Electronic Control System of LED-Induced CNTs Photo-Ignition for Improved Fuels Combustion in Advanced Engines

The use of carbon nanotubes (CNTs) in the combustion and propulsion sector, which is the object of this work, is due to the discovery of photo-ignition properties of such nano-material, when they are exposed to an intense luminous flash [1]. This phenomenon allows obtaining fuels combustion system more efficient and clean (HCCI engine) [2]. Most of the literature studies involve a Xe-lamp to ignite the CNTs mixed with metal catalyst; the use of this light source is not without criticism because it requires very high supply voltages, has an intrinsic mechanical instability, and it can’t work at frequencies required by an automotive engine running [3]. A LED-based ignition system can be considered the optimum solution, because LEDs have high luminous efficiency, higher mechanical stability and for the absence of frequency limitations. In this work, a LEDs-based experimental setup used to perform combustion tests of gaseous fuels, by means of photo-ignition of MWCNTs/FeCp2, has been proposed (Fig. 1). The setup uses a multi-LED ignition-system, placed outside the combustion chamber, convoying the light emitted by each LED source into the chamber by a fiber optic. The electronic section drives and controls the LED sources, synchronizing temporally them with the input of the enriched air-fuel mixture. Moreover, it will also handle and monitor all physical / environmental parameters involved in the combustion process, such as temperature and pressure inside the combustion chamber, etc. In order to obtain a light pulse of controlled duration, a driving and control electronic system was realized (Fig. 2). The white power LEDs (Cree XHP70) were driven by proper LED drivers; to generate a single light pulse, a pulsed signal is applied to the enable control input of each LED driver. This last signal is obtained on PC audio channel by proper LabVIEW application and after conditioning by an interface board. A four LEDs source was used to perform ignition tests on the dry mixtures MWCNTs/FeCp2 to obtain energy density comparable to which obtained with the Xe lamp. In the Figs. 3a and b, the setup used to perform ignition tests on dry mixtures MWCNTs/FeCp2, is shown; the driving and control unit is constituted by four LED drivers, the interface board and the PC with LabVIEW application (Fig. 3a), whereas tests area with the four LEDs source and the power/energy meter (Thorlabs PM100D) equipped with pyroelectric sensor (Thorlabs ES145C) are shown in Fig. 3b. The light source is placed at 1cm at least from the pyroelectric sensor and then from CNTs sample (Fig. 3b). Using this experimental setup, the minimum pulse durations needed to ignite the MWCNTs/FeCp2 samples for the different concentrations by weight, are determined. Known the light source intensity, the minimum ignition energy of the MWCNTs/FeCp2 samples for the considered concentrations, are calculated (Fig. 4).