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Studies have been published which address fast filling of Natural Gas Vehicle (NGV) fuel containers. Diggins states that NGV fuel containers cannot be fully filled during a fast fill, and that all-composite fuel containers cannot be filled as full as other types of fuel containers. There are issues in this prior work which may have a significant effect on the author’s conclusions. Fast fill testing conducted by Powertech Labs shows the Lincoln Composites’ fuel container has significantly better fill performance than projected by Diggins. Testing of a dispenser control system by Kountz and Blazek demonstrates all types of fuel containers can be properly filled with proper dispenser control algorithms and performance.

Natural gas-fueled vehicles impose unique requirements on exhaust aftertreatment systems. Methane conversion, which is very difficult for conventional automotive catalysts, may be required, depending on future regulatory directions. Three-way converter operating windows for simultaneous conversion of HC, CO, and NOx are considerably more narrow with gas engine exhaust. While several studies have demonstrated acceptable fresh converter performance, aged performance remains a concern. This paper presents the results of a durability study of eight catalytic converters specifically developed for natural gas engines. The converters were aged for 300 hours on a natural gas-fueled 7.0L Chevrolet engine operated at net stoichiometry. Catalyst performance was evaluated using both air/fuel traverse engine tests and FTP vehicle tests. Durability cycle severity and a comparison of results for engine and vehicle tests are discussed.

The composition of natural gas delivered through the pipeline varies with time and location around the USA. These variations are known to affect engine performance and emissions through changes in fuel metering characteristics and knock resistance of the fuel. High output, low emissions natural gas engines are being developed that take advantage of the high knock resistance of natural gas. These optimized engines are operated close to knock-limited power where changes in fuel knock resistance can cause operational problems. Octane tests were conducted on natural gas blend fuels using a CFR octane rating engine. Two relationships between motor octane number and fuel composition were established. A correlation for motor octane number versus the reactive hydrogen-carbon ratio was developed, and octane weighting factors, which used the molar composition of the fuel to predict motor octane number, were also found.

Natural gas vehicle (NGV) fuel energy storage density is a key issue, particularly in many heavy-duty applications where compressed natural gas may have unattractively low energy density. For these uses, benefits can be derived by using liquefied natural gas (LNG). From a market perspective, LNG can play a role for transportation because it is available in various areas of the United States and throughout the world. This paper provides a general overview of LNG use for vehicles and specifically an analysis of factors governing the behavior of this cryogenic fluid in a confined vessel. This is intended to provide an understanding of the cause/effect relation between LNG fuel composition, tank heat influx, and rate of fuel usage or storage time.

There is growing interest in using natural gas in vehicles in the U.S. and worldwide. Factors driving this development include desire for domestic energy use and diversification, reduced emissions, and fuel cost savings. As an engine and vehicle fuel, natural gas has many favorable characteristics as well as attributes that present technical and market challenges. A primary element of addressing these challenges is understanding the chemical and physical properties of natural gas and knowledge of the possible ramifications associated with gas composition variations.