Split exhaust engine with idle check valve

Abstract

The disclosure provides a split exhaust engine with an idle check valve. Methods and systems are provided for reducing exhaust residuals during light load conditions in a split exhaust engine via a check valve. In one example, a scavenge exhaust manifold may be maintained above a threshold pressure by introducing fresh air into the scavenge manifold during a valve overlap period, the scavenge manifold coupled to a cylinder of an engine and coupled to an intake passage of the engine.

Description

technical field [0001] The present specification generally relates to methods and systems for increasing combustion stability and reducing exhaust valve opening losses in split exhaust engine operation utilizing direct injection. Background technique [0002] The engine may use a boosting device, such as a turbocharger, to increase engine power density. However, engine knock may occur due to elevated combustion temperatures. Knocking is especially problematic under supercharged conditions due to the high charge temperature. The inventors herein have realized that knocking can be reduced and engine efficiency can be improved by using an engine system with a split exhaust system in which a first exhaust manifold recirculates exhaust gas (EGR) The compressor upstream of the exhaust manifold directs the exhaust to the intake passage of the engine, and the second exhaust manifold directs exhaust gas to the turbine of the turbocharger in the exhaust passage of the engine. In su...

AI Technical Summary

Problems solved by technology

This valve overlap period can negatively impact fuel economy and combustion stability at light engine loads

Although the period of valve overlap can be reduced or eliminated at low loads by advancing exhaust valve timing, the resulting loss of exhaust valve opening can reduce fuel economy, negating any potential benefit of reduced valve overlap

On the other hand, if the exhaust valve timing is retarded to reduce exhaust valve losses, internal exhaust residues may increase, reducing combustion stability

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