In this paper, a complete analysis of the injection system behaviour and the air-fuel mixing process when using different diesel-RME blends (biodiesel percentages of 5%, 30% and 100%) was carried out. For this purpose, the mass flow rate and the momentum flux were measured to characterize the hydraulic behaviour of a standard common-rail injection system with the three different fuels. The tests were developed with long injection pulses, in order to achieve quasi-steady conditions. From this analysis, the following conclusions can be drawn. (1) Despite the fact that biodiesel is a fuel of higher density, the mass flow rate measurements obtained are markedly similar, and only slight differences are found for the pure RME fuel. (2) As seen before in the literature, the discharge coefficient has an asymptotic behaviour with respect to the Reynolds number, increasing as the Reynolds number becomes higher. Because of their higher viscosities, blends with a higher percentage of biodiesel show lower values of the Reynolds number for the same pressure conditions, so that the discharge coefficient is significantly lower, especially at low injection pressures. The effect of the discharge coefficient compensates for the effect of the density, leading to similar stationary mass flow rates, as stated before. (3) The measured momentum fluxes are similar for the three fuels, as was seen with the mass flow rates. As a consequence, similar outlet effective velocities were also found. Together with the hydraulic characterization, spray visualization tests were developed for several conditions. It can be immediately seen that blends with a low percentage of RME behave similarly, while pure biodiesel shows a significantly higher spray penetration and a smaller spray angle. This is an indicator of a less efficient air-fuel mixing process, probably owing to poorer atomization of the fuel, as introduced in previous studies. Furthermore, the turbulent spray theory was used to estimate the characteristic mixing lengths and times for the tested conditions. Higher values of these parameters are obtained for the pure RME fuel, while B5 and B30 behave similarly.
Consequences of using biodiesel on the injection and air-fuel mixing processes in diesel engines
Folgen der Biodiesel-Anwendung bei der Einspritzung und Gemischbildung in Dieselmotoren
2013
12 Seiten, 16 Bilder, 1 Tabelle, 30 Quellen
Aufsatz (Zeitschrift)
Englisch
Consequences of using biodiesel on the injection and air–fuel mixing processes in diesel engines
SAGE Publications | 2013
|Consequences of using biodiesel on the injection and airfuel mixing processes in diesel engines
Online Contents | 2013
|Consequences of using biodiesel on the injection and air-fuel mixing process in diesel engines
Kraftfahrwesen | 2013
|Fuel Injection in Diesel Engines
SAGE Publications | 1985
|Fuel Injection of Diesel Engines
Emerald Group Publishing | 1931
|