Chamber deposits

Bert, J.A., J.A. Gething, T.J. Hansel, H.K. Newhall, R.J. Peyla and D.A. Voss (1983), A gasoline additive concentrate removes combustion chamber deposits and reduces vehicle octane requirement . SAE paper No. 83-1709, Fuels and Lubricants meeting, San Francisco, CA. 

MOCVD Reactions. A great deal of interest has been generated by the availability of two metallo-organic titanium compounds, tetrakis-diethylamino titanium (TDEAT) andtetrakis-dimethylamino titanium (TDMAT). These precursors make possible the deposition of TiN at lower temperature.[ " k l These compounds are liquid at room temperature. A flow of helium bubbling through the warm precursor entrains the vapor into the deposition chamber. Deposition temperature is approximately 320°C. The following reactions occur ... 

Deposits can form within the combustion chamber of a gasoline engine. These deposits are complex in nature and can contain components from fuel combustion, from the lubricating oil, and from some additives. Typically, the heavier fuel and lubricant components such as condensed aromatics and bright stocks contribute most significantly to combustion chamber deposits. 

There is much concern about the emissions which result when fuel sulfur combusts (i.e., sulfur oxides). These gaseous products further react to form environmental pollutants such as sulfuric acid and metal sulfates. Active sulfur and certain sulfur compounds can corrode injection systems and contribute to combustion chamber deposits. Under low-temperature operating conditions, moisture can condense within the engine. Sulfur compounds can then combine with water to form corrosive acidic compounds. 

Fuel stability is an indication of the sediment- and gum-forming tendency of fuel. Gums and sediment can cause filter plugging and combustion chamber deposits and result in sticking of pumping and injection system components. 

As a result of this, unbumed fuel can remain in the combustion chamber to be drawn into the crankcase with the oil lubricating the piston cylinder, or it can remain within the upper part of the cylinder to carbonize and form combustion chamber deposits. Piston ring and land groove deposits can also form. 

Additive-induced combustion chamber deposits form near the intake valve. The deposit forms directly onto the surface and has a waxy appearance. These deposits do not undergo alterations as do fuel-derived deposits. Also, additive-induced deposits do not readily flake off of the combustion chamber surface. The effect of engine design on combustion chamber deposit formation is being investigated. 

Can lead to an increase in combustion chamber deposits under low-temperature, low-load, low-speed, or stopping and starting driving conditions, moisture condensation can occur deposits can result. 

A high 90% point and end point can lead to poor mixing in the combustion chamber, increased hydrocarbon emissions, combustion chamber deposits, and crankcase dilution. 

An increase in the concentration of high-boiling-point components in fuel can enhance combustion chamber deposits high-end-point fuel high D-86 residue fuel... 

High-viscosity lubricating oil bright stock can enhance combustion chamber deposits... 

Driving profile may be predominantly city, stop and go, short trip this may lead to the formation of combustion chamber deposits... 

Use ASTM D-86 T-90 method temperature, end point, and residue may be high these high-boiling-point components can contribute to combustion chamber deposits... 

A combustion process which is initiated solely by a timed spark and in which the flame front moves completely across the combustion chamber in a uniform manner at a normal velocity. In such a process there is no sudden release of energy from the fuel-air mixture, nor are there any auxiliary sources of ignition from combustion-chamber deposits, hot spark plugs, overheated valves, or other hot surfaces within the combustion chamber. Engine roughness associated with high gas loads and mechanical deflections of engine a components can accompany normal combustion. 

Hot Spots. Combustion-Chamber Deposits) Surface ignition is the initiation of a flame front by any hot surface other than the spark discharge prior to the arrival of the normal flame front. The flame front or fronts so established propagate at normal velocities. This phenomenon can be further subdivided into preignition and postignition. 

Analytical data on combustion chamber deposits accumulated from leaded fuel show the presence of both carbonaceous material and lead salts. An analysis of the extreme outer layer of deposits which have been causing surface ignition, however, shows that very little carbon is present and that nearly all the deposit is made up of lead salts (24, 41) This observation suggests that the carbonaceous portion of the deposit is consumed in the process of ignition, which is in agreement with the idea that glowing carbonaceous material is an important source of surface ignition (14). 

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