Simultaneous Use of Natural Gas and Petrol as an Engine Fuel

This work investigates the use of mixtures of natural gas and low octane petrol as a fuel for a spark ignition engine. The high octane rating of natural gas allows the engine to be operated with advanced ignition timing, which would normally cause 'end gas knock' with a low octane fuel The high energy density and high flame speed of the petrol allows high power output to be achieved. In the engine tested, a mixture of the two fuels (approximately 75% petroV2S% natural gas) allowed power output close to that of using high octane petrol to be achieved. The benefits are in reduction of lead and other emissions, reduced fuel cost and reduced exhaust temperatures compared with use of petrol alone.