Multipoint ignition by flame dispersion

Abstract

In conventional piston engines exothermic chemical reactions occur in flames that are tightly localized in space. This is a cause of many problems encountered in engine combustion, such as knock and cycle-to-cycle variability. An alternative to the classical combustion process based on the propagation of the flame can be the initiation of exothermic reactions by a set of ignition centers causing multipoint initiation of combustion. This can be achieved by spreading the chemically active hot gases through the combustion chamber. In practice this has been done by combustion-product recirculation or by the use of jets. Numerous investigations have been reported on the combustion system in which a jet of chemically active hot gases is dynamically introduced into the main combustion chamber causing multipoint ignition of a premixed charge. The jet has been generated either by burning a rich mixture in a large prechamber, in a small torch cell, or by the discharge of a relatively large amount of electrical energy in a small cavity to produce a jet of plasma. A way to reduce significantly the energy to generate the plasma jet has been proposed and has proved to be especially advantageous fur burning mixtures near their flammability limits.