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The widely accepted best practice for spark-ignition combustion is the four-valve pent-roof chamber using a central sparkplug and incorporating tumble flow during the intake event. The bulk tumble flow readily breaks up during the compression stroke to fine-scale turbulent kinetic energy desired for rapid, robust combustion. The natural gas engines used in medium- and heavy-truck applications would benefit from a similar, high-tumble pent-roof combustion chamber. However, these engines are invariably derived from their higher-volume diesel counterparts, and the production volumes are insufficient to justify the amount of modification required to incorporate a pent-roof system. The objective of this multi-dimensional computational study was to develop a combustion chamber addressing the objectives of a pent-roof chamber while maintaining the flat firedeck and vertical valve orientation of the diesel engine.

The new Beijing Automotive Industry Corporation (BAIC) engine, an evolution of the 2.3L 4-cylinder turbocharged gasoline engine from Saab, was designed, built, and tested with close collaboration between BAIC Motor Powertrain Co., Ltd. and Southwest Research Institute (SwRI®). The upgraded engine was intended to achieve low fuel consumption and a good balance of high performance and compliance with Euro 6 emissions regulations. Low fuel consumption was achieved primarily through utilizing cooled low pressure loop exhaust gas recirculation (LPL-EGR) and dual independent cam phasers. Cooled LPL-EGR helped suppress engine knock and consequently allowed for increased compression ratio and improved thermal efficiency of the new engine. Dual independent cam phasers reduced engine pumping losses and helped increase low-speed torque. Additionally, the intake and exhaust systems were improved along with optimization of the combustion chamber design.

Cooled exhaust gas recirculation (EGR) is widely applied in modern diesels to effectively control nitric oxides (NOx) emission. However, unfiltered high-pressure loop EGR leads to EGR cooler fouling and loss of its effectiveness. Reduced EGR cooler effectiveness often leads to increased NOx emission through increased intake charge temperature and/or reduced EGR flows. Therefore, there is a desire to avoid EGR cooler fouling and its associated problems. Filtering the EGR upstream from the EGR cooler is considered a potential solution to preserve EGR cooler effectiveness over long operating periods and simplify the control of the EGR system. The effect of EGR filter filtration efficiency on the EGR cooler effectiveness was investigated at Southwest Research Institute (SwRI). Alantum, a filter manufacturer from Korea, developed EGR filters having 50 and 70 percent filtration efficiency for this study. A 2008 calibration, V8, A350 International diesel engine was used in this work.

To counter the adverse impact on the formation of harmful unregulated emissions such as nitro-polycyclic aromatic hydrocarbons (NPAH), catalyst companies and researchers have been developing catalytic coatings that have the capability of suppressing the formation of NO2. NO2 is formed at low exhaust temperatures with potentially greater concentrations at part load engine operation. Haldor Topsoe, a catalyst company from Denmark, developed such a catalytic coating for DPFs. A sample was provided to Southwest Research Institute (SwRI) to conduct this research with a view of potentially improving NO2-suppressing formulations in the future. The Haldor Topsoe diesel particulate filter (DPF) with its novel coating was tested together with three other DPFs and the results confirmed the capability of this DPF to suppress the formation of NO2. This characteristic was apparent in all five engine test modes selected to cover the full engine operating range.

Four-way catalyst system consisting of diesel oxidation catalyst (DOC), diesel particulate filter (DPF) and lean NOx trap (LNT) with alternative combustion such as low temperature combustion (LTC) and premixed controlled compression ignition (PCCI) is one of the effective ways to achieve the US Tier 2 Bin 5 and future European emissions for light duty diesel vehicles. However, thermal responses such as substrate temperature and temperature gradient of each catalyst component in the exhaust treatment system are different under different combustion modes and operation conditions. One exhaust treatment component's performance or durability can not be sacrificed for the sake of another. In this paper, thermal management strategies for exhaust treatment component temperature and temperature gradient by controlling lean and rich conditions of low temperature combustions as well as premixed controlled combustion, EGR rate and exhaust flow are demonstrated on a Renault G9T600 engine.

A new diesel engine system adopting alternative combustion with rich and near rich combustion, and an airflow-dominant control system for precise combustion control was used with a 4-way catalyst system with LNT (lean NOx trap) to achieve Tier II Bin 5 on a 2.2L TDI diesel engine. The study included catalyst temperature control, NOx regeneration, desulfation, and PM oxidation with and without post injection. Using a mass-produced lean burn gasoline LNT with 60,000 mile equivalent aging, compliance to Tier II Bin 5 emissions was confirmed for the US06 and FTP75 test cycles with low NVH, minor fuel penalty and smooth transient operation.