IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 7, Issue 4 (Jul. - Aug. 2013), PP 30-36 www.iosrjournals.org www.iosrjournals.org 30 | Page Improving the Heat Transfer Rate for Multi Cylinder Engine Piston and Piston Rings Ravi Manohar 1 , V.Mahanandi Reddy 2 1 ( Mechanical Engineerig,G.Pulla Reddy Engineerig College (Autonomous) /J Ntu Anantapur , India) 2 (Mechanical Engineerig,G.Pulla Reddy Engineerig College (Autonomous) /J Ntu Anantapur , India ) Abstract: The four stroke otto engine uses just one of the four strokes to perform work. This causes various problems: The engine runs jerkily, and this can only be prevented by a large flywheel, which needs a lot of space and weights pretty much in addition. In this thesis, thermal loads and pressures produced in the multi cylinder petrol engine Toyota 86 Car by varying compression ratios 14:1, 15:1, 18:1, 20:1 and 25:1 are calculated by mathematical correlations And also calculating the effect of these thermal loads on piston and piston rings by varying materials Cast Iron, Aluminum Alloy 6061 for piston and Cast Iron and Steel for piston rings.FEA transient thermal analysis is performed on the parametric model to validate the effect of thermal loads on piston and piston rings for different materials. The optimum value of compression ratio and the better material is determined by analysis results to improve the heat transfer rate of multi cylinder engine piston and piston rings. Dynamic analysis is done on the piston by applying the pressures developed and also static analysis by applying the maximum pressure. Keywords: Multi cylinder engines, Piston, Piston rings, Compression ratio, Materials, FEA analysis I. 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. A piston ring is a split ring that fits into a groove on the outer diameter of a piston in a reciprocating engine such as an internal combustion engine or steam engine. II. Compression Ratio The compression ratio of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity. In a piston engine it is the ratio between the volume of the cylinder and combustion chamber when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke. 2.1 Effect Of Compression Ratio On Engine Performance In an internal combustion engine, a piston compresses a large volume of a mixture of fuel and air into a very small space. The ratio of the maximum piston volume to the minimum compressed volume is called the compression ratio. Compressing the fuel and air will make them burn faster, which (though I'm not sure directly how) makes the engine run better. There are secondary benefits to high compression ratios, too. High compression ratio engines burn both much more cleanly and much more efficiently than lower-compression engines. The increase in efficiency is due to the additional heat and Brownian motion caused by compression fully vaporizing the fuel, considering how much work is put into cooling the fuel-air mix in turbocharged cars. Another issue is engine efficiency as a function of RPMs. An engine limits power by reducing the intake of fuel and air to an engine; if only half the fuel and air is entering a piston, the compression ratio is effectively halved as well. 2.2 Specifications Of Toyota 86 Engine Type 4-Stroke multi cylinder petrol engine, Cylinder bore = 86mmStroke length = 86mm Speed = 2000rpm Fuel consumption = 0.25kg/BP/hr Higher calorific value of fuel = 47000kj/kg, Maximum gas pressure = 5N/mm²