Abstract
The classical ignition for internal combustion motors uses switch and an ignition coil that multiply the car battery voltage 12-13 v up to few tenths of thousands volts in order to initiate the spark between the spark-plug electrodes. The timing of the ignition spark must be correlated and synchronized with the piston position into the motor cylinder. The development of an electronic ignition system for internal combustion motors, clean and efficient, requires a fast and complete burn of the poor combustion mixture at high pressure. The ignition sparks provided by the classical spark plug do not always assure a fast and complete combustion of the mixture hydrocarbon-air.
The previous studies have demonstrated that a reducing of pollutant emissions of the motors (HC, CO, NOx) can be obtained by using a low concentration of hydrocarbons in the mixture with air, which implies a lower consumption of fuel.
In order to improve the quality of the combustion a lot of technical solutions have been found to be effective, among which on can mention: ignition in a burned gases, Pulse Jet Combustor, multi-electrode spark plug, pulsed Laser ignition, Corona and Glidarc discharges, etc.
Another solution have been proposed by Nakamura which uses more ignition points for a cylinder equipped with several classical spark plugs. He noticed that the combustion cycle evolves faster, the compression ratio of the motor increase and the poor mixture of hydrocarbons leads to a decreasing of some pollutants and in the same time a higher efficiency of the combustion.
Taking into account the principles mention above three ignition systems have been proposed and tested in a high pressure (10 bar) air reactor:
- the double spark system that used two simultaneous sparks generated by pulsed a high voltage power supply, which have been tested and analyzed from electrical and optical point of view;
- the DBD volumetric discharge system that use the propriety of this type of discharge to generate more plasma channels, therefore a higher homogeneity of the plasma;
- the gliding arc discharge system, which permits a simplification of the ignition system and a reducing of the electrical insulation level.
The experimental tests and analyze have demonstrated that the ignition devices proposed above are applicable in real conditions of functioning of a one cylinder motor. The research proposed refers to the testing, validation and implementation of an ignition device for an internal combustion motor in order to increase the rapidity and the quality of the fuel combustion, therefore the reducing of pollutant emissions. The method consists in the generation of an electrical discharge between the spark plug electrodes able to assure a larger and more homogenous volume of the plasma in the cylinder. Among the principles mention above the first one has been proved to be more effective and easier to set up from a technical point of view. The two ignition sparks are obtained by interposing between the electrodes of a classical spark plug of an auxiliary electrode. The testing set up of two-spark plug required a pulsed power supply that use an ignition coil driven by a micro system with AT89S52. The power supply used for the experiments permitted the shift control of the pulses and therefore the possibility to control the ignition timing of the combustion process. The experiments done in a high pressure chamber with air showed that the two sparks breaks down at a time interval of hundreds of nanoseconds and their total length have been about 2 mm.
The ignition system was tested on a mono-cylinder 4 times motor aiming the combustion and mechanical parameters analysis. Different types of pulses was tested in order to adapt the ignition timing to the mechanical parameters of the motor. The combustion was analyzed quantitative and qualitative as well.
Function on the results to be obtained the research team is looking forward to apply for a patent. On can mention that the ignition system proposed can be applicable in other domains than automotive. The bilateral project aim to conclude and develop a previous research, with the possibility of a technological transfer and involved not only senior researcher but also young graduated students.
