For a cylinder 10 cm in diameter, the time required for a pressure disturbance. What is the difference between knocking and detonation in ic. A rotating detonation engine rde is a proposed engine using a form of pressure gain combustion, where one or more detonations continuously travel around an annular channel. The high velocity knock, usually called detonation,will produce severe damage of the engine and is avoided by the electronic engine control. Detonation is when the fuel explodes rather than burning. Main trends in detonation engine development are discussed. Sep 24, 2015 detonation is a great thing if youre taking in a fireworks show or maybe watching macgyver. Pulse detonation engine seminar report, ppt, pdf for. In a properly functioning engine, the charge burns with the flame front progressing smoothly from the point of ignition across the combustion chamber. Mild detonation may increase engine wear, though some engines can operate with mild detonation regularly. In an ic engine, combustion chamber is an integral part of the working fluid circuit principle of operation. Option 2 is to command less spark advance timing in the main ignition map. Thermofluids and turbomachinery assignment 20112012 6 p a g e performance characteristics table test no 1 2 3 4 5 6 7 8 raw torque nm 6. Knocking in spark ignition internal combustion engines occurs when combustion of some of the.
Knock, detonation, pinging, preignition, etc are basically two things. Detonation refers to a type of abnormal combustion that is usually preceded by preignition. Knocking, in an internalcombustion engine, sharp sounds caused by premature combustion of part of the compressed airfuel mixture in the cylinder. It was found that detonation can occur in modern internal combustion. The air motion so organized inside the combustion chamber and the turbulence of the air passes across the fuel jet tears it into fine particles. It can result in detonation and can damage the engine altogether. The effect of energy intensification on the formation of. Ci engines are often called diesel engines, especially in the nontechnical community. In order to improve fuel economy, engines are equipped with sensors to measure the amount of unburnt fuel in the exhaust and to measure the oxygen content in the inlet air. There are different types of ic engines that can be classified on the following basis. Mild detonation is called knocking because of the noise that can be heard when it happens at low power settings. A knocking or pinging noise may be heard at low speeds but at high speeds detonation may not be audible especially in performance or competition engines, which may have performance exhaust systems and may be noisier anyway. Different engines with different shaped combustion chambers may have different.
Internal combustion engine performance characteristics. Some engines, such as liquid cooled 2stroke engines found in snowmobiles, watercraft and motorcycles, have a very common detonation failure mode. The high pressure and hightemperature of the compression stroke combine with the. The work done and thus torque would be the same each engine cycle.
Computer simulation of an internal combustion engine. Detonation generally caused by fuel with a low octane rating is the tendency for the fuel to preignite or autoignite in an engine s combustion chamber. What typically happens is that when detonation occurs the piston expands excessively, scurfs in the bore along those four spots and wipes material into the ring grooves. The engine is pulsed because the mixture must be renewed in the combustion chamber between each detonation wave and the next. The violence of detonation also causes a reduction in power. Thermofluids and turbomachinery assignment 20112012 4 p a g e fuel energy rapidly. Commonly used symbols, subscripts, and abbreviations 1. Detonation occurs when the pressure and temperature inside the cylinder become higher than the critical pressure and temperature of the fuel. Knocking also called knock, detonation or spark knock, pinking in uk english or pinging in us english in sparkignition internal combustion engines occurs when combustion of the airfuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of airfuel mixture explode outside the envelope of the normal combustion front. The united states military chose to invest in the rotating detonation engine s research and development, in part, because the technology is easily scaleable the size of the engine can be increased, and power production will also be increased.
Visualization of autoignition and pressure wave during. In fact, its probably best if you avoid detonation at all costs where your engine is concerned. Phenomenon of knock in ci engine is called knocking and phenomenon of knock in petrol engine is called detonation. Mild detonation is present in all engines at some time. Detonation occurs when excessive heat and pressure in the combustion chamber causes the airfuel mixture to ignite on its own. However, the problems reported with hydrogen ic engines include backfiring, power loss, and knocking at higher outputs. Blend primary reference fuels isooctane and normal heptane so its knock. Internal combustion engines can be classified internal combustion engines ca n be classified n be classified as c as cas continuous ic engines and ontinuous ic engines and intermittent ic engines. Knocking is generally not heard at high speed and power settings because of the noise developed in air intake or exhaust system is louder and masks. In addition to this knocking puts a limit on the compression ratio at which an. Detonation or knocking in ic engines mechanical engineering.
A fuels octane number is determined by measuring what blend of these two hydrocarbons. Top because this position is at the top of most engines not always, and dead because the piston stops at this point. How the rotating detonation engine works howstuffworks. Airfuel mixture in the combustion chamber inside the cylinder is ignited, either by a spark plug in case of spark ignition. Jan 31, 2009 knocking also called knock, detonation or spark knock, pinking in uk english or pinging in us english in sparkignition internal combustion engines occurs when combustion of the airfuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of airfuel mixture explode outside the envelope of the normal combustion front. Internal combustion engine handbook sae international. Pdf knocking combustion research is crucially important because it determines. For the first time knock problem was investigated in internal combustion engines by draper 1935. What is the difference between knocking and detonation in. The mixture is ignited by the spark, normally in the centre of the cylinder, and a flame front moves from the spark towards the outside of the cylinder in a controlled burn. In continuous ic in continuous ic engines engines engines products of products of. Knocking produces a loud pulsating noise and pressure waves. Ill add a couple of thoughts that come to mind when i think about knocking and detonation. However, severe detonation can cause engine failure in minutes.
The effects of detonation may be anywhere from arbitrary to severe. A higher flame speed of hydrogen leads to good thermal efficiencies because rapid combustion in hydrogen ic engine can be achieved, however it increased heat loss at the cylinder wall 5 and also causes engine knock under. Detonation is a great thing if youre taking in a fireworks show or maybe watching macgyver. Many engines operate in light detonation quite regularly, and some can withstand moderate detonation for extended periods of time without damage. Spark knock is a pinging noise, rattling or knocking which might be heard while the engine is working hard under load passing on the highway, towing a trailer, driving up a mountain, etc. Many late model engines have a knock sensor on the engine that responds to the frequency vibrations characteristically produced by detonation typically 68khz.
Detonation means the sudden and violent knocks experienced in an internal combustion engine by engineering means, this knock is set up by a highpressure wave giving loud pulsating noise this occurs when it strikes against cylinder walls, cylinder head, and piston. What is the difference between knocking and detonation. Hydrogen fuel is an effective alternate fuel in making a pollutionfree environment with higher efficiency. Every wonder what that metallic rattling is coming from your engine or that your car sounds like it is dragging a chain behind it. Knocking combustion research is crucially important because it determines engine. Computational simulations and experimental results have shown that the rde has potential in transport and other applications. Feb 09, 2017 knocking and detonation is physically same like nosiy sound. Feb 24, 2014 the aim of this project is detecting knock during combustion of biodieselhydrogen fuel and also the knock is suppressed by timed injection of diethyl ether dee with biodieselhydrogen fuel for different loads.
Internal combustion engines can be classified internal combustion engines ca n be classified n be classified as c as cas continuous ic engines and ontinuous ic engines and. Under normal conditions, the combusting air and fuel mixture inside the combustion chamber ignites in a controlled manner. Theoretically, a pde can operate from subsonic up to a hypersonic flight speed of roughly mach 5. Knocking is the noise you hear caused by detonation,which is an explosion or uncontrolled burning inside the cylinder of a reciprocating engine. But for ci engines higher the compression ratio, lesser is the ignition delay and lesser probability of detonation or diesel knock occurring. Researchers say the rotating detonation engine could also be adapted to generate electric power for allelectric ships and planes. What typically happens is that when detonation occurs the piston expands excessively, scurfs in the bore along those four spots and wipes material into the. As air and fuel is drawn into the combustion chamber during the intake stroke, this hot spot will preignite the air fuel mixture without any spark from the spark plugs. Bore diameter of the cylinder or diameter of the piston face, which is the same minus a very small clearance. Because of the noise that it makes, detonation is called engine knock or pinging in cars. In detonative combustion, the results expand at supersonic speed. Effect of knocking in spark ignition in a fourstroke engine authors. The spark plugs ignites the injected fuel and explosion is started. Symbols a crank radius ac clearance volume af effective flow area ap port area av valve cross sectional area aw exposed total cylinder area bo cylinder bore co sound speed cf flow coefficient cp specific heat at constant pressure cv specific heat at constant volume d diameter d diameter h specific enthalpy h height hg heat transfer.
When knock, detonation, or preignition occurs, the airfuel mixture is ignited at an improper time in the cycle. The higher the specific output of the engine, the more likely it is to sustain detonation damage. The application of ethanol in engines with a high compression ratio is favoured because of its high knock resistance, due to a higher octane number 31, and high heat of evaporation 32 in comparison with gasoline, reducing the temperature of the mixture and resulting in increased engine power and efficiency 15,33. May 11, 2011 every wonder what that metallic rattling is coming from your engine or that your car sounds like it is dragging a chain behind it. It is caused due to the propagation of a high speed pressure wave created by the autoignition of end portion of unburnt fuel. Effect of knocking in spark ignition in a fourstroke engine.
But in ci engines, knocking is due to ignition delay, and hence it is least harmful. This early before the spark plug fires ignition of fuel creates a shock wave throughout the cylinder as the burning and expanding fuelair mixture collides with the piston that is. Study of knocking effect in compression ignition engine. May 25, 2014 we use your linkedin profile and activity data to personalize ads and to show you more relevant ads. Engines the loud pulsating noise heard within the engine cylinder of an i.
Engine knock under acceleration spark knock is a pinging noise, rattling or knocking which might be heard while the engine is working hard under load passing on the highway, towing a trailer, driving up a mountain, etc. Explore pulse detonation engine with free download of seminar report and ppt in pdf and doc format. Knocking combustion in sparkignition engines sciencedirect. Detonation is an uncontrolled combustion event which occurs after the spark event. Composition factor the detonation or knocking in ci engine. A pulse detonation engine pde is a type of propulsion system that uses detonation waves to combust the fuel and oxidizer mixture. Study of knocking effect in compression ignition engine with. In fact ideal world the same amount of torque would be produced at any engine speed. Detonation is not an optimum situation, but its not necessarily destructive. The most important works that carried out theoretical. We use your linkedin profile and activity data to personalize ads and to show you more relevant ads. Whenever detonation occurs, you have several options assuming youre sticking with the fuel in question.
It was found that detonation can occur in modern internal combustion engines under high energy density conditions. The resulting knock or ping is the sound of the pistons slamming against the cylinder walls. Jul 22, 2019 detonation generally caused by fuel with a low octane rating is the tendency for the fuel to preignite or autoignite in an engine s combustion chamber. Knocking should not be confused with preignitionthey are two separate events. Knocking also knock, detonation, spark knock, pinging or pinking in spark ignition internal combustion engines occurs when combustion of some of the airfuel mixture in the cylinder does not result from propagation of the flame front ignited by the spark plug, but one or more pockets of airfuel mixture explode outside the envelope of the normal combustion front. Topdeadcenter tdc position of the piston when it stops at the furthest point away from the crankshaft.
Powerpoint slide on knocking in ic engines compiled by raja hossain. Pdf knocking combustion in sparkignition engines researchgate. Many times these terms are used interchangeably though they are technically different. On the other hand, the size of the detailed chemical reaction mechanism for the h 2 o 2 is acceptable for the numerical computing to reveal the detonation onset mechanism and the. Option 1 is to enrich the fuel mixture and test to verify that detonation is avoided with no loss in power. Pelican parts forums porsche forums porsche 911 technical forum. The usage of hydrogen in compression ignition engine leads to production of.
Also explore the seminar topics paper on pulse detonation engine with abstract or synopsis, documentation on advantages and disadvantages, base paper presentation slides for ieee final year mechanical engineering me or production automobile students for the year 2019 2020. In an ic engine, combustion chamber is an integral part of the working fluid circuit. Knocking is generally not heard at high speed and power settings because of the noise developed in air intake or exhaust system is louder and masks it. The knock sensor produces a voltage signal that signals the computer to momentarily retard ignition timing until the detonation stops. Knocking and detonation is physically same like nosiy sound. Well, that is called detonation or knocking or pinging depending. It is most often caused by a hot spot formed in the combustion chamber. Mathematical modeling of knocking combustion and created. Knocking and detonation are not what you want occurring in your engine 2.
Option 3 is to tolerate the detonation if its slight. Knocking in ic engine combustion abnormal occurring in the combustion chamber give sudden pressure rise accompanied by a metallic, hammer like sound leading to loss of performance and possible engine damages. V ganesan, internal combution engines, professor department of mechanical engineering indian institute of technology, madras chennai. Preignition in single cylinder engine will result in a steady reduction in speed and. Prolonged and intense knocking can break the piston or the engine, though it is can also endure this slight issue for thousands of miles. An internal combustion engine ic engine is a type of combustion engine that converts chemical energy into thermal energy, to produce useful mechanical work. Hydrogen is considered as a widely used alternative fuel in ic engines, which is also troubled by the severe knock problem making it hard to be used in a high load operation condition. Engines have either one main combustion chamber open chamber indirect injection idi fuel injection into the secondary chamber of an engine with a divided combustion chamber. The aim of this project is detecting knock during combustion of biodieselhydrogen fuel and also the knock is suppressed by timed injection of diethyl ether dee with biodieselhydrogen fuel for different loads. Electronic ignition in piston gasoline engine is required because of intake vacuum and incompatible long duration compression pulse structure limitations in the cylinder.