Comparison of Variable Valve Actuation, Cylinder Deactivation and Injection Strategies for Low-Load RCCI Operation of a Light Duty Engine

Shaver

et al. 2018

Cylinder deactivation is an effective strategy to improve diesel engine fuel efficiency and aftertreatment thermal management when implemented through deactivation of both fueling and valve motion for a set of cylinders. Brake power is maintained by injecting additional fuel into the remaining activated cylinders. The initial deactivation of cylinders can be accomplished in various ways, the two most common options being to trap freshly inducted charge in the deactivated cylinders or to trap combusted gases in the deactivated cylinders. The choice of trapping strategy dictates the in-cylinder pressure characteristics of the deactivated cylinders and has potential to affect torque, oil consumption, and emissions upon reactivation. The effort described here compares these trapping strategies through examination of in-cylinder pressures following deactivation. Proponents of each trapping strategy exist; however, the results discussed here suggest no significant performance differences. As an example, the in-cylinder pressures of both trapping strategies converge as quickly as seven cycles, less than 1 s, after deactivation at curb idle conditions.

Section: Introductionmentioning

confidence: 99%

Comparative study of diesel engine cylinder deactivation transition strategies

Shaver

et al. 2018

“…Several prior efforts have considered steady-state diesel engine operation at low loads during CDA. Bharath et al 13 simulated CDA and other variable valve actuation (VVA) strategies during near-idle low-temperature combustion operation. It was determined that CDA was a promising strategy due to higher combustion efficiency in the active cylinders and superior thermal management performance via lower exhaust flow rates and elevated exhaust gas temperatures.…”

Section: Introductionmentioning

confidence: 99%

Experimental assessment of diesel engine cylinder deactivation performance during low-load transient operations

Joshi

et al. 2019

Fuel-efficient aftertreatment thermal management in modern diesel engines is a difficult challenge, especially during low-load operation. This study explores the performance of cylinder deactivation in a diesel engine during low-load operation following highway cruise through experimental evaluation of two drive cycles, specifically extended idle and repeated heavy heavy-duty diesel truck creep cycles. Cylinder deactivation operations are shown to maintain comparable aftertreatment thermal management performance to conventional thermal management operation while reducing fuel up to 40% during extended idle operation. This fuel efficiency improvement coincides with engine-out emission reductions of 72% for soot and 52% for NOx. Cylinder deactivation also shows improved thermal management compared to a more fuel-efficient conventional operation.

“…Diesel engine CDA, during which both the valve motion and fuel injection are disabled in the deactivated cylinders, can enable fuel savings and improvements in aftertreatment thermal management as a result of lower airflow at low-to-moderate load operating conditions, via lower pumping work and air-to-fuel ratios, respectively. 6–13 Joshi et al 14,15 observed up to 3.4% fuel savings as a result of CDA implementation at low-load operating conditions during the heavy-duty federal test procedure (HD-FTP).…”

Section: Introductionmentioning

confidence: 99%

Dynamic cylinder activation in diesel engines

Shaver

et al. 2018

Cylinder deactivation has been recently demonstrated to have fuel savings and aftertreatment thermal management benefits at low to moderate loads compared to conventional operation in diesel engines. This study discusses dynamic cylinder activation as an effective variant to fixed diesel engine cylinder deactivation. The set of inactive and active cylinders varies on a cycle-by-cycle basis during dynamic cylinder activation. This enables greater control over forcing frequencies of the engine, thereby allowing the engine to operate away from the drivetrain resonant frequency at all engine speeds, while maintaining similar fuel savings, thermal management, and emission characteristics as fixed cylinder deactivation. Additional benefits of dynamic cylinder activation include a reduction in the consecutive number of cycles a given cylinder is deactivated, and more even cylinder usage. Enablement of engine operation without exciting drivetrain resonant frequencies at similar fuel efficiency and emissions as fixed cylinder deactivation makes dynamic cylinder activation a strong candidate to augment the benefits already demonstrated for fixed cylinder deactivation.