Knocking

This type of explosion is important in engines where detonation can vary from an incipient stage, often referred to as pinking, to a more severe condition known as knocking. ... 

Most of the ethylene dichloride produced is utilized for the manufacture of vinyl chloride, which may be obtained from it by pyrolysis or the action of caustic soda. Large quantities are also used in anti-knock additives for gasoline. As a solvent It has been displaced by trichloroethylene and tetrachloroelhyJene. U.S. production 1978 4-75 megatonnes. 

The various additives used to obtain the required properties include anti-knock compounds, anti-oxidants, metal deactivalors, anti-icing additives, etc. 

PbEu (anti-knock agents), radiation and sound shields, in paints, high quality glass. World production 1980 4 0 megatonnes. Lead compounds are toxic and hazardous to health. 

Figure 5.3 gives an example of a combustion diagram recorded during knocking conditions. This is manifested by intense pressure oscillations which continue during a part of the expansion phase. 

The term detonation often employed to describe knocking is incorrect because the phenomenon can not be attributed to the propagation of a flame in the supersonic region, accompanied by a shock wave.. 

Knocking should be absolutely avoided because if allowed to continue it will cause severe mechanical and thermal problems (Eyzat et al., 1982), which can... 

In order to characterize the behavior of motor fuels or their components with regard to knocking resistance but without involving chemical composition criteria which are complex and not easy to quantify, the traditional method that has been universally employed for more than 50 years consists of introducing the concept of octane number. 

The other compound is n-heptane which has little resistance to knocking and is given the number, 0 ... 

Adapted in each case to obtain maximum knocking intensity, it is usually between 1.05 and 1.10. 

For vehicles, special attention is most often focused on the knocking potential encountered at high motor speeds in excess of 4000 rpm for which the consequences from the mechanical point of view are considerable and lead very often to mechanical failure such as broken valves or pistons, and rupture of the cylinder head gasket. Between RON and MON, it is the latter which better reflects the tendency to knock at high speeds. Conversely, RON gives the best prediction of the tendency to knock at low engine speeds of 1500 to 2500 rpm. 

The lead alkyls inhibit auto-ignition which, by intermediary of lead oxide, PbO, increases the resistance to knocking. 

The Octane Requirement Increase, ORI, is a phenomenon manifested by the appearance of knocking and is due to the increase in engine octane demand with time. This phenomenon is correlated with the increase of solid deposits in the combustion chamber. Although the causes have not been determined with certainty, some companies have patented additives which modify the deposits. The effect is to limit the increase in octane demand (Bert et al., 1983 Chevron, 1988 Nelson et al., 1989). 

Product characterization aims at defining their end-use properties by means of conventional standard measurements related as well as possible — and in any case, being the object of a large consensus— to end-use properties. We cite for example that octane numbers are supposed to represent the resistance of gasoline to knocking in ignition engines. 

A knock out vessel may on the other hand be followed by a variety of dehydrating systems depending upon the space available and the characteristics of the mixture. On land a continuous dehydration tank such as a wash tank may be employed. In this type of vessel crude oil enters the tank via an inlet spreader and water droplets fall out of the oil as it rises to the top of the tank. Such devices can reduce the water content to less than 2%. 

Electrons interact with solid surfaces by elastic and inelastic scattering, and these interactions are employed in electron spectroscopy. For example, electrons that elastically scatter will diffract from a single-crystal lattice. The diffraction pattern can be used as a means of stnictural detenuination, as in FEED. Electrons scatter inelastically by inducing electronic and vibrational excitations in the surface region. These losses fonu the basis of electron energy loss spectroscopy (EELS). An incident electron can also knock out an iimer-shell, or core, electron from an atom in the solid that will, in turn, initiate an Auger process. Electrons can also be used to induce stimulated desorption, as described in section Al.7.5.6. 

A popular electron-based teclmique is Auger electron spectroscopy (AES), which is described in section Bl.25.2.2. In AES, a 3-5 keV electron beam is used to knock out iimer-shell, or core, electrons from atoms in the near-surface region of the material. Core holes are unstable, and are soon filled by either fluorescence or Auger decay. In the Auger... 

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