Research On Air-fuel Ratio Model Of Vehicle Gasoline Engines In Transient Conditions

With the climate warming as the issues of common concern around the world , promote low-carbon life is our common responsibility. The increasing quantity of the automobile causes serious problems such as pollution and energy crisis.Air-Fuel Ratio (AFR) has an important effect on gasoline engine's drive ability, economical and exhaust emissions. According to the engine combustion equation we can know that only when the gasoline engine's Air-Fuel Ratio infinitely close to the theoretical value, the engine can have sufficient burning and get greatest power. Electronic Fuel Injection (EFI) system with Three-way Catalyst (TWC) is a good method to minimize emissions. If we want to have the highest convert ratio of vehicle emissions by Three-way Catalyst, we must keep the AFR in a very small range close to the theoretical value. So, keeping the AFR of engine on transient conditions has important practical value. Model based AFR control technology has become a hotspot in gasoline engine control research. However, especially during transient conditions , AFR could have a excursion because of manifold air flow and fuel film dynamics, so controlling of AFR this time is very important. Model based AFR control strategy requires accurate engine model first. Mean Value Engine Model (MVEM) is a non-linear model, but it is enough accurate and has a simple form and can satisfy real-time control, so it's a ideal model. Manifold air flow dynamic model and fuel film model constitute AFR model. But during the transient conditions, when the fuel is introduced into the intake manifold, the fuel film formed on the manifold wall because of the fuel flow dynamics, which affect the control precision of air fuel ratio. In order to control the engine air-fuel ratio more precisely, the study on fuel film model is very important.In the paper, the model has been simulated both during steady and transient operations and then validated by bench experiments. The fuel film model is also been revised and simulated, after that, two characteristic parameters of some operations have been identified. At last, the validating way is the integration of simulation and experiment through some situation, we can prove that the fuel film model base on the two parameters can describe the fuel dynamics in engine, and offer the strong academic gist for AFR control during transient conditions.