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Ammonia and hydrogen can be produced from water, air and excess renewable electricity (Power-to-fuel) and are therefore a promising alternative in the transition from fossil fuel energy to cleaner energy sources. An Homogeneous-Charge Compression-Ignition (HCCI) engine is therefore being studied to use both fuels under a variable blending ratio for Combined Heat and Power (CHP) production. Due to the high auto-ignition resistance of ammonia, hydrogen is required to promote and stabilize the HCCI combustion. Therefore the research objective is to investigate the HCCI combustion of varying hydrogen-ammonia blending ratios in a 16:1 compression ratio engine. A specific focus is put on maximizing the ammonia proportion as well as minimizing the NOx emissions that could arise from the nitrogen contained in the ammonia. A single-cylinder, constant speed, HCCI engine has been used with an intake pressure varied from 1 to 1.5 bar and with intake temperatures ranging from 428 to 473 K. Stable combustion was achieved with up to 70 %vol. ammonia proportion by increasing the intake pressure to 1.5 bar, the intake temperature to 473 K, and the equivalence ratio to 0.28. From pure hydrogen to 60 %vol. ammonia proportion, the combustion efficiency only lost 0.6 points. Pure hydrogen Indicated Mean Effective Pressure (IMEP) was limited to 2.7 bar to avoid ringing (i.e. too high pressure rise rate) but blended with ammonia the IMEP safely reached 3.1 bar. For pure hydrogen, NOx emissions were below 6 ppm. For hydrogen-ammonia blends, NOx were between 750 and 2000 ppm. Exhaust Gas Recirculation (EGR) operations significantly reduced NOx emissions through a reduced oxygen availability but with a noticeable negative effect on combustion efficiency due to lower in-cylinder temperatures. Moreover, performed simulations showed the production of significant N2O quantities for combustion temperatures under 1400 K. Ammonia showed to be an effective fuel for HCCI conditions and EGR revealed i

Ammonia and hydrogen can be produced from water, air and excess renewable electricity (Power-to-fuel) and are therefore a promising alternative in the transition from fossil fuel energy to cleaner energy sources. An Homogeneous-Charge Compression-Ignition (HCCI) engine is therefore being studied to use both fuels under a variable blending ratio for Combined Heat and Power (CHP) production. Due to the high auto-ignition resistance of ammonia, hydrogen is required to promote and stabilize the HCCI combustion. Therefore the research objective is to investigate the HCCI combustion of varying hydrogen-ammonia blending ratios in a 16:1 compression ratio engine. A specific focus is put on maximizing the ammonia proportion as well as minimizing the NOx emissions that could arise from the nitrogen contained in the ammonia. A single-cylinder, constant speed, HCCI engine has been used with an intake pressure varied from 1 to 1.5 bar and with intake temperatures ranging from 428 to 473 K. Stable combustion was achieved with up to 70 %vol. ammonia proportion by increasing the intake pressure to 1.5 bar, the intake temperature to 473 K, and the equivalence ratio to 0.28. From pure hydrogen to 60 %vol. ammonia proportion, the combustion efficiency only lost 0.6 points. Pure hydrogen Indicated Mean Effective Pressure (IMEP) was limited to 2.7 bar to avoid ringing (i.e. too high pressure rise rate) but blended with ammonia the IMEP safely reached 3.1 bar. For pure hydrogen, NOx emissions were below 6 ppm. For hydrogen-ammonia blends, NOx were between 750 and 2000 ppm. Exhaust Gas Recirculation (EGR) operations significantly reduced NOx emissions through a reduced oxygen availability but with a noticeable negative effect on combustion efficiency due to lower in-cylinder temperatures. Moreover, performed simulations showed the production of significant N2O quantities for combustion temperatures under 1400 K. Ammonia showed to be an effective fuel for HCCI conditions and EGR revealed i

type:Journal Article, A basic approach to blind source separation is to define an index representing the statistical dependency among the output signals of the separator and minimize it with respect to the separator's parameters. The most natural index might be mutual information among the output signals of the separator. In the case of a convolutive mixture, however, since the signals must be treated as a time series, it becomes very complicated to concretely express the mutual information as a function of the parameters. To cope with this difficulty, in most of the conventional methods, the source signals are assumed to be independent identically distributed (i.i.d.) or linear. Based on this assumption, some simpler indices are defined, and their minimization is made by such an iterative calculation as the gradient method. In actual applications, however, the sources are often not linear processes. This paper discusses what will happen when those algorithms postulating the linearity of the sources are applied to the case of nonlinear sources. An analysis of local stability derives a couple of conditions guaranteeing that the separator stably tends toward a desired one with iteration. The obtained results reveal that those methods, which are based on the minimization of some indices related to the mutual information, do not work well when the sources signals are far from linear

type:Journal Article, Numerical instability occurs in an analysis of a vibration with magnetic damping, or an electromagnetic and structural coupled problem. In this paper, the numerical instability of the coupled analysis is examined by the finite element in time. It is confirmed that the simultaneous method is unconditionally stable even if the magnetic field and the time increment are large. For the staggered method, we obtain the conditions where the numerical instability occurs., source:DOI:10.1109/20.877694

type:Journal Article, Numerical instability occurs in analyses of an electromagnetic and structural coupled problem or a magnetic damping problem when the matrix equations of structure and eddy current are solved alternately. In this paper, an augmented staggered method is proposed for the coupled analysis. The stability of this method is demonstrated for the magnetically damped vibration by finite element analyses. According to the characteristic equation obtained from the recurrence relation of this time integration scheme, it is confirmed that this method is unconditionally stable for the intensity of magnetic field and the size of time increment.

Nanocomposites based on polypropylene (PP) and unmodified Montmorillonite were prepared using a novel elaboration route based on a water-assisted extrusion process. Unmodified Montmorillonite, high shear compounding together with injection of aqueous suspension and reactive processing technology were used. Different aqueous suspensions containing cationic or anionic surfactants, and a compatibilizer (PP-g-MA) were injected during extrusion to promote clay dispersion. For a comparison purpose, a commercial PP/clay masterbatch was melt mixed to PP. Structural, morphological, and rheological characterizations indicate clearly that the cationic suspensions ease the dispersion of clay platelets in the PP matrix. No full exfoliation is, however, obtained, and the system remains still less homogeneous than the nanocomposite based on the commercial masterbatch. Nevertheless, mechanical and thermal characterizations of the nanocomposites based on cationic surfactants demonstrate the efficiency to disperse clay in the polymer matrix, and the effect on the ductility compared to usual PP nanocomposites is promising. POLYM. ENG. SCI., 49:2276-2285, 2009. (C) 2009 Society of Plastics Engineers

This paper presents the theoretical study of the heat transfer and friction characteristics in the natural convection film boiling on an inclined surface and a sphere, the forced convection film boiling over a horizontal plate, and the stagnation flow film boiling when radiation is appreciable. The boiling liquid is either at the saturation temperature or subcooled. The two phase flow and heat transfer problems have been formulated exactly within the framework of boundary layer theory with the consideration of the shear stress and vapor velocity at the liquid-vapor interface. Through the use of the similarity transformation expressions are obtained to determine the vapor film thickness, skin friction, and heat transfer rate. It is disclosed that the presence of surface radiation results in an increase in the heat transfer rate and a decrease in the skin friction.