Modeling and Control of Air-Fuel Ratio in Internal Combustion Engines

Effective management of the ratio between air and fuel in internal combustion engines underpins both performance optimisation and emissions reduction. The air–fuel ratio (AFR) determines combustion temperature, pollutant formation and fuel consumption. Accurate modelling of the dynamic processes governing air intake, fuel injection, wall wetting and exhaust gas recirculation is essential to predict AFR transients during rapid throttle changes or load shifts. A variety of approaches—ranging from physics-based mean value engine models to data-driven observers—have been developed to estimate internal states and uncertain parameters in real time. Control strategies combine feedforward schemes, based on engine maps and disturbance anticipators, with robust feedback loops employing techniques such as model predictive control, sliding-mode regulation and fuzzy-logic algorithms. Recent trends emphasise adaptive and stochastic controllers that can accommodate time-varying delays, non-linearities and fuel composition uncertainty. Advances in computational power and sensor technologies have enabled hardware-in-the-loop testing and deployment of sophisticated controllers in road vehicles, marine and aviation engines, with a view to meeting ever-stricter global emission standards and enhancing fuel economy.

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Modeling and Control of Air-Fuel Ratio in Internal Combustion Engines publication trend

The graph below shows the total number of articles in modeling and control of air-fuel ratio in internal combustion engines across all publications each year (not limited to Nature Index journals).

Technical terms

Air–Fuel Ratio (AFR): The mass ratio of air to fuel in the engine’s intake mixture, critical for combustion efficiency and emissions control.

Mean Value Engine Model (MVEM): A simplified, averaged dynamical model of engine processes over one or more cycles, used for real-time control design.

Model Predictive Control (MPC): A control methodology that uses an internal model to predict system behaviour and optimise control actions over a future horizon.

References

1. Adaptive Air-Fuel Ratio Regulation for Port-Injected Spark-Ignited Engines Based on a Generalized Predictive Control Method. Energies (2019).
2. Intake Air Mass Observer Design Based on Extended Kalman Filter for Air-Fuel Ratio Control on SI Engine. Energies (2019).
3. Modeling of two-stroke aviation piston engines for control applications. Advances in Mechanical Engineering (2023).