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The Internal Combustion Engine
This site gives an overview of all the techniques used to study combustion processes and a guide to aid the understanding of the combustion cycle as a whole.
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 by the spark in the combustion chamber. The gas produced in this reaction rapidly expands forcing the piston down the cylinder on the power stroke. The basic components for a combustion cycle in a four stroke engine are the combustion chamber (cylinder), piston, intake port and outlet or exhaust port. The piston reciprocates inside the cylinder, exhaust and intake ports open and close 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 (Otto 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, 1-2-4-3 or 1-3-4-2). The flywheel then helps smooth out the linear movement of the pistons.
| The four stroke internal combustion engine | The combustion chamber | |
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Four stroke (Otto) cycle |
Within the field of engine research many experimental techniques have been developed to take measurements within the combustion chambers of internal combustion engines. There are many different aspects to the combustion process, by studying these various aspects to develop a more detailed understanding of the combustion cycle, low emission more efficient engines may be developed. This website outlines the basic techniques that have been developed to study the combustion processes within internal combustion engines and the typical results that have been produced. The majority of combustion research centres around seven main areas of measurement within the combustion cycle:
Pressure | Temperature | Flow | Fuel injection spray | Combustion chemistry | Flame | Soot particulate
Lubrication measurements may also be considered but have not been included on this website. This is because although lubrication facilitates the combustion cycle, it is not generally directly involved in the combustion processes. Most measurement techniques are either intrusive or non-intrusive, often requiring some degree of modification to the engine for the various probes or for optical access. As a large proportion of measurement techniques are now optically based, this website also covers some of the methods that have been developed for optical access into the combustion chamber.
The direction that combustion research is now heading, is towards using non-intrusive techniques to perform most measurements in the combustion chamber. The general aim is to develop methods that can be applied to production engines rather than modified research engines. The applications of this type of technology will be improving engine design and developing smarter engine management and control systems with continuous combustion cycle monitoring.
This web page was created by S.J. Clarke and M. Hotchkiss as part of their third year engineering project. The aim of the project is to look into areas of research in gas turbines and internal combustion engines, and to show where they fit in along the combustion cycle.
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