Optimization of Injection Strategies to Reduce Emission for 2-cycle Engine

Starting 2015 all new diesel locomotive have to meet stringent emission requirements of 95% lower particulate and 75% lower NOx. Various approaches [1] and strategies have been implemented by the smaller diesel engine manufacturers to address this requirement. Exhaust gas recirculation (EGR), high pressure injection, multiple injection [2-3] e.t.c are few examples of reducing emissions inside the cylinder. Although this approach is tried by many heavy duty engine manufactures but not the optimal choice at this moment. On the other hand use of controlled after-treatment device has gained huge popularity in the heavy-duty diesel engine world. Most of the in cylinder NOx reduction strategies applied in 4-stroke engine does not translate very well for 2-cycle engine especially due to the scavenging process. Hence advanced simulation tools were used to understand the scavenging process to predict the optimal combustion characteristics to meet future emission standard.

This paper explores a wide range of injection strategies with advanced analytical optimization tools to lower emission for a 2-cycle engine. Analytical simulations were conducted for a calibrated Electro Motive Diesel 710 Tier-2 Engine. Sets of injection parameter where carefully chosen based on prior test and simulation data. Gradient based optimization technique method of moving asymptotes is used to find the optimal injection parameter and piston bowl shape. Simulations were done for the scavenging process to calculate the residual EGR and ensure the accuracy of combustion model. Results will be shown as compared to the baseline calibrated model. Optimal strategies developed in this work will be tested in single cylinder test cell and will be presented later.