International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE) ISSN: 0976-1353 Volume 18 Issue 2 – NOVEMBER 2015.
DESIGN OPTIMIZATION AND TRANSIENT THERMAL ANALYSIS OF FOUR STROKE PETROL ENGINE CYLINDER HEAD H.Sumithra#1, B. Sandhya Rani*2 #1
*2
M.Tech Student, Department of Mechanical Engineering, GATES Institute of Technology, Gooty
Associate Professor in Department of Mechanical Engineering, GATES Institute of Technology, Gooty
fuel is released inside the engine and used directly for mechanical work, as opposed to an external combustion engine in which a separate combustor is used to burn the fuel. The internal combustion engine was conceived and developed in the late 1800s. It has had a significant impact on society, and is considered one of the most significant inventions of the last century. The internal combustion engine has been the foundation for the successful development of many commercial technologies. For example, consider how this type of engine has transformed the transportation industry, allowing the invention and improvement of automobiles, trucks, airplanes and trainsThe components of a reciprocating internal combustion engine, block, piston, valves, crankshaft and connecting rod have remained basically unchanged since the late 1800s. The main differences between a modern day engine and one built 100 years ago are the thermal efficiency and the emission level. For many years, internal combustion engine research was aimed at improving thermal efficiency and reducing noise and vibration. As a consequence, the thermal efficiency has increased from about 10% to values as high as 50%. Since 1970, with recognition of the importance of air quality, there has also been a great deal of work devoted to reducing emissions from engines. Currently, emission control requirements are one of the major factors in the design and operation of internal combustion engines. represent the problem of heat transfer the model of the engine was analyzed. The temperature at the beginning of induction is that of clearance gases. Temperature in the cylinder falls rapidly as the cool charge is inducted. The temperature then rises during compression and is increased to a maximum by combustion process. The expansion process later decreases the temperature and the exhaust process then rapidly drops the gases temperature. During the process of converting thermal energy to mechanical energy, high tempera tures are produced in the cylinders of the engine as a result of combustion process. Large portion of heat is transferred to the piston, cylinder head and walls. Unless this excess heat is carried away and these parts are adequately cooled, the engine will be damaged . A cooling system must be provided not only to prevent damage to the vital parts of the engine, but the
Abstract--Cylinder head plays the most important role in the working of engine, at elevated temperatures the engine will be overheated, which affects the performance of engine. This affect can be reduced by increasing the surface area of cylinder head without increasing the weight. This project involves in design and modification of four stroke petrol engine cylinder head, to increase the heat dissipation rate. In this the concentration was taken on the fins to increase the surface area. The cylinder head existing four fins are replaced with five fins without increasing the mass of the fins. Design of cylinder head was done by using CATIA software, which is advanced parametric design software, developed by Dasssults Systems. The model was designed in part module and drafting work was done in drafting module to show the dimensions with orthographic views. Analysis was done in the ANSYS Software, which works based on FEA. In this transient thermal analysis was done on the model before modification and after modification with different materials and for each material the results were compared, finally the appropriate material was suggested with design modification. In an automotive powertrain system, one of the most critical components is the cylinder head, which possesses the complicated mechanical structure coupled with a sophisticated combustion process. With the ever-increasing demand for higher engine power, the requirement for the cylinder head’s loadbearing capacity is also increasing. In addition, lightweight design is also being pursued for the cylinder head, which is important for better fuel economy and vehicle safety. Key words: Dissipation, Thermal conductivity, Transient.
I.
INTRODUCTION
We almost take our Internal Combustion Engines for granted don‟t we? All we do is buy our vehicles, hop in and drive around. There is, however, a history of development to know about. The compact, well-toned, powerful and surprisingly quiet engine that seems to be purr under your vehicle‟s hood just wasn‟t the tame beast it seems to be now. It was loud, it used to roar and it used to be rather bulky. In fact, one of the very first engines that had been conceived wasn‟t even like the engine we know so well of today. An internal combustion engine is defined as an engine in which the chemical energy of the 73
International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE) ISSN: 0976-1353 Volume 18 Issue 2 – NOVEMBER 2015. temperature of these components must be maintained within certain limits in order to obtain maximum performance from the engine. Adequate cooling is then a fundamental requirement associated with reciprocating internal combustion engines. Hence a cooling system is needed to keep, from not getting so hot as to cause problems and yet to permit it to run hot enough to increase maximum efficiency operation. The duty of the cooling system in other words, is to keep the engine from gettingnot too hot and at the same time not to keep it cool. Some of the fundamental cooling problems and the cooling systems in general use were discussed in [1] & [2].
Duffin [9] established the proposition of Schmidt [8] on firm ground through a rigorous mathematical analysis using calculus of variation.in this project the fins consists in the cylinder head was modified. Modeling Of Cylinder Fin: Creation of a 3-D model in CatiaV5R20 can be performed using three workbenches i.e., sketcher, modeling and assembly.Cylinder along with fin was modeled in Catia. The dimensions of the cylinder along with fin were taken from commercially available bike data sheet. Fins with different geometries (circular and rectangular) were modeled using Catia. Sketcher: Sketcher is used to create two-dimensional representations of profiles associated within the part. We can create a rough outline of curves, and then specify conditions called constraints to define the shapes more precisely and capture our design intent. Each curve is referred to as a sketch object. Creating a new sketch: To create a new sketch, chose StartMechanical DesignSketcherthen select the reference plane or sketch plane in which the sketch is to be created.
The material used for cylinder head at one time was cast iron, because of good wearing qualities. As the technology developed, aluminum alloy replaced cast iron as cylinder head material due to its light weight, high thermal conductivity, easier to machine during production and attractive in appearance. The major drawback of the aluminum cylinder head is its softness and is costly. Aircooled cylinder heads with cooling fins are made of aluminum alloy on account of high heat transfer coefficient of aluminum. This gives a cooler combustion chamber and allows higher compression ratios without danger of detonation, and some of the important information regarding cylinder head was mentioned in [3]. Effective cylinder cooling is crucial to prevent engine failure in improving its thermal efficiency and service life. A higher temperature of charge in the combustion chamber may be preferred for higher engine efficiency. However this high temperature may adversely affect engine elements and cause consierable thermaltribological problems discussed in [4]. The heat conducted through solids, walls or boundaries has to be continuously dissipated to the surroundings or environment to maintain the system in a steady state condition. Heat transfer by convection between a surface and the fluid surrounding It can be increased by attaching to the surface thin strips of metals called „fins‟, also referred as „extended surfaces‟. Heat transfer through extending surfaces was studied extensively in the literature [5-6]. The mathematical analysis of convective fins was first provided by Gardner [7], based on the assumption of constant conductivity and a uniform coefficient of convective heat transfer along the fin surface. The heat flow due to conduction depends on the temperature gradient and the cross-sectional area. On the other hand, the convective heat transfer depends on the local temperature excess and the surface area. The rate of heat transfer from the fin of a given volume can be maximized by a proper selection of the cross-sectional area and the surface area of the fin from its base to tip. In other words, the designer has to find theprofile geometry for a given fin volume that will maximize the rate of heat transfer. This aspect of fin design was first appreciated by Schmidt [8], who proposed a heuristic reasoning to show that the heat conduction in optimum thin fins has to be one dimensional and every section of the fin will be equally effective in dissipating the thermal energy.
II.
SKETCH PLANE
The sketch plane is the plane that the sketch is located on. The sketch plane menu has the following options: Face/Plane:With this option, we can use the attachment face/plane icon to select a planar face or existing datum plane. If we select a datum plane, we can use the reverse direction button to reverse the direction of the normal to the plane
Fig. Model with catia before modification
Fig.Model with catia after modification
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FINITE ELEMENT MODELLING
International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE) ISSN: 0976-1353 Volume 18 Issue 2 – NOVEMBER 2015. thermal loads The original model is modeled in Catia. After the generation of geometric model a parasolid Model of the cylinder head is generated in Catia which is imported into Ansys using the parasolid translator. Couple field analysis is carried out in Ansys using structural solid 187 and thermal solid 87 elements. The main objective of the paper is to observe the stress distribution and deflections at the fins area in both radial and axial directions. Also the heat dissipation in the cylinder head can be increased by changing the material properties.
The heat transfer model was created based on a fabricated engine that is going to be used for research purpose. Boundary condition to the problem was modeled based on standard heat transfer that would occur normally in a twostroke engine at steady state. This model was done with temperature distribution (conduction) at the spark plug location and convection is applied over the fin surface. Boundary Conditions Since the cooling system of the engine uses air, convection boundary is defined on all the outer surfaces (at fins) of the engine assembly. The value is taken as 19.33 W/mK from running engine calculation. The engine speed used is the maximum theoretical speed which is 60 Km/hr and a transient analysis is done for 600 second the time the engine is running. This is to see the amount of heat that is transferred during the time and does it cause a lot of displacement to the engine components.
A coupled-field analysis is a combination of analyses from different engineering disciplines (physics fields) that interact to solve a global engineering problem; hence, we often refer to a coupled-field analysis as a multiphysics analysis. When the input of one field analysis depends on the results from another analysis, the analyses are coupled. Some analyses can have one-way coupling. For example, in a thermal stress problem, the temperature field introduces thermal strains in the structural field, but the structural strains generally do not affect the temperature distribution.
To capture the physics of the problem and to estimate the stresses correctly, the model is finely meshed using solid 187\solid 87 elements. Total number of elements in the model 43341 Total number of nodes in the model 45267
3.1Temperature Distribution in the cylinder head for the different Materials . Set the initial temperature as 12500C Analysis Settings: step end time 600 Sec Right click on Analysis settings – Insert – Convection – enter the film coefficient as 19.317W/mK bulk (final Temp) as 300C. 3.2 Thermal Stress Distribution in the cylinder head for the Material Aluminum-92 Temperature distribution contours
Fig 2. Mesh Model of Cylinder head before modification
The cylinder head is subjected to forced convection on the fins and conduction on the spark plug area at the centre of the cylinder head. The mathematical formulation, the variation of temperature in the cylinder head and the rate of heat loss for steady one-dimensional heat transfer.
IV.
Fig 3.Temperature distribution contour of cylinder head shown in bottom view for time at 600S before modification
RESULTS AND DISCUSSIONS
To perform the couple field (Thermal & Structural) analysis of the Cylinder head, and optimize the material properties to reduce stresses and deflections due to 75
International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE) ISSN: 0976-1353 Volume 18 Issue 2 – NOVEMBER 2015. Fig8. Temperature distribution contour of cylinder head shown for time at 600s After Modification
Temperature(0c) Before modification
665.74
After modification
449.91
3.4 Thermal Stress Distribution in the cylinder head for the material (silicon nitrate)
Fig 4. Temperature distribution contour of cylinder head shown in top view for time at 600S after modification
Temperature(0c) Before modification
671.45
After modification
459.68 Fig7. Temperature distribution contour of cylinder head shown for time at 600S Before Modification
3.3 Temperature Distribution in the cylinder head for the Material Aluminum-96: Temperature distribution contours
Fig9. Thermal stress (Von Mises) distribution contour of the cylinder head has shown in bottom view for time at 600 seconds for Material SI-Ni
Fig7. Temperature distribution contour of cylinder head shown for time at 600S Before Modification
Temperature(0c) Before modification
505.73
After modification
294.95
V.
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CONCLUSION
International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE) ISSN: 0976-1353 Volume 18 Issue 2 – NOVEMBER 2015. After doing the three different coupled (thermal & structural) analysis with three different materials, we found that the maximum stresses for those three materials. Before Modification For Material Aluminum-92, Material Aluminum-96 and Material Aluminum- Silican Nitrate the maximum temperatures are 671.45,665.74 and 505.73. After Modification For Material Aluminum-92, Material Aluminum-96 and Material Aluminum- Silican Nitrate the maximum temperatures are 459.68,449.91and 294.95.Finally we concluded that the Silican Nitrate was the best material among all because it is more Factor of Safety than other two and the FOS should always more than one. The Model weight is reduced after modification from 1.643kg to 1.627kg at a Density of 3000Kg/m3 . REFERENCES [1]
[2] [3] [4]
[5]
Paul W.Gill, James H. Smith, JR., and Eugene J. iurys., 1959, Internal combustion engines-Fundamentals, Oxford & IBH Publishing Company. Dr. Kirpal Singh, 2004, Automobile engineering vol.II, Standard Publishers Distributors, Delhi. Prof.R.B.Gupta, 1998, “Automobile engineering,” Satya Prakashan, Incorporating, Tech India Publications. Wang,Q., Cao,Y., and Chen,G., 1996b “Piston assembly design for improved thermal tribological performance.” Tribology transactions, vol.39 pp.483- 489Compression Ignition Engines, Sadhana Vol. 29, Part 3, pp 275-284. Lienhard, J.H.,IV, and Lienhard,J.H.,V, 2004, A Heat Transfer Textbook Phlogistan, Cambridge, MA.
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