IP 615: Determination of ignition delay and derived cetane number (DCN) of middle distillate fuels – Ignition delay and combustion delay determination using a constant volume combustion chamber with direct fuel injection

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  • Method adopted/last revised: 2015
  • Method reapproved: None
  • REF/ISBN: IP615-2937259
  • Status: New
  • First printed in STM books: April 2015


This standard specifies a test method for the quantitative determination of ignition and combustion delays of middle distillate fuels intended for use in compression ignition engines. The method utilizes a constant volume combustion chamber with direct fuel injection into heated, compressed synthetic air. A dynamic pressure wave is produced from the combustion of the product under test. An equation is given to calculate the derived cetane number (DCN) from the ignition and combustion delays determined from the dynamic pressure curve.

This standard is applicable to middle distillate fuels, fatty acid methyl esters (FAME) and blends of diesel fuels and FAME. 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-sulphur diesel fuel oils. However, users applying this standard 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.

This standard covers the ignition delay range from 2,47 ms to 4,09 ms and combustion delay from 3,71 ms to 6,74 ms (67 DCN to 39 DCN).

NOTE 1 The combustion analyser can measure shorter or longer ignition and combustion delays, but precision is not known.

NOTE 2 There is no information about how DCNs outside the 67 to 39 range compares to EN ISO 5165.

NOTE 3 For the purpose of this standard, the expression “% (V/V)” is used to represent the volume fraction (φ), and “% (m/m)” the mass fraction (ω).



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