Trunk Type Piston Figure 2: Models of Pistons 4. RESULTS AND DISCUSSION Designed models shown in Fig. 2 were transported to ANSYS in which fine meshing was generated on these models. Load applied and boundary conditions are considered same in the analysis only material is changed. Fig. 3 shows the analysis of equivalent strain in flat type piston made of Aluminum (Fig. 3a) and cast Iron (Fig. 3b). Fig. 3a: Equivalent Strain in Al Piston Fig. 3b: Equivalent Strain in Cast Iron Fig. 3: Analysis of Equivalent strain in Flat type Piston From Fig. 3a and Fig. 3b, it is clear that induced strain is high in the centre of top surface and moreover it can be noticed that strain is high in the piston made of cast iron. Similar analysis is also performed for equivalent stresses as shown in Fig. 4. From Figure it is clear that equivalent stress is higher in the hole, meant for pin. Copyright 2018 Published by IJESR. All rights reserved 18

6 Further it can be observed that magnitude of induced equivalent stress is higher in case of Aluminum piston (Fig. 4a) as compared to cast iron piston (Fig. 4b) Figure 4a: Equivalent Stresses in Al Piston Figure 4b: Equivalent Stresses in Cast Iron Fig. 4: Analysis of equivalent stresses in Flat type Piston Similarly analysis of equivalent strain is also performed on trunk shaped piston as shown in Fig. 5. In Fig. 5a, Aluminum is considered as piston material and cast iron is selected as piston material in Fig. 5b. Equivalent strain found to be maximum at the centre of top surface and further it is for in the piston made of aluminum. Fig. 5a: Analysis of equivalent strain in Aluminum Piston Fig. 5b: Analysis of equivalent strain in cast iron piston Fig. 5: Analysis of equivalent strain in trunk type piston In Fig. 6, analysis of equivalent stress is performed in trunk type piston. It is observed that the magnitude of stress is more at the centre of the trunk surface as shown in Fig. 6a and 6b. Also it can be observed that stress is higher in aluminum piston as compare to cast iron with trunk shape. Copyright 2018 Published by IJESR. All rights reserved 19

7 Fig. 6a: Analysis of equivalent stresses in Aluminum Piston Fig. 6b: Analysis of equivalent stresses in Cast Iron Piston Fig. 6: Analysis of equivalent stresses in trunk type piston 5. CONCLUSION From this communication, following conclusions are drawn. 1. In flat type piston equivalent strain is higher in cast iron piston as compare to aluminum but in trunk type piston it s higher in aluminum piston. 2. In flat type piston equivalent stress is higher at the hole, mean for pin but in trunk type piston equivalent stress is higher at the centre of the top surface. 3. Whether piston is flat type or trunk type, higher stress is found in the piston made of aluminum. By aforementioned points it is concluded that piston made cast iron is better as compared to aluminum and trunk shape is better as compare to flat. REFERENCES [1] Singh RC, Lal R, Ranganath MS, Chaudhary R. Failure of piston in IC engines: A review. International Journal of Modern Engineering Research 2014; 4(9): [2] Ji S, Watson D, Fan Z, White M. Development of a super ductile diecast Al Mg Si alloy. Material Science and Engineering A 2012; 556: [3] Rajam Ch. V, Murthy PVK, Murali Krishna MVS. Linear static structural analysis of optimized piston for bio-fuel using ANSYS. International Journal of Mechanical and Production Engineering Research and Development 2013; 3(2): [4] Zhang H, Lin Z, Xu D. An analysis to thermal load and mechanical load coupling of a gasoline engine piston. Journal of Theoretical and Applied Information Technology 2013; 48 (2): [5] Chougule SS, Khatawate VH. Piston Strength Analysis Using FEM. International Journal of Engineering Research and Applications 2013; 3 (2): [6] Georgiev RP, Dr. Pedro Villanueva Roldan Dk. Design a four-cylinder Internal Combustion EnginE. International Journal of Mechanical Engineering Research & Applications. 2013; 1(5). [7] Sonar DK, Chattopadhyay M. Theoretical Analysis of Stress and Design of Piston Head using CATIA & ANSYS. International Journal of Engineering Science Invention 2015; 4 (6): Copyright 2018 Published by IJESR. All rights reserved 20