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Reducing criteria pollutants while reducing greenhouse gases is an active area of research for commercial on-road vehicles as well as for off-road machines. The heavy duty on-road sector has moved to reducing NOx by 82.5% compared to 2010 regulations while increasing the engine useful life from 435,000 to 650,000 miles by 2027 in the United States (US). An additional certification cycle, the Low Load Cycle (LLC), has been added focusing on part load operation having tight NOx emissions levels. In addition to NOx, the total CO2 emissions from the vehicle will also be reduced for various model years. The off-road market is following with a 90% NOx reduction target compared to Tier 4 Final for 130-560 kW engines along with greenhouse gas targets that are still being established. The off-road market will also need to certify with a Low Load Application Cycle (LLAC), a version of which was proposed for evaluation in 2021.

The commercial vehicle industry continues to move in the direction of improving brake thermal efficiency while meeting more stringent diesel engine emission requirements. This study focused on demonstrating future emissions by using an exhaust burner upstream of a conventional aftertreatment system. This work highlights system results over the low load cycle (LLC) and many other pertinent cycles (Beverage Cycle, and Stay Hot Cycle, New York Bus Cycle). These efforts complement previous works showing system performance over the Heavy-Duty FTP and World Harmonized Transient Cycle (WHTC). The exhaust burner is used to raise and maintain the Selective Catalytic Reduction (SCR) catalyst at its optimal temperature over these cycles for efficient NOX reduction. This work showed that tailpipe NOX is significantly improved over these cycles with the exhaust burner.

Commercial vehicles require fast aftertreatment heat-up in order to move the SCR catalyst into the most efficient temperature range to meet upcoming NOX regulations. Today’s diesel aftertreatment systems require on the order of 10 minutes to heat up during a cold FTP cycle. The focus of this paper is to heat up the aftertreatment system as quickly as possible during cold starts and maintain a high temperature during low load, while minimizing fuel consumption. A system solution is demonstrated using a heavy-duty diesel engine with an end-of-life aged aftertreatment system targeted for 2027 emission levels using various levels of controls. The baseline layer of controls includes cylinder deactivation to raise the exhaust temperature more than 100° C in combination with elevated idle speed to increase the mass flowrate through the aftertreatment system. The combination yields higher exhaust enthalpy through the aftertreatment system.

Commercial vehicles require fast aftertreatment heat up in order to move the selective catalyst reduction (SCR) into the most efficient temperature range to meet upcoming NOx regulations. Heavy duty cylinder deactivation (CDA) is an important technology to meet these regulations. One of the challenges with implementing CDA in the heavy-duty market is to ensure acceptable engine and vehicle vibration. The purpose of this paper is to mitigate CDA vibration on a vehicle to acceptable levels. Emphasis was placed at the idle operating condition. Idle is the most challenging operating mode to enable, as deactivating cylinders reduces the frequency of the forcing function due to engine firing, which leads to a need to isolate these lower frequencies. A focused modal analysis of the engine (source), frame (path), and cabin (path/receiver) was used to characterize the vehicle system.

Commercial vehicles require continual improvements in order to meet fuel emission standards, improve diesel aftertreatment system performance and optimize vehicle fuel economy. Aftertreatment systems require significant space claim which makes vehicle packaging a challenge. Today’s diesel engines require valvetrain lash adjustment settings at distinct intervals to ensure proper valvetrain performance. This requires removing the engine rocker cover to access the valvetrain rocker arms for setting lash. Setting lash for compact vehicle applications sometimes requires removing the aftertreatment system to provide access to the rocker cover prior to setting lash. Then, the rocker cover is reinstalled followed by the aftertreatment system making the lash setting process time consuming and complex.

Diesel engine exhaust has been an area of research since the early 80's because of their harmful nature. The upcoming EPA regulations require substantial reductions in NOx and Particulate Matter (PM) and an aftertreatment system will likely be needed to meet these regulatory emissions levels. A more advanced technology in Aftertreatment system uses in-line fuel reformer to convert injected diesel fuel to hydrogen-rich reformates. It is used as the rich component for regenerating the Lean NOx Trap (LNT). The LNT regeneration process produces ammonia (NH3) that enables further NOx reduction in a downstream Selective Catalytic Reduction (SCR). A Diesel Particulate Filter (DPF) provides PM reduction capability in the system. The high conversion efficiency of regeneration cycle demands complete vaporization and uniform distribution of the injected fuel. Computational Fluid Dynamics simulation is effective in optimizing geometrical parameters to achieve the above requirements.