A novel algorithm is proposed for the automatic segmentation of diesel spray images and the calculation of their macroscopic parameters. The algorithm automatically detects each spray present in an image, and therefore it is able to work with diesel injectors with a different number of nozzle holes without any modification. The main characteristic of the algorithm is that it splits each spray into three different regions and then segments each one with an individually calculated binarization threshold. Each threshold level is calculated from the analysis of a representative luminosity profile of each region. This approach makes it robust to irregular light distribution along a single spray and between different sprays of an image. Once the sprays are segmented, the macroscopic parameters of each one are calculated. The algorithm is tested with two sets of diesel spray images taken under normal and irregular illumination setups.

A study to experimentally analyze the effect of cavitation on the mixing process in diesel nozzles was carried out. The mixing process was studied through the spray cone angle. It was characterized in two different scenarios: with the liquid length (nearly realistic conditions, that is, evaporative but non-reactive spray) and the heat release fraction (fully realistic conditions, that is, evaporative and reactive spray). In both studied scenarios, the increase in spray cone angle caused by the cavitation phenomenon, which leads to a better mixing process, has been confirmed. Nevertheless, when the variations of the effective injection velocity and the spray cone angle obtained by comparing a cylindrical nozzle (i.e. a nozzle that promotes the cavitation phenomenon) with a conical nozzle (i.e. a nozzle that inhibits this phenomenon) were analyzed together, it was found that, for the cases studied here, the mixing process worsens with the cylindrical nozzle.

A methodology to characterise the pressure losses in quasi-steady conditions (i.e. at full needle lift) of common rail diesel injectors was developed. The aim was to quantify the error when experimental results of nozzle internal flow are compared with computational fluid dynamics results, where pressure losses are usually neglected. The proposed methodology is based mainly on experimental tests that are complemented with some approximate calculations, based on the physics of the phenomenon, to take into account the effect of the needle deformation. The results obtained in the work lead to two important conclusions: on the one hand, that it is dangerous to extrapolate results relative to the injection (internal flow, spray atomization, spray penetration, etc.) and combustion processes from low permeability nozzles (e.g. single-hole nozzles) to high permeability nozzles (e.g. multi-hole nozzles), and, on the other hand, that the comparison of these results between experiments and computational fluid dynamics simulations should be carried out carefully, because the pressure losses in the injector can be high under certain conditions. Finally, people working on the study of the injection and/or combustion processes, through experiments or simulations, will find here some interesting information to better know the actual injection pressure to be used in their analysis and/or simulations.

An experimental study was performed to explore the influence of dwell time on the hydraulic interactions between injection events using pilot injection strategy, split injection strategy, post injection strategy and a solenoid diesel injector. To do so, a sweep of dwell time from 0.55 up to 2 ms using all multiple injection strategies and levels of rail pressure, of 80, 100 and 120 MPa, and single level of back pressure, of 5 MPa, was performed. The hydraulic interactions between injection events were characterized through the second injection hydraulic delay and second injection mass in an injection discharge curve indicator equipped with all the components required for its operation and control. In order to define the operating conditions of the multiple injection strategies, to ensure the same injected fuel mass in all cases, the characteristic curves of injection rate for the solenoid diesel injector studied were obtained. The second injection hydraulic delay increases with dwell time values in the range of 0.55–0.9 ms for all multiple injection strategies and levels of rail pressure tested. Conversely, the second injection hydraulic delay decreases with dwell time values higher than 0.9 ms. Moreover, the second hydraulic delay depends mainly on the dwell time and not on the injected fuel mass during the first injection event. The second injection mass increases with dwell values less than 0.6 ms. By contrast, the second injection mass is not significantly affected by that of the first injection at a dwell time higher than 0.6 ms.

Pyrolysis of plastic waste generates alternative fuels that are useful for thermal devices. However, it is the subsequent fractionation process that truly distinguishes itself, refining these fuels to a quality comparable to petroleum derivatives such as diesel and gasoline, thereby making them suitable for direct use in internal combustion engines. This study evaluated the effect on emissions of an internal combustion engine fueled with waste plastic oil diesel-like fuel and its blend with biodiesel. The tests were conducted on-road using a typical light-duty diesel vehicle for passenger or courier transportation. Three tests were carried out, the first one with petroleum diesel (D100) as the reference fuel, the second one with waste plastic oil diesel-like fuel (WPO-DL), and the last with a blend of 80% WPO-DL and 20% biodiesel obtained from waste cooking oil (WPO-DL80WCO20). The main findings were a reduction in the generation of NOx when using WPO-DL. However, using WPO-DL increased the production of CO and HC, attributed to the presence of more heavy hydrocarbons compared to that of D100. Additionally, for the WPO-DL80WCO20 blend under acceleration conditions HC decreased under all acceleration conditions. These findings demonstrate that the distilled fuel obtained from the pyrolytic oil product of non-recyclable plastic waste by conventional methods would contribute to the global energy transition and reduce the presence of tons of non-recyclable plastic waste by traditional methods.