Crankcase gaseous and particle emissions in common rail diesel engine

Abstract

In this study, the crankcase gas temperature, flow rate, gaseous emissions (NOx, CO and HC) and particle emissions (particle size distribution, number and mass concentration, geometric mean diameter) compared with tailpipe are investigated in a light-duty common rail diesel engine. It is shown that the emissions from the crankcase are mainly affected by the second in-cylinder pressure peak. The crankcase gas temperature varies between 52 °C and 68 °C, and the crankcase gas flow rate slightly increases with load and speed but does not vary much with injection timing. The CO emission from crankcase is about 2%−5% of that from tailpipe, the NOx emissions are only about 1% and the HC emissions are more than 10%. The blow-by gas percentage is 10−8 order and reduces with heavier engine load and faster engine speed. The blow-by HC emission percentage varies from 5% to 35%. As engine load is increased and engine speed is decreased, the nuclei mode particles of crankcase reduce and the accumulation mode particles increase. Furthermore, the particle total number concentration increases with load but decreases with speed and retarding injection timing. The total mass concentration increases with load but rises and falls with speed and injection timing. The crankcase particle geometric mean diameter based on mass is nearly twice larger than that of tailpipe, while the ones based on number are rarely different except the higher load.

Particle Number Measurements Directly from the Tailpipe for Type Approval of Heavy-Duty Engines

“…Interestingly, the levels >23 nm and the sub-23 nm fraction measured by the two concepts of proportional and fixed dilution were the same with and without the crankcase ventilation connected to the tailpipe. This can be explained by the size distributions typically found at the crankcase ventilation, which have the majority of particles >10 nm, and in most case even above 30 nm [31][32][33].…”

Assessment on the consequences of injection strategies on combustion process and particle size distributions in Euro VI medium-duty diesel engine

“…23 These particles are mainly agglomerated of soot primary particles, on whose surface there is volatile material which is absorbed. 24,25 The high combustion temperature and rich equivalence ratio zones are the two main factors that favor the formation process of soot particles and can occur both in premixed and non-premixed combustion. The formation of the first precursors and their evolution to the final solid particles is mainly based on the following steps: pyrolysis, nucleation, surface growth, agglomeration and oxidation.…”