4.2 ENGINES AND MOTORS Internal Combustion Engines Engine vs motor An is a machine that can convert some form of energy, obtained from a fuel, into useful mechanical power or motion. If the engine produces kinetic energy from a fuel source, it is called a ; if it produces kinetic energy from a pre-processed "fuel", for instance electricity or compressed air, it is called a . engine prime mover motor Internal combustion engines (ICE) are the most common form of heat engines, i.e. engines that produce motion from heat, and they are used in vehicles, boats, ships, airplanes, and trains. They are named as such because they generate mechanical power from the chemical energy released by fuel combustion which occurs in a confined space called the combustion chamber. Many of the automotive engines are , which get their name from the four distinct phases that occur in the engine during operation. Internal combustion engines four-stroke ICEs Main parts The contains the . The more an engine has, the more power it is capable of producing and the engines are classified by the number – usually from 1 to 12 – and of the cylinders . engine block cylinders cylinders alignment 1 Inside each cylinder, a , a cylindrical structure whose top surface is the , moves up and down: this movement is called . are present on the circumference of each piston where some are placed, in order to prevent friction and leakage. Engine is the volume generated by all the pistons inside the cylinders in a single movement from the ( ) to the ( ). piston crown reciprocating Grooves rings 1 displacement top dead centre TDC bottom dead centre BDC 2 There is a that has an "I" shape structure: one end is connected to each piston and the other one to the , which converts the linear (up and down) motion of the piston into a rotational motion. connecting rod crankshaft A protects these parts and retains lubricating oil, which is pumped to the different engine parts. crankcase The has openings for air to flow into the cylinders and out for burned gases expulsion. engine head The , placed in the cylinder heads and operated by a , allow fuel and air to enter the combustion chamber and let the exhaust fumes out. intake and exhaust valves camshaft DO Go online and find the possible positions and numbers of cylinders in a reciprocating engine. For example, what does “Ferrari V12s” mean? 1 MORE Piston rings are very important parts in an engine: they the combustion chamber to ensure minimal loss of gas, improve heat transfer from the piston to the cylinder wall, maintain the correct quantity of oil between the piston and the cylinder wall, regulating engine oil consumption by scraping oil from the cylinder walls back to the 1 seal oil sump. MORE Top Dead Centre is the position of the piston when it is at the very top of its stroke inside the cylinder; Bottom Dead Centre is the opposite, when the piston is at the very bottom of its stroke. 2