Evaluation of RME (rapeseed methyl ester) and mineral diesel fuels behaviour in quiescent vessel and EURO 5 engine Luigi Allocca, Ezio Mancaruso * , Alessandro Montanaro, Luigi Sequino, Bianca Maria Vaglieco Istituto Motori e CNR, Napoli, Italy article info Article history: Received 26 May 2014 Received in revised form 15 September 2014 Accepted 19 September 2014 Available online 16 October 2014 Keywords: Biofuel Injection process Diesel engine Pollutant emission Optical diagnostic abstract Alternative diesel fuels for internal combustion engines have grown significantly in interest in the last decade. This is due to the potential benefits in pollutant emissions and particulate matter reduction. Nevertheless at possible increase in nitrogen oxide (NO x ), and almost certainly increase of fuel con- sumption have been observed. In this paper, mineral diesel and RME (rapeseed methyl ester) fuels have been characterized in a non- evaporative spray chamber and in an optically-accessible single-cylinder engine using a Common Rail injector (8 holes, 148  cone opening angle and 480 cc/30s@10 MPa flow number) to measure the spatial fuel distribution, the temporal evolution and the vaporizationecombustion processes. The injection process and mixture formation have been investigated at the Urban Driving Cycle ECE R15: 1500 rpm at 0.2 MPa of break mean effective pressure. Characteristic parameters of the spray like penetration length and liquid fuel distribution have been analysed and they have been correlated with the exhaust gaseous and particulate matter emissions. In the spray-analysis in non-evaporative conditions, short events (pilot) are mostly affected by asymmetries in the fuel distributions with noticeable standard deviations at low injected quantities. In the engine tests, the jets reached immediately the stabilization. A comparative analysis on the liquid phase of the spray, in non-evaporative and evaporative conditions, has permitted to investigate better the mixture formation. Its effect on pollutant emissions has been analysed for both fuels. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction In the last two decades the diesel engine has met the increasing demand of economy/performances of the powertrain conjugated with the legislative requirements of exhaust emission reduction, particularly focused on nitrogen oxides (NO x ) and PM (particulate matter). These results have been achieved thanks to the substantial progresses in the fuel injection equipments (Common Rail) and combustion managing that make large use of the electronic control. First (FAME (fatty acid methyl ester)) and second (Fischer-Tropsch) generation of alternative diesel fuels comply this challenge without any modification with the powertrain, coupling these potential emission reductions to the advantage of biodegradability/non- toxicity of the fuel and the global benefits on CO 2 cycle due to renewable fonts [1e3]. These fuels are generally referred as bio- diesel for diesel engine applications and regulation permits mix- tures up to 20% in volume to mineral diesel fuel. However, some differences appear in the chemical-physical characteristics of biodiesels, with respect to the mineral diesel fuel, that affect the air-fuel mixture preparation and the combus- tion in the engine. The spray characteristics have been widely analysed to study the influence of injection pressure and cylinder backpressure on the fuel penetration [4e8]; moreover attempts in determining the fuel-bulk and droplet fragmentation have been carried out [9]. Some differences in the fuel injection rate have been found resulting biodiesel quantities lower than mineral fuels. This has been related to the different density and viscosity of the fluids [10]. Finally, effects of biodiesels on the injection apparatus have been widely investigated to associate the deposit formation in the injector system to the quality and composition of the fuel [11,12]. These sediments have been observed inside the injector body, on the piston, on nozzle needle but, especially, in the spray-holes resulting in a reduced flow and dispersion modification of the * Corresponding author. Tel.: þ39 081 7177187; fax: þ39 081 2396097. E-mail addresses: l.allocca@im.cnr.it (L. Allocca), e.mancaruso@im.cnr.it (E. Mancaruso), a.montanaro@im.cnr.it (A. Montanaro), l.sequino@im.cnr.it (L. Sequino), b.m.vaglieco@im.cnr.it (B.M. Vaglieco). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2014.09.050 0360-5442/© 2014 Elsevier Ltd. All rights reserved. Energy 77 (2014) 783e790