F2008-09-059
Researchers of Influence of Aging Processes on Properties of Rapeseed Oil Methyl Esters and Their Mixtures with Diesel Oil
Fatty acids of methyl esters (FAME) are applied as the fuel in pure form - biodiesel B100, or as addition into diesel oils as the B10 biodiesel, the B20 biodiesel etc. FAME has poor resistance on the oxygenation and changes of other essential parameters during aging which have an essential influence on the NOx emission. This feature causes that biodiesel parameters get worse during storages, distributions and exploitation in vehicles. The change of parameters biodiesel causes not only the worsening of fuel exploitive properties but also increasing of the NOx emission level. Observations on the NOx emission level show that increasing of the NOx emission level holds together with viscosity increasing. Researches with laser-equipment PDPA of the atomizing process showed that with increasing of biodiesel content in fuel the Sauter Diameter (D32) of sprayed fuel is increased. The Sauter Diameter increases with time of aging biodiesel, what can additionally unfavourably influence on the level of emission exhaust gases. Performed research results of samples aging processes of RME accomplishing requirements of the EN 14214 standards, diesel oil accomplishing requirements of the EN 590, base diesel oil and mixtures of base diesel oil and RME containing of 1%, 5% and 20% RME are presented in paper. Determinations of the influence of the fuel kind and the aging process on the acid number, the kinematic viscosity, turbidity temperature, flows and the cold filter blocking of fuel samples were the aim brought over research, as well as the aging RME influence on elastomers comparatively with fresh RME. The process of fuel samples aging was enforced by the sun influence, the elevated temperature and water. Fuel samples were aged in laboratory conditions in 15 and 60 weeks. After that term the changes of investigated properties of fuels with relation to of the same proprieties in initial conditions were determined. Research showed that in spite of the presence of antioxidative additions in RME, RME is characterized in the same conditions more intensive aging than diesel oil both containing antioxidative additions and without ones. Most of all compounds of acid and resin character are created during aging, what causes increasing of the acid number. The highest increasing in acid number value has RME. The fastest RME aging causes high temperature, and, in the second order, the contact with air. An influence of these factors for diesel oil is inverse. In similar conditions aging the increment of value of the acid number RME to containing additions is greater than pure diesel oil and diesel oil with additions. The RME aging (with antioxidative additions) and its mixtures with diesel oils cause only the viscosity increase and practically does not influence on changes of other parameters at low temperature. The water presence intensifies the process of RME aging, especially at the longer contact. The aging RME is more active with relation to of elastomers than fresh RME (of standard parameters). The aging RME has higher about approx. 15-90% (depending on the elastomer kind) increase of mass or volume and up to 15% decreasing of elastomer hardness. An essential new aspect of the paper is relation determine between change of biodiesel properties during aging and the NOx emission level which is connected mostly with viscosity increasing, what causes to increasing of droplets of sprayed fuel unfavourably influencing on the emission level. The counteraction increasing viscosity with additions, as well as the viscosity decreasing is an efficient way decreasing of the NOx emission.
Session: Alternative Fuels I