Explosions are either detonations or deflagrations. It is spontaneous combustion of end gas remaining charge in the combustion chamber. Pdf relationship between superknock and preignition. Detonation is not unique to engine knocking at all. For this reason a theory based on streamlines is the most attractive. Subsonic, typically 1 ms and 7 to 10 bar starting at ambient pressure detonation. 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. Are they mainly different due to timing like knock is very near tdc and det is during the compression. Over the last decades, extensive studies have been performed to investigate the effects of various factors on ci knocking characteristics 8. Detonation is the result of an amplification of pressure waves, such as sound waves, occurring during the combustion process when the piston is near top dead center tdc.
Pinging vs detonation gas engine noises karmakanix. In a detonation, the reaction front moves at a speed greater than the speed of sound, driving the shock front immediately preceding it. Sympathetic detonation of ammonium nitrate and ammonium nitratefuel oil by r. Study of knocking effect in compression ignition engine. After pipe is filled with a mixture the detonation is initiated at the open or sealed end of the pipe. Knocking is generally not heard at high speed and power settings because of the noise. Detonation velocities at atmospheric pressure and am fig. We use your linkedin profile and activity data to personalize ads and to show you more relevant ads. 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.
Here we will examine how it is used, and describe some tests of the theory. Detonation occurs when excessive heat and pressure in the combustion chamber causes the airfuel mixture to ignite on its own. Describe the differences between deflagration and detonation. Visualization study on the flowfield of rotating detonation. Fuel begins to burn and rapidly transitions to a detonation, or powered shock. Knocking should not be confused with preignitionthey are two separate events. Therefore, it is necessary to study the autoignition and knocking characteristics under different combustion modes and reveal the similarities and differences between them.
Optical study on autoignition and knocking characteristics of. In the case of either knocking pinging and detonation, the noise is generated by a combination of factors. Superknock is the severe engine knock triggered by preignition. Difference between knocking and detonation compare the. Detonation is sometimes called knocking, but that is just confusing. The high velocity knock, usually called detonation,will produce severe damage of the engine and is avoided by the electronic engine control. The experiment was conducted on a turbocharged gasoline direct injection engine with compression ratio of 10. This produce knocking sound and hence called knocking. A mild detonation will simply heat the engine but if it is severe, it may even result in fracture of the piston or other damages to the engine.
The phenomenon of detonation was first observed and described by harry ricardo during experiments carried out between 1916 and 1919 to discover the reason for. I agree with your oppion about the difference between kocking combusion and detonation. If there is still no indication of gun detonation following step 7. It is caused due to the propagation of a high speed pressure wave created by the autoignition of end portion of unburnt fuel. I saw the suggestion on merging this article with engine knocking. Les study of deflagration to detonation mechanisms in a.
The major difference is how the two being their process. Simulations of detonation wave propagation in rectangular. The injectors of fuel and oxidizer are located at the seal end of the pipe. Definition of detonation the sudden and violent release of mechanical, chemical or nuclear energy from a confined space which creates a shock wave that travels at supersonic speeds. The detonation velocity for the mixed explosives can be estimated by a similar pathway to the detonation pressure. Describe the difference s between deflagration and detonation. The detonation process is also core to the pulse detonation engine no cylinders among many other things which is why i found it. Whenever detonation occurs, you have several options assuming youre sticking with the fuel in question.
What reaction affects the explosive propagation reaction through a. Austria as you know the guncotton has nearly 3 nitro groups no2 per cellulose molecule guncotton is a really extremely long molecule and. The engine was operated at an engine speed of 1750 rmin and the brake mean effective pressure of 2. Murphy 3 abstract an investigation was made of the distances over ihich sympathetic detona tion of ammonium nitrate an and ammonium nitratefuel oil anfo might be expected. If there is no indication of gun detonation, repeat steps 7.
This simple theory is the basis for almost all calculations made for the design of devices driven by high explosives. Deflagration is done by heat or flame while detonation is done by shockwave. If additional fuel is vaporized inside the combustion chamber the pressure in the cylinder will rise, and, while the valvesports are still open, reduce the volumetric efficiency, and. Feb 09, 2017 knocking and detonation is physically same like nosiy sound. What is the difference between knocking and detonation. Results in excessive pressure, temperature and unstable pressure pulse shock wave. Dec 30, 20 knocking is the sound of a destroyed bearing. What is the difference between explosion and detonation.
The difference between detonation and burning is that a burning mixture simply burns at a very fast rate, usually not exceeding the speed of sound, needing other methods to produce an explosion. 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. Engines the loud pulsating noise heard within the engine cylinder of an i. The strong increase of knock intensity at the earliest st could be explained by such a transition, leading locally to very high pressure levels in the. The resulting knock or ping is the sound of the pistons slamming against the cylinder walls. Structure of a detonation from high speed photography and soot tubes 3d cellular structure, constantly changing cell width. In a different article, well look more closely at the normal combustion event, and explore how our use of the engine controls throttle, mixture and prop affect what. Propagation of detonation across a gasgap between two. Detonation or knocking in ic engines mechanical engineering. Phenomenon of knock in ci engine is called knocking and phenomenon of knock in petrol engine is called detonation. Hydrogen fuel is an effective alternate fuel in making a pollutionfree environment with higher efficiency. Ill add a couple of thoughts that come to mind when i think about knocking and detonation. Therefore the velocities meas ured in mixtures containing 34.
The effects of detonation may be anywhere from arbitrary to severe. What is the difference between knocking and detonation in ic. Spontaneous combustion of the endgas, or remaining airfuel mixture in the chamber. Development of a new model for the calculation of the. See the image carefully, you can see the wave arc in top. Visualization study on the flowfield of rotating detonation 25th icders august 27, 2015 leeds 3 table 1 presents the supply conditions and the working parameters of the detonation process for cases these two cases, detonating h 2 air and ch 4 o 2 respectively. I wanted to understand the difference between knock, which afaik is when the octane rating is to low for the compression ratio and causes the gas to heat to ignation, and detonation, when the car ignites the gas prematurely. From the technical point of view detonation is a very undesirable process that can damage engines. Schematically, the detonation wave is shown in the figure here. Option 2 is to command less spark advance timing in the main ignition map. If to merge means also move, ie the original article willo ceases to exist then i am against this.
Option 3 is to tolerate the detonation if its slight. We get asked this question a lot, and rightfully so. 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. 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. It showed pipelines being blown up the one with the explosion showed a progressive destruction down the pipeline while in the one with the detonation the entire pipeline blew up simultaneously. Sep 24, 2015 detonation is a great thing if youre taking in a fireworks show or maybe watching macgyver. Detonation always comes after normal combustion has been started by the spark plug. Detonation is basically a phenomenon which is similar to the many explosions taking place at the same moment. Explain the differences between burning and shock to. Detonation is similar to explosion with the difference lying in the fact that the rapid increase in volume is so high that production of supersonic shock wave takes place. The spark plugs ignites the injected fuel and explosion is started. Detonation is a great thing if youre taking in a fireworks show or maybe watching macgyver. Pulse detonation rocket engines operate by injecting propellants into long cylinders that are open on one end and closed on the other.
Geoer, it is easiest to follow the streamlines and take the difference between the specific entropy at the back of the detonation driving zone and that at the detonation front, and adding the differences together. Knocking and detonation are not what you want occurring in your engine 2. Normal combustion expands out, but the gasses on the edge of the flame front compress and begin combusting spontaneously. What reaction affects the explosive propagation reaction through a deflagrating explosive. If you dont understand exactly what each of these events are and how they occur, you wont know how to prevent them from happening, or possibly even recognizing when it happens. Supersonic high pressure shock front ahead of the reaction zone i. The detonation calorimeter was seen as an effective way of measuring any additional stored energy liberated by the aluminum during an actual detonation. Detonation wave is a shock wave in a reactive medium that is sustained by energy released in chemical reactions that the shock itself triggers and sustains. The horsepower will depend on the volumetric efficiency of the engine which is a function of the pressure difference between ambient air and cylinder pressures.
It is the phenomena of generation of shock wave due to impulsive energy transfer. Detonation, on the other hand, occurs almost simultaneously through the whole mass of the mixture. Optical study on autoignition and knocking characteristics. The heat of detonation was evaluated using a detonation bomb calorimeter developed for drdcv19. 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. What is the difference between knocking and detonation in. The key difference between knocking and detonation is that, knocking brings several drawbacks to the engine such as, overheating of spark plug points, erosion of the combustion chamber surface and rough, inefficient operation whereas detonation can cause abrasion, mechanical damage and overheating in engines. Detonation, on the other hand, occurs almost simultaneously through the. In the frame of the wave, the fresh mixture enters the shock at speed d, starts burning in the reaction zone until completely. Relationship between superknock and preignition article pdf available in international journal of engine research 162. In summary most of the abovementioned 3d simulations focus on describing the structure of the detonation front and few deal with the mechanism of the detonation. The actual knocking or ringing sound of detonation is due to these pressure waves pounding against the insides of the combustion chamber and the piston top, and is. I installed the sniper efi on a 383 backed by a 700r4 in an 85 c10. Prediction of detonation pressure and velocity of explosives.
About 50 years ago i saw a video that illustrated the difference between an explosion and a detonation. The difference between knocking and detonation is that, knocking brings some several drawbacks to the engine such as, overheating of spark plug points, erosion of the combustion chamber surface and rough, inefficient operation whereas detonation can cause abrasion, mechanical damage and overheating in engines. Option 1 is to enrich the fuel mixture and test to verify that detonation is avoided with no loss in power. Mild detonation is called knocking because of the noise that can be heard when it happens at low power settings. Comparisons of the calculated detonation parameters with their differences from the appropriate experimental values are presented in. If we go thorough the combustion inside compressed ignition ci engine and spark ignitionsi engine then difference will be clear. The details of the apparatus have been previously described18,20,21. A detonation explosion can be started at some hot spot, such as the sharp edge of an accidental dent, or the tip of some component heated up by the initial heat produced during initial detonation. Prediction of detonation pressure and velocity of xplosives 83 can be obtained when p emaxi is known. What is the difference between knocking and detonation in ic engine. The burning mixture expands and acts like a piston pushing a leading shock and supporting the detonation. Difference between knocking and detonation pdf downloadgolkes. 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 pressure caused by detonation product on sealed end produces thrust. Fauquignon has presented the classical theory of detonation. It is also frequently called pinging, or in the uk pinking due to the characteristic sound of detonation. If it continues for a long time it may overheat the cylinder and spark plug so as to ignite. The calculated detonation pressure p is in kbar, and the detonation velocity d is in m s1. In fact, its probably best if you avoid detonation at all costs where your engine is concerned. Detonation definition and meaning collins english dictionary. The usage of hydrogen in compression ignition engine leads to production of. High explosives do not need to be confined to function. May 25, 2014 we use your linkedin profile and activity data to personalize ads and to show you more relevant ads. When gas fills a cylinder, an ignitersuch as a spark plugis activated.
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