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1 ISSN Available online at International ejournals International ejournal of Mathematics and Engineering 206 (2013) MODELING AND ANALYSIS OF DIESEL ENGINE PISTON 1 Department of Mechanical Engineering, Nimra College of Engineering & Technology, Vijayawada. A.P. India Department of Mechanical Engineering, Nimra College of Engineering & Technology, Vijayawada, A.P. India ABSTRACT: As the emission norms are becoming stringent day by day, the engine manufacturers are concentrating more on reducing the engine emissions like CO, HC, NO x and particulate matter (PM). For the reduction of these above said engine exhaust emissions, combustion system plays very important role. For effective combustion system, various parameters like combustion pressure, compression ratio, proper fuel mixing and ignition timing etc are very important. In this scenario, lot of research has been carried out on arriving at a piston design which can give effective fuel mixing, high compression ratio using a re-entrant combustion bowl shape. Due to high market competition in automotive sector, it has become always important to produce ancillary components for minimum cost at the same time satisfying all the necessary requirements. So there is a need for the piston design which can give all the above said capabilities. At the same time, it should be light weight, low cost, structurally and thermally withstandable at very high pressure and temperature conditions that will occur in the combustion process. In this way, there is a lot of demand for understanding the process of evaluation of piston geometry for various loading conditions like thermal, mechanical and inertial loads. In this Project, it has been decided to study a particular piston design and its capability for various above said loads. In this work, initially planning to make a piston model using solid modeling software Pro-E. It has been decided to mesh the geometry and analyze using commercially available software tool ANSYS. For the analysis input conditions and process of analysis, lot of literature survey has been done. Initially, thermal analysis of the piston will be carried out to predict the temperature distribution of the piston. For thermal analysis of piston, basic necessary thermal boundary conditions like bulk gas temperatures and heat transfer

2 coefficients have been obtained from literature survey. Temperature of the piston due to its working in high combustion environment will itself act as thermal load causing stress to the component. High combustion gas pressures will act as a mechanical loads and cause major stresses in the critical features of the piston. Once after thermal analysis of the piston, for judging the critical features of the piston geometry, a detailed structural analysis will be carried out for various loading conditions like thermal load and mechanical load. After assessing the piston for various loads, it has been decided to calculate the factor of safety for the piston using Soderberg s criterion. KEYWORDS: Combustion Systems, Piston, ANSYS, Thermal Analysis, Gas Temperature, Thermal Load, Mechanical loads, Structural Analysis. 1. INTRODUCTION: 1.1 The Internal Combustion Engine: The internal combustion engine converts chemical energy into useful mechanical energy by burning fuel. Chemical energy is released when the fuel-air mixture is ignited in the combustion chamber. The gas produced in this reaction rapidly expands forcing the piston down the cylinder on the power stroke. The piston reciprocates inside the cylinder, exhaust and intake ports open and closes during various stages of the cycle. The movement of the piston up or down the cylinder makes up one stroke of the four stroke cycle. The linear motion is then converted to rotary motion by the crankshaft. The crankshaft is shaped to balance the pistons which are fired in a particular order to reduce engine vibration (typically for a 4-cylinder engine, or ). The flywheel then helps smooth out the linear movement of the pistons. 1.2 Parts of Internal Combustion Engine: The basic components for a combustion cycle in a four stroke engine are as follows 1. Cylinder 2. Piston 3. Valves 4. Connecting Rod 5. Crank 6. Crank Shaft 7. Flywheel 1.3 Diesel Engine: A diesel engine (also known as a compression-ignition engine) is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber during the final stage of compression. This is in contrast to sparkignition engines such as a petrol engine (gasoline engine) or gas engine (using a gaseous fuel as opposed to gasoline), which uses a spark plug to ignite an air-fuel mixture. The diesel engine is modeled on the Diesel cycle. The engine and thermodynamic cycle were both developed by Rudolf Diesel in Diesel Cycle Operation: The Diesel cycle is the cycle used in the Diesel (compression-ignition) engine. In this cycle the heat is transferred to the working fluid at constant pressure. The process corresponds to 1995

3 the injection and burning of the fuel in the actual engine. The cycle in an internal combustion engine consists of induction, compression, power and exhaust strokes Induction Stroke: The induction stroke in a Diesel engine is used to draw in a new volume of charge air into the cylinder. As the power generated in an engine is dependent on the quantity of fuel burnt during combustion and that in turn is determined by the volume of air (oxygen) present, most diesel engines use turbochargers to force air into the cylinder during the induction stroke. From a theoretical perspective, each of the strokes in the cycle complete at Top Dead Centre (TDC) or Bottom Dead Centre (BDC), but in practicality, in order to overcome mechanical valve delays and the inertia of the new charge air, and to take advantage of the momentum of the exhaust gases, each of the strokes invariably begin and end outside the 0, 180, 360, 540 and 720 (0) degree crank positions Compression Stroke: The compression stroke begins as the inlet valve closes and the piston is driven upwards in the cylinder bore by the momentum of the crankshaft and flywheel. The purpose of the compression stroke in a Diesel engine is to raise the temperature of the charge air to the point where fuel injected into the cylinder spontaneously ignites. In this cycle, the separation of fuel from the charge air eliminates problems with auto-ignition and therefore allows Diesel engines to operate at much higher compression ratios than those currently in production with the Otto Cycle. Fig.1.1: Induction Stroke Compression Ignition: Compression ignition takes place when the fuel from the high pressure fuel injector spontaneously ignites in the cylinder. In the theoretical cycle, fuel is injected at TDC, but as there is a finite time for the fuel to ignite (ignition lag) in practical engines, fuel is injected into the cylinder before the piston reaches TDC to ensure that maximum power can be achieved. This is synonymous with automatic spark ignition advance used in Otto cycle engines. Fig.1.2: Compression Stroke 1996

4 Fig.1.3: Compression Ignition Power Stroke: The power stroke begins as the injected fuel spontaneously ignites with the air in the cylinder. As the rapidly burning mixture attempts to expand within the cylinder walls, it generates a high pressure which forces the piston down the cylinder bore. The linear motion of the piston is converted into rotary motion through the crankshaft. The rotational energy is imparted as momentum to the flywheel which not only provides power for the end use, but also overcomes the work of compression and mechanical losses incurred in the cycle (valve opening and closing, alternator, fuel injector pump, water pump, etc.). Fig.1.4: Power Stroke Exhaust Stroke: The exhaust stroke is as critical to the smooth and efficient operation of the engine as that of induction. As the name suggests, it's the stroke during which the gases formed during combustion are ejected from the cylinder. This needs to be as complete a process 1997

5 as possible, as any remaining gases displace an equivalent volume of the new charge air and leads to a reduction in the maximum possible power. Fig.1.5: Exhaust Stroke Exhaust and Inlet Valve Overlap: Exhaust and inlet valve overlap is the transition between the exhaust and inlet strokes and is a practical necessity for the efficient running of any internal combustion engine. Given the constraints imposed by the operation of mechanical valves and the inertia of the air in the inlet manifold, it is necessary to begin opening the inlet valve before the piston reaches Top Dead Centre (TDC) on the exhaust stroke. Likewise, in order to effectively remove all of the combustion gases, the exhaust valve remains open until after TDC. Thus, there is a point in each full cycle when both exhaust and inlet valves are open. The number of degrees over which this occurs and the proportional split across TDC is very much dependent on the engine design and the speed at which it operates. Fig.1.6: Exhaust and Inlet Valve Overlap 1998

6 1.5 Piston: International ejournal of Mathematics and Engineering 206 (2013) Fig.1.7 Piston of 4-Stroke Engine In general, a piston is a lubricated sliding shaft that fits tightly inside the opening of a cylinder. Its purpose is to change the volume enclosed by the cylinder, to exert a force on a fluid inside the cylinder, to cover and uncover ports, or some combination of these. Piston in I.C. engines play an important role in transferring the energy generated on combustion chamber to connecting rod and thereby to crank shaft. The various parts of the piston are shown in the fig During running of the engine forces are induced on the piston. They are as follows. 1. Normal force: This force is concentrated on piston by pressure of explosion by gas and air. We assume that this force is equal in every point of piston surface area; therefore, this force will act directly up on piston rod. 2. Transverse Force: These transverse forces are tolerable in a smaller engine; a larger engine's much greater forces would cause an intolerable degree of wear on the piston and cylinder, as well as increasing overall friction in the engine. 3. Inertia Force: The Inertia Forces are caused due to the high speed of the engine and is maximum at top dead centre (TDC) i.e., at the top of the stroke. 1999

7 2.LITERATURE REVIEW: 2.1 GENERAL: This chapter discusses the details of literature survey of the piston structural and thermal analysis work done for assessing the integrity of the structure for various loading conditions like temperatures and pressures. This chapter also discusses the literature survey of experimental work done for measuring the above said work. 2.2 STEADY STATE AND TRANSIENT ANALYSIS: Piston in the engine will be operating under vary critical temperature loads. These temperature loads will be varying from time to time in a cycle. These temperatures will be higher during firing stroke and lower during the other strokes. It is always difficult to assess the piston temperature for various gas temperatures. So steady state thermal analysis will be carried out for predicting the piston temperatures for worst case loading conditions i.e. peak temperatures or for an average bulk gas temperature. 2.3 EXPERIMENTAL WORK: Gerhard Woschni, Johann Fieger [9] determined more than 60 temperature distributions in a piston of high speed diesel engine from measured temperature at 20 discrete points of the piston for varied engine operating conditions and different cooling conditions. They were evaluated to determine the heat flux through the piston and the heat transfer coefficients at the boundaries. 3.DEFINITION OF PROBLEM: 3.1 GENERAL: In this Project the Factor of Safety for the 4-Stroke Diesel Engine Piston has been found by conducting the Mechanical, Thermal and Thermo-Mechanical analysis. The details of Inputs required for FEM analysis of the piston are taken from literature study and are shown below. 3.2 ENGINE SPECIFICATIONS: Type 4-Stroke NA DI Diesel No of Cylinders 4 Inline Bore x Stroke (mm) 88.9 x Displacement (cubic cm) 2523 Compression ratio 17 Rated Speed 3200 Rated power (Kw) 3200 rpm Max. torque 1500 rpm Max. Pressure (bar) Table 3.1: Engine Specifications 2000

8 3.3 INPUT MATERIAL PROPERTIES OF THE PISTON: For Mechanical and Thermal Analysis: Material Aluminium Density (g/cc) 2.7 Young s Modulus (Gpa) 67.5 Thermal Conductivity (W/m k) Poisson s ratio 0.34 Thermal Expansion Coefficient (/ o c) 2.38E-05 Table 3.2: Input material properties for Mechanical and Thermal Analysis For Thermo-Mechanical Analysis: Temperature ( o c) Density (g/cc) Young s Modulus (Gpa) Thermal Conductivity (W/m k) Poisson s ratio Thermal Expansion Coefficient (/ o c) 2.1x x x x10-5 Table 3.3: Input material properties for Thermo-Mechanical Analysis 4. METHODOLOGY: Basically in this Project Solid Model of a Piston is developed in Pro-E and is further imported into the Ansys Package for Analysis Phase. So here the two Software s used are 4.1 Pro-E: 1. Pro-E 2. Ansys INTRODUCTION ABOUT PRO-E: Pro/ENGINEER, PTC's parametric, integrated 3D CAD/CAM/CAE solution, is used by discrete manufacturers for mechanical engineering, design and manufacturing Created by Dr. Samuel P. Geisberg in the mid-1980s, Pro/ENGINEER was the industry's first successful parametric, 3D CAD modeling system. The parametric modeling approach uses parameters, dimensions, features, and relationships to capture intended product behavior and create a recipe which enables design automation and the optimization of design and product development processes. This powerful and rich design approach is used by companies whose product strategy is family-based or platform-driven, where a prescriptive design strategy is critical to the success 2001

9 of the design process by embedding engineering constraints and relationships to quickly optimize the design, or where the resulting geometry may be complex or based upon equations PART MODELING: In Part modeling you can create a part from a conceptual sketch through solid feature-based modeling, as well as build and modify parts through direct and intuitive graphical manipulation. The Part Modeling Help introduces you to the terminology, basic design concepts, and procedures that you must know before you start building a part. Part Modeling shows you how to draft a 2D conceptual layout, create precise geometry using basic geometric entities, and dimension and constrain your geometry. You can learn how to build a 3D parametric part from a 2D sketch by combining basic and advanced features, such as extrusions, sweeps, cuts, holes, slots, and rounds. Finally, Part Modeling Help provides procedures for modifying part features and resolving failures ABOUT PART: Pro/ENGINEER Part enables you to design models as solids in a progressive threedimensional solid modeling environment. Solid models are geometric models that offer mass properties such as volume, surface area, and inertia. If you manipulate any model, the 3-D model remains solid DESIGN CONCEPTS: You can design many different types of models in Pro/ENGINEER. However, before you begin your design project, you need to understand a few basic design concepts: Design Intent Before you design your model, you need to identify the design intent. Design intent defines the purpose and function of the finished product based on product specifications or requirements. Capturing design intent builds value and longevity into your products. This key concept is at the core of the Pro/ENGINEER feature-based modeling process. Feature-Based Modeling Pro/ENGINEER part modeling begins with creating individual geometric features one after another. These features become interrelated to other features as you reference them during the design process. Parametric Design The interrelationships between features allow the model to become parametric. So, if you alter one feature and that change directly affects other related (dependent) features, then Pro/ENGINEER dynamically changes those related features. This parametric ability maintains the integrity of the part and preserves your design intent. Associativity Pro/ENGINEER maintains design intent outside Part mode through associativity. As you continue to design the model, you can add parts, assemblies, drawings, and other associated objects, such as piping, sheet metal, or electrical wiring. All of these functions are fully associative within Pro/ENGINEER. So, if you change your design at any level, your project will dynamically reflect the changes at all levels, preserving design intent. 2002

10 4.2 SOLID MODELLING OF THE PISTON: Solid modeling of the piston has been done with Pro-Engineer software package. In Pro- Engineer one of the three available planes has been selected i.e. G.P plane (in this plane the GP central line will lie. A semi-circle has been drawn in this plane and extruded both sides of the GP plane i.e. below is open end side and other side is compression height side. Then a plane has been drawn which is offset to the T-T plane. Using this new plane boss has been a modeled by using protrusion command. A GP hole has been modeled by using cut option. Draft has been done for the easy removal casting. Then the pistons grooves have been done using cut revolve command. Then piston bowl has been made with revolve cut option with the specified off-set. Fig4.1: Solid model of the piston 4.3ANSYS: INTRODUCTION TO FINITE ELEMENT METHOD: The basic idea in the Finite Element Method is to find the solution of complicated problems with relatively easy way. The Finite Element Method has been a powerful tool for the numerical solution of a wide range of engineering problems. Applications range from deformation and stress analysis of automotive, aircraft, building, defense, and missile and bridge structures to the field of analysis of dynamics, stability, fracture mechanics, heat flux, fluid flow, magnetic flux, seepage, and other flow problems. With the advances in computer technology and CAD systems, complex problems can be modeled with relative ease. Several alternate configurations can be tried out on a computer before the first prototype is built. The basics in engineering field are must to idealize the given structure for the required behaviour. In the Finite Element Method, the solution region is considered as many small, interconnected sub regions called Finite elements HISTORICAL BACKGROUND: The Finite Element Method has been presented in 1956 by Turner, Clough, Martin and Topp. The name Finite Element Method was first coined by R.W.Clough. Important early contributions were those of J.H.Argyris and O.C.Zienckiwicz and Y.K.Cheung. Since the early 2003

11 1960 s, a large amount of research has been devoted to the technique, and a very large number of publications on the Finite Element Method are now available. The Finite Element Method was initially developed for structural mechanics but later on it was applied to heat transfer, fracture mechanics, flow and coupled field problems NEED FOR FINITE ELEMENT METHOD: To predict the behaviour of structure the designer adopts three tools such as analytical, experimental and numerical methods. The analytical method is used for the regular sections of known geometric entities or primitives where the component geometry is expressed mathematically. The solution obtained through analytical method is exact and takes less time. This method cannot be used for irregular sections and the shapes that require very complex mathematical equations. On the other hand the experimental method is used for finding the unknown parameters of interest THE PROCESS OF FINITE ELEMENT METHOD: The Finite Element Method is used to solve physical problems in engineering analysis and design. The physical problems typically involve an actual structure component subjected to certain loads. The idealization of the physical problem to a mathematical model requires certain assumptions that together lead to differential equations governing the mathematical model. The Finite Element Analysis solves the mathematical model, which describes the physical problem. The FEM (Finite Element Method) is a numerical procedure; it is necessary to assess the solution accuracy. If the accuracy criteria are not met, the numerical solution has to be repeated with refined solution parameters until a sufficient accuracy is reached FIELD AND BOUNDARY CONDITIONS: The field variables such a displacements, strains and stresses must satisfy the governing conditions, which can be mathematically expressed in the form of differential equations. For structure mechanic problems the boundary conditions may be kinematic i.e., where the displacements (and slopes i.e., derivative of displacement) maybe prescribed, or static i.e., where forces (and moments) may be prescribed. Initial values maybe given in the problems where time is involved. The specified temperature or heat flow/heat flux or convections maybe specified in thermal analysis STEPS INVOLVED IN FINITE ELEMENT MODELING: The method is based on stiffness analysis. Stiffness is defined as the force required for unit displacement and is the reciprocal of flexibility. In this method the structure is assumed to be built up of numerous connected tiny elements. From this comes the name Finite Element Method. Extremely complex structures also can be simulated by proper arrangement of these elements. The most commonly used elements are beams, plates and solid prismatic shapes etc. The points interconnecting the elements are called nodes. The broad steps in the finite element method when it is applied to structural mechanics is as follows: 2004

12 1. Divide the continuum into a finite number of sub regions (or elements) of simple geometry such as line segments, triangles, quadrilaterals. (Square and rectangular elements are subsets of quadrilateral), tetrahedrons and hexahedrons (cubes) etc. 2. Select key points on the elements to serve as nodes where conditions of equilibrium and compatibility are to be enforced. 3. Assume displacement functions within each element so that the displacements at each generic point depend on the nodal values. 4. Satisfy strain-displacement and stress-strain relationships within a typical element. 5. Determine stiffness and equivalent nodal loads for a typical element using work or energy principles. 6. Develop equilibrium equations for the nodes of the discritized continuum in terms of the element contributions. 7. Solve the equilibrium for the nodal displacements. 8. Calculate support reactions at restrained nodes if displaced. 9. Determine strains and stresses at selected points within the elements APPLICATIONS OF FINITE ELEMENT METHOD: Finite Element Method comes under this category of discretization methods. R.W.Clough appears to be the first to use this term of finite element. Since early 1960 s there has been much progress in the method. The method requires a large number of computations requiring a fast computer. In fact digital computer advances have been responsible for the expanding usage of the Finite Element Method. The Finite Element Method was initially developed to solve structural problems. Its use, of late, has been rapidly extended to various fields. The diversity of applications of the method can be seen from the following Table 1, which still by no means can be claimed as complete since fields of usage are being continuously diversified. Application Areas of Finite Element Method S.No. Fields Typical Examples. Structural Mechanics (Deflection & Stress Analysis of Structures) A. Two Dimensional Analysis B. Three Dimensional Analysis C. Bending of Plates 2. Soil and Rock Mechanics In plane stresses, stretching of plates, gravity dams, Axi-symmetric solid shells, rocket, motors, machine parts such as shafts, beam bridges etc. 3-D trusses, space frames such as cranes, thin walled structure like machine tools, transmission towers, nuclear towers, nuclear reactors, ship structures, radar domes, building dams, shell roofs, arches, drilling platforms etc. Floor slabs, thin walls of machine tool structure, ship decks, aircraft and spacecraft panels. Foundation layers, rock joints, pavements, stability of excavation such as river banks, embarkments, open pit and underground mining problems etc. 2005

13 3. Thermal analysis and Fluid mechanics Transient and steady state temperature distribution, thermal strain and stresses in mechanical and civil structures. 4. Hydro-elasticity Hydrodynamic, Hydrostatic and Air bearings. Reservoir-dam interactions, sloshing of liquids in flexible containers etc. 5. Dynamics Natural frequencies and mode shapes of structures. Response to arbitrary dynamic loading such as wind explosions, water waves, earthquakes etc. 6. Noise Problems Determination of acoustic pressure fields in ducts and enclosed spaces. Structural acoustic interaction problems etc. 7. Coupled Field and Contact Problems Structural and thermal coupling residual stresses, contact stresses and gap condition, air gap insulation. 8. Composites Analysis of layered shell and solids, FRP, ceramic and metal matrix composites, interlaminar and boundary layered stresses. 9. Fracture Mechanics Strain energy release rates, stress, intensity factor, J- integrals. Table 4.1: Application areas of FEM 4.4 FEA SOFTWARE ANSYS: INTRODUCTION: Dr. John Swanson founded ANSYS Inc. in 1970 with a vision to commercialize the concept of computer-simulated engineering, establishing himself as one of the pioneers of Finite Element Analysis (FEA). ANSYS Inc. supports the ongoing development of innovative technology and delivers flexible, enterprise-wide engineering systems that enable companies to solve the full range of analysis problem, maximizing their existing investments in software and hardware. ANSYS Inc. continues its role as a technological innovator. 2006

14 EVOLUTION OF ANSYS PROGRAM: ANSYS has evolved into multipurpose design analysis software program, recognized around the world for its many capabilities. Today the program is extremely powerful and easy to use. Each release hosts new and enhanced capabilities that make the program more flexible, more usable, and faster. In this way, ANSYS helps engineers meet the pressures and demands of the modern product development environment OVERVIEW OF THE PROGRAM: The ANSYS is a flexible, robust design analysis and optimization package. The software operates on major computers and operating systems, from PC s to workstations to supercomputers. ANSYS features file computability throughout the family of products and across all platforms. ANSYS design data access enables user to import computer-aided design models into ANSYS, eliminating repeated work. This ensures enterprise-wide, flexible engineering solution for all ANSYS users REDUCING DESIGN AND MANUFACTURING COSTS WITH ANSYS FEA: The ANSYS program allows engineers to construct computer models or transfer CAD models of structures, products, components, or systems; apply operating loads or other design performance conditions; and study physical responses, such as stress levels, temperature distributions, or the impact of electromagnetic fields. 4.5 PROCEDURE FOR ANSYS ANALYSIS: A static analysis can be either linear or non-linear. In this work we have considered nonlinear transient analysis. The procedure for ANSYS analysis consists of three main steps: 1. Build the model. 2. Obtain the solution. 3. Review the results. Build the model: In this step, we specify job name and analysis title and then define the element types, element real constants, material properties and the model geometry element types- both linear and non-linear structural elements are allowed. The ANSYS element library contains over 80 different element types. A unique number and prefix identify each element type. E.g.: PLANE-71, SOLID-96, BEAM-94 and PIPE-16. Material properties:young s modulus [Ex] must be defined for static analysis. If we have to apply inertia loads [such as gravity], we define mass properties such as density [DENS]. 2007

15 Similarly if we apply thermal loads [temperatures], we define coefficients of thermal expansion [ALPX]. Obtain the solution: In this step we define the analysis type and options, apply loads and initiate the finite element solution. This involves three phases: a. Pre-Processor phase b. Solution Phase c. Post-Processor phase The following Table shows the brief description of the steps followed in each phase. Pre-Processing phase Solution phase Post-Processing phase 1. Geometry definitions 1. Element matrix formation 1. Post solution operation 2. Mesh generation 2.Overall matrix 2.Post data printout (for reports) triangularization 3.Constraint and load 3. Calculation of 3. Post data scanning definitions displacement, stress, etc. 4. Model displays 4. Post data display 5. Material definitions Table 4.2: Steps followed in Ansys Software. (a)pre-processor: Pre-Processor has been developed so that the same program is available on micro, mini, super-mini and mainframe computer system. This allows easy transfer of models from one system to the other. Pre-Processor is an interactive model builder to prepare the finite element model and input data. The solution phase utilizes the input data developed by the pre-processor, and does the solution according to the problem definition. It creates input files to the visualization of results on the graphics screen. It displays the displacements, stresses, temperatures, etc. on the screen in the form of contours. Model Generation (Solid Modeling): It is generally more appropriate for large or complex models, especially 3-D models over solid volumes. Allows us to work with relatively small number of data items. Supports the use of primitives of areas and volumes (such as polygonal and cylindrical volumes) and Boolean operations (integration, subtractions, etc.) for the top down construction of the model. Facilitates the use of ANSYS program s design optimization features. It is required for adaptive meshing. Readily allows modifications to geometry. Facilitates changes to be made to the element distribution and it is not bound to one analysis model. Requires large amount of CPU sometimes. For small and simple models, it is sometimes cumbersome requiring more data entries than direct generation. 2008

16 Can fail (the program will not be able to generate the finite element mesh) under certain circumstances. Geometric definitions: There are four different geometric entities in pre-processor namely key points, lines, areas and volumes. These entities can be used to obtain the geometric representation of the structure. All the entities are independent of each other and have unique identification labels. Key points: Key points are points in 3-D space. Key point is a basic entity and usually the first entity to create. The key points can be generated by various ways; by individual definition, by transferring existing key points and from the other entities; e.g. intersection of two lines, key point at the corners etc. Lines: A line is generally a 3-D curve defined by using a parametric cubic equation. Lines can be generated from a number of grids. Sweeping a specified grid about a given axis through a desired included angle can generate a circular arc. Area: An area is a 3-D surface defined using a parametric cubic equation. Areas can be generated using four key points or four-line method, depending on the geometry. Some inbuilt areas like circle, rectangle, and polygon can be generated directly to the required size. Volumes: Volume, in general, is a 3-D solid region defined by using a parametric cubic equation. Similar to areas, volumes also have parametric directions. Using two or four areas, they can be generated. Spinning an area about an axis with another area can also generate volumes. Volumes of cylinder, prism and sphere can be directly created to required sizes. (b) SOLUTION: The solution phase deals with the solution of the problem according to the problem definitions. All the tedious work of formulating and assembling of matrices are done by the computer and finally displacements and stresses are given as output. Some of the capabilities of ANSYS are given below. 1. Structural static analysis. 2. Structural dynamic analysis. 3. Structural buckling analysis. i. Linear buckling. ii. Non-linear buckling. 4. Structural non-linear ties. 5. Static and dynamic kinematics analysis. 6. Thermal analysis. 7. Electromagnetic field analysis. 8. Electric field analysis. 9. Fluid flow analysis. i. Computational fluid dynamics. 2009

17 ii. Pipe flow. 10. Coupled-field analysis. 11. Piezoelectric analysis. (c) POST PROCESSOR: The post-processing phase of the ANSYS program follows the preprocessing and solution phases. With this portion of the program, the user may easily obtain and operate on the results calculated in the solution phase through a very complete set of userfriendly post-processing features. These results may include displacements, temperatures, strains and stresses, velocities and heat flows. The output from the post-processing phase of the program is in display and/or tabular report form. Because the post-processing phase is fully integrated with the ANSYS preprocessing and solution phases, the user can examine results immediately. It is a powerful user-friendly post-processing program. Using interactive color graphics, it has extensive plotting features for displaying results obtained from FEM. One picture of analysis results can often reveal in seconds what would take engineer hours to assess from numerical printout. The engineer may also see important aspect of the results that could be easily missed in stock of printout. Employing state of the art image enhancement techniques, it facilities viewing of contours of stresses, displacements, temperatures etc. 5.ANALYSIS: 5.1 Mechanical Analysis of Piston: Mechanical or Structural analysis of the piston has been carried out to find out the Stress distribution. This Structural analysis of piston has been carried out with commercial software ANSYS. Piston half section has been used for the analysis. It has been meshed with element type solid 45. Meshed piston has been show in Fig Total no of elements used are Structural load i.e. Pressure has been applied on various areas like crown, land, ring grooves, pin boss and inner portion of the piston skirt. Value of the Pressure has been applied based on literature survey (i.e., Max. Pressure taken from the Input). The obtained Stress distribution of the piston has been shown in Fig Fig.5.1: Meshed Model of the Piston Structural Analysis. Fig.5.2: Von Misses Stress distribution in in the Piston 2010

18 The figure illustrates the variation of Von Misses stress in the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. Variation of colors represents the variation of stresses in the Piston. The different values of stresses (in MPa) are shown in the above figure. Fig.5.3: Stress distribution in X-direction in the Piston The figure illustrates the variation of stresses in X-direction of the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. Variation of colors represents the variation of stresses in the Piston. The different values of stresses (in MPa) are shown in the above figure. Fig.5.4: Stress distribution in Y-direction in the Piston The figure illustrates the variation of stresses in Y-direction of the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. Variation of colors represents the variation of stresses in the Piston. The different values of stresses (in MPa) are shown in the above figure. 2011

19 Fig.5.5: Stress distribution in Z-direction in the Piston The figure illustrates the variation of stresses in Z-direction of the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. Variation of colors represents the variation of stresses in the Piston. The different values of stresses (in MPa) are shown in the above figure. 5.2 Thermal Analysis of Piston: Thermal analysis of the piston has been done to find out the temperature distribution. This thermal analysis of piston has been carried out with commercial software ANSYS. Piston half section has been used for the analysis. It has been meshed with element type solid 70. Meshed piston has been show in Fig.5.6. Total no of elements used are Convective loads i.e. bulk temperatures and Convective heat transfer coefficients have been applied on various areas like crown, land, ring grooves, pin boss and inner portion of the piston skirt. Convective heat transfer coefficient values for the crown portion of the piston have been calculated from Seale Taylor s formula and for other portions have been taken from the literature survey and based on experience. Bulk temperatures values have been applied based on literature survey and based on past experience. The obtained temperature distribution of the piston has been shown in Fig.5.7. Seale Taylor s formula Convective heat transfer coefficient In bowl h = 1.46 exp (25 (r) 1.5 ) / 1 + exp (25 (N) 1.5 ) Crown top h = 1.46 exp (25 (2N-r) 1.5) / 1+ exp (25 (N) 1.5 ) Where N = D/3 D is piston diameter r- Radial distance from the center of the bowl The following boundary conditions have been applied Crown bowl T = 700 deg C, h = Kw/m 2 k Crown top T= 700 deg C, h= 0.91 Kw/m 2 k Top land T=180 deg C, h= 0.7 Kw/m 2 k 2nd land & 3rd land T= 140 deg C, h= 0.7 Kw/m 2 k Skirt T= 120 deg C, h=0.7 Kw/ m 2 k Top groove bottom T= 140 deg C, h= 12 Kw/ m 2 k 2012

20 2 nd groove bottom T= 140 deg C, h= 5 Kw/ m 2 k Under the crown T= 92 degc, h= 0.4 Kw/ m 2 k Gudgeon Pin boss area T= 130 deg C, h= 0.4 Kw/ m 2 k These inputs have been taken based on Seale Taylor s formula, from literature, past experience, by parametric study and Federal Mogul guidelines. 5.3 Thermal Stress Analysis of Piston: Stress analysis has been carried out to find out thermal deflection of the piston. In this stress analysis, element type solid 45 has been chosen. Thermal boundary conditions like temperatures have been applied on nodes by importing temperatures obtained from thermal analysis. The gudgeon pin bore upper side has been constrained about an arc of 120deg in Y- direction and symmetric boundary conditions have been applied Steps involved in Thermal Analysis of Piston: Step 1: Set Preferences Main Menu Preferences In the Preferences for GUI Filtering dialog box, click on the box next to Thermal so that a tick mark appears in the box. Click OK. Step 2: Specify Element Type Main Menu Preprocessor Element Type Add/Edit/Delete Add... Pick Solid in the left field and Brick 8node 70 in the right field. This is the mesh element we will be using to obtain our solution. Click Apply to select this element. Step 3: Specify material properties Preprocessor Material Props Material Models Thermal Conductivity Isotropic i. Conductivity : ii. Thermal Expansion coefficient:2.38 E-05 iii. Density : 2700 Step 4: Define Analysis TypeSolution Analysis Type New Analysis Steady state Step 5: Apply Constraints Solution Define Loads Apply Thermal Temperature On Areas Pick the areas by mouse click (You can go to File Menu PlotCtrls Areas, to find the areas) Click "ok". Step 6: Solve the System Main Menu Solution Current LS Click "ok" Click "close" after the solution is done and close the window of commands. 2013

21 Step 7: Review the results Main Menu General Postprocessor Plot Results Contour Plot Nodal Solution Choose the results you want to review, for example, Temperature Gradient Solution Temperature Gradient sum Click "ok" Fig.5.6: Meshed Model of the Piston in Thermal Analysis Fig.5.7: Temperature distribution in the Piston The figure illustrates the variation of Temperature in on the Piston. The value of Maximum temp. is found to be C. The value of Minimum temp. is found to be C. Variation of colors represents the variation of temperature on the Piston. The different values of temperatures (in 0 C) are shown in the above figure. Fig.5.8: Von Misses Stress distribution in the Piston The figure illustrates the variation of Von Misses stress in the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. 2014

22 Variation of colors represents the variation of stresses in the Piston. The different values of stresses (in MPa) are shown in the above figure. Fig.5.9: Thermal Stress distribution in X-direction in the Piston The figure illustrates the variation of thermal stresses in X-direction of the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. Variation of colors represents the variation of stresses in the Piston. The different values of stresses (in MPa) are shown in the above figure. Fig.5.10: Thermal Stress distribution in Y-direction in the Piston 2015

23 The figure illustrates the variation of thermal stresses in Y-direction of the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. Variation of colors represents the variation of stresses in the Piston. The different values of stresses (in MPa) are shown in the above figure. Fig.5.11: Thermal Stress distribution in Z-direction in the Piston The figure illustrates the variation of thermal stresses in Z-direction of the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. Variation of colors represents the variation of stresses in the Piston. The different values of stresses (in MPa) are shown in the above figure. Fig.5.12: Thermal Gradient in X-direction in the Piston The figure illustrates the variation of thermal gradient in X-direction of the Piston. The value of Maximum thermal gradient is found to be C/m. The value of Minimum thermal gradient is found to be C/m. Variation of colors represents the variation of thermal gradient in the Piston. The different values of thermal gradient (in 0 C/m) are shown in the above figure. 2016

24 Fig.5.13: Thermal Gradient in Y-direction in the Piston The above figure illustrates the variation of thermal gradient in Y-direction of the Piston. The value of Maximum thermal gradient is found to be C/m. The value of Minimum thermal gradient is found to be C/m. Variation of colors represents the variation of thermal gradient in the Piston. The different values of thermal gradient (in 0 C/m) are shown in the above figure. Fig.5.14: Thermal Gradient in Z-direction in the Piston The above figure illustrates the variation of thermal gradient in Z-direction of the Piston. The value of Maximum thermal gradient is found to be C/m. The value of Minimum thermal gradient is found to be C/m. Variation of colors represents the variation of thermal gradient in the Piston. The different values of thermal gradient (in 0 C/m) are shown in the above figure. 2017

25 Fig.5.15: Thermal Gradient Vector sum in the Piston The figure illustrates the variation of thermal gradient Vector sum of the Piston. The value of Maximum thermal gradient is found to be C/m. The value of Minimum thermal gradient is found to be E-04 0 C/m. Variation of colors represents the variation of thermal gradient in the Piston. The different values of thermal gradient (in 0 C/m) are shown in the above figure. Fig.5.16: Thermal flux in X-direction in the Piston The above figure illustrates the variation of thermal flux in X-direction of the Piston. The value of Maximum thermal flux is found to be W/m 2. The value of Minimum thermal flux is found to be W/m 2. Variation of colors represents the variation of thermal flux in the Piston. The different values of thermal flux (in W/m 2 ) are shown in the above figure. 2018

26 Fig.5.17: Thermal flux in Y-direction in the Piston The above figure illustrates the variation of thermal flux in Y-direction of the Piston. The value of Maximum thermal flux is found to be W/m 2. The value of Minimum thermal flux is found to be W/m 2. Fig.5.18: Thermal flux in Z-direction in the Piston The above figure illustrates the variation of thermal flux in Z-direction of the Piston. The value of Maximum thermal flux is found to be W/m 2. The value of Minimum thermal flux is found to be W/m 2. Variation of colors represents the variation of thermal flux in the Piston. The different values of thermal flux (in W/m 2 ) are shown in the above figure. 2019

27 Fig.5.19: Thermal flux Vector sum in the Piston The above figure illustrates the variation of thermal flux Vector sum of the Piston. The value of Maximum thermal flux is found to be W/m 2. The value of Minimum thermal flux is found to be W/m 2. Variation of colors represents the variation of thermal flux in the Piston. The different values of thermal flux (in W/m 2 ) are shown in the above figure. 5.4 Thermo-Mechanical Analysis: Thermo-Mechanical analysis of the piston has been carried out to find out the Stress distribution. This analysis of piston has been carried out with commercial software ANSYS. Piston half section has been used for the analysis. It has been meshed with element type solid 45. Meshed piston has been show in Fig Total no of elements used are Structural load i.e. Pressure and thermal load i.e. bulk temperatures and respective Thermal Expansion coefficients has been applied on various areas like crown, land, ring grooves, pin boss and inner portion of the piston skirt. The obtained Stress distribution of the piston has been shown in Fig Steps Involved In Thermo-Mechanical Analysis: Step 1: Ansys Utility Menu File clear and start new do not read file ok File change job name enter new job name TSA ok File change title enter new title xxx ok Step 2: Define the analysis as a Thermal analysis Main Menu Preference check THERMAL ok Step 3: Preprocessor Element Type Add/Edit/Delete Add Thermal solid solid 45 ok Material properties enter the properties ok Step 4: Preprocessor Meshing: Size controls Manual size Areas pick all element edge edge length Free ok 2020

28 Mesh Areas picks all ok Step 5: Preprocessor Physics Environment Write enter the TITLE Thermal ok Physics Environment clear OK Preprocessor Element type switch element type Thermal to Structural ok Preprocessor Material Properties Material Models Thermal Enter the properties from Input ok. Physics Environment Write enter the title structural ok Step 6: Apply the load Solution Analysis type New analysis Static ok Solution Physics Environment Read Thermal ok( if physics option is not available click un abridged menu ) Solve current LS OK (Solution is done is displayed ) close Main menu Finish Step 7: Review the results Main Menu General Postprocessor Plot Results Contour Plot Nodal Solution Choose the results you want to review, for example, DOF Solution, Displacement vector sum Click "ok" Step 8: Save the file File Menu Save as Jobname.db Fig.5.20: Meshed Model of the Piston in Thermo-Mechanical Analysis 2021

29 Fig.5.21: Von Misses Stress distribution in the Piston The figure illustrates the variation of Von Misses stress in the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. Variation of colors represents the variation of stresses in the Piston. The different values of stresses (in MPa) are shown in the above figure. Fig.5.22: Thermo-Mechanical Stress distribution in X-direction in the Piston The figure illustrates the variation of thermo-mechanical stresses in X-direction of the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. 2022

30 Fig.5.23: Thermo-Mechanical Stress distribution in Y-direction in the Piston The figure illustrates the variation of thermo-mechanical stresses in Y-direction of the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. Fig.5.24: Thermo-Mechanical Stress distribution in Z-direction in the Piston The figure illustrates the variation of thermo-mechanical stresses in Z-direction of the Piston. The value of Maximum stress is found to be MPa. The value of Minimum stress is found to be MPa. Variation of colors represents the variation of stresses in the Piston. The different values of stresses (in MPa) are shown in the above figure. 6.CALCULATIONS: According to Soderberg criterion, 2023

31 Where, F.S = Factor of Safety Mechanical (or) Structural Analysis: For Aluminium, F.S = 1.96 Thermal Analysis: = 2024

32 For Aluminium, F.S = 3.4 Thermo-Mechanical Analysis: = For Aluminium, F.S = RESULTS:The Results obtained from the Ansys Software tool are shown in the below tabular forms. 2025

33 Structural Analysis: Component Maximum Value Minimum Value Stress in X-direction (Mpa) Stress in Y-direction (Mpa) Stress in Z-direction (Mpa) Von Misses Stress (Mpa) Table 7.1: Results of Structural Analysis. Thermal Analysis: Component Maximum Value Minimum Value Temperature ( o C) Thermal Gradient in X-direction ( o C/m) Thermal Gradient in Y-direction ( o C/m) Thermal Gradient in Z-direction ( o C/m) Thermal Gradient Vector sum ( o C/m) E-04 Thermal Flux in X-direction (W/m 2 ) Thermal Flux in Y-direction (W/m 2 ) Thermal Flux in Z-direction (W/m 2 ) Thermal Flux Vector sum (W/m 2 ) Stress in X-direction (Mpa) Stress in Y-direction (Mpa) Stress in Z-direction (Mpa) Von Misses Stress (Mpa)