Static and Thermal Analysis of Piston and Piston Rings

Transcription

1 Static and Thermal Analysis of Piston and Piston Rings M.Srinadh 1, K. Rajasekhara Babu 2 1 M.Tech Student, Mechanical Engineering Dept, Bapatla Engineering College, A.P, India 2 Assistanat. Professor, Mechanical Engineering Dept, Bapatla Engineering College, A.P, India Abstract A piston is a component of reciprocating engines, reciprocating pumps, compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. The piston transforms the energy of the expanding gasses into mechanical energy. The piston rides in the cylinder liner or sleeve. Pistons are commonly made of aluminum or cast iron alloys The present project to designed a piston for 1300cc diesel engine car and taken 3 different profile rings.a 2D drawing is created from the calculations. The piston and piston rings are modeled using Pro/Engineer software, The stress and displacement are analyzed for the piston and piston rings by applying pressure on it in Structural analysis. By observing the analysis results, we can decide whether our designed piston is safe or not under applied load conditions. The thermal flux, thermal temperature distribution is analyzed by applying temperatures on the piston surface in Thermal analysis. The structural and thermal analysis were also done on the piston and piston rings model using Cast iron, Aluminum Alloy A360 and Zamak. By comparing both the material analysis and decided which material is better for manufacturing of Piston and piston rings. Structural and Thermal analysis were also performed in ANSYS software. Key Words: piston, piston rings, Structural analysis, thermal analysis, ANSYS *** INTRODUCTION TO PISTON often complicated in design, are heat treated in various The piston transforms the energy of the expanding gasses ways, and are plated with other metals. Piston rings are into mechanical energy. The piston rides in the cylinder of two distinct classifications: compression rings and oil liner or sleeve. Pistons are commonly made of aluminum control rings. or cast iron alloys. To prevent the combustion gasses 1.2 MATERIALS FOR THE PISTON from bypassing the piston and to keep friction to a Cast Iron, Aluminum Alloy and Cast Steel etc. are the minimum, each piston has several metal rings around it. common materials used for piston of an Internal These rings function as the seal between the piston and Combustion Engine. Cast Iron p istons are not suitable for the cylinder wall and also act to reduce friction by high speed engines due its more weight. These pistons minimizing the contact area between the piston and the have greater strength and resistance to wear. cylinder wall. The rings are usually made of cast iron and The Aluminum Alloy Piston is lighter in weight coated with chrome or molybdenum. Most diesel engine and enables much lower running temperatures due to its pistons have several rings, usually 2 to 5, with each ring higher thermal conductivity. The coefficient of expansion performing a distinct function. The top ring(s) acts of this type of piston is about 20% less than that of pure primarily as the pressure seal. The intermediate ring(s) aluminum piston but higher than that of cast iron piston acts as a wiper ring to remove and control the amount of and cylinder wall. To avoid seizure because of higher oil film on the cylinder walls. The bottom ring(s) is an expansion than cylinder wall, more piston clearance oiler ring and ensures that a supply of lubricating oil is required to be provided. It results in piston slap after the evenly deposited on the cylinder walls engine is started but still warming up and tends to Ashwani Kumar et al [1] The main objective of this separate the crown from the skirt of the piston. research work is to investigate and analyze the stress distribution of piston at actual engine condition. 2. MODELING M.afzaalmalik et al [2] The piston top ring in an 2.1 Design Calculations automotive ring piston system plays a very crucial role Density of diesel = 820 to 950 kg/cm at 15 c during the engine start up and normal operating = kg/cm³ conditions Density = kg/mm³ 1.1 PISTON RINGS Diesel C 10 H 22 to C 15 H 28 = C 15 H 28 Piston rings are used on pistons to maintain gastight seals Molecular weight of C 15 H 28 =208g/mole between the pistons and cylinders, to aid in cooling the Mass =density volume piston, and to control cylinder-wall lubrication. About m = one-third of the heat absorbed by the piston passes m = kg through the rings to the cylinder wall. Piston rings are R = J/mol K 51 M.Srinadh, K. Rajasekhara Babu

2 PV = m R T P = N/mm² Piston Head Gas pressure p = N/mm² Outside diameter of piston = 69.6 mm σ t = bending tensile stress = 35-40MPa for cast iron Temperature at the centre of the piston head T c = 425 c to 450 c Temperature at the edge of the piston head T e = 200 c to 225 c T c T e = 220 c for cast iron Thickness of the ribs = to = 5.25 (or) mm Piston Ring Radial thickness of the ring t 1 = D P w = pressure of gas on the cylinder wall P w = to N/mm² σ t = 85 MPa to 110MPa for CI rings t 1 =69.6 = 2.35mm axial thickness t 2 = D/10n R n R = no. of rings = 3 t 2 = =2.32mm or t 2 = 0.7 t 1 to t 1 = to 2.35 mm Width of top land b 1 = t h to 1.2 t h =15.75 to 18.9 mm The width of other ring land (distance between the ring grooves) b 2 = 0.75t 2 to t 2 =1.74 to 2.32 mm The gap between the free ends of the ring = 3.5t 1 to 4t 1 = to 9.4 mm Piston Barrel (Cylindrical portion of the Piston) Thickness of piston barrel t 3 = radial depth of piston ring groove b= t =2.75mm t 3 = = 9.338mm The piston wall thickness towards the open end t 4 =0.25t 3 to 0.35t 3 t 4 = mm 1. Piston Skirt Maximum gas load on the piston Length of the piston skirt L= 0.65D to 0.8D = mm Length of ring section = 7 b 2 =16.24 Total length of the piston L = length of the skirt +length of the ring section +top land = = 90.82mm d 0 = outside diameter of the piston pin l 1 =length of the piston pin in the bush of the small end of the connecting rod = 0.45D = l 1 = 31.32mm Load on the piston due to gas pressure p = N Load on the piston pin due to bearing pressure or bearing load = bearing pressure bearing area P= d 0 l 1 = bearing pressure at the small end of the connecting rod bushing d 0 = Bearing pressure of tin bronze =50MPa The mean diameter of the piston bosses = 1.4 d 0 = 37.17mm 2.2 2D DRAWINGS OF THE PISTON Fig 2.1 2D Drawing of the piston P= p P= maximum gas pressure P= P= N Maximum side thrust on the cylinder R= = N 52 M.Srinadh, K. Rajasekhara Babu Fig.2.2 showing the piston profile in Pro/E in step2 3. ANALYSIS

3 Static Analysis--Used to determine displacements, stresses, etc. under static loading conditions. Both linear and nonlinear static analyses, Nonlinearities can include plasticity, stress stiffening, large deflection, large strain, hyper elasticity, contact surfaces, and creep. A thermal analysis calculates the temperature distribution and related thermal quantities in a system or component. Typical thermal quantities of interest are: The temperature distributions The amount of heat lost or gained Thermal gradients Thermal fluxes. 3.1 MATERIAL PROPERTIES Cast iron: Density g/cm 3 Ultimate Tensile strength -900 MPa Yield tensile strength -600 MPa Modulus of elasticity -150 GPa Poisson ratio Specific heat -506J/kg-K Thermal conductivity -45W/m-K MES HING Fig 4.1 piston model Aluminum A360: Density g/cm 3 Ultimate Tensile strength -300MPa Yield tensile strength -180MPa Modulus of elasticity -71GPa Poisson ratio Specific heat -963J/kg-K Thermal conductivity -113W/m-K ZAMAK: Density g/cm 3 Ultimate Tensile strength -240MPa Modulus of elasticity -96 GPa Poisson ratio Specific heat -420J/kg-K Thermal conductivity -113W/m-K Fig 4.2 meshed model of piston Fig 4.2 shows the meshed model. Default solid brick element was used to mesh the components. The shown mesh method was called tetra hydra mesh. MATERIAL: CAS T IRON TOTAL DEFORMATION 3.2 BOUNDARY CONDITIONS: a) Temperature on piston head b) Convection on total body c) Pressure on piston head d) Constrained at piston pin holes 4. RESULTS AND DISCUSSION Structural And Thermal Analysis Of Piston PIS TON 53 M.Srinadh, K. Rajasekhara Babu Fig 4.3 deformation with cast iron From fig 4.3 it shows the total deformation of the piston is mm. ELAS TIC STRAIN

4 Fig 4.4 strain with cast iron EQUIVALENT VON-MIS ES STRESS Fig 4.7 Total heat flux distribution From fig 4.7it can be found that the maximum heat flux is 8.3W/mm 2 and the minimum heat flux is 1.02e - 6 W/mm 2 By taking properties of Aluminum and ZAMAK materials to piston head the analysis performed and results are plotted STRUCTARAL AND THERMAL ANALYS IS OF RECTANGULARFACE RING MATERIAL:CASTIRON TOTAL DEFORMATION Fig 4.5 Distribution of von-mises stress From fig it can be found that the equivalent von-mises stress is 97Mpa. TEMPERATURE Fig 4.8 Deformation with cast ironfrom fig 4.8 the total deformation of the model can be determined. The maximum and minimum values are found to be MAX: mm and MIN: mm ELAS TIC STRAIN Fig 4.6 Temperature distribution with cast iron From the fig temperature distribution of the piston is determined. The maximum temperature is at the top of the piston is C. Fig 4.9 strain with cast iron 54 M.Srinadh, K. Rajasekhara Babu

5 From fig the strain values for cast iron model can be determined. It can be observed that the maximum and minimum values are MAX : and minimum values are MIN: 1.00e -4. EQUIVALENT VON-MIS ES STRESS Fig 4.10 Distribution of von-mises stress From fig the stress values of cast iron can be determined. It can be observed that the maximum and minimum values of stress are MAX: 90 Mpa and Mpa. TEMPERATURE From the fig total heat flux of cast iron can be determined. The maximum and minimum values of heat flux are found to be MAX: 7.67 W/mm 2 By taking properties of Aluminum and ZAMAK materials to piston rings the analysis performed and results are plotted STRUCTARAL AND THERMAL ANALYS IS OF PIS TON Table structaral and thermal analysis of piston cast iron Alumin ium A360 ZAMA K DEFORMA TION (mm) STRAIN (mm/mm) STRESS (Mpa) HEAT FLUX (W/mm 2 ) STRUTURAL AND THERMAL ANALYS IS OF RINGS DEFORMATION: Table no. 4.2 deformation of rings Deformatio Aluminu Cast Iron Zamak n(mm) m (A360) rectangular E-05 semi circular E-05 Taper face E-05 Fig 4.11 Temperature distribution with from the fig the temperature distribution for cast iron can be determined. It can be found that the maximum value of temperature occurs at the top of the ring of C. ELAS TIC STRAIN: Table no.4.3 elastic strain of rings Strain(mm/ m Aluminum Cast Iron Zamak m) (A360) rectangular E-05 semi circular E-05 Taper face E-05 STRESS: Table no. 4.4 stress of rings Stress(Mpa) Cast Iron Aluminum (A360) Zamak Rectangular semi circular Fig 4.12 Total heat flux distribution Taper face M.Srinadh, K. Rajasekhara Babu

6 Table no.4.5 total heat flux of rings Heat flux Cast Aluminum Zama (w/mm 2 ) Iron (A360) k rectangular semi circular Taper face Graph no 4.3 illustrates that minimum stress of 72Mpa accounted for taper face ring with Aluminium. TOTAL DEFORMATION Graph no 4.4 total heat flux vs different rings Graph no 4.4 illustrates that semicircular face ring with zamak accounted maximum heat flux of 14 W/mm 2 Graph no 4.1deformation vs different rings Graph no 4.1 illustrates the semicircular face ring with zamak accounted minimum deformation ELAS TIC STRAIN STRUCTARAL AND THERMAL ANALYS IS OF PIS TON AND PIS TON RINGS DEFORMATION Table no. 4.6 deformation of piston and rings Deformation (mm) Cast Iron Aluminum Zamak rectangular E-03 semi circular E-03 Taper face E-03 Graph no 4.2 strain vs different rings Graph no 4.2 illustrates that minimum strain of 0.8e -5 accounted for semicircular face ring with zamak. STRESS STRAIN Table no.4.7 elastic strain of piston and piston rings Strain (mm/mm) Cast Iron Aluminum Zamak rectangular E-04 semi circular E-04 Taper face E-04 STRESS Table no. 4.8 stress of piston and pistonrings Stress (Mpa) Cast Iron Aluminum Zamak rectangular semi circular Graph no 4.3 stress vs different rings 56 M.Srinadh, K. Rajasekhara Babu Taper face

7 Table no.4.9 total heat flux of piston and pistonrings Heat flux (W/mm 2 ) Cast Iron Aluminum Zamak rectangular Graph no 4.7 illustrates that minimum stress of 122Mpa accounted for semicircular face ring with Aluminium semi circular Taper face TOTAL DEFORMATION Graph no 4.8 total heat flux vs different rings Graph no 4.8 illustrates that semicircular face ring with zamak accounted maximum heat flux of 14 W/mm 2 Graph no 4.5 deformation vs different rings Graph no 4.5 illustrates the rectangular face ring with A360 accounted minimum deformation STRAIN Graph no 4.6 strain vs different rings Graph no 4.6 illustrates that minimum strain of accounted for rectangular face ring with zamak. STRESS Graph no 4.7 stress vs different rings 4. CONCLUSIONS piston and Ring s calculations are done for 1300cc diesel engine. Modeling of piston and Ring s are prepared using parametric software creo(pro-engineer) and assembled. Assembly was exported to Ansys work bench to conduct structural and thermal analysis. In the analysis piston and Ring s were analyzed using 3 various materials Cast iron, Aluminum(A360) and Zamak.According to the results obtained from AnsysZamak material for piston is selected. In the analysis 3 different rings were analyzed using 3 various materials Cast iron, Aluminum and Zamak.In 3 different ring profiles semicircular face ring is best as per the ansys results in deformations, strains and heat flux. Zamak is having low deformation and high heat flux properties compare to other 2 materials. As per above results piston with Zamak is having high heat flux value than traditional materials. As per analyses values Zamak is having good value so we can use Zamak. REFERENCES [1]. Thermo-Mechanical and Vibration Analysis of the I.C. Engine Piston made of Sic reinforced ZrB2 composite using Finite Element Method (ANSYS) [2]. M. afzaalmaliket al Modeling of Piston Top Ring Lubrication by considering Cylinder Out-of- Roundness in Initial Engine Start up Proceedings of the World Congress on Engineering 2010 Vol II [3]. Design, Analysis and Optimization of Three Aluminum Piston Alloys Using FEA [4]. Mr. v.n. kongari design and analysis of piston ring International Conference on Mechanical & Industrial Engineering, 02nd June-2013, Bengaluru, [5]. R Mr.K.Kadambanathan Fatigue analysis of a diesel piston ring by using FEA Proceedings of the National Conference on Emerging Trends In Mechanical Engineering 2k M.Srinadh, K. Rajasekhara Babu

8 [6]. v. s. n. ch.dattu et al Thermal Analysis on New Piston Rings Face Profile ISSN , ISO 9001:2008 Certified Journal, Volume 4, Issue 3, March 2014) [7]. K VenkateswaraRao et al Modeling, Analysis and Optimization of Diesel Engine Piston IJREAT International Journal of Research in Engineering & Advanced Technology, Volume 2, Issue 1, Feb-Mar, 2014ISSN: [8]. Dr. Ahemad Thermal Effects on Diesel EnginePiston andpiston Compression Rings Eng&tech.journal vol. 27 NOV [9]. Automobile engineering by Dr.kirpalsingh vol.2 [10] I. C engines by v. ganeshan 58 M.Srinadh, K. Rajasekhara Babu