Characterisation of soot agglomerates from engine oil and exhaust system for modern compression ignition engines

Fayad, Mohammed A.; Martos, Francisco J.; Herreros, José Martín; Dearn, Karl D.; Tsolakis, Athanasios

doi:10.1177/14680874231188487

Cited by 1 publication

(1 citation statement)

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“…Oil droplets of different size can be produced in several ways: due to the rotation of crankshaft and other engine components [8][9][10]; due to high flow rates of gas over the lubricant film around the piston ring gaps [11][12][13]; due to air flow through the piston rings and liner interface [14]; due to oil accumulation and blow-off from oil drain holes and the piston skirt [15]; due to the condensation of oil vapor in cool regions of the crankcase [16][17][18][19]; etc. The blow-by gases are the gases leaking to the crankcase mainly from the combustion chamber through piston rings and defects in the stuffing box mostly during the highpressure combustion phase [20]. Other sources of blow-by gases are leaky valve stems, turbocharger, etc.…”

Section: Introductionmentioning

confidence: 99%

Crankcase Explosions in Marine Diesel Engines: A Computational Study of Unvented and Vented Explosions of Lubricating Oil Mist

Ivanov,

Frolov,

Semenov

et al. 2023

JMSE

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Accidental crankcase explosions in marine diesel engines are presumably caused by the inflammation of lubricating oil in air followed by flame propagation and pressure buildup. This manuscript deals with the numerical simulation of internal unvented and vented crankcase explosions of lubricating oil mist using the 3D CFD approach for two-phase turbulent reactive flow with finite-rate turbulent/molecular mixing and chemistry. The lubricating oil mist was treated as either monodispersed with a droplet size of 60 μm or polydispersed with a trimodal droplet size distribution (10 μm (10 wt%), 250 μm (10 wt%), and 500 μm (80 wt%)). The mist was partly pre-evaporated with pre-evaporation degrees of 60%, 70%, and 80%. As an example, a typical low-speed two-stroke six-cylinder marine diesel engine was considered. Four possible accidental ignition sites were considered in different linked segments of the crankcase, namely the leakage of hot blow-by gases through the faulty stuffing box, a hot spot on the crankpin bearing, electrostatic discharge in the open space at the A-frame, and a hot spot on the main bearing. Calculations show that the most important parameter affecting the dynamics of crankcase explosion is the pre-evaporation degree of the oil mist, whereas the oil droplet size distribution plays a minor role. The most severe unvented explosion was caused by the hot spot ignition of the oil mist on the main bearing and flame breaking through the windows connecting the crankcase segments. The predicted maximum rate of pressure rise in the crankcase attained 0.6–0.7 bar/s, whereas the apparent turbulent burning velocity attained 7–8 m/s. The rate of heat release attained a value of 13 MW. Explosion venting caused the rate of pressure rise to decrease and become negative. However, vent opening does not lead to an immediate pressure drop in the crankcase: the pressure keeps growing for a certain time and attains a maximum value that can be a factor of 2 higher than the vent opening pressure.

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