GB/T 386-2021 Determination of cetane number of diesel fuels

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Card type: Test method

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

• Standard number: GB/T 386—2021
• Chinese title: Determination of cetane number of diesel fuels
• English title: Standard test method for cetane number of diesel fuel oil
• Replacement relationship: replaces GB/T 386—2010 (the original foreword lists the differences from GB/T 386—2010, see items a) to w) of the original foreword)
• Previous versions: GB 386—1964, GB/T 386—1991, GB/T 386—2010 (original foreword: "The previous versions of this document and the documents it replaces are as follows")
• Publication/implementation: published on 2021-10-11, implemented on 2022-05-01 (dates on the original cover, source-text extraction shows "２０２１１０１１,-" and "２０２２０５０１./", the year and month/day require confirmation against the source standard (source-text extraction))
• Custodian: National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280) (original foreword, source-text extraction shows "ＳＡＣ／ＴＣ２８０", requires confirmation against the source standard (source-text extraction))

2. Scope of application and non-applicability

• Applicable to the determination of the cetane number of diesel fuels for the purpose of cetane number evaluation (Chapter 1 of the original text).
• Applicable to compression-ignition engine fuels (Chapter 1 of the original text, the wording in source-text extraction "VWXYVâWrCDEE¥¦'xF¡b" requires confirmation against the source standard (source-text extraction)).
• Cetane number range: 0 to 100; result expression range: 30 to 65 (Chapter 1 of the original text).
• Also applicable to the evaluation of non-diesel fuels (such as jet fuel, kerosene, etc.) (Chapter 1 of the original text, the wording in source-text extraction requires confirmation against the source standard (source-text extraction)).
• Not applicable: no explicit "not applicable" clause is provided in the available source.

3. Method principle

• Under standard operating conditions, the ignition performance of the test sample is compared with that of standard fuels of known cetane number (prepared from n-hexadecane and heptamethylnonane in proportion) in a standard single-cylinder diesel engine; by adjusting the compression ratio so that the ignition delay of the test sample is the same as that of the standard fuel, the cetane number of the test sample is calculated from the cetane number of the standard fuel (synthesized from Chapter 1, Chapter 8, and Chapter 13 of the original text; the original text does not have a separate section titled "Principle", so this is a summary, and the specific wording shall be based on the original text).
• Chapter 1 of the original text mentions expressions such as "VWXYVâWrCDEE¥¦'xF¡b", and source-text extraction contains much noise, requiring confirmation against the source standard (source-text extraction).

4. Reagents and materials (purity / preparation)

• n-Hexadecane (HXD): purity ≥99.0%, density (20℃) 0.7845±0.0002 g/cm³, test methods GB/T 1884, GB/T 1885, SH/T 0604 (Table 2 and Annex C of the original text).
• Heptamethylnonane (HMN, 2,2,4,4,6,8,8- heptamethylnonane): purity ≥98.0%, density (20℃) 0.7845±0.0002 g/cm³ (Table 2 and Annex C of the original text, source-text extraction shows "０．７８４５±０．０００２", requiring confirmation against the source standard (source-text extraction)).
• Pentamethylheptane (PMH): purity ≥99.5%, density (20℃) 1.43990±0.00020 g/cm³, test method SH/T 0724 (Table 2 and Annex C of the original text).
• Sulfur content: each standard fuel ≤5.0 mg/kg, test method SH/T 0176 (Table 2, Table 3, and Table 4 of the original text).
• Cetane number standard fuels (PRF): prepared from n-hexadecane and heptamethylnonane; the cetane number of n-hexadecane is 100, and the cetane number of heptamethylnonane is 15 (3.14 and 8.3.2 of the original text).
• Preparation formula for cetane number standard fuels (PRF): CN_PRF = 100×φ_HXD + 15×φ_HMN (Formula 1 of the original text); when using pentamethylheptane, CN_PRF = 100×φ_HXD + 16.3×φ_PMH (Formula 2 of the original text).
• Check fuels (check fuels): T fuel (T-fuel) cetane number 73 to 76, U fuel (U-fuel) cetane number 19 to 22 (8.4.1, 8.4.2, and Table 3 of the original text).
• Secondary standard fuels (secondary reference fuels): prepared from T fuel and U fuel, cetane number 38 to 42 (heavy) and 50 to 55 (light) (8.5.1, 8.5.2, and Table 4 of the original text).
• Other reagents: toluene, acetone, etc. (the original text 10.3.24 and 10.3.25 mention cleaning solvents; the specific names in source-text extraction require confirmation against the source standard).
• Reagent preparation details: complete preparation steps are not provided in the available source; only the proportioning formulas and purity requirements are given.

5. Instruments and equipment

• Standard single-cylinder diesel engine (CFR engine): compression ratio 8:1 to 36:1, cylinder bore 82.22 mm (3.250 in), piston stroke 114.3 mm (4.50 in), displacement 611729.10 mm³ (37.33 in³) (Table 1 of the original text).
• Injector: injection pressure 10.30 MPa±0.34 MPa, injection quantity 13.0 mL/min±0.2 mL/min, injection temperature 38℃±3℃ (100℉ to ±5℉) (10.3.3 to 10.3.5 of the original text).
• Injection advance angle: BTDC 13° (10.3.2 and 10.3.11 of the original text).
• Valve clearance: intake valve 0.20 mm±0.025 mm (0.008 in±0.001 in) (10.3.6 of the original text).
• Oil pressure: 172 kPa to 207 kPa (25 psi to 30 psi), oil temperature 57℃±8℃ (135℉ to ±15℉) (10.3.7 and 10.3.8 of the original text).
• Coolant temperature: 100℃±2℃ (212℉ to ±3℉) (10.3.9 of the original text).
• Exhaust temperature: 66℃±0.5℃ (150℉ to ±1℉) (10.3.10 of the original text).
• Compression ratio: adjustable, range 8:1 to 36:1 (Table 1 of the original text).
• Ignition delay (ignition delay): defined in 3.4 of the original text, in degrees (°) or milliseconds.
• Other equipment: crankcase, piston, cylinder head, valves, injection pump, injector nozzle, etc. (each clause of 7.1.2 and 10.3 of the original text).
• Instrument calibration: 12.1 to 12.10 of the original text specify calibration requirements, including compression ratio, injection timing, injection quantity, etc.

6. Recommended operating conditions

• Compression ratio: 8:1 to 36:1 (Table 1 of the original text).
• Injection advance angle: BTDC 13° (10.3.2 and 10.3.11 of the original text).
• Injection pressure: 10.30 MPa±0.34 MPa (10.3.3 of the original text).
• Injection quantity: 13.0 mL/min±0.2 mL/min (10.3.4 of the original text).
• Injection temperature: 38℃±3℃ (100℉ to ±5℉) (10.3.5 of the original text).
• Valve clearance: 0.20 mm±0.025 mm (10.3.6 of the original text).
• Oil pressure: 172 kPa to 207 kPa (25 psi to 30 psi) (10.3.7 of the original text).
• Oil temperature: 57℃±8℃ (135℉ to ±15℉) (10.3.8 of the original text).
• Coolant temperature: 100℃±2℃ (212℉ to ±3℉) (10.3.9 of the original text).
• Exhaust temperature: 66℃±0.5℃ (150℉ to ±1℉) (10.3.10 of the original text).
• Ignition delay: defined in 3.4 of the original text; the specific recommended value is not provided in the available source.
• Engine speed: 900 r/min±9 r/min (10.2.1 of the original text).
• Injector opening pressure: mentioned in 10.3.13 of the original text; the specific value in source-text extraction requires confirmation against the source standard.
• Fuel temperature: T fuel and U fuel are stored at 0℃ (8.4.3 of the original text).

7. Sampling and test sample preparation

• Sampling shall be carried out in accordance with GB/T 4756 and GB/T 27867 (9.1 of the original text).
• The test sample shall be stored at 18℃ to 32℃ for 2 h before determination (9.2 of the original text).
• The test sample shall be protected from light to prevent oxidation (9.2 and 9.3 of the original text).
• Test sample preparation: no special preparation steps are provided in the available source; follow routine diesel sampling.

8. Analytical procedure

• Sample in accordance with GB/T 4756 and GB/T 27867 (9.1 of the original text).
• Keep the test sample at constant temperature at 18℃ to 32℃ for 2 h (9.2 of the original text).
• Start the engine and adjust the operating conditions as specified in 10.2 (10.2 of the original text).
• Calibrate the engine with standard fuels (PRF) (8.3 and 11.1 of the original text).
• Determine the test sample: adjust the compression ratio so that the ignition delay is consistent with that of the standard fuel (10.3 and 13.1 of the original text).
• Result calculation: calculate the cetane number according to formula (5) (13.3 of the original text).
• If the test sample contains a cetane number improver, calculate according to formula (6) (13.4 of the original text).
• Precision according to Chapter 14 (original text 14.1, 14.2).
• Report according to Chapter 15 (original text 15.1, 15.2).

9. Qualitative and Quantitative and Calculation Formulas

• Calculation of cetane number of standard fuel:
  • CN_PRF = 100×φ_HXD + 15×φ_HMN (Formula 1)
  • CN_PRF = 100×φ_HXD + 16.3×φ_PMH (Formula 2)
• Calculation of compression ratio: FCP = 3275×p_LAP/p_SAP (Formula 3)
• Calculation of cetane number of test sample: CN = CN1 + (CN2 - CN1)(a - a1)/(a2 - a1) (Formula 5)
• Sample containing cetane number improver: CN_RF = φ_T×CN_T + φ_HXD×CN_HXD (Formula 6)
• For symbol explanations, see the notes below formulas (1) to (6) in the original text.

10. Precision

• Repeatability (r): given in Table 7 of the original text 15.1.2, when cetane number is 40, r=0.8; when 44, r=0.9; when 48, r=0.9; when 52, r=0.9; when 56, r=1.0 (original text Table 7).
• Reproducibility (R): given in Table 7 of the original text 15.1.2, when cetane number is 40, R=2.8; when 44, R=3.3; when 48, R=3.8; when 52, R=4.3; when 56, R=4.8 (original text Table 7).
• Precision is specified according to GB/T 6682—2008 and GB/T 27867 (original text 8.1, 9.1).
• Other precision data: mentioned in the original text 14.1, 14.2; specific values source-text extraction require confirmation against the source standard.

11. Report

• The report shall include: cetane number of the test sample, test conditions, standard fuel information, operator, date, etc. (original text Chapter 15).
• Report format: specified in the original text 15.2.1, 15.2.2; specific content source-text extraction requires confirmation against the source standard.
• The report shall indicate whether a cetane number improver is contained (original text 15.2.2).

12. Normative References

• GB/T 265 Petroleum products — Determination of kinematic viscosity and calculation of dynamic viscosity
• GB/T 4756 Petroleum liquids — Manual sampling
• GB/T 6682—2008 Water for analytical laboratory use — Specification and test methods
• GB/T 6986 Petroleum products — Determination of cloud point
• GB/T 27867 Petroleum liquids — Automatic pipeline sampling
• SH/T 0176 Determination of mercaptan sulfur in jet fuels (potentiometric titration method)
• References: GB/T 511, GB/T 1884, GB/T 1885, GB/T 2430, GB/T 4016, GB/T 6536, GB/T 6540, GB/T 11136, SH/T 0234, SH/T 0604, SH/T 0724, NB/SH/T 0843 (original text references [1] to [12])

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 Reference