An investigation into the ICCI mode to low engine load extension and its achievable operational range at different intake pressure

Abstract

In this paper, the effect of biodiesel and butanol direct injection strategies, intake conditions were modulated to extend the ultra-low engine load and optimize the engine performance at different intake pressure in a brand-new dual-fuel combustion mode called intelligent charge compression ignition (ICCI). A four-cylinder, direct injection, turbocharger diesel engine was modified into the ICCI mode on the fourth cylinder to take this experiment. The results indicated that increased butanol energy ratio and retarded biodiesel direct injection timing allowed the engine to achieve high efficiency and stable combustion under the indicated mean effective pressure (IMEP) of 1 bar and 2 bar. The maximum indicated thermal efficiency was above 43% and 44% at the IMEP of 1 bar and 2 bar, respectively. A higher butanol energy ratio and more retarded biodiesel injection timing increased the ignition duration, and shortened the combustion duration, leading to the higher nitrogen oxide (NOx) emissions and lower hydrocarbon and carbon monoxide emissions. The applicable intake pressure for ICCI steady operation could ease the combustion efficiency and adjust combustion phasing, optimizing heat release profiles. The intake pressure shown insignificant effect on the indicated thermal efficiency and pollutant emissions when the engine load increased to the IMEP of 8 bar to 12 bar. However, the NOx emissions were ultra-low when the IMEP was 4 bar to 10 bar for all intake pressure conditions, in which the NOx emissions were less then 40 ppm. The unregulated emissions were further reduced at higher intake pressure, but with an increase of particle matter emissions.