Influence Of Fuel Composition On Deposit Formation In High-Speed Diesel Engines 480229
On the background of the wide speed and load variations to which high-speed Diesel engines are subjected, the author diagnoses the temperature conditions under which two different types of unburned fuel deposits may be formed. Solid carbon particles (“soot”) are predominantly the product of incomplete combustion at full throttle or high temperature operation while liquid polymerized fuel fractions are experienced in increasing amounts at the low combustion chamber temperatures synonymous with light loads and reduced speeds.
Although some faulty engine conditions may be the cause of excessive soot formation, the author blames most deposits of this nature on the presence of high-boiling or even residual fractions and the poor burning quality of predominantly aromatic fuels.
Large differences in the magnitude of low temperature fuel deposits were found by the author without much relation to the commonly used fuel inspection data. Howeven, when correlated with the chemical composition of the fuel, prevalence of paraffinic hydrocarbons and presence of a certain percentage of olefinic material appear to be of decidedly beneficial effect.
Better fuel selection depending on the engine operating conditions and use of specially treated Diesel fuels are advocated as the safest way to avoid premature engine failures due to deposit formation.
In spite of best preventive maintenance practices, the operators of Diesel-powered equipment find themselves at times confronted with untimely and unexpected engine break-downs which may be directly attributed to the impairment of vital engine components by resinous and carbonaceous deposits.
Compression rings will be found stuck in their grooves, oil control rings obstructed by carbon particles and piston skirts covered with hard, varnish-like coatings. Valves may be kept from properly seating by gum deposits on seats and stems, cylinder bores irregularly lapped out by coke-like residues on the pistons and the lubricating oil supply restricted by sludge accumulations.
Since any one of these troubles not only deprives the operator of his source of revenue but also entails a sizeable repair bill, such engine failures have been for many years the cause of a spirited feud between the service personnel of the two industries involved.
The engine manufacturer points with righteous indignation to the fact that these deposits were not in the engine when it was built. The petroleum supplier, in turn, can always prove for his side that both the fuel as well as the lubricating oil are meeting all specifications and are being used to full satisfaction in other engines of the same make.
After much discussion pro and con, failures of this nature must then be usually booked down as caused by “factors beyond the control of man.”