Abstract
Cylinder deactivation (CDA) is a fuel consumption reduction technology for gasoline engines. Skip fire is a new type of CDA because the load and the density of firing cylinder are in proportion to the torque demand. However, it is difficult to realize because valves need to be switched between valve deactivation and normal operation stroke by stroke. The Electromagnetic valve train (EMVT) provides a fully flexible control method to achieve skip fire. In the paper, a new skip fire strategy based on electromagnetic intake valve train (EMIV) is proposed. Then, the oxygen concentration of the exhaust pipe, energy losses, in-cylinder pressure of the skipped cycle and exhaust gas recirculation (EGR) rate of the firing cycle are studied by the 1D simulation in GT-Power. The results shows the majority of gas sucked into the skipped cylinder is exhaust gas by reasonable control of IVO and IVC, and the exhaust oxygen-rich can be avoided. Meanwhile, EGR rate of the firing cylinder and energy losses of the skipped cylinder are maintained at lower level. At the conditions of 1200 and 1600 rpm, fuel economy has been improved respectively 8.1%-16.6% and 6.4%-14.6% when the brake mean effective pressure (BMEP) ranges from 0.4MPa to 0.2MPa.
Highlights
Due to the restriction of the air flow into the cylinders by the throttle, the pumping mean effective pressure (PMEP) is large at part load conditions for throttled internal combustion engines
The oxygen concentration in the exhaust pipe and the exhaust gas recirculation (EGR) rate of the firing cycle at different IVC are illustrated in Fig. 6 when the intake valve opens at 180CA
The oxygen concentration increases little with the delay of IVC before 430CA, because most gas sucked into the skipped cycle is exhaust gas and the corresponding residual exhaust gas in the intake manifold reduced rapidly resulting in a sharp decline in the EGR rate of the firing cycle
Summary
Due to the restriction of the air flow into the cylinders by the throttle, the pumping mean effective pressure (PMEP) is large at part load conditions for throttled internal combustion engines. The minimum in-cylinder pressure of skipped cycles is about 0.006MPa that may lead to oil being drawn in cylinder, even if the decrease of trapped exhaust gas is beneficial to reduce the air spring losses [9]. Millo et al [10] proposed a fixed CDA mode strategy based on MultiAir system They studied the pumping losses and oxygen concentration in the exhaust line, and got the optimal intake valve closing timing. The minimum pressure of inactive cylinder wasn’t mentioned and they didn’t study the effects of intake valve opening on pumping losses and oxygen concentration
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