UNE-EN ISO 4264:2019

This document specifies a procedure for the calculation of the cetane index of middle-distillate fuels from petroleum-derived sources. The calculated value is termed the cetane index by four-variable equation . Throughout the remaining text of this document, the term cetane index implies cetane index by four-variable equation.

This document is not applicable to fuels containing additives for raising the cetane number, nor to pure hydrocarbons, nor to distillate fuels derived from coal. It is applicable to fuels containing non-petroleum derivatives from tar sand and oil shale.

NOTE 1 This document was originally developed using a matrix of fuels, some of which contain non-petroleum derivates from tar sands and oil shale. Other cetane index equations have since been developed which can be more applicable to tar sands products.

NOTE 2 The cetane index is not an alternative way to express the cetane number; it is a supplementary tool, to be used with due regard for its limitations.

NOTE 3 The cetane index is used to estimate the cetane number of diesel fuel when a test engine is not available to determine this property directly, or when insufficient sample is available for an engine rating. In cases where the cetane number of a fuel has been previously established, the cetane index can be used to verify the cetane number of subsequent samples of that fuel, provided the fuel s source and mode of manufacture remain unchanged.

The recommended range of fuel properties for application of this document is as follows:

Fuel property

Recommended range

Cetane number

32,5 56,5

Density at 15 °C, kg/m3

805,0 895,0

10 % (V/V) distillation recovery temperature, °C

171 259

50 % (V/V) distillation recovery temperature, °C

212 308

90 % (V/V) distillation recovery temperature, °C

251 363

Within the recommended range of cetane number (32,5 to 56,5), the expected error of the prediction via the cetane index equation will be less than ± 2 cetane numbers for 65 % of the distillate fuels examined. Errors may be greater for fuels whose properties fall outside the recommended range of application.

As a consequence of sample-specific biases observed, the expected error may be greater even when the fuel s properties fall inside the recommended range of application. Therefore, users are advised to assess the required degree of prediction agreement to determine the fitness-for-use of the prediction.

NOTE 4 Sample specific biases were observed for distillate fuels containing FAME.