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Real-Time Estimation of Intake O 2 Concentration in Turbocharged Common-Rail Diesel Engines
Abstract:
Automotive engines and control systems are more and more
sophisticated due to increasingly restrictive environmental
regulations. Particularly in both diesel and SI lean-burn engines
NOx emissions are the key pollutants to deal with and sophisticated
Engine Management System (EMS) strategies and after-treatment
devices have to be applied. In this context, the in-cylinder oxygen
mass fraction plays a key-role due its direct influence on the NOx
formation mechanism. Real-time estimation of the intake O₂ charge
enhances the NOx prediction during engine transients, suitable for
both dynamic adjustments of EMS strategies and management of
aftertreatment devices.
The paper focuses on the development and experimental validation
of a real-time estimator of O₂ concentration in the intake manifold
of an automotive common-rail diesel engine, equipped with
turbocharger and EGR system. The paper analyzes the air intake
process and the influence of the exhaust gas recirculation system
based on a mean value modeling approach. All variables required are
available at EMS level, thus allowing an on-board implementation
without extra costs for additional sensors.
The accuracy of the developed estimator is assessed by comparing
simulated and experimental trajectories of O₂ concentration,
measured by a Universal Exhaust Gas Oxygen (UEGO) sensor located in
the intake manifold. The experimental tests were carried out at the
test bench, imposing severe engine transients. The results evidence
that the O₂ estimator presents a good accuracy versus experiments
and offers significant opportunities for improving engine control
and after-treatment devices management during transient
operation.