Numerical Analysis of the Effects of Biodiesel Unsaturation Levels on Combustion and Emission Characteristics under Conventional and Diluted Air Conditions

Abstract

This work presents a numerical analysis of spray combustion and associated emissions formation for methyl esters of soybean (SME) and coconut (CME) in a constant volume bomb and a light-duty diesel engine. SME and CME were used to represent biodiesel fuels with high and low unsaturation levels, respectively. In the constant volume bomb, diesel engine-like conditions were used, where two ambient oxygen (O2) levels of 15% and 21% (by mole fraction) were specified to study the effects of exhaust gas recirculation on the combustion and soot formation of biodiesel fuels. As the ambient O2 level increased to 21%, the lift-off length (LOL) was reduced by 25%, while the maximum soot volume fraction (SVF) at quasi-steady state was 4 times higher. The effects of unsaturation levels were next investigated under 21% ambient O2 level. When the unsaturation level was increased, the ignition delay (ID) periods and LOL did not vary significantly as a relative difference of less than 10% was observed between both. A higher local equivalence ratio (φ) and hence maximum SVF were observed in the SME combustion. A higher adiabatic flame temperature (T) of approximately 40 K was also recorded in the SME test case. Additionally, higher soot formation and oxidation rates were found for SME. In the diesel engine cases at 21% ambient O2 level, the φ–T distributions and in-cylinder peak pressures predicted for SME and CME were identical. Meanwhile, the peak soot formation rate predicted for SME was increased by 7% as compared to that of CME. Similarly, the peak soot oxidation due to O2 calculated for SME was 30% higher than that of CME, while the oxidation rates due to hydroxyl (OH) were similar for both fuels. For the tested conditions, the rates of production of acetylene (C2H2) and nitrogen oxides (NO x ) were increased by 43% and 12%, respectively, as a result of the increase in unsaturation level.

Reactor microbiome enriches vegetable oil with n-caproate and n-caprylate for potential functionalized feed additive production via extractive lactate-based chain elongation

“…MCC-enriched oils may also find application as biofuels or biochemicals precursors. For instance, MCC-enriched waste-derived oil may be converted into less polluting biodiesels due to their potential lower unsaturation levels compared to conventional biodiesel [ 64 ]. LCC triglycerides in the enriched oil may be hydrolyzed to convert the resulting LCC and MCC salts into chemicals or aviation fuels through (non-)Kolbe electrolysis [ 65 ].…”

Effect of Olive Mill Wastewaters on Scenedesmus Sp. Growth, Metabolism and Phenols Removal

“…during single supply strategy. As recorded in this Table 3, the dominant fatty acids extracted from Scenedesmus cells grown under 40% OMW and 80% OMW conditions, respectively, are those of the C16 and C18 series (70.96 and 72.34% of the total fatty acids), respectively, which can allow to have a good quality biodiesel [38]. There is no clear effect in the fatty acid pro le as OMW concentration increased, whereas it showed a slightly lower saturated fatty acid content (19.98%) and higher polyunsaturated content (42.82%) under 80% OMUF addition as compared with 80% OMW addition (25.93 and 1.72%, respectively), the best concentration for lipid production.…”

Effect of olive mill wastewaters on Scenedesmus sp. growth, metabolism and polyphenols removal

“…cells grown under 40% OMUF conditions, are those of the C16 and C18 series, which can lead to a good quality biodiesel. 54 The fatty acids profile of Scenedesmus sp. cultivated with 40% OMUF during single-stage cultivation was characterized by an increase of C16:1 from 7.5% to 15.9% and C18:2 from 26.7% to 34.4% and a decrease of C16:0, C18:0 and C18:1 as compared to the control condition.…”