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In this article, two of the most used methods for diesel spray macroscopic characterization are presented; the first one is the likelihood ratio test method (LRT) and the second one is the Otsu's thresholding method (OTM). Both methods are applied to different diesel sprays visualized in a high‐pressure nitrogen chamber obtaining better results with the LRT in terms of both contour determination and coherence of the results. Finally, the influence of the algorithm used for the segmentation on the macroscopic characterization measurements is observed.

This paper describes a particular procedure, based on ASTM D7214 and ASTM E 2412, which has been defined to improve oil oxidation quantification in used engine oils. Taking into account typical problems that can be found in this type of samples, thermal oxidation and fuel dilution, response on FT-IR spectra has been analyzed considering also the effect of oil formulation. Two special zones have been considered inside the typical wave number range for oxidation quantification, where those problems can be detected and assessed more easily. Zone A between 1,725 cm , where esters as main products for detection of fuel dilution problems when diesel engine is operating with biodiesel.

Injection rate shaping is one of the most attractive alternatives to multiple injection strategies; however, its implementation has been for long time impeded by limitations in the injector technology and therefore, the experimental information available in the literature about this topic is lacking.In this work, a novel prototype common-rail injector featuring direct control of the nozzle needle by means of a piezo-stack (direct-acting) allowed a fully flexible control on the nozzle needle movement and enabled the implementation of alternative injection rate shapes typologies. This state of the art injector, fitted with a 7-hole nozzle, was tested at real engine conditions studying the spatial-temporal evolution of CH* and OH* chemiluminescence intensity produced by the fuel combustion. A wide test matrix was performed in an optically accessible hot-spray test rig to understand the influence that partial needle lift and alternative injection rate shapes have on the Diesel ignitionThe results showed that alternative injection rate profiles have a substantial impact on the ignition event affecting the premixed phase of the combustion and the location where the ignition takes place. Moreover, the results proved that the modifications in the internal flow caused by the partial needle lift are reflected on the ignition timing: although partial needle lift and injection pressure have similar effects on the mass flow rate, in the first case the ignition delay is reduced, while in the second the combustion is delayed as a consequence of a different spray development. IntroductionFuel-air mixing process, combustion and emission phenomena are necessarily linked together in direct injection Diesel engines [1][2][3][4][5]. In a scenario where the global emission standards require higher engine performances in terms of combustion efficiency and emissions reduction, all the efforts by the engine community to improve the understanding of the fuel atomization, spray development and combustion are largely justified.Over the past decades, many studies have been carried out to develop a better understanding of the mixing process [6][7][8] and of the fuel ignition [9][10][11][12]. Experimental facilities, such as optically accessible engines [13] and test rig cells [11,14] combined with imaging techniques [5,15], have become the most common tools used in spray research. Throughout the years, the efforts put in place in these studies generated an accurate and deep understanding of the injection combustion event in Diesel engines.On the other hand, several activities have been performed to advance the flexibility of the fuel injection system, achieving significant improvements [2]. Most of these systems are operated with electro-hydraulic actuation, where the fuel injector is activated using either a solenoid or a piezo-stack; however, the opening of the injector itself is produced by the pressure difference at the two sides of the needle limiting the injection control to an on-off mode. As a consequence of that, multiple in...

Low viscosity engine oils (LVO) are considered key contributor for improving fuel economy in internal combustion engines (ICE). Attending that the use of LVO could imply a variation in tribological states found in ICE, this work's aim is to test LVO in real fleet, with emphasis on engine wear and oil key performance indicators. This test comprised 39 buses, two engine technologies and four different lubricants. For each sample, the elemental composition of the wear debris by ICP-AES and HTHS viscosity of the oil were measured among other properties. The results showed that, with a correct oil formulation, there is no significant difference when using LVO in terms of engine wear, HTHS viscosity variation and oil consumption.

ElsevierMacian Martinez, V.; Serrano Cruz, JR.; Dolz Ruiz, V.; Sánchez Serrano, J. (2013 AbstractThis article describes a methodology for the optimization of a bottoming cycle as a waste heat recovering system in vehicles. The methodology is applied to two particular cases in order to evaluate the preliminary energetic and technical feasibility of the implementation of a bottoming cycle in a heavy duty diesel (HDD) engine considering two different criteria. Initially, a study of the different waste heat sources of the engine is described. In this study, the power and exergy of each heat source is quantified, in order to evaluate which sources are suitable to be used in the bottoming cycle. The optimum working fluids to run the cycles are selected (water and R245fa). Then, the ideal Rankine cycle is optimized for the two different working fluids and different sets of heat sources (all the available heat sources and the sources with high exergy respectively) throughout the engine operating range, reaching a maximum improvement of 15 % of the fuel consumption of the engine. Later, a study of the minimum temperature difference between the hot and cold flow of the heat exchangers is described. The improvements in fuel consumption and the size of the installed heat exchanger are related to this temperature difference. Finally, the non-ideal behavior of the machines (pump and expander) is analyzed, obtaining a maximum improvement of 10 % in brake specific fuel consumption (bsfc).