Mark A. Shost

Ammonia sensor for closed-loop SCR control

Selective Catalytic Reduction (SCR) is the dominant solution for meeting future NOx reduction regulations for heavy-duty diesel powertrains. SCR systems benefit from closed-loop control if an appropriate exhaust gas sensor were available. An ammonia sensor has recently been developed for use as a feedback element in closed-loop control of urea dosing in a diesel SCR aftertreatment system. Closed-loop control of SCR dosing enables the SCR system to be robust against disturbances and to meet conformity of production (COP) and in-use compliance norms.

Design and Benefits of Dynamic Skip Fire Strategies for Cylinder Deactivated Engines

Cylinder deactivation is a fuel consumption reduction technology for throttled internal combustion engines and other engines with thermal efficiency loss at part cylinder load. Recent production implementations, deactivating fixed sets of cylinders under part-load operating conditions, have had limited “fly zones” due to issues with drivability and noise, vibration and harshness (NVH). Dynamic skip firing, which in its ultimate form incorporates anytime, any-cylinder deactivation, continuously varies the number of firing cylinders, along with cylinder load, obtaining flexible control of acoustic and vibrational excitations from the engine, and allowing an expanded operational envelope with fewer drive ability/NVH issues. This paper outlines design considerations of dynamic skip fire operational strategies, discusses implementation of the system on a vehicle, and presents benefits to fuel economy and NVH.