In response to growing evidence that the cetane number of a diesel fuel may not give an adequate description of the combustion quality of that fuel in commercial diesel engines, the Light Duty Diesel Combustion Group of the Coordinating Research Council sponsored a project to study the combustion process in the Cooperative Fuel Research cetane engine. The engine was equipped with modern sensors and a computer data acquisition and processing system. A set of ten test fuels, selected to represent a relatively wide range of properties, was obtained from other test programs for which data would be available for comparison.
The results for the cetane engine tests showed a strong correlation between cetane number and ignition delay for all fuels tested. Also, a higher cetane number was generally reflected in better engine performance, emissions, and heat release results in the cetane engine. Comparison of test results with data from another program indicated that there were similarities between the cetane engine and an IDI engine but correlation with a DI engine was poor. Conclusions are that revised instrumentation and carefully controlled test procedures can yield consistent results from the cetane engine, however, a strong correlation between these results and the performance of a given fuel in modern design DI and IDI engines has not been established.