Fuel-efficient thermal management in diesel engines via valvetrain-enabled cylinder ventilation strategies

• Published in: International journal of engine research 2021-02, Vol.22 (2), p.430-442
• Main Authors: Gosala, Dheeraj B, Shaver, Gregory M, McCarthy, James E, Lutz, Timothy P
• Format: Article
• Language: English
• Subjects: Air flow; Deactivation; Diesel engines; Energy efficiency; Engine cylinders; Exhaust gases; Firing (igniting); Fuel consumption; Fuel economy; Fuel injection; Gas exchange; High temperature; Manifolds; Reduction; System effectiveness; Thermal management; Valve trains; Ventilation
• ISSN: 1468-0874; 2041-3149
• DOI: 10.1177/1468087419867247

Modern diesel engine aftertreatment systems require elevated temperatures for effective reduction of engine-out emissions. Maintaining elevated aftertreatment temperatures in a fuel-efficient manner is a challenge, especially at low-load engine operation where engine-outlet temperatures are low; therefore, higher engine-outlet temperatures are typically achieved via increased fuel consumption. Previous studies have demonstrated that strategies such as cylinder deactivation (method where there is neither valve motion nor fuel injection in a subset of cylinders, thereby isolating the deactivated cylinders from the gas exchange process) and cylinder cutout (method where there is no fuel injection in a subset of cylinders, implemented with high recirculated gas rates) reduce fuel consumption while elevating engine-outlet temperatures, by reducing the overall airflow through the engine. This article introduces and characterizes “non-fired cylinder ventilation” as alternate means to achieve fuel-efficient aftertreatment thermal management, by reduction of overall airflow through the engine. Fuel injection is deactivated from a subset of cylinders during non-fired cylinder ventilation, and the non-firing cylinders participate in the gas exchange process with the same manifold at a time, thereby reducing the intake-to-exhaust manifold gas exchange through the cylinders. It is demonstrated that non-fired cylinder ventilation shows similar fuel efficiency and thermal management as cylinder deactivation when the valves of the non-firing ventilated cylinders are open by at least 4 mm, due to similar, negligible, gas-exchange losses, while non-fired cylinder ventilation with lower valve lifts enables elevated engine-outlet temperatures with relatively higher fuel consumption than cylinder deactivation. Non-fired cylinder ventilation strategies demonstrate 75 °C higher temperatures at fuel-neutral conditions, and up to 35% fuel savings at similar temperatures, compared to six-cylinder operation.