Thermodynamic analysis of working process effective indicators of a diesel engine with an open and closed crankcase ventilation system

Introduction (problem statement and relevance). This article provides up-to-date information analysis of the crankcase gases bypass effect from the crankcase ventilation system to the compression ignition engine intake. The paper considers the information on the variants of the crankcase ventilation systems of modern engines. The article reveals the necessity to analyze the engine working process at the design and development stage of a closed crankcase ventilation system. The legislative requirements for the implementation of the ventilation system to ensure safe environmental performance have been indicated. The purpose of the study was to assess both open and closed ventilation system effect on the crankcase space indicators, in particular, on the average specific fuel consumption, with reference to a high-performance automobile engine with compression ignition.Methodology and research methods. Theoretical and computational studies were carried out with the help of mathematical statistics and thermodynamics methods in a one-dimensional setting. The verification of the calculations reliability was carried out by comparing the simulation data and the results the internal combustion engine experimental studies.Scientific novelty and results. A thermodynamic model of a high-performance automobile engine compression ignition V8 CHN 12/13 with an open and closed ventilation system of the crankcase space has been developed. The model made it possible to evaluate the effect of crankcase gases bypass back to the engine cylinder intake.Practical significance. The developed thermodynamic models confirmed the insignificant effect on the working process of the V8 CHN 12/13 engine by bypassing crankcase gases back to the cylinder inlet.

On Blow-by Aerosol Sources in a Single-Cylinder Crankcase Environment

Crankcase aerosol contributes to the particulate matter (PM) emissions of combustion engines equipped with an open crankcase ventilation system. In case of closed crankcase ventilation, the aerosol forms deposits that diminish engine efficiency, performance, and reliability. Such issues are best avoided by highly efficient filters combined with in-engine reduction strategies based on a quantitative understanding of aerosol sources and formation mechanisms in a crankcase environment. This paper reports key findings from a study of aerosol spectra in the range of 0.01 μm to 10 μm obtained from a 1.3-L single-cylinder engine under well-defined conditions. Supermicron particles were formed mainly by cooling jet break-up when the piston was positioned in TDC, while at BDC aerosol generation decreased by about 90 % because the oil jet was short and thus stable. Motoring the engine yielded an additional peak around 0.7 μm. It is associated with oil atomization at the piston rings and increased strongly with cylinder peak pressure. No significant contribution of the bearings could be identified at peak pressures below 116 bar. Engine speed had only a minor effect on aerosol properties. Operating the engine in fired mode increased the submicron aerosol concentration substantially, presumably because high(er) peak pressures boost aerosol generation at the piston rings, and because additional particles may have formed from recondensing oil vapor generated at hotspots. Soot or ash aerosols could not be identified in the crankcase aerosol, because they may have been integrated into the bulk oil.

Liner Design to Reduce Unburned Hydrocarbon Exhaust Emissions

Large natural gas engines that introduce premixed fuel and air into the engine cylinders allow a small fraction of fuel to evade combustion, which is undesirable. The premixed fuel and air combust via flame propagation. Ahead of the flame front, the unburned fuel and air are driven into crevices, where conditions are not favorable for oxidation. The unburned fuel is a form of waste and a source of potent greenhouse gas emissions. A concept to vent unburned fuel into the crankcase through built-in slots in the liner during the expansion stroke has been tested. This venting process occurs before the exhaust valve opens and the unburned fuel sent into the crankcase can be recycled to the intake side through a closed crankcase ventilation system. The increased communication between the cylinder and the crankcase changes the ring pack dynamics, which results in higher oil consumption. Oil consumption was measured using a sulfur tracer technique. Careful design is required to achieve the best tradeoff between reductions in unburned hydrocarbon emissions and oil control.