Internal combustion engine “ICEV” redirects here. For the form of water ice, see Ice more familiar four-stroke and two-stroke piston engines, V. For the high speed train, see ICE V. along with variants, such as the six-stroke piston engine An internal combustion engine (ICE) is a heat engine and the Wankel rotary engine. A second class of internal combustion engines use continuous combustion: gas tur- bines, jet engines and most rocket engines, each of which are internal combustion engines on the same principle as previously described.[1][2] Firearms are also a form of in- ternal combustion engine.[2] Internal combustion engines are quite different from external combustion engines, such as steam or Stirling engines, in which the energy is delivered to a working fluid not consisting of, mixed with, or contaminated by combustion products. Working fluids can be air, hot wa- ter, pressurized water or even liquid sodium, heated in a boiler. ICEs are usually powered by energy-dense fuels such as gasoline or diesel, liquids derived from fossil fu- els. While there are many stationary applications, most ICEs are used in mobile applications and are the domi- nant power supply for vehicles such as cars, aircraft, and boats. Typically an ICE is fed with fossil fuels like natural gas or petroleum products such as gasoline, diesel fuel or fuel oil. There’s a growing usage of renewable fuels like biodiesel for compression ignition engines and bioethanol Diagram of a cylinder as found in 4-stroke gasoline engines.: or methanol for spark ignition engines. Hydrogen is C – crankshaft. sometimes used, and can be made from either fossil fuels E – exhaust camshaft. or renewable energy. I – inlet camshaft. P – piston. R – connecting rod. S – spark plug. V – valves. red: exhaust, blue: intake. 1 History W – cooling water jacket. gray structure – engine block. Main article: History of the internal combustion engine where the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal com- bustion engine the expansion of the high-temperature and high-pressure gases produced by combustion apply direct force to some component of the engine. The force is ap- 2 Etymology plied typically to pistons, turbine blades, or a nozzle. This force moves the component over a distance, transform- At one time, the word engine (from Latin, via Old French, ing chemical energy into useful mechanical energy. The ingenium, “ability”) meant any piece of machinery — a first commercially successful internal combustion engine [1] sense that persists in expressions such as siege engine.A was created by Étienne Lenoir around 1859 and the first “motor” (from Latin motor, “mover”) is any machine that modern internal combustion engine was created in 1864 produces mechanical power. Traditionally, electric mo- by Siegfried Marcus. tors are not referred to as “Engines"; however, combus- The term internal combustion engine usually refers to an tion engines are often referred to as “motors.” (An electric engine in which combustion is intermittent, such as the engine refers to a locomotive operated by electricity.) 1 2 4 CLASSIFICATION 3 Applications Combined cycle power plant Reciprocating engine as found inside a car generators are used for backup power and for providing Reciprocating piston engines are by far the most com- electrical power to areas not connected to an electric grid. mon power source for land and water vehicles, includ- Small engines (usually 2‐stroke gasoline engines) are a ing automobiles, motorcycles, ships and to a lesser ex- common power source for lawnmowers, string trimmers, tent, locomotives (some are electrical but most use Diesel chain saws, leafblowers, pressure washers, snowmobiles, engines[3][4]). Wankel engines are used in some automo- jet skis, outboard motors, mopeds, and motorcycles. biles and motorcycles. Where very high power-to-weight ratios are required, internal combustion engines appear in the form of 4 Classification combustion turbines. Powered aircraft typically uses an ICE which may be a reciprocating engine. Airplanes can instead use jet engines and helicopters can instead employ There are several possible ways to classify internal com- turboshafts; both of which are types of turbines. In addi- bustion engines. tion to providing propulsion, airliners employ a separate Reciprocating: ICE as an auxiliary power unit. By number of strokes • Two-stroke engine • Four-stroke engine (Otto cycle) • Six-stroke engine By type of ignition • Compression-ignition engine • Spark-ignition engine (commonly found as gasoline engines) By mechanical/thermodynamical cycle (these 2 cycles do not encompass all reciprocating en- gines, and are infrequently used): Big Diesel generator used for backup power • Atkinson cycle ICEs drive some of the large electric generators that • Miller cycle power electrical grids. They are found in the form of combustion turbines in combined cycle power plants with Rotary: a typical electrical output in the range of 100 MW to 1 GW. The high temperature exhaust is used to boil and su- • Wankel engine perheat water to run a steam turbine. Thus, the efficiency is higher because more energy is extracted from the fuel than what could be extracted by the combustion turbine Continuous combustion: alone. In combined cycle power plants efficiencies in the range of 50% to 60% are typical. In a smaller scale Diesel • Gas turbine 5.1 Structure 3 • Jet engine • Rocket engine The following jet engine types are also gas turbines types: •Ramjet • Turbojet • Turbofan • Turboprop 5 Reciprocating engines See also: Diesel engine and Gasoline engine 5.1 Structure Bare cylinder block of a V8 engine The base of a reciprocating internal combustion engine is the engine block, which is typically made of cast iron or aluminium. The engine block contains the cylinders. In engines with more than one cylinder they are usually ar- Piston, piston ring, gudgeon pin and connecting rod ranged either in 1 row (straight engine) or 2 rows (boxer engine or V engine); 3 rows are occasionally used (W en- gine) in contemporary engines, and other engine config- wall of the piston is termed its crown and is typically flat urations are possible and have been used. Single cylinder or concave. Some two-stroke engines use pistons with a engines are common for motorcycles and in small engines deflector head. Pistons are open at the bottom and hollow of machinery. Water-cooled engines contain passages in except for an integral reinforcement structure (the piston the engine block where cooling fluid circulates (the water web). When an engine is working the gas pressure in the jacket). Some small engines are air-cooled, and instead of combustion chamber exerts a force on the piston crown having a water jacket the cylinder block has fins protrud- which is transferred through its web to a gudgeon pin. ing away from it to cool by directly transferring heat to Each piston has rings fitted around its circumference that the air. The cylinder walls are usually finished by honing mostly prevent the gases from leaking into the crankcase to obtain a cross hatch, which is better able to retain the or the oil into the combustion chamber. A ventilation oil. A too rough surface would quickly harm the engine system drives the small amount of gas that escape past by excessive wear on the piston. the pistons during normal operation (the blow-by gases) The pistons are short cylindrical parts which seal one out of the crankcase so that it does not accumulate con- end of the cylinder from the high pressure of the com- taminating the oil and creating corrosion. In two-stroke pressed air and combustion products and slide continu- gasoline engines the crankcase is part of the air–fuel path ously within it while the engine is in operation. The top and due to the continuous flow of it they do not need a 4 5 RECIPROCATING ENGINES separate crankcase ventilation system. Engine block seen from below. The cylinders, oil spay nozzle and half of the main bearings are clearly visible. Valve train above a Diesel engine cylinder head. This engine uses rocker arms but no pushrods. of the connecting rod attached to the gudgeon pin is called The cylinder head is attached to the engine block by nu- its small end, and the other end, where it is connected to merous bolts or studs. It has several functions. The cylin- the crankshaft, the big end. The big end has a detachable der head seals the cylinders on the side opposite to the half to allow assembly around the crankshaft. It is kept pistons; it contains short ducts (the ports) for intake and together to the connecting rod by removable bolts. exhaust and the associated intake valves that open to let The cylinder head has attached an intake manifold and the cylinder be filled with fresh air and exhaust valves that an exhaust manifold to the corresponding ports. The in- open to allow the combustion gases to escape. However, take manifold connects to the air filter directly, or to a 2-stroke crankcase scavenged engines connect the gas carburetor when one is present, which is then connected ports directly to the cylinder wall without poppet valves; to the air filter. It distributes the air incoming from these the piston controls their opening and occlusion instead. devices to the individual cylinders. The exhaust manifold The cylinder head also holds the spark plug in the case of is the first component in the exhaust system. It collects the spark ignition engines and the injector for engines that use exhaust gases from the cylinders and drives it to the fol- direct injection. All CI engines use fuel injection, usually lowing component in the path.