Ignition Quality of Diesel Fuels as Expressed in Cetene Numbers 320007
THE paper is an account of some further experiences and views on the subject of ignition in oil engines, which, with the advent of the high-speed Diesel engine, has received much attention of late. The Delft Engine Laboratory of the Royal Dutch Shell Group has been working on oil-engine fuels for nearly four years, with the aid and assistance of all the group's chemical and physical specialists. It had already been working on ignition problems before the high-speed engine was introduced, these problems belonging to a continuous series. Though ignition problems have become of paramount importance in present-day high-speed engines, they have always played a certain rôle with certain fuels also in low-speed engines which were not sufficiently recognized.
After discussing the three phases of combustion in compression-ignition engines, the authors analyze the fuel characteristics relating to ignition, describe engine tests for rating fuels and state that it was found expedient to base all ignition data obtained on reference fuels, for which, on theoretical considerations, cetene and mesitylene were suggested. This proved to be very effective, as the former substance ignites most readily in a normal engine, the latter not at all.
Fuel behavior in four different engines was studied to ascertain the degree of correlation, and charts are presented to illustrate the results obtained. The ignition quality and thermal stability of fuels are discussed in some detail, and a fuel formula to serve for estimating the ignition quality of straight distillate fuel oils from natural crudes is presented.
The general subject of ignition is considered, including nuclear ignition, and several special cases of curious ignition phenomena with regard to ignition problems are cited. In the general remarks on Diesel-engine design, the phenomena that are presumed to take place within the engine are reviewed, desiderata that are to be considered are stated, and an endeavor is made to combine these two groups so as to obtain guiding principles for design.