Engine cleanliness

There are no official specifications for obtaining a minimum level of engine cleanliness from a fuel. However, all additives in France are subject to approval by the Direction des Carburants (DHYCA), with the objective of having data that prove, first of all, the product to be harmless, and second, the product s effectiveness. Likewise, the automotive manufacturers, in establishing their specifications, set the minimum performance to be obtained by the fuel with regard to engine cleanliness. 

On cracked naphthas. Hydrofining provides not only desulfurization, but also improvements in gum, stability, and engine cleanliness characteristics. 

Poly(a-olefins) or PAOs, polyol esters and diesters are now used in automotive and marine engine oils. To understand how an ester lubricates, it is important to consider its behavior in the different lubrication regimes, especially boundary lubrication when the properties of the bulk lubricant (e.g. viscosity) are of minor importance. The chemical properties of the lubricant responses under extreme conditions will become increasingly important. The polar ester will preferentially stick to the surface of metal when a small amount of ester is added to a low viscosity nonpolar fluid (PAO), (Randles, 1999 Spikes, 1999). When the two metal surfaces come closer together, the polar ester molecules stay in the contact zone. The use of fully synthetic engine oil formulations has produced some improvement in viscosity control and engine cleanliness in the piston and valve train areas over petroleum-based oils (Boehringer, 1975 Frame et ah, 1989 Kennedy, 1995 Lohuis and Harlow, 1985). 

L-24-A-78 Engine Cleanliness Under Severe Condition Using the Petter AVB Supercharged Diesel Engine... 

These blends provide reduced wear, better engine cleanliness, longer oil change intervals, slightly improved fuel economy, and lower oil consumption rates than are experienced with conventional petroleum-based lubricants [48]. However, their much greater cost limits their use to the fraction of the automotive market where their advantages outweigh this factor [49]. 

Marine diesel cylinder lubricants are total loss lubricants. In their brief operational life their main functions are to provide a strong oil film between the cylinder liner and the piston rings, hold partially burnt fuel residues in suspension so promoting engine cleanliness, and neutralise acids formed by the combustion of sulphur compounds in the fuel. Marine diesel cylinder lubricants are therefore formulated to combat mechanical, abrasive and corrosive wear. 

Classification is by definition used preponderantly in the treatment of raw materials. However, these raw materials find their way into chemical processing per se and thus become of interest to the chemical engineer, particularly when the products to be treated reaci better when of a defined cleanliness, size, gravity, or moisture content. 

Occasionally, however, it may be impossible to be certain that a piece of equipment is spotlessly clean, especially if it has contained a residual oil or a material that polymerizes. If this is the case, or if there is some doubt about its cleanliness, then the hazards and the necessary precautions should be made known to the workshop or the other company. This can be done by attaching a certificate to the equipment. This certificate is not a work permit. It does not authorize any work but describes the state of the equipment and gives the other company sufficient information to enable it to carry out the repair or modification safely. Before issuing the certificate, the engineer in charge should discuss with the other company the methods it proposes to use. If the problems are complex, a member of the plant staff may have to visit the other company. The following incidents show the need for these precautions. 

Carbon residue is expressed as a percentage by weight of the original sample of the fuel, with the amount determined by burning a given quantity in a scaled container until all that remains is carbon residue. The amount of carbon residue left within the combustion chamber of the engine has a direct bearing upon the internal deposits and affects the cleanliness of combustion, particularly the smoke emissions at the exhaust stack. 

The oil in a refrigeration system should remain as clean as it is when it enters the compressor (unlike that of the automobile engine which is quickly contaminated by fuel, water, carbon and atmospheric dust). The condition of the compressor oil is therefore a direct indication of the physical and chemical cleanliness of the system. 

This volume addresses many of the unit operations listed in List I and depicted in Figure 15. The chemistry and chemical engineering principles behind these operations are described, and future directions and needs are suggested. The final chapter indicates the problems associated with the extreme purity and cleanliness demanded by IC processing. 

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