Design, Modeling and Material Optimization of Engine Piston for 150cc Motor Cycle

ABSTRACT:

The piston is a “heart” of the engine and its working condition is the worst and one of the key parts of the engine in the working environment. Its design should be structurally and thermally sustainable. This paper shows the design calculations and modeling of the piston by NX UNIGRAPHICS software to gain a result, which improves and optimizes the structure of the piston. Piston is made of cast aluminum because of its high heat transfer rate. One important thing to take care while using it (cast aluminum) is, because it expands appreciably on heating so right amount of clearance needs to be provided or else it will lead the engine to seize. For eliminating above problem in this project I am going to replace cast aluminum LM25with Aluminum Alloy 6082-T651. This material has high strength and Elongation. The aim of project is to design a piston for 150cc engine using Design calculations. Creating 3D model by using parameters obtained in calculation and 2D model of piston. For 3D and 2D modeling, used CAD software is UNIGRAPHICS NX9.

INTRODUCTION
A piston is a component of reciprocating engines, reciprocating pumps, gas 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. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder wall. The piston of an internal combustion engine is acted upon by the pressure of the expanding combustion gases in the combustion chamber space at the top of the cylinder. This force then acts downwards through the connecting rod and onto the crankshaft. The connecting rod is attached to the piston by a swiveling gudgeon pin (US: wrist pin). This pin is mounted within the piston: unlike the steam engine, there is no piston rod or crosshead. The pin itself is of hardened steel and is fixed in the piston, but free to move in the connecting rod. A few designs use a ‘fully floating’ design that is loose in both components. All pins must be prevented from moving sideways and the ends of the pin digging into the cylinder wall, usually by circlips. Gas sealing is achieved by the use of piston rings. These are a number of narrow iron rings, fitted loosely into grooves in the piston, just below the crown. The rings are split at a point in the rim, allowing them to press against the cylinder with a light spring pressure. Two types of ring are used: the upper rings have solid faces and provide gas sealing; lower rings have narrow edges and a U-shaped profile, to act as oil scrapers. There are many proprietary and detail design features associated with piston rings.

Pistons are cast from aluminum alloys. For better strength and fatigue life, some racing pistons may be forged instead. Early pistons were of cast iron, but there were obvious benefits for engine balancing if a lighter alloy could be used. To produce pistons that could survive engine combustion temperatures, it was necessary to develop new alloys such as Y alloy and Hiduminium, specifically for use as pistons. A few early gas engines had double-acting cylinders, but otherwise effectively all internal combustion engine pistons are single-acting. During World War II, the US submarine Pompano was fitted with a prototype of the infamously unreliable H.O.R. double-acting two-stroke diesel engine. Although compact, for use in a cramped submarine, this design of engine was not repeated.

Analysis of piston

Sequence of steps:
1. Importing the piston model from UNIGRAPHICS NX9.
2. Defining the Thermal Environment.
3. Defining the Structural Environment.

4. Solution phase-assigning loads and solving.
5. Post processing and viewing the results.

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Design, Modeling and Material Optimization of Engine Piston for 150cc Motor Cycle