File Name: comparison of si and ci engines writer.zip
Spark Ignition engine are those types of the engine where the combustion of the fuel occurs with the help of Spark Plug. In this type of engine, the Air-fuel mixture comes from the carburetor and enters the engine cylinder through the valves and then fuel is compressed in the compression stroke and finally, a spark is given by the spark plug to ignite the air-fuel mixture and we get power stroke. The engine where the rise in temperature and pressure during compression is sufficient to cause spontaneous ignition of the fuel.
Engine is a machine that converts some form of energy into mechanical work. Internal combustion engines can be divided according to several characteristics.
An internal combustion engine ICE is a heat engine in which 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 combustion engine, the expansion of the high- temperature and high- pressure gases produced by combustion applies direct force to some component of the engine. The force is applied typically to pistons , turbine blades , a rotor , or a nozzle. This force moves the component over a distance, transforming chemical energy into useful work. This replaced the external combustion engine for applications where weight or size of the engine is important.
An internal combustion engine ICE is a heat engine in which 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 combustion engine, the expansion of the high- temperature and high- pressure gases produced by combustion applies direct force to some component of the engine. The force is applied typically to pistons , turbine blades , a rotor , or a nozzle. This force moves the component over a distance, transforming chemical energy into useful work.
This replaced the external combustion engine for applications where weight or size of the engine is important. The term internal combustion engine usually refers to an engine in which combustion is intermittent , such as the more familiar four-stroke and two-stroke piston engines, along with variants, such as the six-stroke piston engine and the Wankel rotary engine.
A second class of internal combustion engines use continuous combustion: gas turbines , jet engines and most rocket engines , each of which are internal combustion engines on the same principle as previously described. In contrast, in external combustion engines , such as steam or Stirling engines , energy is delivered to a working fluid not consisting of, mixed with, or contaminated by combustion products.
Working fluids for external combustion engines include air, hot water, pressurized water or even liquid sodium, heated in a boiler. ICEs are usually powered by energy-dense fuels such as gasoline or diesel fuel, liquids derived from fossil fuels. While there are many stationary applications, most ICEs are used in mobile applications and are the dominant power supply for vehicles such as cars, aircraft and boats.
ICEs are typically powered by fossil fuels like natural gas or petroleum products such as gasoline , diesel fuel or fuel oil. Renewable fuels like biodiesel are used in compression ignition CI engines and bioethanol or ETBE ethyl tert-butyl ether produced from bioethanol in spark ignition SI engines. Renewable fuels are commonly blended with fossil fuels. Hydrogen , which is rarely used, can be obtained from either fossil fuels or renewable energy. Various scientists and engineers contributed to the development of internal combustion engines.
In , John Barber developed the gas turbine. In Thomas Mead patented a gas engine. Also in , Robert Street patented an internal combustion engine, which was also the first to use liquid fuel , and built an engine around that time. In , John Stevens built the first American internal combustion engine.
In , De Rivaz fitted his invention to a primitive working vehicle — "the world's first internal combustion powered automobile". In , Samuel Brown patented the first internal combustion engine to be applied industrially. In , Nicolaus Otto patented the first atmospheric gas engine.
In , American George Brayton invented the first commercial liquid-fuelled internal combustion engine. In , Nicolaus Otto , working with Gottlieb Daimler and Wilhelm Maybach , patented the compressed charge, four-cycle engine. In , Karl Benz patented a reliable two-stroke gasoline engine. Later, in , Benz began the first commercial production of motor vehicles with the internal combustion engine.
In , Rudolf Diesel developed the first compressed charge, compression ignition engine. In , Robert Goddard launched the first liquid-fueled rocket. In , the Heinkel He became the world's first jet aircraft. At one time, the word engine via Old French , from Latin ingenium , "ability" meant any piece of machinery —a sense that persists in expressions such as siege engine. A "motor" from Latin motor , "mover" is any machine that produces mechanical power. Traditionally, electric motors are not referred to as "engines"; however, combustion engines are often referred to as "motors".
An electric engine refers to a locomotive operated by electricity. In boating, an internal combustion engine that is installed in the hull is referred to as an engine, but the engines that sit on the transom are referred to as motors. Reciprocating piston engines are by far the most common power source for land and water vehicles , including automobiles , motorcycles , ships and to a lesser extent, locomotives some are electrical but most use Diesel engines  .
Rotary engines of the Wankel design are used in some automobiles, aircraft and motorcycles. These are collectively known as internal-combustion-engine vehicles ICEV. Where high power-to-weight ratios are required, internal combustion engines appear in the form of combustion turbines or Wankel engines.
Powered aircraft typically uses an ICE which may be a reciprocating engine. Airplanes can instead use jet engines and helicopters can instead employ turboshafts ; both of which are types of turbines. In addition to providing propulsion, airliners may employ a separate ICE as an auxiliary power unit.
Wankel engines are fitted to many unmanned aerial vehicles. ICEs drive large electric generators that power electrical grids.
Combined cycle power plants use the high temperature exhaust to boil and superheat water steam 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 engine alone.
In a smaller scale, stationary engines like Gas engine or Diesel generators are used for backup or for providing electrical power to areas not connected to an electric grid. 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 arranged either in 1 row straight engine or 2 rows boxer engine or V engine ; 3 rows are occasionally used W engine in contemporary engines, and other engine configurations are possible and have been used.
Single cylinder engines are common for motorcycles and in small engines of machinery. Water-cooled engines contain passages in the engine block where cooling fluid circulates the water jacket. Some small engines are air-cooled, and instead of having a water jacket the cylinder block has fins protruding away from it to cool by directly transferring heat to the air.
The cylinder walls are usually finished by honing to obtain a cross hatch , which is better able to retain the oil. A too rough surface would quickly harm the engine by excessive wear on the piston. The pistons are short cylindrical parts which seal one end of the cylinder from the high pressure of the compressed air and combustion products and slide continuously within it while the engine is in operation. The top wall of the piston is termed its crown and is typically flat or concave.
Some two-stroke engines use pistons with a deflector head. Pistons are open at the bottom and hollow except for an integral reinforcement structure the piston web. When an engine is working, the gas pressure in the combustion chamber exerts a force on the piston crown which is transferred through its web to a gudgeon pin. Each piston has rings fitted around its circumference that mostly prevent the gases from leaking into the crankcase or the oil into the combustion chamber.
A ventilation system drives the small amount of gas that escapes past the pistons during normal operation the blow-by gases out of the crankcase so that it does not accumulate contaminating the oil and creating corrosion.
In two-stroke gasoline engines the crankcase is part of the air—fuel path and due to the continuous flow of it they do not need a separate crankcase ventilation system. The cylinder head is attached to the engine block by numerous bolts or studs.
It has several functions. The cylinder head seals the cylinders on the side opposite to the pistons; it contains short ducts the ports for intake and exhaust and the associated intake valves that open to let the cylinder be filled with fresh air and exhaust valves that open to allow the combustion gases to escape. However, 2-stroke crankcase scavenged engines connect the gas ports directly to the cylinder wall without poppet valves; the piston controls their opening and occlusion instead.
The cylinder head also holds the spark plug in the case of spark ignition engines and the injector for engines that use direct injection. All CI engines use fuel injection, usually direct injection but some engines instead use indirect injection. SI engines can use a carburetor or fuel injection as port injection or direct injection.
Most SI engines have a single spark plug per cylinder but some have 2. A head gasket prevents the gas from leaking between the cylinder head and the engine block. The opening and closing of the valves is controlled by one or several camshafts and springs—or in some engines—a desmodromic mechanism that uses no springs. The camshaft may press directly the stem of the valve or may act upon a rocker arm , again, either directly or through a pushrod.
The crankcase is sealed at the bottom with a sump that collects the falling oil during normal operation to be cycled again. The cavity created between the cylinder block and the sump houses a crankshaft that converts the reciprocating motion of the pistons to rotational motion. The crankshaft is held in place relative to the engine block by main bearings , which allow it to rotate. Bulkheads in the crankcase form a half of every main bearing; the other half is a detachable cap.
In some cases a single main bearing deck is used rather than several smaller caps. A connecting rod is connected to offset sections of the crankshaft the crankpins in one end and to the piston in the other end through the gudgeon pin and thus transfers the force and translates the reciprocating motion of the pistons to the circular motion of the crankshaft. The end of the connecting rod attached to the gudgeon pin is called its small end, and the other end, where it is connected to the crankshaft, the big end.
The big end has a detachable half to allow assembly around the crankshaft. It is kept together to the connecting rod by removable bolts. The cylinder head has an intake manifold and an exhaust manifold attached to the corresponding ports. The intake manifold connects to the air filter directly, or to a carburetor when one is present, which is then connected to the air filter.
It distributes the air incoming from these devices to the individual cylinders. The exhaust manifold is the first component in the exhaust system. It collects the exhaust gases from the cylinders and drives it to the following component in the path.
The exhaust system of an ICE may also include a catalytic converter and muffler. The final section in the path of the exhaust gases is the tailpipe. The top dead center TDC of a piston is the position where it is nearest to the valves; bottom dead center BDC is the opposite position where it is furthest from them.
While an engine is in operation, the crankshaft rotates continuously at a nearly constant speed. In a 4-stroke ICE, each piston experiences 2 strokes per crankshaft revolution in the following order. Starting the description at TDC, these are:  . The defining characteristic of this kind of engine is that each piston completes a cycle every crankshaft revolution. The 4 processes of intake, compression, power and exhaust take place in only 2 strokes so that it is not possible to dedicate a stroke exclusively for each of them.
Starting at TDC the cycle consist of:. While a 4-stroke engine uses the piston as a positive displacement pump to accomplish scavenging taking 2 of the 4 strokes, a 2-stroke engine uses the last part of the power stroke and the first part of the compression stroke for combined intake and exhaust.
The work required to displace the charge and exhaust gases comes from either the crankcase or a separate blower.
Hydrocarbon-based fuels which are gasoline, diesel, natural gas, and liquefied petroleum gas LPG have been generally used in the diesel and gasoline engines as a fuel. In this study, hydrocarbon-based fuels such as alkanes paraffins , naphthenes cycloparaffins , alkenes olefins , alkynes acetylenes , and aromatics benzene derivatives have been classified. Their molecular structure and properties have been comprehensively explained. In addition to this, some of the important fuel properties of the commonly used fossil-based fuels such as gasoline and diesel in the internal combustion engine have been evaluated. Thus, hydrocarbon derivative fuels which are diesel, gasoline, natural gas, and liquefied petroleum gas LPG have been investigated as an internal combustion engine fuel. Their physical and chemical properties were explained and compared to each other.
SI engine is known or called Spark Ignition engine. In this engine, the combustion of fuel are done by Spark Plug. CI engine is called a combustion Ignition engine. In this engine, the combustion of fuel are done by injection of fuel into the hot compressed air. Let me know if you understand or not with the use of the comment box below. Amardeep will share information related to Mechanical Engineering in this platform. He is the author, editor at themechanicalengineering.
Hey readers, here in this article I mentioned the overview of SI and CI Engine, and then state the differences between SI and CI Engine. [PDF AVAILABLE].
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Petrol engine British English or gasoline engine American English is an internal combustion engine with spark-ignition , designed to run on petrol gasoline and similar volatile fuels. In most petrol engines, the fuel and air are usually pre-mixed before compression although some modern petrol engines now use cylinder- direct petrol injection. The process differs from a diesel engine in the method of mixing the fuel and air, and in using spark plugs to initiate the combustion process. In a diesel engine, only air is compressed and therefore heated , and the fuel is injected into very hot air at the end of the compression stroke , and self-ignites. With both air and fuel in a closed cylinder, compressing the mixture too much poses the danger of auto-ignition — or behaving like a compression-ignition engine.
Joseph O. This article titled Comparative factors in spark ignition and compression ignition engines for sustainable technological economy, compares the differences between the both types of internal combustion engines, with respect to their working principles. The spark ignition SI engines, uses petrol or gasoline as fuel, while in compression ignition CI engines, diesel is used as fuel. Petrol engines are lightweight and achieve higher speed while diesel engines, on the other hand, are heavy engines and achieve lesser speeds.
Ассоциативный ряд? - по-прежнему недоумевал Дэвид.
Стояла полная тишина, и он внимательно прислушался. Ничего. Вроде бы на нижней ступеньке никого. Может, ему просто показалось. Какая разница, Стратмор никогда не решится выстрелить, пока он прикрыт Сьюзан.
Черный ход представлял собой несколько строк хитроумной программы, которые вставил в алгоритм коммандер Стратмор. Они были вмонтированы так хитро, что никто, кроме Грега Хейла, их не заметил, и практически означали, что любой код, созданный с помощью Попрыгунчика, может быть взломан секретным паролем, известным только АНБ. Стратмору едва не удалось сделать предлагаемый стандарт шифрования величайшим достижением АНБ: если бы он был принят, у агентства появился бы ключ для взлома любого шифра в Америке. Люди, знающие толк в компьютерах, пришли в неистовство.
Киллер щелкнул миниатюрным тумблером, и очки превратились в дисплей. Опустив руки, он незаметными быстрыми движениями соединял кончики пальцев. Перед его глазами появилось сообщение, которое он должен был отправить. ТЕМА СООБЩЕНИЯ: П.
Хейл понял, что попал в яблочко. Но невозмутимость Стратмора, очевидно, подверглась тяжкому испытанию. - Кто тебе это сказал? - спросил он, и в его голосе впервые послышались металлические нотки.