Linear Parameter-Varying Lean Burn Air-Fuel Ratio Control for a Spark Ignition Engine
| Autor: | Matthew A. Franchek, Feng Zhang, Imad Hassan Makki, Karolos M. Grigoriadis |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Thermal efficiency
Engineering business.industry Mechanical Engineering Control engineering Fuel injection Automotive engineering Computer Science Applications law.invention Internal combustion engine Control and Systems Engineering law Fuel efficiency Air–fuel ratio Inlet manifold business Instrumentation Lean burn Information Systems Petrol engine |
| Zdroj: | Journal of Dynamic Systems, Measurement, and Control. 129:404-414 |
| ISSN: | 1528-9028 0022-0434 |
| DOI: | 10.1115/1.2745849 |
| Popis: | In 2003, U.S. consumed about 20 million barrels of oil per day. The gasoline for cars and light trucks accounts for 45% of the total oil consumption. Lean burn technology for gasoline engines has drawn great attention during the past decade, largely due to its potential for improving fuel economy and reducing CO2 emissions 1. A lean burn engine is designed to operate at high intake manifold pressure with an air-fuel ratio greater than 10 and less than 23. Consequently, combustion efficiency can be improved through reduced pumping losses and enhanced thermodynamic efficiency. Compared to the conventional port fuel injection PFI engine, the gasoline lean burn engine presents a new set of challenges to the engine control community. The main challenge for lean burn technology is that, under lean operating conditions, the conventional three-way catalyst TWC system is no longer effective in reducing NOx pollutants. A special TWC with NOx trapping and conversion capabilities, known as lean NOx trap LNT, has to be used downstream of the conventional TWC to meet the government emission standards. During the lean operation, NOx in the feed gas is stored in the LNT. When the stored NOx reaches a certain threshold, the trap must be purged by switching to rich operation for a short period of time to regenerate the storage capacity and recover the efficiency. The NOx released from the LNT during the purge period is converted into non-polluting nitrogen by the rich air-fuel mixture 2‐5. Properly managing the storage and purge cycles is critical for achieving the fuel economy and NOx emission control targets of the lean burn gasoline engine. The desired tailpipe air-fuel ratio profile reference air-fuel ratio is defined by the LNT purge control 6,7, with the objectives of optimizing fuel economy while satisfying emission constraints. Therefore, it is necessary to design a controller to regulate the tailpipe air-fuel ratio to follow the air-fuel reference for both the NOx storage phase lean operation and the purge phase rich operation in order to accomplish the LNT purge control. In this paper, we concentrate on the air-fuel ratio control for the storage phase, that is, the design of the “outer-feedback loop” air-fuel ratio controller is considered. A linear universal exhaust gas oxygen UEGO sensor is used downstream of the LNT to measure the tailpipe air-fuel ratio. The air-fuel ratio controller to be designed is used to generate the commanded air-fuel ratio for the fuel injection system. During the storage phase when the engine is operating under lean conditions, the air-fuel ratio is selected to i meet the driver’s demand, ii maximize fuel economy, and iii satisfy other constraints, such as lean burn limit 7. These requirements dictate the set-point selection, and the optimal choice for the air-fuel ratio in the storage phase is usually a constant set-point for steady state operation. |
| Databáze: | OpenAIRE |
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