Numerical Investigation of Advanced Low Temperature Combustion Techniques in Diesel Engine

摘要

Diesel engines, also known compression ignition (CI) engines, are more popular over gasoline engines due to their undisputed benefit of fuel economy. However, diesel engines primarily produce oxides of nitrogen (NO_x) and particulate matter (PM) which are toxic for human health as well as environmental. Hence, regulatory bodies are imposing stringent restrictions on these pollutants. Recent studies suggested that in-cylinder solutions like low temperature combustion (LTC) and multiple injection strategies are efficient techniques to reduce these emissions. In this work, Converge computational fluid dynamics (CFD) tool was used to simulate combustion for experimentally optimized LTC and optimum two-shot injection with LTC strategies to get a better understanding of in-cylinder processes and emission formation. A lower peak combustion temperature, lower percentages of oxygen (O_2) and less available time for the reactions with optimized LTC run and optimum two-shot injection strategies were the reason behind a significant reduction in NO_x (～98%) emissions with these strategies. Results of the study showed that a downward motion of piston for most of the period during fuel injection with optimized LTC strategy improved the mixing rate of fuel with surrounding air. As a result, lower PM emissions were achieved with optimized LTC strategy.