Recent studies concluded that the use of ammonia in SI engines is possible thanks to an ignition booster or promoter. In this paper, the improvement of premixed ammonia/air combustion for internal combustion engines is studied as a function of performance and exhaust pollutants in a Spark-Assisted Compression Ignition single-cylinder engine, which supports a higher compression ratio (CR). For the first time, pure NH3 combustion was performed over a large range of engine operating conditions. The study concludes that neat ammonia can be used over a large operating range, here driven by the intake pressure, using a classical ignition device with a CR of 14–17 at 1000 rpm. The comparison with previous data obtained in a current single-cylinder SI engine clearly shows the potential of this engine mode, even for very low loads and various engine speeds (650, 1000, 2000 rpm), in spite of an initial aerodynamic that is not optimized to enhance flame-turbulence interaction. Kinetic simulations provide some explanations about exhaust emission behaviour, especially unburnt NH3, H2, NOx and N2O.
Power integration is a key issue to reduce the volume and weight of electronic devices in power applications. But, transformers produced using classical planar assembly are limited in design. Spark Plasma Sintering (SPS) is a relatively new technology to produce multimaterial compact system with higher density and using lower sintering temperature. The purpose of this study is to manufacture of a cubic-centimeter size transformers for high frequency application using SPS. The prototype presented in this paper is composed of two spiral copper coils separated by an insulated layer and encapsulated in ferrite powder. The assembly is then co-sintered by SPS. The magnetic material used for the transformers is a nickel-zinc based ferrite, with copper substitution to allow sintering at low temperatures. The low conductivity of this mixed-ferrite ensures operation in the frequency range of 1 to 20 MHz of our final system. Computed tomography scanning has been used to optimize the design of the co-sintered structures. Effects of the composition of the ferrite and the sintering temperature on the transformation ratio are discussed. It is shown that a ferrite with very low conductivity is required to ensure galvanic insulation, as there is a direct contact between the copper spirals and the magnetic parts.
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