Effects of premixed n-heptane from the intake port on the combustion characteristics and emissions of biodiesel-fuelled engines

Abstract

The combustion characteristics and emissions of biodiesel-fuelled direct-injection (DI) compression ignition engines with the addition of n-heptane from the intake port were investigated on a single-cylinder engine. The experimental results revealed that the homogeneous charge compression ignition (HCCI) combustion of the premixed n-heptane had important effects on the overall combustion characteristics and emission levels. The heat release curves exhibited a three-stage combustion mode, which includes the low-temperature reaction (LTR), high-temperature reaction (HTR) of n-heptane, and diffusion burn of biodiesel. On increase in the premixed ratio of the n-heptane, the peak values of both the LTR and the HTR increased linearly. When the overall equivalence ratio is kept constant, the HCCI combustion of premixed n-heptane had a moderate effect on the ignition timing of the biodiesel fuel, and the maximum heat release rate during the third-stage combustion decreased with increase in the premixed ratio. Regarding the regulated emissions, partial substitute of DI biodiesel by port injection of n-heptane caused the carbon monoxide and hydrocarbon emissions to deteriorate in comparison with those of the neat biodiesel engines. For low to medium equivalence ratios, the premixed combustion of heptane resulted in a decrease in the nitrogen oxide (NO x ) emission, but had little effect on the smoke opacity. For a higher equivalence ratio, it was very interesting to find that both the NO x emissions and the smoke opacity were suppressed substantially by an n-heptane premixed ratio of 20-25 per cent.

Influence of biodiesel blends produced in Colombia on a Diesel engine

“…Accordingly, the lack of efectivness on atomization rates has a negative effect on the combustion process and engine performance. This effect was also shown in other investigations on biodiesel blends [20,21].…”

Experimental Study of Autoignition Characteristics of the Ethanol Effect on Biodiesel/n-Heptane Blend in a Motored Engine and a Constant-Volume Combustion Chamber

“…5 And some also use n-heptane as the surrogate of diesel, mixed with the biodiesel. 6,7 Considering that mixing three fuels significantly alters the physicochemical and ignition quality behavior of one single fuel, understanding the mixture autoignition characteristics of such blends will ensure that the fuels will serve well in their application. The onset of combustion in a diesel engine is governed by the ignition delay period between the start of injection (SOI) and start of combustion (SOC), wherein complex fuel-dependent physical and chemical phenomena play a crucial role.…”

“…Many researchers studied biodiesel–diesel-ethanol blends to improve the emission pollutions of diesel engines . And some also use n -heptane as the surrogate of diesel, mixed with the biodiesel. , …”