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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


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Last updated: 2021-11-10