What is the difference between knocking and detonation in ic. It is a fundamental specification for combustion engines. What is knocking detonation pre ignition knocking detonation pre ignition in petrol engine method to avoid knocking in petrol engine octane number knocking detonation pre ignition in diesel engine. The detonation in compressedignition engine has also been given. Knocking and detonation is physically same like nosiy sound. What is the difference between knocking and detonation in. Knocking combustion causes major engine damage, and also reduces the efficiency. Developing a deto nation engine operating without need of periodic igni tion and continuously injecting fuel would greatly re duce difficulties in designs of, in particular, detonation combustion aerospace thrusters. Faa phak, page 618 detonation can be caused by a number of factors, but generally they relate to a situation outside of the engine s design. It occurs during the process of combustion of the s. Knocking and detonation are not what you want occurring in your engine 2. Detonation, or engine knock, occurs simply when fuel preignites before the. This means fuels having higher octane rating have poor cetane rating and viceversa. A developmental, flightlike engine could be ready for demonstration by 2005 and a fullscale, operational engine could be finished about four years later.
These ic engine study notes will help you to get conceptual deeply knowledge about it. Continuous detonation engine and effects of different types. Supposing that ignition occurs only after great delay. Since the chapmanjouguet detonation speed d cj for the end gas is predicted to be 1867 ms, the bright blue flame from image c to image h is clearly a selfsustained detonation wave. Jun 21, 2015 a pulse detonation engine, or pde, is a type of propulsion system that uses detonation waves to combust the fuel and oxidizer mixture. Combustion may be defined as a relatively rapid chemical combination of hydrogen and carbon in fuel with oxygen in air resulting in liberation of energy in the form of heat. The phenomenon of detonation was first observed and described by harry ricardo.
Ill add a couple of thoughts that come to mind when i think about knocking and detonation. Effect of knocking in spark ignition in a fourstroke engine. Detonationpre ignition and the outboard motor one of the most common causes of major internal engine damage results from the abnormal combustion conditions that have plagued the internal combustion engine since its beginning, namely detonation and preignition, or surface ignition. Knocking combustion in sparkignition engines sciencedirect. The comparison between detonation in sparkignition and compressionignition engines has been done. Prolonged and intense knocking can break the piston or the engine, though it is can also endure this slight issue for thousands of miles.
The effects of detonation may be anywhere from arbitrary to severe. Feb 24, 2014 the usage of hydrogen in compression ignition engine leads to production of knocking or detonation because of its lower ignition energy, wider flammability range, and shorter quenching distance. In addition to this knocking puts a limit on the compression ratio at which an engine can be. Knocking or also called detonation in ic engines, in ignition spark engine, occurs when the incorrect ignition of the air fuel mixture in the some cylinder occurs while other cylinders correctly combust and produce the power stroke at the correct time. It is one of the major factors that controls the fuelair mixing in diesel engines. The simplest deleterious effects are typically particle wear caused by moderate knocking, which may further ensue through the engine s oil system and cause wear on other parts before being trapped by the oil filter. Use knock sensor to control spark retard so as to operate close to engine knock limit 7. What is the meaning of knocking and detonation in i. May 25, 2014 we use your linkedin profile and activity data to personalize ads and to show you more relevant ads.
Phenomenon of knock in ci engine is called knocking and phenomenon of knock in petrol engine is called detonation. What is the difference between knocking and detonation in ic engine. Detonation or knocking in ic engines mechanical engineering. Continuous detonation engine aeronautics and astronautics. Delay period is directly related to knocking in ci engine. The engine community pushes ever nearer to the limits of power output. If the engine does not accelerate easily when given some throttle, downshift to a lower gear. Categories mechanical engineering tags detonation, detonation factors, education, engine detonation, engine knocking, engineering, engineering education, i. The high velocity knock, usually called detonation,will produce severe damage of the engine and is avoided by the electronic engine control. The engine is pulsed because the mixture must be renewed in the combustion chamber between each detonation wave initiated by an ignition source. Its a sudden combustion of the end gas ahead of the flame front due to increase in charge pressure and temperature higher than self ignition. Causing sudden pressure changes in the cylinder up to 10x.
Diesel engines 4 and 2 stroke industrial diesel engine. Jul 22, 2019 the effects of detonation may be anywhere from arbitrary to severe. But bigger engine, which weigh more and cost more to build and maintain are not always better ii. Pdf knocking combustion in sparkignition engines researchgate. This causes variation in the pressure waves which causes a production of sound like the sound. 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 still traveling towards topdeadcenter. Engines the loud pulsating noise heard within the engine cylinder of an i. As a result, a reliablyfunctioning detonation engine has not been developed until now. A discussion of heat value as it relates to the internal combustion engine may help provide a better understanding of the difference between high and low heat value. It is caused due to the propagation of a high speed pressure wave created by the autoignition of end portion of unburnt fuel. However, severe detonation can cause engine failure in minutes.
Digester gas is the most practical of the manufactured or byproduct group. In a combustion engine, the static compression ratio is calculated based on the relative volumes of the combustion chamber and the cylinder. 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. Another way to add power is to make a normal sized engine more efficient. Detonation or knocking in ic engines detonation or knocking in i. In diesel engines, only air is send into the combustion chamber during induction. As the flame propagates across combustion chamber, end gas is compressed causing pressure, temperature and density to increase. This means that a powerful explosion is trying to expand a cylinder chamber that is shrinking in size, attempting to reverse the direction of the piston and the engine. A change in engine speed, changes temptime and pressuretime relationships. Study of knocking effect in compression ignition engine. If these factors are controlled, then the detonation can be avoided.
An extensive delay periodcan be due to following factors. But for ci engines higher the compression ratio, lesser is the ignition delay and lesser probability of detonation or diesel knock occurring. Continuous detonation engine one of the current interests in the hypersonic propulsion system is the detonation engines which offer significant advantage in cycle efficiency. As they often learn cylinder chamber combustion processes can quickly gravitate to engine failure. For this reason engines with cylinder diameters larger than 250 mm are almost always of ci type. What is the difference between knocking and detonation in internal. This air is compressed during the compression stroke and towards the end of. Engine speed inc in engine speed increases the air motion and turbulence, reduces id time slightly in ms, in terms of ca degrees id increases almost linearly. Ci diesel engine a scheme of ci engine, b diesel cycle a glow plug piston crankshaft combustion chamber precombustion chamber prechamber oil exhaust outlet b pressure, mpa ratio of volumes vv 2. At that point, the glowing item can cause preignition and rapid destruction of the cylinder. I wont explain it here in detail as the question doesnt demand for it.
Manufacturing pulse detonation rocket engines is simple and inexpensive. Flame propagation, engine flame trace, detonation, preignition, flame high speed. This article defines two types of engine failures, detonation and preignition, that are as insidious in nature to users as they are hard to recognize and detect. So, we have understood that in a spark ignition engine combustion is initiated, you know. Detonation generally caused by fuel with a low octane rating is the tendency for the fuel to preignite or autoignite in an engines combustion chamber.
Engine valves, for instance, would likely be a sophisticated version of automobile fuel injectors. Rapidly mix fuel and air in gasoline direct injection engines. Todays heavier bikes and taller gearing can easily push a high performance engine into a lugging condition which increases loads on engine components, causes detonation, builds excessive heat and increases fuel consumption. But so far goes my knowledge, due to heterogeneous mixture of ci engine, fuel will. Upon teardown, forensic analysis would reveal the telltale signs of both detonation and preignition damage, although its the preignition that ultimately did the engine in. Physical factors affecting ignition delay combustion chamber design. Pulse detonation engine and continuous detonation wave. Difference between knocking and detonation pdf downloadgolkes.
Knocking is more or less unavoidable in diesel engines, where fuel is injected into. Detonation methane number compression ratio ignition timing load inlet air temperature airfuel ratio emissions. It was found that detonation can occur in modern internal combustion engines under high. Fuel is injected into the cylinders late in compression stroke through one or more injectors into highly compressed air in the combustion chamber. While the early years saw many insurmountable at the time obstacles whose answers would only come as. Hcci homogeneous charge compression ignition technology has been around for a long time but has recently received renewed attention and enthusiasm. What is the difference between knocking and detonation. Detonation or engine knocking refers to violent noises, heard in an engine, giving a pinging sound during the process of combustion. Detonation, or engine knock, occurs simply when fuel preignites before the piston reaches scheduled spark ignition. Causes of detonation in petrol and diesel engines sage journals. The dynamic compression ratio is a more advanced calculation which also takes into account gasses entering and exiting the cylinder during the compression phase.
In the quest for everimproving fuel efficiency and emissions reduction, an old and very promising idea has found new life. Feb 09, 2017 knocking and detonation is physically same like nosiy sound. Past development in detonation engines has mainly focused on pulsed detonation engines pde, where intermittent 1d combustion across a shock propagating in a tube is. Similarly, overheating may cause additional wearandtear on the engine, be relatively harmless or cause the engine to catch on fire and break. Internal combustion ic engine study notes handwritten. Because of the noise that it makes, detonation is called engine knock or pinging in cars.
Most engines used a fixed compression ratio, however a variable compression ratio engine is able to adjust the compression ratio while the engine is in operation. Oct 02, 2017 method to avoid knocking in petrol engine octane number knockingdetonationpre ignition in diesel engine. Turbocharger and supercharger to increase the output of any engine more fuel can be burned and make bigger explosion in every cycle. Study of knocking effect in compression ignition engine with.
730 388 338 961 662 579 901 1285 1204 284 669 1010 332 869 820 1640 449 780 826 527 306 910 1107 858 854 80 1364 1549 326 648 1416 776 217 826 403 994 168 999 360