Summary

The increasing interest for less polluting energy sources and the recent availability to the final user in the Brazilian market has motivated the use of natural gas as an alternative fuel for internal combustion engine vehicles. In the search for engineering tools to improve internal combustion engines design and optimization, the present work is focussed on the development of a two-dimensional numerical model to simulate a spark-ignition engine fuelled by a mixture of air and methane as a natural gas simplification. Here, attention is directed to physical and chemical phenomena associated to the fluid flow, combustion and heat transfer processes that take place inside the cylinder. To this extent, the problem is formulated through several conservation and constitutive equations, from which the numerical model is then developed to predict the engine performance. Results are provided for some physical proprierties, such as in-cylinder pressure and temperatures, mass flow rates at intake and exhaust systems, combustion rate and heat transfer rate to cylinder walls, besides velocity, turbulence intensity and temperature fields. The effects of the engine operation parameters on the engine performance are assessed through predictions of indicated power, torque and specific fuel consumption as well as volumetric and thermal efficiencies. The results were consistent with available data for production engines and show the models potential as a research and design tool.

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