Relationship between carbon concentration in a fuel and characteristics of flame propagation with a magnitude of ion current

The practicability of using ionization probes for the investigation of fuel consumption in a piston engine is proved in the paper. It is shown that in order to expand the functionality, to increase the reliability of operation and accuracy of the processing of the ionization probe signal it is essential to know the influence of the fuel chemical composition and characteristics of turbulent flame propagation (velocity and width). In this connection, the paper presents theoretical and experimental research of the influence of turbulent flame propagation velocity, the width of the turbulent burning zone, the composition of the fuel-air mixture and the content of carbon in it on the indications of the ionization probe – the ion current. The work carried out resulted in obtaining functional dependence of ion current on carbon concentration in the fuel and characteristics of turbulent flame propagation. Experiments on the engine showed that if the excess air factor is in the range of 0.8 to 1.1 the agreement between the design and experimental values of the ion current in the first and second phases of combustion is over 83 per cent. The results of the work can be used to predict and monitor the propagation velocity and the width of the turbulent flame front in the combustion chamber of an internal combustion engine with the help of an ionization probe.