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The subject of this paper is to discuss the use of advanced combustion controls of direct injection diesel engines, to achieve simultaneous improvements in thermal efficiency while maintaining minimum pollutant emissions. In recent years, the emissions produced in the transportation sector are becoming increasingly scrutinized, leading to significantly strengthened emissions legislations with regard to NOx and CO2, especially under Real Driving Emission (RDE) conditions. Therefore, diesel combustion improvements are key to overcoming these challenges. This paper reports the following two innovative Diesel combustion control technologies to realize the objectives mentioned above. 1 Combustion improvement by accurate Combustion Rate Shaping (CRS), CRS enables direct control of in-cylinder pressure trace and heat release rate.

Future diesel engine legislation Tier 4 / Stage V and EU6d demand further improvements to reduce CO2 while keeping the already low NOx emissions levels. For US trucks a more strict limit of 0.2 g/bhp-hr NOx emissions need to be achieved. In this trade-off, system costs and complexity of the after-treatment are defining the constraint in which the common rail fuel injection system layout has to be defined. The increase of rail pressure was in the past the major step to control the soot emissions in view of low engine-out NOx emissions by applying massive EGR. With the on-going development of NOx-aftertreatment by Selective Catalytic Reduction (SCR), conversion efficiencies of up to 97% allow to reduce the EGR usage and rail pressure usage. In that context, the steepness of injection rate, the nozzle flow rate and the injection pressure are remaining parameters to control the NOx emissions.

The coming Diesel powertrains will remain as key technology in Europe to achieve the stringent 2025 CO2 emission targets. Especially for applications which are unlikely to be powered by pure EV technology like Light Duty vehicles and C/D segment vehicles which require a long driving range this is the case. To cope with these low CO2 targets the amount of electrification e.g. in form of 48V Belt-driven integrated Starter Generator (BSG) systems will increase. On the other hand the efficiency of the Diesel engine will increase which will result in lower exhaust gas temperatures resulting in a challenge to keep the required NOx reduction system efficiencies under Real Drive Emissions (RDE) driving conditions. In order to comply with the RDE legislation down to -7 °C ambient an efficient thermal management is one potential approach. Commonly utilized means to increase exhaust gas temperature are late injection and/or intake throttling, which enable sufficient NOx reduction efficiency.

In order to comply with emission regulation, reach their profitability targets and minimise the in-use cost of their vehicles, OEMs are seeking solutions to optimise their aftertreatment systems. For Selective Catalytic Reduction (SCR) system engineers, one of the most important challenges is to reduce the system's cost, while keeping its high level of NOx emission reduction performance. Ways to achieve this cost reduction include 1. using an engine out NOx estimation model instead of a NOx sensor upstream of the SDPF (DPF coated with SCR) catalyst and 2. eliminating the Ammonia Slip Catalyst (ASC) downstream of the SDPF catalyst. Achieving these challenging targets requires actions on the complete SCR system, from the optimisation of mixing and uniformity in the SDPF catalyst to the development of robust controls. To face these challenges, a novel exhaust reverse flow concept with a blade mixer was developed.