Knocking in si and ci engine pdf

In rcci the combustible mixture with two fuels is made before combustion starts early injection of high reactivity fuel. Jet fuel vs diesel vs gasoline how they burn and what color are they. Knocking combustion in sparkignition engines sciencedirect. 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. 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. Theoretical diagram of pressure crank angle diagram is shown in figure below. And in compression ignition ci engine, the air is compressed within the cylinder and the heat of. Pdf the aim of this project is detecting knock during combustion of biodiesel hydrogen fuel and. Engine trouble, engine knocking, factors affecting knocking. No doubt, particular kind of sound from the engine is the definition of knock but its not precise and complete. Under normal operating conditions, combustion is initiated towards the. It is desired that as soon as the fuel is injected into the cylinder, it starts burning, but in practical situations this never happens as there is always a time lag between the injection of the fuel and burning of the fuel. Partthrottle knock is a transient phenomenon and is a nuisance to the driver. When knocking combustion occurs, highfrequency pressure oscillations can be observed.

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 engines combustion chamber. Knocking in spark ignition internal combustion engines occurs when combustion of some of the. 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. In case of the ci engine the burning of fuel occurs due to compression of air. Flame propagation stage flame propagation stage 333. What is the difference between knocking and detonation in. Ci engine is known as the combustion ignition engine. 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.

Pdf knocking combustion in sparkignition engines researchgate. Knock is most critical at wot and at low speed because of its persistence and potential for damage. Hydrogen fuel is an effective alternate fuel in making a pollutionfree environment with higher efficiency. The rate of pressure rise may be as high as 10 bar per degree crank rotation in compressionignition engines.

Optical study on autoignition and knocking characteristics of. In rcci the combustible mixture with two fuels is made before combustion starts early injection of high reactivity. It is desired that as soon as the fuel is injected into the cylinder, it starts burning, but in practical situations this never happens as there is always a time lag. Lec 1 introduction to ic engines indian institute of. Certain chemical changes must first occur for knock to happen. A low compression ratio permitting only a marginal self ignition temperature to be reached. Investigating knock in an industrial sparkignition engine by large. Knocking is more or less unavoidable in diesel engines, where fuel is. Normal and abnormal knockabnormal knockknock free or knocking. Effect of knocking in spark ignition in a fourstroke engine.

Required quality of fuel for compression ignition ci systems. Knocking is due to auto ignition of end portion unburned charge in combustion chamber. Fuel must be injected into the cylinder at the desired time of combtibustion in ci engines. Generally fuels rating is given for their antiknock qualities. Pdf study of knocking effect in compression ignition engine with. Apr 25, 2017 jet fuel vs diesel vs gasoline how they burn and what color are they. And ci engines in sparkignition engines, the autoignition of. The combustion process of the knocking case has two stages.

Engine coolant rocker arm cover rocker arm valve spring cylinder head exhaust valve. In ci engines, the compression ratio for air is 16 to 20. In racing and high performance engines detonation is responsible for more problems than any other cause. Engine knock arises from autoignition of the end gas ahead of the propagating flame. The usage of hydrogen in compression ignition engine leads to production of. The rating of fuels is done by defining two parameters called octane number and cetane number for gasoline and diesel oil respectively. Phenomenon of knocking diesel engine engines free 30. In ci engine, the earliest auto ignition is necessary to avoid knocking 3. Delay period is directly related to knocking in ci engine. Study of knocking effect in compression ignition engine with. In order to decrease the tendency of knock it is necessary to decrease the ignition delayand. Bajpai3 1 assistant professor, mechanical engineering department, piet, nagpur19, maharashtra, india 2 assistant professor, mechanical engineering department, piet, nagpur19, maharashtra, india.

The two chemical drops normally used are, ethyl nitrate 33gmsus gallon 29gmsus gallon amyl nitrate higher the cetane number of the fuel, lower is the chances of knocking. Those 7 aspects are engine speed, cycle efficiency, fuel used, time of knocking, cycle operation, pressure generated and constant parameter during cycle. Theoretical diagram of pressure crank theoretical diagram of pressure crank. 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. Engines only air is compressed through a high compression ratio 14. In a properly functioning engine, the charge burns with the flame front progressing smoothly from the point of ignition across the combustion chamber. 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.

Also, a good fuel for sparkignition engine is a poor fuel for compressionignition engine. Study of knocking effect in compression ignition engine. In a normal, flamepropagation combustion, the heat release rate increases smoothly to a maximum, and then progressively decreases as the entire m. High reactivity ci engine like fuel is sprayed and act as the combustion initating fuel. Hey reader, i have also explained the other many differences you can check that too. And in compression ignition ci engine, the air is compressed within the cylinder and the heat of this compression air is used to ignite the fuel.

But for ci engines higher the compression ratio, lesser is the ignition delay and lesser probability of detonation or diesel knock occurring. With change in load, the quantity of fuel injected is changed, varying the airfuel ratio. Optical study on autoignition and knocking characteristics. In a ci engine, irrespective of load, at any given speed, an approximately constant supply of air enters the cylinder. Strictly speaking, knocking is a phenomenon that can be defined as spontaneous ignition or autoignition of fresh charge in the cylinder at various pinpoint locations. Pdf knocking combustion research is crucially important because it determines engine. Composition factor the detonation or knocking in ci engine can be reduced by using certain fuel additives which would increase the cetane number of the fuel. Current optical highstrength engine was equipped with a dualfuel injection system and tests were operated at engine speed rmin for both cisi modes. Fuel is injected into the cylinders late in compression stroke through one or more injectors into highly compressed air in the combustion chamber.