Estimation of In-cylinder Trapped Gas Mass and Composition
To meet the constantly restricting emission regulations and develop better
strategies for engine control systems, thorough knowledge of engine behavior
is crucial. One of the characteristics to evaluate engine performance and its
capability for power generation is in-cylinder pressure. Indeed, most of the
diagnosis and control signals can be obtained by recording the cylinder
pressure trace and predicting the thermodynamic variables [3].
This study investigates the correlation between the in-cylinder pressure and
total trapped gas mass [10] with the main focus on estimating the in-cylinder
gas mass as a part of a lab measuring procedure using the in-cylinder pressure
sensors, or as a real-time method for implementation in an engine control unit
that are not equipped with the cylinder pressure sensors. The motivation is
that precise determination of air mass is essential for the fuel control system
to convey the most-efficient combustion with lower emissions delivered to the
after-treatment system [10].
For this purpose, a six-cylinder Diesel engine is used for recording the engine
speed, engine torque, measuring the cylinder pressure profile resolved by
the crank angle, intake and exhaust valve phasing as well as intake and exhaust
manifold pressures and temperatures. Next, the most common ways of estimating
the in-cylinder trapped gas mass are studied and the most reliable ones are
investigated in-depth and a model with the acceptable accuracy in different
operating conditions is proposed, explained and implemented. The model in has a
thermodynamics basis and the relative errors is lower than ±3% in all the
investigated tests. Afterwards, the most important findings are highlighted,
the sources of errors are addressed and a sensitivity analysis is performed to
evaluate the model robustness. Subsequently, method adjustment for other
operating conditions is briefly explained, the potential future work is pointed
and a complete set of results is presented in Appendix B.
Sepideh Nikkar
2017
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Last updated: 2021-11-10
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