Diesel engines are the most commonly used internal combustion engines nowadays, especially in European transportation. This preference is due to their low consumption and acceptable driveability and comfort. However, the main disadvantages of traditional direct injection Diesel engines are their high levels of noise, nitrogen oxides (NO x ) and soot emissions, and the usage of fossil fuels. In order to tackle the problem of high emission levels, new combustion concepts have been recently developed. A good example is the premixed charge compression ignition (PCCI) combustion, a strategy in which early injections are used, causing a burning process in which more fuel is burned in premixed conditions, which affects combustion noise. The use of a pilot injection has become an effective tool for reducing combustion noise. The main objective of this paper is to analyze experimentally the pollutant emissions, combustion noise, and performance of a Diesel engine operating under PCCI combustion with the use of a pilot injection. In addition, a novel methodology, based on the decomposition of the in-cylinder pressure signal, was used for combustion noise analysis. The results show that while the PCCI combustion has potential to reduce significantly the NO x and soot emission levels, compared to conventional Diesel combustion strategy, combustion noise continues to be a critical issue for the implementation of this new combustion concept in passenger cars.

Elsevier Bermúdez, V.; Luján, JM.; Pla Moreno, B.; Linares Rodríguez, WG. (2011). Effects of low pressure exhaust gas recirculation on regulated and unregulated gaseous emissions during NEDC in a light-duty diesel engine. Energy. 36(9):5655-5665.

Over recent decades, direct injection diesel engines have become the propulsion systems most commonly used in automotive vehicles in Europe. Their leading position in the European market is due to improvements in performance, driveability and their capacity for facing the increasingly restrictive standards to which are subject. Nevertheless, their main drawbacks are related to the emission levels, the use of fossil fuels and the engine noise. To mitigate the first two problems, alternative fuels are being used in these engines with encouraging results. The impact of these fuels on engine noise might therefore be analyzed in order to evaluate the feasibility of such a solution. In this work the effect of diverse alternative fuels on emissions, performance and engine noise quality was analyzed. Compared with standard diesel fuel, results show a scarce variation of combustion noise quality whereas soot level decreases, NO x emissions increase and specific consumption deteriorates.

Research efforts in the automotive sector focus on developing new combustion concepts for mitigating the emissions of nitrous oxides and soot of conventional Diesel combustion. One of the most promising concept is the Premixed Charge Compression Ignition. In this, the fuel burns in premixed conditions, avoiding the formation of soot whereas nitrous oxides are controlled using large amounts of exhaust gas recirculation. Because of the premixed combustion, high fuelburning velocities are produced, whence combustion noise is deteriorated. In order to mitigate this drawback, different blends of gasoline and Diesel fuels are being considered due to their suitability for this combustion characteristics. The effect of these fuel blends on emissions, performance and engine noise is analysed in this paper with the aim to provide additional knowledge of the fundamental issues of this particular combustion mode. The study also includes sweeps of both the start of injection and the amount of exhaust gas recirculation, in order to evaluate further degrees of freedom in the optimisation of the engine settings. Results show that the consideration of the engine noise together with both performance and emissions, reduces dramatically the margin of variation of the combustion settings, limiting therefore the operation range of the engine.

Context: like many others, today the aeronautical industry has been forced to implement methods to mitigate the damage produced to the environment due to the emission of polluting gases and in doing so, confront the problem of global warming. In this context, research on the use of alternative fuels is of paramount importance, in particular the study of engine performance when using blends of Colombian Biodiesel based on palm oil with Jet A1.Method: as a starting point, we made a review of the state of the art so as to select which engine to study and then the alternative fuels to be used. Simultaneously, Colombian biodiesel based on palm oil was selected, as it has been shown to be a fuel with good performance when it is blended in percentages of 10%, 20% and 50%. Each of the blends were tested in the laboratory to obtain their viscosity, density and calorific values. A spreadsheet program was developed to conduct the analysis, which contemplated the physical properties of mixtures and engine parameters, as well as emissions of nitrous oxides (NOx), atomization and combustion produced by the use of mixtures. The results were compared against those of the Gasturbine simulation softwareResults: CFM 56-5B was chosen as the appropriate engine for the study, because it is currently the most used in the Colombian aeronautical industry. On the other hand, none of the alternative fuel blends generates the same engine performance when using Jet A1. The blends E10 and E20 have a similar behavior, with the novelty of generating less amount of NOx emissions and improving the atomization of the fuel.Conclusions:  When the engine’s performance with conventional fuel is comparing with Biodiesel mixtures, a decrease of the thrust is produced as the percentage of Biodiesel in the mixture increases. Because the mixtures of alternative fuel have a lower calorific value fuel consumption in these cases is always greater. However, when comparing the NOx levels produced, a decrease of this pollutant is observed when using Biodiesel blends. It is worth noting that it is of great interest for future work to evaluate other pollutant emissions and, in turn, the behavior of other types of Biodiesel in jet engines.Language: Spanish.