Impact of Combination of EGR, SCR, and DPF Technologies for the Low-Emission Rail Diesel Engines

Abstract

The EU emission standards for new rail diesel engines are becoming more stringent: stage IV emission targets have just come into effect, while stage V is in under considerations. Both exhaust gas recirculation (EGR) and selective catalytic reduction (SCR) technologies can be used to reduce nitric oxide (NOx) emissions, while the PM emission control requires a diesel particulate filter (DPF). The use of SCR requires on-board storage of urea, while the use of DPF needs to take into account its impact on engine efficiency performance. Both of these technologies require specific studies when applied to the rail engines; in particular, it becomes necessary to evaluate the engine performance trade-offs in order to evaluate how these technologies can be utilized efficiently in rail applications in order to meet current and future emission standards. The present study assesses the application of these technologies in diesel railcars on a quantitative basis using oneand three-dimensional numerical simulation tools. In particular, the study considers a 560-kW railcar engine with the use of different technology combinations for NOx reduction: SCR or EGR + DPF, and EGR + DPF + SCR. The NOx and PM emission performances are evaluated over the C1 homologation cycle and, in the case of the DPF, over an approximated railcar driving cycle as well. Several BSNOx targets were considered: 2 g/kWh, 1 g/kWh, and 0.4 g/kWh. Simulation results indicate that EGR + DPF + SCR-based solution is necessary to achieve stage IV emission limits for the 560-kW engine. On the other hand, SCR-based solutions have the potential to go beyond the stage IV NOx limit through scaling up the size of the SCR device and the on-board urea storage.

Lean-Burn Natural Gas Engines: Challenges and Concepts for an Efficient Exhaust Gas Aftertreatment System

“…The careful combination of optimally adapted and coordinated measures, i.e. including exhaust gas recirculation, allowed meeting tight emission limits for lean-operated diesel engines in the past [31]. Hence, there is confidence that the remaining technical challenges for meeting forthcoming ultra-low emission standards can similarly be solved for lean-operated natural gas engines, possibly via a system as schematically proposed in Fig.…”

Impact of Pilot Injection on Combustion and Emission Characteristics of a Low-Speed Two-Stroke Marine Diesel Engine

“…However, it tended to increase the emissions of particulate matter (PM), and the soot deposits generated from engine components might decrease the power density and the durability of the engines [11]. The other ways to reduce conventional pollutant emissions included implementing various exhaust gas after-treatment devices such as diesel particulate filters (DPFs) [12][13][14] and selective catalytic reduction (SCR) [14][15][16]. The drawbacks of these after-treatment devices are high capital and maintenance costs.…”

“…Figure14. Impact of pilot injection mass ratio on the distribution of temperature, fuel-air equivalence ratio, NOx formation, and soot formation at the moment of 90% accumulative heat release (q90) for various injection cases.…”

Conceptual design of chemical devices

“…For example, computer‐aided molecular design has been commonly used to design molecular and formulated products. [ 5‐10 ] However, despite the numerous studies in the past two decades that provide domain‐specific knowledge for designing various types of chemical products, [ 11‐48 ] as summarized in Table S1, a general design framework for chemical devices such as air purifiers, [ 38 ] catalytic converter, [ 39,40 ] hemodialysis device, [ 41 ] biosensor, [ 42,43 ] dehumidifier, [ 44‐47 ] and osmotic pump [ 48 ] is still missing. Consequently, the design of chemical devices is still largely done by trial and error based on the engineer's knowledge and experience.…”