Energies (Feb 2022)
A Study on the Effect of Inlet Air Pollution on the Engine Component Wear and Operation
Abstract
This paper systematically reviews the research progress in the field of the influence of air pollutants in the engine inlet on the accelerated wear of the elements of the association: piston, piston rings, cylinder liner (P-PR-CL), and plain bearing (journal–panel). It was shown at the outset that the primary component of air pollution is road dust. Its main components are dust grains of hard minerals (SiO2, Al2O3), which penetrate the oil film area between two frictionally mating surfaces causing their abrasive wear. Therefore, the effect of three dust parameters (grain size and hardness, and dust concentration in air) on the accelerated wear of the friction pair: piston, piston rings, cylinder liner(P-PR-CL), and plain bearing (journal–pan) is presented extensively. It was noted that the wear values of the same component were obtained by different researchers using different testing techniques and evaluated by different indices. It has been shown that the greatest wear of two frictionally cooperating surfaces is caused by dust grains with sizes equal to the thickness of the oil film at a given moment, which in typical combustion engine associations assumes varied and variable values in the range of 0–50 µm. The oil film thickness between the upper ring and the cylinder liner varies and depends on the crankshaft rotation angle, engine speed and load, and oil viscosity, and takes values less than 10 µm. It was shown that the maximum wear of the cylinder liner, resulting from the cooperation with the piston rings, occurs in the top dead centre (TDC) area and results from unfavorable (high temperature, low piston speed) operating conditions of these elements. From the extensive literature data cited, it follows that abrasive wear is caused by dust grains of specific dimensions, most often 5–20 µm, the greater the wear the greater the hardness of the grains and the sulfur content of the fuel. At the same time, it was shown that the main bearing, crankshaft bearing, and oil ring experienced maximum wear by a different range of particle size, respectively: 20–40, 5–10, and 20–80 μm. It was shown that the mass of dust that enters the engine cylinders and thus the wear of the components is determined by the concentration of dust, the value of which is definitely reduced by the air filter. However, it was pointed out that the low initial filtration efficiency and the presence of large dust grains in the purified air in the initial period of the filter operation (after replacement of the filter element with a new one) may have an impact on the accelerated wear of mainly (P-PR-CL) association. The next stage of the paper presents the effects of excessive wear of the cylinder liner and piston rings of the engine, resulting from actual vehicle operation and bench tests on the decrease in compression pressure and engine power, increase in the intensity of exhaust gas blow-by into the oil sump and increase in oil consumption and exhaust gas toxicity. This paper addresses the current problem of the effect of engine inlet air contaminants on the performance of the air flow meter, which is an essential sensor of the modern internal combustion engine. The phenomenon of deposition of contaminants (mineral dust, salt, carbon deposit, and moisture) on the measuring element (wire or layer anemometer) of the air flow meter has been analyzed. The empirical results presented show that the mineral dust layer on the measuring element of the air flow meter causes a 17.9% reduction in output voltage, and the dust and oil layer causes a 46.7% reduction in output voltage. This affects the decrease in engine power and exhaust toxicity.
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