Christophe Proust

In this paper, new experimental results describing the shock wave propagation in the open air up to 10 kms away from a detonating charge of hundreds of kgs of ammonium nitrate-fuel oil explosive. About 300 blasts were performed. The raw data for some typical experiments are appended to this article as a supplementary material. The experimental conditions are described in this paper, and a global analysis is proposed comparing the usual blast prediction methods to the experimental results.Measurements reveal a significant discrepancy as compared to the models. A systematic bias is observed and an important scattering the larger, the greater the distance to the explosion. The bias seems mostly due to the shooting conditions and topography whereas the scattering would largely result from atmospheric conditions at distances larger than 1500 m from the explosion pad. To some extent, it might even be concluded that the overpressure at large distances depends much more on the atmospheric conditions than on the explosive charge. However, even having detailed weather conditions at our disposal, the relevant information to account for this could not be clearly identified. From CFD simulations, it seems that the vertical gradient of sound velocity and wind velocity would be the most important aspects. Much more work is required, and it is believed that the present data could help the modelers.

Production of energy from lignocellulosic biomass using internal combustion engines (ICE) is desirable, provided that costs can be reduced. The recalcitrance of lignocellulosic biomass requires additional treatments for second-generation biofuel conversion processes, falling short of sustainability goals and profit margins. Rather than transforming solid biomass to liquid or gaseous fuels through multistep processes, this paper explores the direct use of biomass powder below 200 μm in an engine. Reducing biofuel production to a single milling process offers the chance to downscale biofuel production for implementation at the local level, through standalone or hybrid installations with other renewable energies. In scenarios using intermittent energies such as solar or wind, production of biomass powder can be operated during low demand periods to store surplus energy which can be later used for generating power on demand. To test the feasibility of this concept, four biomasses (rice husk, chestnut wood, pine bark, and wheat straw) were micronised to an average particle size of 20 μm and fuelled in an instrumented ICE. Our results confirm that an ICE can start and run with various biomass types at a wide range of operating regimes without any assistance. During these tests, efficiencies up to 17.5% were observed with powdered rice husk, using an intake temperature of 40 °C. Emissions (CO, NO_x, and SO₂) were found to be within acceptable operating limits of available aftertreatment technologies. This first assessment of the compared combustion behaviour of different biomass powders in ICE highlights the fact that the challenges associated with this alternative biofuel demand a cross-disciplinary approach from research domains such as dust explosion prevention, biomass combustion and engine technology.