MYPIBLOGs

What is Engine?

A machine with moving parts that converts power into motion.

or

An Engine is a device which transforms the chemical energy of a fuel into thermal energy and uses this thermal energy to produce mechanical work. Engines normally convert thermal energy into mechanical work and therefore they are called heat engines.

Probably the most intuitive way to differentiate between them is the type of energy each engine uses for power.

Thermal(heat) engines

A heat engine is any closed-cycle device that extracts heat from a hot reservoir, does useful work, and then exhausts heat to a cold reservoir. A closedcycle device is one that periodically returns to its initial state, repeating the same process over and over. A heat engine can do useful work for as long as it is attached to its reservoirs.

A refrigerator is a variant of a heat engine A refrigerator is any closed-cycle device that uses external work to remove heat from a cold reservoir and to exhaust heat to a hot reservoir.

Internal combustion engines (IC engines)

The internal combustion engine is an engine in which the combustion of fuel and an oxidizer (typically air) occurs in a confined space called a combustion chamber. This exothermic reaction creates gases at high temperature and pressure, which are permitted to expand. The defining feature of an internal combustion engine is that useful work is performed by the expanding hot gases acting directly to cause movement of solid parts of the engine, by acting on pistons, rotors, or even by pressing on and moving the entire engine itself. 

This contrasts with external combustion engines, such as steam engines, which use an external combustion chamber to heat a separate working fluid, which then in turn does work, for example by moving a piston or a turbine. 

The term Internal Combustion Engine (ICE) is almost always used to refer specifically to reciprocating piston engines, Wankel engines and similar designs in which combustion is intermittent. However, continuous combustion engines, such as jet engines,most rockets and many gas turbines are also internal combustion engines

External combustion engines (EC engines)

External combustion engines uses their fuel to heat a gas or a vapour through the walls of an external chamber, and the heated gas or vapour is then transferred to the power cylinder. 

Therefore they require a heat exchanger, or boiler to take in heat, and as their fuels are burnt externally under steady conditions, they can in principle use any fuel that can burn, including agricultural residues or waste materials There are two main families of external combustion engines; steam engines which rely on expanding steam (or occasionally some other vapour) to drive a mechanism; orStirling engines which use hot air (or some other hot gas).

Reaction engines

A reaction engine is an engine or motor that produces thrust by expelling reaction mass, in accordance with Newton's third law of motion. This law of motion is most commonly paraphrased as:

For every action force there is an equal, but opposite, reaction force.

Examples:Jet engines, Rocket engines, Pump-jet