The influence of fatty acid methyl ester profiles on inter-cycle variability in a heavy duty compression ignition engine

• Published in: Fuel (Guildford) Vol. 116; pp. 140 - 150
• Main Authors: Pham, P.X., Bodisco, T.A., Ristovski, Z.D., Brown, R.J., Masri, A.R.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.01.2014; Elsevier
• Subjects: Alternative fuels; Applied sciences; Biodiesel; Biomass; Blends; Carbon chain length; Compressing; Energy; Energy. Thermal use of fuels; Engines; Exact sciences and technology; Fuels; Ignition; Inter-cycle variability; Kernel density estimation; Methyl alcohol; Natural energy; Peak pressure; Unsaturation degree; Unsaturation degree; Carbon chain length; Kernel density estimation; Biodiesel; Inter-cycle variability; Alternative fuel; Diesel fuel; Fuel cycle; Biofuel; Combustion; Biomass; Oxygen content; Fatty acids; Density; Standards; Heat liberation; Common rail; Particle emission; Compression ignition engine; Fuel mixture; Performance; Fatty acid methyl ester; Methanol
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2013.07.100

•Inter-cycle variations have been tested for biodiesels and their blends with diesel.•Kernel density estimation is used to estimate the key cyclic variation parameters.•Correlations between the inter-cycle variabilities and oxygen ratio are shown.•The biodiesel molecular profiles affect the cyclic variations significantly.•Number of particle per mass unit of biodiesels is much higher than that of diesel. With the advent of alternative fuels, such as biodiesels and related blends, it is important to develop an understanding of their effects on inter-cycle variability which, in turn, influences engine performance as well as its emission. Using four methanol trans-esterified biomass fuels of differing carbon chain length and degree of unsaturation, this paper provides insight into the effect that alternative fuels have on inter-cycle variability. The experiments were conducted with a heavy-duty Cummins, turbo-charged, common-rail compression ignition engine. Combustion performance is reported in terms of the following key in-cylinder parameters: indicated mean effective pressure (IMEP), net heat release rate (NHRR), standard deviation of variability (StDev), coefficient of variation (CoV), peak pressure, peak pressure timing and maximum rate of pressure rise. A link is also established between the cyclic variability and oxygen ratio, which is a good indicator of stoichiometry. The results show that the fatty acid structures did not have a significant effect on injection timing, injection duration, injection pressure, StDev of IMEP, or the timing of peak motoring and combustion pressures. However, a significant effect was noted on the premixed and diffusion combustion proportions, combustion peak pressure and maximum rate of pressure rise. Additionally, the boost pressure, IMEP and combustion peak pressure were found to be directly correlated to the oxygen ratio. The emission of particles positively correlates with oxygen content in the fuel as well as in the air–fuel mixture resulting in a higher total number of particles per unit of mass.