A multivariate statistical analysis to evaluate and predict ignition quality of marine diesel fuel distillates from their physical properties

Ignition quality of diesel fuels used in compression ignition engines is mainly described by their respective Cetane Number (CN). The most widely accepted method for CN measurement is the ASTM D613, involving a variable compression ratio Cooperative Fuel Research (CFR) engine. However in the recent years other alternative methods based on a Constant Volume Combustion Chamber (CVCC) concept have gained significant popularity mainly due to lower cost of acquisition, maintenance and operation, still being able to provide accurate results. Other widely accepted parameters for the characterization of ignition quality of diesel fuels are cetane indices. These are empirical mathematical equations, based on simple physicochemical properties (such as density and distillation characteristics) and usually correlate well with CN. However, they are accurate enough within narrow limits and are very prone to produce misleading results when involving modern fuels, or biofuels and their blends. In this work, an effort was made to investigate the room for improvement for the prediction of CN, apart from the use of the most widely accepted method of Calculated Cetane Index (CCI), standardized by ASTM D4737, with regard to today's used marine diesel fuels. A total of 47 distillate marine diesel fuels (with high sulfur content compared to automotive diesel fuels) has been employed in order to create multivariate regression models to predict CN equivalents. Thus, useful conclusions were drown in an attempt to evaluate the importance of various physicochemical properties with regard to ignition quality, as well as a first step to the potentiality of revaluation of empirical mathematical models currently in use.