Abstract
A major challenge for internal combustion engines (ICEs), and diesel engines, in particular, is the reduction of exhaust emissions, essentially nitrogen oxides (NOx) and particulate matter (PM). In this regard, the potential of LPG-diesel blends was evaluated in this work. The LPG and diesel blends were externally prepared by exploiting their perfect miscibility at high pressures. Two diesel-LPG mixtures with 20% and 35% by mass LPG concentrations were tested. In terms of spatial and temporal evolution, the spray characterization was performed for the two blends and pure diesel fuel through high-speed imaging technique. The combustion behavior, engine performance and exhaust emissions of LPG-diesel blends were evaluated through a test campaign carried out on a single-cylinder diesel engine. Diesel/LPG sprays penetrate less than pure diesel. This behavior results from a lower momentum, surface tension and viscosity, of the blend jets in comparison to diesel which guarantee greater atomization. The addition of LPG to diesel tends to proportionally increase the spray cone angle, due to the stronger turbulent flow interaction caused by, the lower density and low flash-boiling point. Because of improved atomization and mixing during the injection phase, the blends have shown great potential in reducing PM emissions, without affecting engine performance (CO2 emissions). The addition of LPG resulted in a significant smoke reduction (about 95%) with similar NOx emissions and acceptable THC and CO emissions. Furthermore, the low cetane number (CN) and high low-heating value (LHV) ensuring leaner air-fuel mixture, and improvements in terms of efficiency, particularly for a blend with a higher concentration of LPG.
Highlights
Any combustion process strongly depends on the fuel properties, as are emissions, which directly impact the environment
With its methodology and analysis conducted, the present study aims to cover the information and the scientific gap with what is present in the literature
The experimental results were divided into two paragraphs: optical characterization of the spray in the different injection conditions and the combustion analysis in terms of engine performance and gaseous emissions employing the blends
Summary
Any combustion process strongly depends on the fuel properties, as are emissions, which directly impact the environment. (LPG)-diesel blends, exploiting the potential of such fuel, such as high efficiency and low emission values of nitrogen oxides (NOx) and particulate matter (PM) [5] This new concept consists of the injection of the LPG-diesel blend (external mixture formation) directly into the combustion chamber during the engine cycle’s high-pressure phase. LPG can provide more flexibility for practical automotive applications as it is easier to manage in terms of storage and it can be stored in a liquid state at a pressure relatively lower than that of natural gas [15] It guarantees a cooling effect of the combustion chamber thanks to evaporation’s latent heat, which allows to increase the power and decrease the exhaust emissions [16]. The information obtained from the spray characterization supports the tests on the single-cylinder, as they provide fundamental information on the spray quality, which strongly affects combustion and emissions
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