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Urea SCR is an established method to reduce NOx in dilute exhaust gas. The method is being used currently with stationary powerplants, and successful trials on motor vehicles have been conducted. The reason most often cited for rejecting urea SCR is lack of urea supply infrastructure, yet urea and other high nitrogen products are traded as commodities on the world market as a fertilizer grade, and an industrial grade is emerging. For a subset of commercial vehicles, urea can be provided by service personnel at designated terminals. But this approach does not support long distance carriers and personal use vehicles. The preferred delivery method is to add urea during vehicle refueling through a common fuel nozzle and fill pipe interface: urea / diesel co-fueling. Aqueous urea is well suited to delivery in this fashion.

In recent years sales of diesel-powered cars and trucks have increased dramatically worldwide. The efforts to raise specific power of diesel engines to allow for smaller and more efficient powertrains should include variable valvetrain technology. Some benefits that might become available with application of camshaft-based variable-valve mechanisms have been studied in [1]. Significant progress has also been reported in the development of camless actuation mechanisms [2, 3]. To fully evaluate the torque improvement opportunities for light duty diesel, the authors have assumed that a camless valvetrain will become available in the future. This will provide the ultimate flexibility to choose timing and duration of valve events to maximize full load torque. Simulation results revealed potential for a substantial increase in engine torque by optimizing the intake and exhaust valve timing together with turbocharger operation.

The air-hybrid engine absorbs the vehicle kinetic energy during braking, puts it into storage in the form of compressed air, and reuses it to assist in subsequent vehicle acceleration. In contrast to electric hybrid, the air hybrid does not require a second propulsion system. This approach provides a significant improvement in fuel economy without the electric hybrid complexity. The paper explores the fuel economy potential of an air hybrid engine by presenting the modeling results of a 2.5L V6 spark-ignition engine equipped with an electrohydraulic camless valvetrain and used in a 1531 kg passenger car. It describes the engine modifications, thermodynamics of various operating modes and vehicle driving cycle simulation. The air hybrid modeling projected a 64% and 12% of fuel economy improvement over the baseline vehicle in city and highway driving respectively.