Introduction of an Automobile Engine Piston

This article explains the functions and design of an automobile engine piston. It discusses the importance of strength, weight, and thermal expansion in piston design. The article also mentions the typical materials used in piston manufacturing and the friction loss associated with piston assembly.

Introduction of an Automobile Engine Piston
A piston is an element of reciprocating engines, reciprocating pumps, pneumatic cylinders and gas
compressors out of the other equivalent machine tool. It is movable element that is placed within a
cylinder with piston rings by customized gas fixed. In an engine, the role of piston is to transmit force
stored in expanding gas within the cylinder to the crankshaft with the help of piston or connecting rod.
The function of piston in pump is reverse and here, the force to be transferred from crankshaft to the
piston in order to compress or eject the fluid in the cylinder. In some other engines, piston has a
different role i.e., it acts as a valve in the cylinder which is to be covered by port.
The piston in automobile engine transform the combustion load to a force on crankshaft. Firstly, starts
the piston, gets accelerated and then stops twice in every crankshaft rotation. A large inertia force is
produced by this reciprocating movement of piston. The inertia force completely based on the piston
and high speed of the operating are produced by less inertia force. While the piston is operating, a
temperature reise of around 150 k is developed from the upper part of piston to its lower. Also the
piston sealing rings are to be supported by it. Therefore, while designing the piston it must comprise
between thermal expansion, weight and strength. The piston must be design with sufficient strength so
that it can bear combustion load and reciprocating load, should exist enough length of the flange to
conduct the piston in the drill, should have expansion control to provide long life working capacity and
the piston rings to be hold perpendicular to the cylinder wall.
Figure 1: Basic of engine car piston

The main functions of the piston are mentioned below:
i) It must be able to create a sliding gas and leak proof joint in the cylinder.
ii) It must transfer the gas pressure to the compact end of the connecting rod.
iii) It must be acting like bearing for the gudgeon pin.
About 50-60% of the mechanical dissipation are consumed by the entire piston assembly of the whole
engine. The typical piston which is having three ring, 60% of the friction loss is accounted for
compression ring, second 30% by compression ring, and lastly 10% by oil control ring. A large pads are
provide to the piston in order to remove the material and bring back the desired weight of the piston.
One of the most important configuration is piston head to anable the combustion process to form a part
of the combustion chamber. The flat top pistons are used which are accessed with low cost and poor
performance having small cut in it to supply valve head clearance. To avail high performance of piston
engine have elevated vault to rise compression load. The piston head should have the sufficint strength
to sustain against the combustion load.
The piston engine in automotive are mostly made of aluminium alloy, usually contain high amount of
silicon to improve toughness with the reduction of whole density, and to be cast or forged.
Reference
[1] M. Priest and C. M. Taylor, “Automobile engine tribology—approaching the surface”, Wear,
vol. 241, pp. 193-203, 2000.
[2] C. R. Ferguson and A. T. Kirkpatrick, “Internal combustion engines: applied thermosciences”,
John Wiley & Sons, 2015.
[3] R. V. Basshuysen and F. Schäfer, “Internal combustion engine handbook-basics, components”,
systems and perspectives, vol. 345, 2004.
[4] G. Ryk and I. Etsion, “Testing piston rings with partial laser surface texturing for friction
reduction”, Wear, vol. 261, pp. 792-796, 2006.
[5] R. Mikalsen and A. P. Roskilly, “The design and simulation of a two-stroke free-piston
compression ignition engine for electrical power generation”, Applied Thermal Engineering,
vol. 28, pp. 589-600, 2008.