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Compressed natural gas
From Wikipedia, the free encyclopedia
CNG may be refueled from low-pressure ("slow-fill") or high-pressure ("fast-fill") systems. The difference lies in the cost of the station vs. the refueling time. There are also some implementations to refuel out of a residential gas line during the night, but this is forbidden in some countries.
CNG cylinders can be made of steel, aluminium, or plastic. Lightweight composite (fibre-wrapped plastic) cylinders are especially benefitical for vehicular use because they offer significant weight reductions when compared with earlier generation steel and aluminium cylinders, which leads to lower fuel consumption.
The equipment required for CNG to be delivered to an Otto-cycle engine includes a pressure regulator (a device that converts the natural gas from storage pressure to metering pressure) and a gas mixer or gas injectors (fuel metering devices). Earlier-generation CNG conversion kits featured venturi-type gas mixers that metered fuel using the Bernoulli principle. Often assisting the gas mixer was a metering valve actuated by a stepper motor relying on feedback from an exhaust gas oxygen sensor. Newer CNG conversion kits feature electronic multi-point gas injection, similar to petrol injection systems found in most of today's cars.
CNG is often confused with LNG. While both are stored forms of natural gas, the key