Finite Element Analysis of IC Engine Piston Using Thermo Mechanical Approach 1 S.Sathishkumar, Dr.M.Kannan and 3 V.Raguraman, 1 PG Scholar, Professor, 3 Assistant professor, 1,,3 Department of Mechanical Engineering, 1,3 SKP Engineering College, Tiruvannamalai, M.A.M.college of Engineering,trichy, Tamil Nadu, India Abstract: The main objective of this research work is to investigate and analyze the stress distribution of piston at actual engine condition. The parameters used for the simulation of piston are its operating gas pressure and material properties. To evaluate the material properties of piston the maximum principal stress, and von mises stresses, & shear stress were calculated. These stresses were calculated for two different materials by comparing Aluminum alloy and cast iron. Composite material provides less stress concentration and more stability at higher temperature. For stability checking at higher temperature thermal analysis were carried out. This research work suggests a new type of Aluminum alloy (composite material) that can sustain at higher temperature (573K) and pressure (6195KPa). The structure of piston was modeled by using CATIA V5R0 software. Finite element modeling and analysis were performed using ANSYS 14. The Maximum with standing temperature & Maximum pressure of the piston were obtained and its stress distribution are analyzed. Keywords: Von Mises, Piston, Thermal Analysis, Pressure, CATIAV5R0, ANSYS14 I. INTRODUCTION Function of the piston The piston as an element of power transmission In the cylinder of an engine, the energy bounded up in the fuel is rapidly converted into heat and pressure during the combustion cycle. The heat and pressure values increase greatly within a very short period of time. The piston as the moving part of the combustion chamber has the task of converting this released energy into mechanical work. The basic structure of the piston is a hollow cylinder, closed on one side, with the segments piston crown with ring belt, pin bass and skirt. Figure 1: Piston Assembly The piston crown transfers the gas forces resulting from the combustion of the fuel air mixture via pin boss, the piston pin, and the connecting rod to the crankshaft. The gas pressure against the piston crown and the oscillating initial forces, reflected to in the following as the inertia force, of the piston and connecting rod constitute the piston force. Due to the redirection of the piston force in the direction of the connecting rod (rod force) an Additional component arises, following the force parallelogram namely the lateral force also known as the normal force. This force pressure the piston skirt against the cylinder bore During a combustion cycle, the lateral Force changes direction several times, which pressures the piston from one side of the cylinder bore to other, due to the existing piston clearance. The most important tasks that the piston must fulfill are Available Online@ 339 Transmission of force form and to the working gas. Variable bounding of the working chamber (cylinder) Sealing off the working chamber Linear guiding of the conrode (trunk piston engines) Heat dissipation Support charge exchange by drawing and Discharging (four-stroke engine) Support mixture formation (by means of Suitable shape of the piston surface on the Combustion chamber side) Controlling charge exchange(in two-stroke Engine) Guiding the sealing elements (piston) Guiding the conrod (for top guided conrode) As the specific engine output increase, so do the requirements on the piston at the same time. A. Different Types of Pistons Various types of pistons are employed on Different engines. This is because each type fulfils Some specific requirements on a particular engine. Some pistons have complex head formation, some Have specially formed skirts, and other has Geometrical, peculiarities. Based on various considerations, the piston may be categorized as Follows: 1. On the basis of head formation: i. Deflector head piston ii. Combustion chamber type piston iii. Domed and depression headed piston. On the basis of skirt profile i. Slipper piston ii. Cut way piston 3. On the basis of skirt piston: i. Solid skirt piston ii. Split skirt piston 4. On the basis of other specialties: i. Cam ground piston ii. Taper piston iii. Oval piston
II. MATERIAL PROPERTY h 1 = 46.8mm Table 1: Property of Aluminum Alloy S/No Material Property Value h c =h- h S h c = Piston Crown Height 1 Young s modulus 7.10E+10 Poisson ratio 0.33 3 Thermal conductivity 09w/m-k 4 Density 710kg/m3 5 Specific heat 900J/kg0C 6 Thermal expansion.0e-05 Table : Property for cast Iron S/No Material Property Value 1 Young s modulus 1.80E+11 Poisson ratio 0.6-0.3 3 Thermal conductivity 7-46 w/m-k 4 Density 6800-7800kg/m3 5 Specific heat 840J/kg0C 6 Thermal expansion 1.00E-05 III. 1) Piston Diameter D= 78 Mm THEORETICAL CALCULATION ) Piston inside diameter Di=D-(s+t+Δt) S= 5 (piston crown wall thickness) t= 3.5 (ring radial thickness ) Δt= 0.8 (ring radial clearance in the piston groove) D i =78-(5+3.5+0.8) D i = 59.4mm 3) Skirt radial thickness (ST) ST= D Di D= piston diameter Di = piston inside diameter ST= 78 59.4 ST=9.3 4) Piston outer diameter (dδ) h 1 +h c = dδ h 1 = height of piston top part dδ = piston pin outer diameter h 1 = 0.60 78 h - Piston Height h S Piston Skirt Height Available Online@ 340 h=88 h S =58 h c = 88-58 h c =30 h1+hc =dδ dδ = 33.6 5) Piston Pin inside Diameter d P = 0.5 78 d P = 19.5 6) Web = di +b b = distance between boss end faces b = 0.4 78 B= 31. Web thickness = 59.4+31. Web thickness =14.1 S/NO IV. = 14.1 PISTON DESIGN DIMENSIONS SIZE RANGES PREFERABLE SIZE 1 Piston Diameter - 78 Piston Height (0.8-1.3)D 88 3 Skirt Height (0.6-0.8)D 58 4 Radial (0.040-0.045)D 3.5 5 Ring Radial (0.70- Clearance 0.95)D 0.8 6 Crown Wall (0.05-0.10)D 5 7 Piston Crown (0.05-0.10)D 7.5 8 Crown Depth - 1.5 9 Top Ring Land Height (0.03-0.05)D 3.5
10 Piston Inner Diameter - 59.4 11 Crown Diameter - 53.36 1 Radial Skirt - 9.3 13 First Piston (0.06- Groove 0.1)D 7.8 14 15 16 Oil Ring Height & Piston Hub Outside Diameter Piston Hub Inside Diameter -Apr 3 (0.- 0.8)D (0.65-0.75)D 33.6 19.5 17 Web - 14.1 18 Top Head - 6 19 Piston Inner Fillet - 1.5 0 Skirt Undercut Height - 5.8 1 Skirt Undercut - 5 Element Description Solid 70 has a 3-D thermal conduction capability. The element has eight nodes with a single degree of freedom, temperature, at each node. The element is applicable to a 3-D, steady-state or transient thermal analysis. The element also can compensate for mass transport heat flow from a constant velocity field. If the model containing the conducting solid element is also to be analyzed structurally, the element should be replaced by an equivalent structural element CATIA V5R0 Model Fig 4: Element Model V. MESHING PISTON MODEL Fig : CATIA Model The piston was designed using CATIA V5 R0 and imported to ANSYS14 Fig 5: Meshed Model In order to avoid complexity the model was divided in to four equal parts & one part is taken for analysis. Load Condition Two type of loads consider for piston assembly are as follows, 1) Pressure ) Temperature Fig 3: ANSYS Model Pressure(kpa) 6195kpa Temperature(k) 573k (head) 493k(Land) 463k(Skirt) Available Online@ 341
A. Pressure b) Principle stress Fig 6: Pressure Load Pressure load is act the on the top portion of the piston,pressure load will be vary according to engine specification, B. Temperature Temperature is another type of load that will act on the piston temperature varying at different portion its expressed below c) Von mises Fig 7: Temperature Distribution of Piston VI. RESULT & DISCUSSION Various result described below the result are 1) Aluminum alloy(alsi) a) Shear stress ) Cast Iron a)shear stress Available Online@ 34
S/NO MATERIAL VMS PS SS 1 Aluminum 9.0E+11 6.6E+11 5.16E+11 b) Principle stress Cast iron 1.34E+1 6.5E+11 7.3E+11 VMS Von mises stress PS- principle stress SS-shear stress CONCLUSION In this work the thermo mechanical analysis for two materials(aluminum alloy, cast iron) was performed, From the model following stresses have been calculated,principle stress, von mises stress, shear stress and it s found that cast iron (134e10 pa) can withstand more stress when compared to aluminum alloy ( 90e9 pa) so its preferred for medium & heavy duty applications c) Von mises stress References [1] Computer Aided Design and Analysis of Piston Mechanism of Four Stroke S.I. Engine. [] Mathura M.L., Sharma, A Course in Internal Combustion Engine R.P. Dhanpat Rai Publication 1997 (i, ii, iii). [3] Shigley, Joseph Edward, Theory of Machines and Mechanisms, Tata McGraw Hill, New York, 003 [4] Khurmi, R.S. and Gupta, J.K., A Textbook of Theory of Machine,4th Edition, Eurasia Publishing House (Pvt.), Ltd, New Delhi, 003 Available Online@ 343