A two-dimensional numerical model for a port-injected natural gas internal combustion engine 2008-36-0364
Environmental and strategic considerations have driven the research and development on the use of alternative fuels in internal combustion engines. Natural gas has recently become available to final users in the Brazilian market and is being used in flex fuel engines. Besides the economic aspects, natural gas is an important model fuel whose understanding enables the study of more complex fuel mixtures. In the search for engineering tools to improve internal combustion engines design and optimization, the present work is focused on the development of a two-dimensional numerical model to simulate a port-injected natural gas internal combustion engine. Here, attention is directed to the development of the model as well as the physical and chemical phenomena associated to the fluid flow, combustion and heat transfer processes that take place inside the cylinder. 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 proprieties, 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 fuel conversion efficiencies for different spark ignition timings, in-cylinder wall temperature and relative air/fuel ratios.