ISO 17507-1:2025

Overview - ISO 17507-1:2025 (MNc method)

ISO 17507-1:2025 defines the MNc method for calculating the methane number (MN) of gaseous fuels used in reciprocating internal combustion engines. The standard specifies a calculation procedure that uses the gas composition as the sole input. It applies to natural gas, biomethane, and their admixtures with hydrogen, producing a calculated methane number (MNc) that quantifies the fuel’s knock resistance.

Key topics and technical requirements

• Composition-based calculation: MNc is determined from the gas composition given as volume fractions at reference conditions (0 °C, 101 325 kPa). Conversion from mole or mass fractions must follow ISO 14912.
• Component grouping: The method groups gas components into experimentally characterized ternary and binary systems and computes the overall MN by combining these group results.
• Optimization algorithms: The MNc procedure applies optimization routines to determine the best-fit mixture representation and derive the methane number.
• Applicability & boundary conditions: The standard defines the valid composition ranges and handling of atypical components (e.g., higher non-methane hydrocarbons or hydrogen admixtures).
• Expression of results and uncertainty: Requirements for reporting MNc, including uncertainty, error and bias, are provided (see Annex C).
• Validation aids: Normative numerical datasets and worked examples are included (Annex A, Clause 6) to support software validation and implementation testing.
• Normative references: ISO 14532 (vocabulary), ISO 14912 (composition conversion), and ISO/IEC Guide 98-3 (GUM) inform terminology, conversions and uncertainty treatment.

Practical applications - who uses ISO 17507-1

• Engine manufacturers (OEMs) for engine specification, warranty and control strategies.
• Gas suppliers and network operators to qualify fuel quality and compatibility with engines.
• Engine operators and fleet managers for operational risk assessment related to knock and fuel blending decisions.
• Instrument and gas analyzer manufacturers implementing GN/engine-control integration and real-time MN calculation.
• Software developers and testing labs validating MN calculation tools using the standard’s example datasets.

Practical benefits include improved safety (reduced knock risk), optimized engine performance, and consistent fuel specification language across the gas and engine sectors.

Related standards and references

• ISO 17507 series (other parts, e.g., Part 2: PKI method)
• Cited/related industry standards: EN 16726, ASTM D8221 (MN method usage)
• ISO 14532, ISO 14912, ISO/IEC Guide 98-3
• ISO 23306 (references MN method)

Keywords: ISO 17507-1:2025, MNc method, methane number, natural gas, biomethane, hydrogen admixture, gaseous fuels, knock resistance, calculated methane number, gas composition, engine compatibility.