Abstract
For port-injected gasoline engines, an innovative strategy of transient fuel-film compensation is proposed to eliminate the impact of fuel-film dynamic effects and improve the transient air fuel ratio control accuracy. A combined fuel-film model composes of a long-term fuel-film and a short-term fuel-film was established. A transient fuel-film compensator model was analyzed in detail. The respective term of the fuel-film model is calculated by a share factor. The decay coefficients control the fuel compensation quantity and the active time. The validity of above models were verified though engine bench tests. The results show that this new strategy can effectively suppress the λ offset during engine transient condition, the transient lambda deviation is less than 5% and stabilized within 1 second.
Highlights
PFI engine transient air-fuel ratio (AFR) accurate control is critical and difficult to achieve low emissions
Since the actual intake air mass increases rapidly,the calculated intake air mass is less than the actual intake air mass, causing a lean mixture; During decelerate process, since the actual intake air mass drops rapidly, the calculated intake air mass is greater than the actual intake air mass, resulting in a rich mixture, as in [3]
The maximum deviation of transient lambda is less than 5%
Summary
PFI engine transient air-fuel ratio (AFR) accurate control is critical and difficult to achieve low emissions. The measured value can not truly reflect the actual value when the intake valve is closed. Changes of intake pressure causes fuel-film to change. There are several existing solutions for fuel-film compensation: conventional PID controller, sliding mode controller, as in [6], neural network controller, as in [7], and model-based fuel-film compensator, as in [8]. Neural networks and model-based controller usually involve complex mathematical theory using numerical integration for differential equations and a large number of matrix operations, as in [9]. This paper first proposes an application-oriented fuelfilm model and a transient fuel-film compensation algorithm, and verifies the correctness of the proposed strategy by engine bench tests
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