Abstract
Cylinder deactivation is a well-known measure for reducing fuel consumption, especially when applied to gasoline engines. Mostly, such systems are designed to deactivate half of the number of cylinders of the engine. In this study, a new concept is investigated for deactivating only one out of four cylinders of a commercial vehicle diesel engine (“3/4-cylinder concept”). For this purpose, cylinders 2–4 of the engine are operated in “real” 3-cylinder mode, thus with the firing order and ignition distance of a regular 3-cylinder engine, while the first cylinder is only activated near full load, running in parallel to the fourth cylinder. This concept was integrated into a test engine and evaluated on an engine test bench. As the investigations revealed significant improvements for the low-to-medium load region as well as disadvantages for high load, an extensive numerical analysis was carried out based on the experimental results. This included both 1D simulation runs and a detailed cylinder-specific efficiency loss analysis. Based on the results of this analysis, further steps for optimizing the concept were derived and studied by numerical calculations. As a result, it can be concluded that the 3/4-cylinder concept may provide significant improvements of real-world fuel economy when integrated as a drive unit into a tractor.
Highlights
In recent years, a multitude of different concepts for realizing an engine operating point shift have been developed and implemented in series applications for both gasoline and diesel engines
Besides classic “downsizing” or “downspeeding” approaches on the one hand and complex operating strategies in hybrid concepts on the other, such an operating point shift can be achieved by so-called “dynamic downsizing”, i.e. the deactivation of one or more cylinders of a multi-cylinder engine depending on the operating point
The losses due to real charge and real combustion are higher in the 3/4-cylinder concept, this is overcompensated by the lower losses due to wall heat transfer, real gas exchange and friction
Summary
A multitude of different concepts for realizing an engine operating point shift have been developed and implemented in series applications for both gasoline and diesel engines. The reasons for the fuel consumption benefits achieved in significant parts of the engine map as well as for certain fuel economy penalties measured in individual operating points will be analyzed in detail using both 1D simulation of the real engine operation and a detailed loss analysis. Based on this analysis, further steps for the optimization of the concept will be identified and evaluated by simulation
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