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Fossil fuel scarcity, global warming and non-constant energy production through renewable energies (wind turbines and photovoltaic cells for example), lead to investigate innovative energy sources and new ways for energy storage. In the present study, magnesium powder has been considered as a new possible energy source. In order to analyze more deeply the magnesium combustion and the generated by-products, short time stable magnesium/air flames have been realized in a combustion chamber using an oxyacetylene flame for ignition. Sieved magnesium samples with two fractions were combusted: 20-50 µm and 50-70 µm. The power delivered by the Mg/air flame was estimated in the range 3-5 kW. The gaseous emissions (O2, CO2 from oxy-acetylene combustion, NO and NO2) were analyzed with on-line analyzers and the particulate emissions were analyzed with an Electrical Low Pressure Impactor (ELPI).The mass concentration of emitted particles whose size is smaller than 10 µm was proved to be very high (up to 35 g/Nm3) and the emitted particles were mainly bigger than 1 µm (84 to 97 wt%). NOx emissions were higher for the 20-50 µm Mg fraction (NO average of 4300 ±200 mg/Nm 3 ) than for the 50-70 µm Mg fraction (NO average of 1100 ±140 mg/Nm 3 ).

Experimental investigations on the effects of hydrogen addition to spark-ignition (SI) engines running under lean and diluted conditions are presented in this paper. Experiments were carried out in a mono-cylinder SI engine with different rates of nitrogen dilution (0 to 20 per cent by volume in the total mixture) and hydrogen/iso-octane blends (from 0 to 80 per cent by volume in the fuel). The study of the impact of hydrogen addition on combustion characteristics and emissions was performed for two different engine speeds and loads. The equivalence ratio, the rate of dilution, and the intake pressure were varied either separately or simultaneously in order to maintain a constant engine load at a fixed hydrogen fraction in the fuel. The lean and dilution operating limits were also determined for all the isooctane/hydrogen/air/nitrogen mixtures investigated, and results show that these limits are extended only when the hydrogen percentage in the fuel is higher than 40 per cent by volume. At a fixed engine load, hydrocarbon (HC) and CO emissions decrease with an increase in the hydrogen fraction in the intake mixture, while NO x emissions are mainly affected by the equivalence ratio and by the amount of dilution. Pumping losses, combustion efficiency and indicated efficiency are also improved with the addition of hydrogen. High values of indicated engine efficiency with low values of HC, NO x , and CO emissions can be achieved by combining hydrogen addition with lean and/or diluted conditions.

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