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With the introduction of the EPA Tier 4 NOx emission limits for rail diesel engines this year, engine developers are forced to implement more advanced emission control technologies such as selective catalytic reduction (SCR) or cooled external exhaust gas recirculation (EGR). The integration and control of these systems for ensuring optimum performance throughout the operating range brings about new challenges on top of the well-known requirement for unconstrained operability in a very wide range of conditions. As a consequence, engines and their subsystems have to be designed for maximum flexibility. The turbocharging system in particular needs to be capable of dealing with extreme ambient conditions associated with high altitudes, hot summers, severe winters, tunnel operation, etc. This flexibility must be achieved without compromising reliability and while ensuring continuous in-use compliance with the emissions standards throughout the life of the installation. At the same time, engine performance should be maintained at the highest level possible. This study demonstrates that all of these targets can be met by combining two-stage turbocharging and EGR with suitable control elements. Two-stage turbocharging, which has become increasingly popular in other industry sectors due to its potential for improving the bsfc / NOx emissions trade-off when used in combination with correspondingly optimized valve actuation (Miller timing), is starting to be adopted also for rail applications. A variety of EGR concepts was proposed or put into practice over the past few years, and the most important or promising of these have been taken into consideration for this study. Extensive simulations of the resulting engine and turbocharging systems have been performed using ABB’s in-house simulation platform, based on a generic engine model that can be considered representative of the rail sector. It is shown that integration of EGR, two-stage turbocharging and appropriate control elements is highly attractive as it offers outstanding operational flexibility and very high fuel efficiency without any compromise in terms of reliability. The selection and specification of control elements and turbocharging system components depends on the EGR concept applied. As is shown below, this can be tailored to the application to ensure optimum performance and flexibility. In view of these obvious benefits, we are very confident that such integrated EGR / two-stage turbocharging systems will be adopted more widely on railway engines.

The results of numerical simulation of the resonator installation effect in the intake system of a diesel engine of dimension 21/21 on wave phenomena, technical, and economic indices are presented. The objective of the study is a diesel engine with eight cylinders: the cylinder diameter is 210 mm, the piston stroke is 210 mm. Diesel (factory designation is 8DM-21/21) is produced at the "Ural diesel-motor plant" (Russia, Ekaterinburg). Numerical simulation was performed in the ACTUS software (Switzerland, Baden). The simulation was performed taking into account the geometric parameters of the elements of the inlet system and the gas-dynamic flow nonstationarity. The article briefly describes the functions and designs of resonators used in the field of engine building. It is shown that the resonator installation in the intake system of the 8DM-21/21 diesel engine significantly changes the gas dynamics of the flow. For example, there is a smoothing of wave phenomena. This leads to an improvement in the quality of gas exchange (an increase in the filling ratio up to 0.5%). At the same time, the specific fuel consumption is reduced by an average of 0.3% while maintaining the power of a diesel engine.