GB/T 11139-1989 Calculation method for cetane index of distillate fuels

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1. Method number / full title / English name / replacement relationship

• Standard number: GB 11139-89
• Chinese title: Calculation method for cetane index of distillate fuels
• English title: Distillate fuels—Calculation of cetane index (original text source-text extraction as "Distill ate fuels-Calcul ation of cetane index")
• Replacement relationship: From the date of implementation of this standard, the former Ministry of Petroleum Industry standard SY 2410-82 "Calculation method for cetane index of diesel fuel" is void.
• Reference adoption: American Society for Testing and Materials standard ASTM D976-80 "Calculation method for cetane index of distillate fuels".
• Approval/implementation: approved by China Petrochemical Corporation 1989-03-17, implemented on 1990-04-01.
• Technical committee/drafting: technical committee and responsible drafting by the Research Institute of Petroleum Processing; main drafter Yang Tianfu.

2. Scope of application and non-applicability

• Scope of application (Chapter 1): This standard specifies the calculation formula and calculation chart for the cetane index of distillate fuels; it is applicable to calculating the cetane index of straight-run distillates, catalytic cracking distillates, and mixtures of these two fuels.
• Non-applicability (limitations in Chapter 7):
  • a. Not applicable to fuels containing cetane number improvers;
  • b. Not applicable to pure hydrocarbons, synthetic fuels, alkylates, coking products, and distillate fuels derived from shale oil and oil sands;
  • c. When used for crude oil, residual oil, and volatile products with a final boiling point below 260℃, its correlation is basically inaccurate.
• Statement in Chapter 4: The cetane index cannot be arbitrarily used to replace the cetane number determined by a standard engine test apparatus.

3. Method principle

Use GB 1884, GB 1885, and GB 6536 respectively to determine the 20℃ density and mid-boiling point of the distillate fuel, then directly calculate by formula or find the cetane index by calculation chart (Chapter 5 Method summary). Note: For the needs of some users, the cetane index can also be found using the "Cetane Index Calculation Table", which can be obtained from the Research Institute of Petroleum Processing.

4. Reagents and materials (purity / preparation)

not provided in the available source.

5. Instruments and equipment

not provided in the available source (the standard only cites the apparatus required by GB 1884 hydrometer method and GB 6536 distillation determination method, and does not list instruments and equipment clauses separately).

6. Recommended operating conditions

not provided in the available source (there are no independent operating condition clauses; the determination conditions are specified by the cited standards GB 1884, GB 1885, GB 6536).

7. Sampling and sample preparation

not provided in the available source.

8. Analysis procedure

• Use GB 1884, GB 1885 to determine the sample 20℃ density ρ20 (g/cm³).
• Use GB 6536 to determine the mid-boiling point B of the sample (℃).
• Calculate according to the formula in 6.1, or find the cetane index according to 6.2 using the calculation chart (nomograph).

9. Qualitative and quantitative determination and calculation formula

• Definitions (Chapter 3):
  • 3.1 Cetane index: a calculated value representing the ignition performance of a distillate fuel in an engine, which can be calculated from the standard density and mid-boiling point of the distillate fuel.
  • 3.2 Standard density: the density of petroleum and petroleum products at the standard temperature (specified in China as 20℃) (g/cm³).
  • 3.3 Mid-boiling point: the corresponding temperature at which 50% volume is distilled when an oil product with a symmetrical distillation curve is distilled under specified conditions (℃).
• Calculation formula (6.1): CI = 431.29 − 1586.88ρ20 + 730.97(ρ20)² + 12.392(ρ20) + 0.0515(ρ20 − 0.554B) + 97.803(lgB)²
  • Where: ρ20—— uses GB 1884 and GB 1885 to determine the density of the sample at 20℃, g/cm³; B—— uses GB 6536 to determine the mid-boiling point of the sample, ℃.
  • Requires confirmation against the source standard (source-text extraction): In the original formula, "0.0515 (P20 - 0.554B" has an unclosed parenthesis, and the term structure is suspected to be missing source-text extraction; "97.803 (1gB) 2" should be 97.803(lgB)². The exact form of each term in the formula is recommended to be verified against the official standard text.
• Calculation chart (6.2): The cetane index of the sample can also be calculated using the following chart (cetane index nomograph); in the chart, ρ20—20℃ density g/cm³; CI— cetane index; B— mid-boiling point (50% recovery temperature) ℃.
• Calculation example (6.3): Given ρ20 = 0.8400 g/cm³, mid-boiling point B = 260℃, substituting into the formula gives CI = 47.8, rounded to an integer as 48; the chart calculation result is 47.5, rounded to an integer as 48.
• Reported value (Chapter 9): The cetane index formula calculation and chart calculation results are expressed as integers; when there is a dispute between the formula calculation result and the chart calculation result, the formula calculation result shall prevail.

10. Precision

• 8.1 The correlation between cetane index and cetane number depends to a large extent on the accuracy of the determination results of both 20℃ density and mid-boiling point.
• 8.2 When the cetane number is in the range of 30~55, the correlation between the cetane index and cetane number of 75% distillate fuels is slightly less than ±2 units; outside this range, the correlation is somewhat poorer. For straight-run fuels, catalytic cracking fuels, and their mixtures, the correlation is best; for mixtures containing more thermal cracking fuels, the correlation is worst.

11. Report

The cetane index formula calculation and chart calculation results are expressed as integers. When there is a dispute between the formula calculation result and the chart calculation result, the formula calculation result shall prevail (Chapter 9).

12. Referenced documents

• GB 1884 Determination of density of petroleum and liquid petroleum products (hydrometer method)
• GB 1885 Petroleum measurement conversion tables
• GB 6536 Determination of distillation of petroleum products
• Reference: ASTM D976-80 "Calculation method for cetane index of distillate fuels"
• Replacement: SY 2410-82 "Calculation method for cetane index of diesel fuel" (void)

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Q&A