Analysis and refinement of Methane Number test procedure for gaseous fuels
Date
2024
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Abstract
Methane Number (MN) is an experimentally determined parameter for quantifying the resistance of gaseous fuels to End Gas Auto Ignition (EGAI). Originating from Leiker et al. in Graz, Austria, MN was introduced as an alternative to traditional gasoline rating techniques due to limitations on maximum obtainable values without extrapolative methods. Through funding provided to AVL, Leiker, et al. explored the impact of gas composition on fuel reactivity, although the specific details of their testing method remain unpublished. Subsequently, refinements to Leiker's proposed analytical method were made by AVL and MWM including digitizing of the AVL experimental data and the use of a computer program. The American Society of Testing Materials (ASTM) developed a standard for calculating a methane number (MNC)based on the gaseous fuel composition using the latest MWM methodology and experimental data. Amidst growing interest in renewable and hydrogen-blended natural gas, uncertainties within the experimental data used in the MNC method have spurred re-evaluation of the MN testing method. The purpose of this research is to create a repeatable method for determining the knock resistance of gaseous fuels analogous to the methods used for gasoline utilizing reference fuel blends of methane, hydrogen, and carbon dioxide. While Leiker, et al. did not disclose details of their MN quantification testing method, numerous research groups have developed their own methods, often without divulging test specifics or operating conditions. Presently, there is no standardized method for experimentally determining the MN of a gaseous fuel. This study aims to establish and share a repeatable method for MN determination using a modified Cooperative Fuel Research Engine (CFR). The investigation includes justification of allowable environmental parameters and operating variation limits, as well as exploring potential adaptations to the original proposed method. A pivotal aspect of the MN method involves identifying and quantifying a Knock Index (KI) parameter during engine operation, a challenge tackled through various approaches. CFR engines, originally designed for gasoline EGAI testing, come equipped with their own knock detection measurement systems. CSU has devised its method for determining a KI, and a comparison between the two systems was conducted to facilitate the publication of a standardized MN testing protocol.
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Subject
engine
hydrogen
power
fuel
combustion
methane