Exhaust thermal management using cylinder deactivation and late intake valve closing

Progressively stricter emission regulations have compelled diesel engine manufacturers to develop new technologies that reduce harmful pollutants like NOx and soot. While manufacturers have previously been able to meet these regulations through the use of on engine technology such as exhaust gas recirculation and multiple pulse injections, exhaust after treatment systems such as diesel particulate filters and selective catalytic reduction systems have become necessary to meet recent stricter policies. While these after treatment systems are incredibly effective at reducing harmful emissions, to operate effectively the system needs to be above a certain temperature level typically between 250 and 300°C. Many methods such as additional fueling or electrical heaters have been explored and used to increase the temperature of the exhaust gases passing through these systems to heat them faster or maintain temperature. The effect of cylinder deactivation, CDA, and late intake valve closing, LIVC, on raising exhaust gas temperatures was studied by performing load sweeps at 1200 RPM. The effect of CDA, CDA and LIVC, and CDA meeting specific NOx targets was analyzed. At low loads, CDA proved to be effective at raising exhaust temperature as well as providing an improvement in brake thermal efficiency, BTE. At higher loads, exhaust gas temperatures were also improved, but with a fuel consumption penalty. The introduction of LIVC in combination with CDA increased exhaust temperatures above 250°C, but did not improve BTE. The last sweeps, which targeted low NOx emissions, required the use of EGR and were able to raise temperatures above 250°C across all loads while meeting the targets. While meeting the targets, BTE was only improved at low loads. The sweeps demonstrated that CDA and CDA combined with LIVC can be an extremely effective technology for raising exhaust gas temperatures even at low loads where exhaust temperatures are usually lowest. In many cases, an improvement in BTE can be accomplished as well