ČSN EN 15195

This document specifies a test method for the quantitative determination of ignition delay of middle distillate fuels intended for use in compression ignition engines. The method utilizes a constant volume combustion chamber designed for operation by compression ignition, and employing direct injection of fuel into compressed air that is controlled to a specified pressure and temperature. An equation is given to calculate the derived cetane number (DCN) from the ignition delay measurement. This document covers the ignition delay range from 2,58 ms to 6,34 ms (76,8 DCN to 33,9 DCN). The combustion analyser can measure shorter or longer ignition delays, but precision is not known. This document is applicable to diesel fuels, including those containing fatty acid methyl esters (FAME) up to 30 % (V/V). The method is also applicable to middle distillate fuels of non-petroleum origin, oil-sands based fuels, blends of fuel containing biodiesel material, diesel fuel oils containing cetane number improver additives and low-sulfur diesel fuel oils. Furthermore, the method is applicable to paraffinic diesel from synthesis or hydrotreatment, containing up to a volume fraction of 7 % FAME. However, users applying this document especially to unconventional distillate fuels are warned that the relationship between derived cetane number and combustion behaviour in real engines is not yet fully understood. The test method is also applicable to the quantitative determination of the ignition characteristics of FAME, especially the ignition delay. However, analysis of the data available, regarding correlation with EN ISO 5165, is inconclusive. So the determination of derived cetane number for FAME fuel, also known as B100, has not been included in the precision determination as in Clause 12.