Piston blow

In 1985 Leppard [156] reported engine measurements, for stoichiometric ethane-air, of pressure and end gas temperature, the latter derived from the energy equation. The occurrence of autoignition agreed closely with prediction based on an earlier chemical model of Westbrook and Dryer [52]. From their engine experiments, Cowart et al. [59] also compared, for iso-octane and -pentane, the predictions of the simplified models of Hu and Keck [75] and Chun et al. [157], and the more detailed kinetic predictions of Westbrook et al. [158]. These were found to simulate the time of knock occurrence if the kinetic data were re-calibrated. This, and the subsequent work of Brussovansky et al. [76], showed the need for accurate allowances for heat transfer and piston blow-by, because of their important effect on the derived end gas temperature. Where end gas temperature can be measured directly this problem is circumvented. 

In piston-type compressors, the oil serves three functions in addition to the main one of lubricating the bearings and cylinders. It helps to seal the fine clearances around piston rings, piston rods and valves, and thus minimizes blow-by of air (which reduces efficiency and can cause overheating). It contributes to cooling by dissipating heat to the walls of the crankcase and it prevents corrosion that would otherwise be caused by moisture condensing from the compressed air. 

In the piston-type compressor the very thin oil thin has to lubricate the cylinder while it is exposed to the heat of the compressed air. Such conditions are highly conducive to oxidation in poor-quality oils, and may result in the formation of gummy deposits that settle in and around the piston-ring grooves and cause the rings to stick, thereby allowing blow-by to develop. 

BlOW-by Combustion gases which are forced past the piston rings and into the crankcase of an internal combustion engine. Blow-by gases may contain NO, SCX, CO, COz,water vapor, hydrocarbon gases, and soot. In combination with water, some of these gases can form corrosive acids. 

The extrusion blow molding process can be continuous or intermittent, as shown in Fig. 14.16. The former, employed commonly for parts less than 1 gal, has a continuously rotating screw extruder, extmding parisons through one or more dies. The latter may use either an accumulator head with a piston-driven extrusion forming of the parison, or a reciprocating screw, such as the one used in injection molding. 

Soot contamination is a common occurrence for in-service diesel engine oils. Soot generally results from piston ring blow-by from the combustion chamber or faulty seals. Soot contamination leads to varnish and sludge and also contains hard carbon particles that increase machinery wear. Detergent and dispersant additives function to clean machinery surfaces and hold soot particles in suspension, maximizing lubricant efficiency. 

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