A study of ignition discharge parameters effects on homogeneous mixtures combustion in engine

The enhancement of the ignition discharge parameters has been proved as an efficient means to control homogeneous lean combustion, but its effects on the burning stages is still controversial. This work presents the results of a study about the effect of a moderate enhancement of the ignition systems on lean homogeneous mixtures combustion in a conventional engine. Three ignition systems were compared: a standard inductive system, (M1) a long duration glow discharge ignition system (M2) and a capacitor discharge system (M3). Effects on combustion, over a wide range of operating conditions were examined, based on the engine outputs and heat release analysis. Durations of the flame development stage and rapid burning stage were correlated to give a measure of the strength of the relationship between them. It was found that a positive influence on combustion efficiency and stability is exercised only at engine idle and light loads, M3 being the most efficient. At high load of the engine, the difference between M3 and M2 almost disappeared and in general, the influence of an increased energy and/or power of the electrical discharge on the engine outputs became insignificant. It was confirmed that the main effect of an increased power or energy of the spark appears on the flame development stage; the influence on the rapid burning stage is generally weak, and is associated with lean mixtures and delayed phasing of combustion process within the engine cycle

On the possible pyrochlore to aurivillius phase transition in the complex oxide CaCd2Bi2Nb4O15

The sample CaCd2Bi2Nb4O15 was synthesised by the standard ceramic method, starting from a mixture of oxides heated up to 1250°C. The chemical composition indicate that the oxide could have an Aurivillius or a substituted pyrochlore structure. The X-ray diffraction and IR spectra suggest a phase transition from pyrochlore, at -196°C, to Aurivillius at room temperature. The DSC analyses performed in the temperature range 20-400°C did not evidenced major phase transitions for the material

Corrosion behavior of some timonb alloys in ringer solution

International audienceThe aim of this study was to investigate the influence of different process parameters as chemical composition, the pH value and immersion time on the corrosion of the some TiMoNb alloys, using different electrochemical techniques such as: cyclic voltammetry, open circuit potential (OCP) measurement, polarization curves and electrochemical impedance spectroscopy (EIS). The alloys were analyzed in the natural pH of the Ringer solution, but also with an acidic modification of the solution (ph = 4) and a basic modification (ph = 8). The more acidic values of pH, the more evident are differences between corrosion behavior of titanium-based alloys depending on their chemical compositions and immersion times. © 2020 SYSCOM 18 S.R.L.. All rights reserved