Impact of biodiesel fuel on cold starting of automotive direct injection diesel engines

The use of biodiesel fuels in diesel engines is gaining attention as a promising solution to control CO2 emissions. Great research efforts have been carried out to identify the impact of biodiesel physical and chemical properties on engine systems and processes. Most of these investigations were performed in warm conditions, but the suitability of biodiesel for starting the engine at under-zero ambient temperatures has not widely evaluated. The surface tension and the viscosity of biodiesel fuels are higher compared to those of standard diesel and, in cold conditions, these differences become critical since the injection fuel rate is largely affected and consequently the combustion process can be deteriorated. In order to improve its flow characteristics at cold temperatures and make them more suitable for low temperatures operation, additives are used in biodiesel fuels. In this paper the suitability of different biodiesel fuels, with and without additives, for cold starting of DI (direct injection) diesel engines has been evaluated. The results have shown that the engine start-ability with pure biodiesel fuels can be largely deteriorated. However, using diesel/biodiesel blends the start-ability of the engine can be recovered with the additional benefit of reducing the opacity peak of the exhaust gasesBroatch Jacobi, JA.; Tormos Martínez, BV.; Olmeda González, PC.; Novella Rosa, R. (2014). Impact of biodiesel fuel on cold starting of automotive direct injection diesel engines. Energy. 73:653-660. doi:10.1016/j.energy.2014.06.062S6536607

Characteristics of LPG-diesel dual fuelled engine operated with rapeseed methyl ester and gas-to-liquid diesel fuels

AbstractA Liquefied Petroleum Gas (LPG)-diesel dual fuelled combustion experimental study was carried out to understand the impact of the properties of the direct injection diesel fuels, such as rapeseed methyl ester (RME) and gas-to-liquid (GTL), on combustion characteristics, engine performance and emissions. The experimental results showed that up to 60% of liquid fuel replacement by LPG was reached while keeping engine combustion variability within the acceptable range and obtaining clear benefits in the soot-NOx trade-off. However, the amount of LPG was limited by adverse effects in engine thermal efficiency, HC and CO emissions. LPG–RME showed a good alternative to LPG-diesel dual fuelling, as better engine combustion variability, HC, CO and soot behaviour was obtained when compared to the other liquid fuels, mainly due to its fuel oxygen content. On the other hand, NOx emissions were the highest, but these can be balanced by the application of EGR. LPG–GTL dual fuelling resulted in the highest NOx emissions benefit over a wide range of engine operating conditions. The high cetane number and the absence of aromatic of GTL are the main parameters for the more favourable soot-NOx trade-off compared to LPG–ULSD (ultra low sulphur diesel) dual fuelling

Impact of Fischer Tropsch and biodiesel fuels on trade-offs between pollutant emissions and combustion noise in diesel engines

[EN] Over recent decades, direct injection diesel engines have become the propulsion systems most commonly used in automotive vehicles in Europe. Their leading position in the European market is due to improvements in performance, driveability and their capacity for facing the increasingly restrictive standards to which are subject. Nevertheless, their main drawbacks are related to the emission levels, the use of fossil fuels and the engine noise. To mitigate the first two problems, alternative fuels are being used in these engines with encouraging results. The impact of these fuels on engine noise might therefore be analyzed in order to evaluate the feasibility of such a solution. In this work the effect of diverse alternative fuels on emissions, performance and engine noise quality was analyzed. Compared with standard diesel fuel, results show a scarce variation of combustion noise quality whereas soot level decreases, NOx emissions increase and specific consumption deteriorates. (C) 2013 Elsevier Ltd. All rights reserved.This work has been partially supported by Ministerio de Educacion y Ciencia through grant No. TRA2006-13782. L.F. Monico holds the grant 2009/003 from Santiago Grisolia Program of Generalitat Valenciana.Torregrosa, AJ.; Broatch, A.; Plá Moreno, B.; Mónico Muñoz, LF. (2013). Impact of Fischer Tropsch and biodiesel fuels on trade-offs between pollutant emissions and combustion noise in diesel engines. Biomass and Bioenergy. 52:22-33. https://doi.org/10.1016/j.biombioe.2013.03.004S22335

Structural and Energetic Trends of Ethylene Hydrogenation over Transition Metal Surfaces

Density functional theory calculations are used to investigate the catalytic hydrogenation of ethylene to ethane over a wide range of transition metal (TM) surfaces. Assuming the Horuiti-Polanyi mechanism, the enthalpies of adsorption, surface diffusion, and hydrogenation barriers are examined over close-packed surfaces of Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au. Special attention is given to the effects of ethylene and hydrogen coverage on the reaction pathway and activation energies. The previously suggested importance of the balance between di-s and p adsorption modes is reinvestigated, and most metals are found to exhibit a preference for the p state. Hydrogen coverage is found to control the reactant stability and promote a surface distortion which facilitates the hydrogen addition reaction. For all TMs, the calculated activation energies are low and span a narrow range