Most modern diesels, however, rely on electrical systems that also control the combustion process to increase efficiency and reduce emissions. 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. The parts of an engine vary depending on the engine's type. For a four-stroke engine, key parts of the engine include the crankshaft purple , one or more camshafts red and blue and valves.
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 gray and green and for each cylinder there is a spark plug darker-gray , 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 and the downward stroke that occurs directly after the air-fuel mix in the cylinder is ignited is known as a power stroke. A Wankel engine has a triangular rotor that orbits in an epitrochoidal 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 all occur in each stroke of this yoke.
There is a wide range of internal combustion engines corresponding to their many varied applications. Likewise there is a wide range of ways to classify internal-combustion engines, some of which are listed below. Although the terms sometimes cause confusion, there is no real difference between an "engine" and a "motor. A "motor" from Latin motor, "mover" is any machine that produces mechanical power. Traditionally, electric motors are not referred to as "engines," but combustion engines are often referred to as "motors. With that said, one must understand that common usage does often dictate definitions.
Many individuals consider engines as those things which generate their power from within, and motors as requiring an outside source of energy to perform their work. Evidently, the roots of the words seem to actually indicate a real difference. Further, as in many definitions, the root word only explains the beginnings of the word, rather than the current usage. It can certainly be argued that such is the case with the words motor and engine. 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. Common applications include snowmobiles, lawnmowers, weed-whackers, chain saws, jet skis, mopeds, outboard motors, and some motorcycles.
Unfortunately, they are also generally louder, less efficient, and far more polluting than their four-stroke counterparts, and they do not scale well to larger sizes. Interestingly, 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.
Without special exhaust processing, this will also produce very high pollution levels, requiring many small engine applications such as lawnmowers to employ four stroke engines, and smaller two-strokes to be outfitted with catalytic converters in some jurisdictions. 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 boats 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. Engines based on the five-stroke cycle are a variant of the four stroke cycle. Normally the four cycles are intake, compression, combustion and exhaust. The fifth cycle added by Delautour [2] is refrigeration.
Engines running on a five-stroke cycle are up to 30 percent more efficient than an equivalent four stroke engine. In this engine, two diametrically opposed cylinders are linked to the crank by the crank pin that goes through the common scottish yoke. The cylinders and pistons are so constructed that there are, as in the usual two stroke cycle, two power strokes per revolution. However, unlike the common two stroke engine, the burnt gases and the incoming fresh air do not mix in the cylinders, contributing to a cleaner, more efficient operation.
The scotch yoke mechanism also has low side thrust and thus greatly reduces friction between pistons and cylinder walls. The Bourke engine's combustion phase more closely approximates constant volume combustion than either four stroke or two stroke cycles do. It also uses less moving parts, hence needs to overcome less friction than the other two reciprocating types have to. In addition, its greater expansion ratio also means more of the heat from its combustion phase is utilized than is used by either four stroke or two stroke cycles.
These are also cylinder based engines may be either single or two stroke but use, instead of a crankshaft and piston rods, two gear connected, counter rotating concentric cams to convert reciprocating motion into rotary movement. These cams practically cancel out sideward forces that would otherwise be exerted on the cylinders by the pistons, greatly improving mechanical efficiency. The profiles of the cam lobes which are always odd and at least three in number determine the piston travel versus the torque delivered. In this engine, there are two cylinders that are degrees apart for each pair of counter rotating cams.
For single stroke versions, there are the same number of cycles per cylinder pair as there are lobes on each cam, twice as much for two stroke units. The Wankel engine operates with the same separation of phases as the four-stroke engine but with no piston strokes, would more properly be called a four-phase engine , since the phases occur in separate locations in the engine. This engine provides three power "strokes" per revolution per rotor, giving it a greater power-to-weight ratio, on average, than piston engines. With gas turbine cycles notably Jet engines , rather than use the same piston to compress and then expand the gases, instead separate compressors and gas turbines are employed; giving continuous power.
Essentially, the intake gas air normally is compressed, and then combusted with a fuel, which greatly raises the temperature and volume. The larger volume of hot gas from the combustion chamber is then fed through the gas turbine which is then easily able to power the compressor. In some old non-compressing internal combustion engines: In the piston upstroke the exhaust valve was open. This was an attempt at imitating the way a piston steam engine works. Fuels used include petroleum spirit North American term: Gasoline , British term: Petrol , autogas liquified petroleum gas , compressed natural gas, hydrogen , diesel fuel, jet fuel, landfill gas, biodiesel, biobutanol, peanut oil and other vegoils, bioethanol, biomethanol methyl or wood alcohol , and other biofuels.
Even fluidized metal powders and explosives have seen some use. Engines that use gases for fuel are called gas engines and those that use liquid hydrocarbons are called oil engines. However, gasoline engines are unfortunately also often colloquially referred to as "gas engines. The air is compressed by the compressor where a temperature rise occurs. The compressed air is further heated by combustion of injected fuel in the combustion chamber which expands the air. This energy rotates the turbine which powers the compressor via a mechanical coupling. The hot gases are then exhausted to provide thrust.
Gas turbine cycle engines employ a continuous combustion system where compression, combustion, and expansion occur simultaneously at different places in the engine—giving continuous power. Notably, the combustion takes place at constant pressure, rather than with the Otto cycle, constant volume. The Wankel engine rotary engine does not have piston strokes. It operates with the same separation of phases as the four-stroke engine with the phases taking place in separate locations in the engine.
In thermodynamic terms it follows the Otto engine cycle, so may be thought of as a "four-phase" engine. While it is true that three power strokes typically occur per rotor revolution, due to the 3: The drive eccentric shaft rotates once during every power stroke instead of twice crankshaft , as in the Otto cycle, giving it a greater power-to-weight ratio than piston engines. This type of engine was most notably used in the Mazda RX-8 , the earlier RX-7 , and other vehicle models.
The engine is also used in unmanned aerial vehicles, where the small size and weight and the high power-to-weight ratio are advantageous. Forced induction is the process of delivering compressed air to the intake of an internal combustion engine. A forced induction engine uses a gas compressor to increase the pressure, temperature and density of the air. An engine without forced induction is considered a naturally aspirated engine.
Forced induction is used in the automotive and aviation industry to increase engine power and efficiency. It particularly helps aviation engines, as they need to operate at high altitude.
Short Fuse
Forced induction is achieved by a supercharger , where the compressor is directly powered from the engine shaft or, in the turbocharger , from a turbine powered by the engine exhaust. All internal combustion engines depend on combustion of a chemical fuel , typically with oxygen from the air though it is possible to inject nitrous oxide to do more of the same thing and gain a power boost. The combustion process typically results in the production of a great quantity of heat, as well as the production of steam and carbon dioxide and other chemicals at very high temperature; the temperature reached is determined by the chemical make up of the fuel and oxidisers see stoichiometry , as well as by the compression and other factors.
The most common modern fuels are made up of hydrocarbons and are derived mostly from fossil fuels petroleum. Fossil fuels include diesel fuel , gasoline and petroleum gas , and the rarer use of propane. Except for the fuel delivery components, most internal combustion engines that are designed for gasoline use can run on natural gas or liquefied petroleum gases without major modifications.
Large diesels can run with air mixed with gases and a pilot diesel fuel ignition injection. Liquid and gaseous biofuels , such as ethanol and biodiesel a form of diesel fuel that is produced from crops that yield triglycerides such as soybean oil , can also be used.
Engines with appropriate modifications can also run on hydrogen gas, wood gas , or charcoal gas , as well as from so-called producer gas made from other convenient biomass. Experiments have also been conducted using powdered solid fuels, such as the magnesium injection cycle. Even fluidized metal powders and explosives have seen some use. Engines that use gases for fuel are called gas engines and those that use liquid hydrocarbons are called oil engines; however, gasoline engines are also often colloquially referred to as, "gas engines" " petrol engines " outside North America.
The main limitations on fuels are that it must be easily transportable through the fuel system to the combustion chamber , and that the fuel releases sufficient energy in the form of heat upon combustion to make practical use of the engine.
Diesel engines are generally heavier, noisier, and more powerful at lower speeds than gasoline engines. They are also more fuel-efficient in most circumstances and are used in heavy road vehicles, some automobiles increasingly so for their increased fuel efficiency over gasoline engines , ships, railway locomotives , and light aircraft. Gasoline engines are used in most other road vehicles including most cars, motorcycles , and mopeds.
There are also engines that run on hydrogen , methanol , ethanol , liquefied petroleum gas LPG , biodiesel , paraffin and tractor vaporizing oil TVO. Hydrogen could eventually replace conventional fossil fuels in traditional internal combustion engines. Alternatively fuel cell technology may come to deliver its promise and the use of the internal combustion engines could even be phased out.
Although there are multiple ways of producing free hydrogen, those methods require converting combustible molecules into hydrogen or consuming electric energy. Unless that electricity is produced from a renewable source—and is not required for other purposes—hydrogen does not solve any energy crisis. In many situations the disadvantage of hydrogen, relative to carbon fuels, is its storage. Liquid hydrogen has extremely low density 14 times lower than water and requires extensive insulation—whilst gaseous hydrogen requires heavy tankage.
Even when liquefied, hydrogen has a higher specific energy but the volumetric energetic storage is still roughly five times lower than gasoline. However, the energy density of hydrogen is considerably higher than that of electric batteries, making it a serious contender as an energy carrier to replace fossil fuels. The 'Hydrogen on Demand' process see direct borohydride fuel cell creates hydrogen as needed, but has other issues, such as the high price of the sodium borohydride that is the raw material. Since air is plentiful at the surface of the earth, the oxidizer is typically atmospheric oxygen, which has the advantage of not being stored within the vehicle.
This increases the power-to-weight and power-to-volume ratios. Other materials are used for special purposes, often to increase power output or to allow operation under water or in space. Cooling is required to remove excessive heat—over heating can cause engine failure, usually from wear due to heat-induced failure of lubrication , cracking or warping.
Two most common forms of engine cooling are air-cooled and water-cooled. Some engines air or water-cooled also have an oil cooler. In some engines, especially for turbine engine blade cooling and liquid rocket engine cooling , fuel is used as a coolant, as it is simultaneously preheated before injecting it into a combustion chamber. Internal combustion engines must have their cycles started.
In reciprocating engines this is accomplished by turning the crankshaft Wankel Rotor Shaft which induces the cycles of intake, compression, combustion, and exhaust. The first engines were started with a turn of their flywheels, while the first vehicle the Daimler Reitwagen was started with a hand crank.
All ICE engined automobiles were started with hand cranks until Charles Kettering developed the electric starter for automobiles. As diesel engines have become larger and their mechanisms heavier, air starters have come into use. Air starters work by pumping compressed air into the cylinders of an engine to start it turning. There are also starters where a spring is compressed by a crank motion and then used to start an engine. Some small engines use a pull-rope mechanism called "recoil starting," as the rope rewinds itself after it has been pulled out to start the engine.
This method is commonly used in pushed lawn mowers and other settings where only a small amount of torque is needed to turn an engine over. Once ignited and burnt, the combustion products—hot gases—have more available thermal energy than the original compressed fuel-air mixture which had higher chemical energy.
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The available energy is manifested as high temperature and pressure that can be translated into work by the engine. In a reciprocating engine, the high-pressure 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, or TDC. The piston can then proceed to the next phase of its cycle, which varies between engines. Any heat that is not translated into work is normally considered a waste product and is removed from the engine either by an air or liquid cooling system.
Could microwaves cut engine emissions?
Internal combustion engines are heat engines , and as such their theoretical efficiency can be approximated by idealized thermodynamic cycles. The thermal efficiency of a theoretical cycle cannot exceed that of the Carnot cycle , whose efficiency is determined by the difference between the lower and upper operating temperatures of the engine. The upper operating temperature of an engine is limited by two main factors; the thermal operating limits of the materials, and the auto-ignition resistance of the fuel.
All metals and alloys have a thermal operating limit, and there is significant research into ceramic materials that can be made with greater thermal stability and desirable structural properties. Higher thermal stability allows for a greater temperature difference between the lower ambient and upper operating temperatures, hence greater thermodynamic efficiency. Also, as the cylinder temperature rises, the engine becomes more prone to auto-ignition. This is caused when the cylinder temperature nears the flash point of the charge.
At this point, ignition can spontaneously occur before the spark plug fires, causing excessive cylinder pressures. Auto-ignition can be mitigated by using fuels with high auto-ignition resistance octane rating , however it still puts an upper bound on the allowable peak cylinder temperature. The thermodynamic limits assume that the engine is operating under ideal conditions: Real world applications introduce complexities that reduce efficiency.
For example, a real engine runs best at a specific load, termed its power band. The engine in a car cruising on a highway is usually operating significantly below its ideal load, because it is designed for the higher loads required for rapid acceleration. Engine fuel economy is measured in miles per gallon or in liters per kilometres.
The volume of hydrocarbon assumes a standard energy content. There are many inventions aimed at increasing the efficiency of IC engines. In general, practical engines are always compromised by trade-offs between different properties such as efficiency, weight, power, heat, response, exhaust emissions, or noise. Sometimes economy also plays a role in not only the cost of manufacturing the engine itself, but also manufacturing and distributing the fuel. Increasing the engine's efficiency brings better fuel economy but only if the fuel cost per energy content is the same.
For stationary and shaft engines including propeller engines, fuel consumption is measured by calculating the brake specific fuel consumption , which measures the mass flow rate of fuel consumption divided by the power produced. For internal combustion engines in the form of jet engines, the power output varies drastically with airspeed and a less variable measure is used: For rockets, TSFC can be used, but typically other equivalent measures are traditionally used, such as specific impulse and effective exhaust velocity.
Internal combustion engines such as reciprocating internal combustion engines produce air pollution emissions, due to incomplete combustion of carbonaceous fuel. The main derivatives of the process are carbon dioxide CO 2 , water and some soot —also called particulate matter PM. The effects of inhaling particulate matter have been studied in humans and animals and include asthma, lung cancer, cardiovascular issues, and premature death. There are, however, some additional products of the combustion process that include nitrogen oxides and sulfur and some uncombusted hydrocarbons, depending on the operating conditions and the fuel-air ratio.
Not all of the fuel is completely consumed by the combustion process. A small amount of fuel is present after combustion, and some of it reacts to form oxygenates, such as formaldehyde or acetaldehyde , or hydrocarbons not originally present in the input fuel mixture. Incomplete combustion usually results from insufficient oxygen to achieve the perfect stoichiometric ratio. The flame is "quenched" by the relatively cool cylinder walls, leaving behind unreacted fuel that is expelled with the exhaust.
When running at lower speeds, quenching is commonly observed in diesel compression ignition engines that run on natural gas. Quenching reduces efficiency and increases knocking, sometimes causing the engine to stall. Incomplete combustion also leads to the production of carbon monoxide CO. Further chemicals released are benzene and 1,3-butadiene that are also hazardous air pollutants.
Increasing the amount of air in the engine reduces emissions of incomplete combustion products, but also promotes reaction between oxygen and nitrogen in the air to produce nitrogen oxides NO x. NO x is hazardous to both plant and animal health, and leads to the production of ozone O 3.
Ozone is not emitted directly; rather, it is a secondary air pollutant, produced in the atmosphere by the reaction of NO x and volatile organic compounds in the presence of sunlight.
Internal combustion engine - Wikipedia
Ground-level ozone is harmful to human health and the environment. Though the same chemical substance, ground-level ozone should not be confused with stratospheric ozone , or the ozone layer , which protects the earth from harmful ultraviolet rays. Carbon fuels contain sulfur and impurities that eventually produce sulfur monoxides SO and sulfur dioxide SO 2 in the exhaust, which promotes acid rain. In the United States, nitrogen oxides, PM, carbon monoxide, sulphur dioxide, and ozone, are regulated as criteria air pollutants under the Clean Air Act to levels where human health and welfare are protected.
Other pollutants, such as benzene and 1,3-butadiene, are regulated as hazardous air pollutants whose emissions must be lowered as much as possible depending on technological and practical considerations. NO x , carbon monoxide and other pollutants are frequently controlled via exhaust gas recirculation which returns some of the exhaust back into the engine intake, and catalytic converters , which convert exhaust chemicals to harmless chemicals. The emission standards used by many countries have special requirements for non-road engines which are used by equipment and vehicles that are not operated on the public roadways.
The standards are separated from the road vehicles. Significant contributions to noise pollution are made by internal combustion engines. Automobile and truck traffic operating on highways and street systems produce noise, as do aircraft flights due to jet noise, particularly supersonic-capable aircraft. Rocket engines create the most intense noise. Internal combustion engines continue to consume fuel and emit pollutants when idling so it is desirable to keep periods of idling to a minimum. Many bus companies now instruct drivers to switch off the engine when the bus is waiting at a terminal.
This means that a driver can be ordered " by an authorised person Only a few local authorities have implemented the regulations, one of them being Oxford City Council. From Wikipedia, the free encyclopedia. For the form of water ice, see Ice V. For the high speed train, see ICE V.
History of the internal combustion engine. For rotating-crankcase radial -cylindered engines, see Rotary engine. Diesel engine and Gasoline engine. Hydrogen internal combustion engine vehicle. Internal combustion engine cooling. Engineering Fundamentals of the Internal Combustion Engine. Technology Today and Tomorrow.
Extreme Machines on Land. Archived from the original PDF on Mitsubishi Heavy Industries Technical Review. Automobile in American Life and Society. The Romance of Engines. Intergovernment Panel on Climate Change. General Electric Power Generation. After assembling, the air-flask shall be charged to lbs.
Archived from the original on George Sutton, Oscar Biblarz pp. Without phase change hot air engines. Part of the Automobile series. Air filter Blowoff valve Boost controller Butterfly valve Centrifugal-type supercharger Cold air intake Dump valve Electronic throttle control Forced induction Inlet manifold Intake Intercooler Manifold vacuum Naturally aspirated engine Ram-air intake Scroll-type supercharger Short ram air intake Supercharger Throttle Throttle body Turbocharger Twin-turbo Variable-geometry turbocharger Variable-length intake manifold Warm air intake.
Automobile emissions control Catalytic converter Diesel particulate filter Exhaust manifold Glasspack Muffler. Hot rod Lead sled Lowrider Street rod T-bucket. Compact executive Executive Personal. Beale number West number. In an engine, the linear motion of the pistons is converted into rotational motion by the crankshaft.
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The rotational motion is nice because we plan to turn rotate the car's wheels with it anyway. Now let's look at all the parts that work together to make this happen, starting with the cylinders. How Gas Compression-ignition Engines Work. Did cars ever have external combustion engines? How does an electric water pump benefit your engine? Intake stroke Compression stroke Combustion stroke Exhaust stroke. This content is not compatible on this device.