| Internal Combustion Engine |
Article Index for Internal |
Shopping Combustion |
Website Links For Internal Combustion |
Information AboutInternal Combustion Engine |
| CATEGORIES ABOUT INTERNAL COMBUSTION ENGINE | |
| engines | |
| engine technology | |
| energy conversion | |
| auto parts | |
|
This contrasts with External Combustion Engine s, such as Steam Engines and Stirling 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 Engine s 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. In English, there is a small cylinder in which gas and oxygen is inserted. The momentum of the previous force pushes a piston(small cylindrical object, exact size of the cylinder itself) up into the gas and air, causing a compression of the two elements. The two compressed elements are then ignited by a small spark, causing an explosion. The small explosion then causes a pushback force on the piston, shoving it downward. The moving piston spins a small rod which spins other elements outside of the mechanism, causing things to move in a certain pattern. HISTORY engine]] The first internal combustion engines did not have compression, but ran on air/fuel mixture sucked or blown in during the first part of the intake stroke. The most significant distinction between modern internal combustion engines and the early designs is the use of Compression and in particular of in-cylinder compression.
Applications Internal combustion engines are most commonly used for mobile propulsion in automobiles, equipment, and other portable machinery. In mobile equipment internal combustion is advantageous, since it can provide high power to weight ratios together with excellent fuel energy-density. These engines have appeared in transport in almost all Automobile s, Truck s, Motorcycle s, Boat s, and in a wide variety of Aircraft and Locomotive s, generally using Petroleum (called All-Petroleum Internal Combustion Engine Vehicles or APICEVs) . Where very high power is required, such as Jet Aircraft , Helicopter s and large ships, they appear mostly in the form of Turbines . They are also used for Electric Generator s (i.e. 12 V generators) and by industry. OPERATION (or Otto cycle) 1. intake 2. compression 3. power 4. exhaust]] All internal combustion engines depend on the , typically with the oxygen from the air, although other oxidizers such as Nitrous Oxide may be employed. Also see Stoichiometry . The most common modern fuels are made up of Hydrocarbon s and are derived from mostly Petroleum . These include the fuels known as Diesel fuel, Gasoline and Petroleum Gas , and the rarer use of Propane Gas . Most internal combustion engines designed for gasoline can run on Natural Gas or liquefied petroleum gases without major modifications except for the fuel delivery components. Liquid and gaseous Biofuel s, such as Ethanol and Biodiesel , a form of diesel fuel that is produced from crops that yield Triglycerides such as Soy Bean oil, can also be used. Some can also run on Hydrogen gas. All internal combustion engines must achieve ignition in their cylinders to create combustion. Typically engines use either a Spark Ignition (SI) method or a Compression Ignition (CI) system. In the past other methods using hot tubes or flames have been used. PETROLEUM INTERNAL COMBUSTION ENGINES See Also: Petroleum Gasoline Ignition Process Electrical/Gasoline-type ignition systems (that can also run on other fuels as previously mentioned) generally rely on a combination of a Lead-acid Battery and an Induction Coil to provide a high voltage electrical spark to ignite the air-fuel mix in the engine's cylinders. This battery can be recharged during operation using an electricity-generating device, such as an Alternator or Generator driven by the engine. Gasoline engines take in a mixture of air and gasoline and compress to less than 185 psi and use a spark plug to ignite the mixture when it is compressed by the piston head in each cylinder. Diesel Engine Ignition Process Compression ignition systems, such as the Diesel Engine and HCCI engines, rely solely on heat and pressure created by the engine in its compression process for ignition. Compression that occurs is usually more than three times higher than a gasoline engine. Diesel engines will take in air only, and shortly before peak compression, a small quantity of diesel fuel is sprayed into the cylinder via a fuel injector that allows the fuel to instantly ignite. HCCI type engines will take in both air and fuel but will continue to rely on an unaided auto-combustion process due to higher pressures and heat. This is also why diesel and HCCI engines are also more susceptible to cold starting issues though they will run just as well in cold weather once started. Most diesels also have battery and charging systems, however this system is secondary and is added by manufacturers as luxury for ease of starting, turning fuel on and off (which can also be done via a switch or mechanical apparatus), and for running auxiliary electrical components and accessories. Most old engines, however, rely on electrical systems that also control the combustion process to increase efficiency and reduce emissions. ENERGY AND POLLUTION Once ignited and burnt, the Combustion products, hot Gas es, have more available energy than the original compressed fuel/air mixture (which had higher Chemical Energy ). The available energy is manifested as high Temperature and Pressure which can be translated into Work by the engine. In a reciprocating engine, the high pressure product gases inside the cylinders drive the engine's pistons. Once the available energy has been removed, the remaining hot gases are Vented (often by opening a Valve or exposing the exhaust outlet) and this allows the piston to return to its previous position (Top Dead Center - TDC). The piston can then proceed to the next phase of its cycle, which varies between engines. Any Heat not translated into work is normally considered a waste product, and is removed from the engine either by an air or liquid cooling system. Engine Efficiency The efficiency of various types of internal combustion engines vary, but it is lower than . Most internal combustion engines waste about 36% of the energy in gasoline as heat lost to the cooling system and another 38% through the exhaust. The rest, about 6%, is lost to friction. Hydrogen Fuel Injection , or HFI, is an engine add on system that improves the Fuel Economy of internal combustion engines by injecting Hydrogen as a Combustion enhancement into the Intake Manifold . Fuel economy gains of 15% to 50% can be seen. A small amount of hydrogen added to the Intake air-fuel charge increases the octane rating of the combined fuel charge and enhances the flame Velocity , thus permitting the engine to operate with more advanced ignition timing, a higher compression ratio, and a leaner air-to-fuel mixture than otherwise possible. The result is lower Pollution with more power and increased efficiency. Some HFI systems use an on board Electrolyzer to generate the small amount of hydrogen needed in the system, around 5% of total Btu. A small tank of pressurized hydrogen can also be used, but this method necessitates refilling. Hydrogen in liquid form is seldom used because it is difficult to store. There has also been discussion of new types of internal combustion engines, such as the Scuderi Split Cycle Engine , that utilize high compression pressures in excess of 2000 psi and combust after top-dead-center (the highest & most compressed point in an internal combustion piston stroke). The claimed efficiency of this engine, by calculation, is 42%. This has yet to be demonstrated as of March 2007. Engine pollution See Also: Global warming Generally internal combustion engines, particularly reciprocating internal combustion engines, produce moderately high pollution levels, due to incomplete combustion of carbonaceous fuel, leading to Carbon Monoxide and some Soot along with oxides of nitrogen & Sulfur and some unburnt hydrocarbons depending on the operating conditions and the fuel/air ratio. The primary causes of this are the need to operate near the stoichiometric ratio for petrol engines in order to achieve combustion (the fuel would burn more completely in excess air) and the "quench" of the flame by the relatively cool cylinder walls. Quenching is commonly observed in diesel (compression ignition) engines which run on natural gas, when running at lower speed. It dramatically reduces the efficiency and increases knocking and might cause the engine to stall. Diesel engines produce a wide range of pollutants including aerosols of many small particles ( PM10 ) that are believed to penetrate deeply into human lungs. Engines running on Liquified Petroleum Gas (LPG) are very low in Emissions as LPG burns very cleanly and does not contain sulphur or lead.
PARTS engine]] For a Four-stroke engine, key parts of the engine include the Crankshaft (purple), one or more Camshaft s (red and blue) and Valve s. For a Two-stroke engine, there may simply be an exhaust outlet and fuel inlet instead of a valve system. In both types of engines, there are one or more cylinders (grey and green) and for each cylinder there is a Spark Plug (darker-grey), a Piston (yellow) and a Crank (purple). A single sweep of the cylinder by the piston in an upward or downward motion is known as a stroke. The downward stroke that occurs directly after the air/fuel mix passes from the carburetor to the cylinder where it is ignited is known as a power stroke. A Wankel Engine has a triangular rotor that orbits in an Epitrochoid al (figure 8 shape) chamber around an eccentric shaft. The four phases of operation (intake, compression, power, exhaust) take place in separate locations, instead of one single location as in a reciprocating engine. A Bourke Engine uses a pair of pistons integrated to a Scotch Yoke that transmits reciprocating force through a specially designed bearing assembly to turn a crank mechanism. Intake, compression, power, and exhaust occur in each stroke. CLASSIFICATION The fundamental difference between an engine and a motor is that a motor converts electricity into mechanical energy whereas an engine converts thermal energy into mechanical energy. At one time, the word "engine" (from Latin , via Old French , ''ingenium'', "ability") meant any piece of Machinery — a sense the persists in expressions such as '' Siege Engine ''. A "motor" (from Latin ''motor'', "mover") is any machine that produces mechanical Power . Traditionally, Electric Motor s are not referred to as "engines," but combustion engines are often referred to as "motors." (An '' Electric Engine '' refers to Locomotive operated by electricity). However, many people consider engines as those things which generate their power from within, and motors as requiring an outside source of energy to perform their work. Principles of operation Reciprocating :
Rotary :
Continuous combustion: Engine cycle Two-stroke See Also: Two-stroke cycle Engines based on the two-stroke cycle use two strokes (one up, one down) for every power stroke. Since there are no dedicated intake or exhaust strokes, alternative methods must be used to Scavenge the cylinders. The most common method in spark-ignition two-strokes is to use the downward motion of the piston to pressurize fresh Charge in the Crankcase , which is then blown through the cylinder through ports in the cylinder walls. Spark-ignition two-strokes are small and light (for their power output), and mechanically very simple; they are also generally less efficient and more polluting than their four-stroke counterparts. However in single cylinder small motor applications cc for cc, a two-stroke engine produces much more power than equivalent 4 strokes due to the enormous advantage of having 1 power stroke for every 360 degrees of crankshaft rotation (compared to 720 degrees in a 4 stroke motor). Small displacement, crankcase scavenged two-stroke engines have been less fuel-efficient than other types of engines when the fuel is mixed with the air prior to scavenging allowing some of it to escape out of the exhaust port. Modern designs (Sarich and Paggio) use air assisted fuel injection, which avoid this loss and are more efficient than comparably sized four stroke engines. Fuel injection is essential for a modern two-stroke engine in order to meet ever stringent emission standards. Research continues into improving many aspects of two-stroke motors, including direct fuel injection amongst other things. Initial results have produced motors that are much cleaner burning than their traditional counterparts. Two-stroke engines are widely used in Snowmobile s, Lawnmower s, Weed-whacker s, Chain Saw s, Jet Ski s, Moped s, Outboard Motor s and many Motorcycle s. The largest compression-ignition engines are two-strokes, and are used in some locomotives and large ships. These engines use Forced Induction to scavenge the cylinders. An example of this type of motor is the Wartsila-Sulzer turbocharged 2 stroke diesel as used in large container ships. It is the most efficient and powerful engine in the world, with over 50% thermal efficiency for comparison the most efficient small 4 stroke motors are around 43.0% thermal efficiency (SAE 900648), and size is an advantage for efficiency due to the increase in the ratio of volume to area. Four-stroke See Also: Four-stroke cycle Engines based on the four-stroke cycle or Otto cycle have one power stroke for every four strokes (up-down-up-down) and are used in cars, larger Boat s and many light Aircraft . They are generally quieter, more efficient and larger than their two-stroke counterparts. There are a number of variations of these cycles, most notably the Atkinson and Miller cycles. Most truck and automotive diesel engines use a four-stroke cycle, but with a compression heating ignition system. This variation is called the Diesel Cycle . The steps involved here are: 1. Suction stroke - Air and vaporised fuel are drawn in 2. Compression stroke - Fuel vapor and air are compressed and ignited () 3. Power stroke - Fuel combusts and piston is pushed downwards 4. Exhaust stroke - Exhaust is driven out Five-stroke |
|
|