An Optical Investigation of Combustion on a Double Injection Diesel Engine

抄録

It is well known that diesel knock intensity can be reduced by appropriate double injection. The authors have made an optical and theoretical investigation of the combustion mechanism of the pilot fuel. It is known that the pilot fuel burns with a different mechanism corresponding to the injection timing. In the case of retarded pilot injection, e. g., 30°BTDC or later, the ignited mixture initially burns rapidly with intense luminosity under near-stoichiometric conditions. However, the amount of fuel is so small that pressure rise is not sufficient to cause diesel knock. When the pilot injection timing is earlier, weak luminosity is observed because of the relatively weak mixture and low burning velocity, but the flame has enough energy to ignite the main fuel. When the pilot fuel is injected at the scavenging top dead center, intermediate products which show no luminosity shorten the ignition lag of the main fuel.