Pressurized air induction system

#The present description relates generally to methods and systems for controlling a vehicle engine to provide a boosted air charge.

#By incorporating a turbocharger, comprising a compressor driven by a turbine, into an engine of a vehicle, the efficiency and power output of the engine may be improved. The forced induction of extra air into a combustion chamber of the engine proportionally induces the combustion of additional fuel, producing more power than obtained from air intake at ambient pressure. The pressurized, or boosted, air is typically heated during compression and if combusted directly, may increase the risk of engine knock. Thus, boosted air is typically cooled by flowing the air through a charge air cooler (CAC) before entering the engine intake manifold, a process that also increases the density of the air and improves intake throttle response.

#The air compression provided by the compressor of the turbocharger is enabled by the rotation of the turbine. Typically, at least a portion of the exhaust gas is routed to the turbine and the expansion of the exhaust gas causes the turbine to spin. Since the turbine is mechanically coupled to the compressor, as the turbine spins up, so does the compressor. However, there may be a delay between the time when an increase in torque is demanded and when the corresponding boost pressure is provided by the compressor. The delay, also referred to as turbo lag, is due to the turbine's inertia and friction when operating at low engine loads, and corresponds to a duration required for the engine to generate sufficient exhaust gas (e.g., exhaust flow and temperature) to spool up the turbine to drive the compressor. During this turbo lag, boosted engine performance may be degraded.

#FIG. 1 shows an example engine system for a single turbo boosted hybrid vehicle.

#FIG. 2 shows a schematic illustration of an engine adapted with a pressurized air induction system.

#FIG. 3A shows a top view of a first embodiment of the pressurized air induction system.

#The following description relates to systems and methods for providing cold, boosted air to an engine system, such as the system of FIG. 1, via a pressurized air induction system, such as the system of FIG. 2. The pressurized air induction system may include a first and a second air pathway for air flow, each pathway coupled at a first end to a fresh air duct and coupled at a second end to an intake plenum upstream of an engine cylinder. As shown in FIG. 2, the first air pathway may flow fresh ambient air to the engine while the second air pathway may flow air via a compressor and a charge air cooler (CAC). Flow through the first and second pathways may be controlled via individual throttle valves, as shown in the embodiment of FIGS. 3A-3B. Alternatively, the relative flow between the passages may be controlled via a splitter valve, as shown in the embodiment of FIGS. 4A-4B. A controller may be configured to perform a control routine, such as the example routine of FIG. 5, to adjust a position of the valve(s) based on engine speed-load conditions so that an amount of cool, compressed air can be stored in the second passage acting as a reservoir, the compressed air released responsive to an increase in torque demand to reduce turbo lag. The controller may also adjust the valve(s) to discharge any trapped air based on an inferred amount of heat transferred into the air. Example operations of the pressurized air induction system are illustrated herein with reference to FIGS. 6-7. In this way, boosted engine performance is improved.

#FIG. 1 depicts an example of a cylinder of internal combustion engine 10 of a vehicle 5. Engine 10 may be controlled at least partially by a control system including controller 12 and by input from a vehicle operator 130 via an input device 132. In this example, input device 132 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. Cylinder 14 (which may be referred to herein as a combustion chamber) of engine 10 may include combustion chamber walls 136 with piston 138 positioned therein. Piston 138 may be coupled to crankshaft 140 so that reciprocating motion of the piston is translated into rotational motion of the crankshaft. Crankshaft 140 may be coupled to at least one drive wheel of the passenger vehicle via a transmission system. Further, a starter motor (not shown) may be coupled to crankshaft 140 via a flywheel to enable a starting operation of engine 10.

#Engine 10 is a boosted engine comprising a turbocharger 175 for providing a boosted intake air charge. Although engine 10 is shown coupled to one turbocharger, other embodiments of engine 10 may include more than one turbocharger to provide boost. Turbocharger 175 is configured with a compressor 174 and an exhaust turbine 176. The compressor 174 is arranged in an air intake passage 142, which draws fresh ambient air into the engine 10. The compressor 174 is driven by the exhaust turbine 176. Since the compression of air heats the air charge, the boosted air is flowed through a charge air cooler (CAC) 192 where it is cooled before being delivered to engine cylinders. CAC 192 may be a water-air or air-air based heat exchanger. The turbine 176 is positioned in an exhaust passage 148 downstream of the cylinder 14 and upstream of an emission control device 178. Turbine 176 is connected to compressor 174 mechanically by a shaft 180. The rotation of turbine 176 is driven by hot expanding exhaust gas flowing from cylinder 14 through exhaust passage 148 towards emission control device 178, the spinning of turbine 176 at least partially powering the rotation of the compressor via the shaft 180. Engine 10 further includes a pressurized air induction (PAI) system 199 configured to deliver air to cylinder 14. The PAI system 199 includes a bypass duct 194 coupled at a first end to air intake passage 142 at a location upstream of compressor 174 and at a second end to an intake plenum 146. In this way, bypass duct 194 may constitute a first air pathway of the PAI system 199 while air intake passage 142 leading into air intake passage 198 including compressor 174 and CAC 192 constitutes a second air pathway of the PAI system 199. The configuration of the PAI system 199 is elaborated in detail at FIG. 2. Example embodiments of the PAI system 199 are detailed at FIGS. 3A-3B and FIGS. 4A-4B.