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A new technique for measuring ignition quality of diesel fuels has been evaluated. Primarily a constant volume combustion apparatus, the Diesel Fuel Ignition Analyser (DFIA) provides a direct output of ignition delay. Microprocessor control and semi-automatic operation ensure rapid determinations. Tests were performed to find the operating conditions giving the best results in terms of various performance indicators, settling upon 450°C/20bar for combustion air preheat and pressure. A preliminary correlation model based on ignition delay predicted D613 Cetane Number with ± 1.3CN at 95% confidence. More results are required to improve this correlation and define statistical precision of the method.

A combustion-based analytical method, initially developed by the Southwest Research Institute (SwRI) and referred to as the Constant Volume Combustion Apparatus (CVCA), has been further researched/developed by an SwRI licensee (Advanced Engine Technology Ltd.). This R&D has resulted in a diesel fuel Ignition Quality Tester (IQT) that permits rapid and precise determination of the ignition quality of middle distillate and alternative fuels. Its features, such as low fuel volume requirement, complete test automation, and self-diagnosis, make it highly suitable for commercial oil industry and research applications. A preliminary investigation, reported in SAE paper 961182, has shown that the IQT results are highly correlated to the ASTM D-613 cetane number (CN). The objective of this paper is to report on efforts to further refine the original CN model and report on improvements to the IQT fuel injection system.