A new predictive multi-zone model for HCCI engine combustion

Abstract

This work introduces a new predictive multi-zone model for the description of combustion in Homogeneous Charge Compression Ignition (HCCI) engines. The model exploits the existing OpenSMOKE++ computational suite to handle detailed kinetic mechanisms, providing reliable predictions of the in-cylinder auto-ignition processes. All the elements with a significant impact on the combustion performances and emissions, like turbulence, heat and mass exchanges, crevices, residual burned gases, thermal and feed stratification are taken into account. Compared to other computational approaches, this model improves the description of mixture stratification phenomena by coupling a wall heat transfer model derived from CFD application with a proper turbulence model. Furthermore, the calibration of this multi-zone model requires only three parameters, which can be derived from a non-reactive CFD simulation: these adaptive variables depend only on the engine geometry and remain fixed across a wide range of operating conditions, allowing the prediction of auto-ignition, pressure traces and pollutants. This computational framework enables the use of detail kinetic mechanisms, as well as Rate of Production Analysis (RoPA) and Sensitivity Analysis (SA) to investigate the complex chemistry involved in the auto-ignition and the pollutants formation processes. In the final sections of the paper, these capabilities are demonstrated through the comparison with experimental data

Computationally efficient evaluation of optimum homogeneous charge compression ignition operating range with accelerated multizone engine cycle simulation

“…17–20 Neshat and Saray 21 demonstrated good agreement with experimental data for an onion skin model with a wall heat transfer model and zones of equal height. Bissoli et al 22 used a similar model considering a wall function to estimate heat transfer from the outer zone toward cylinder walls. The wall function was adjusted with two constants that depend on engine geometry and are calculated from CFD simulations.…”

Performance Evaluation of Homogeneous Charge Compression Ignition Combustion Engine – A Review

“…Increasing the DI ratio greatly reduces the discharged UHC [21,101]. High levels of UHC and CO are emitted, which are assumed to originate from insufficient combustion, extinguishing, and crevice effects [21,94,102]. CO increases with stratification, so less CO-CO2 oxidation occurs [21].…”

A Multi-Zone Reaction-Based Diesel Combustion Model for Model-Based Control

“…The two-zone model improved the prediction accuracy of cylinder pressure, exhaust gas temperature, emission concentrations and SOC, compared to a single-zone model. More complicated multi-zone models were presented in [9][10][11][12][13] and shown to address the inhomogeneity fairly well. However, these models are too complicated for real-time simulations, and thus, a simplification must be applied.…”

“…Concentration Rate Equations. In a chemical kinetic system, the molecular concentration of species i is defined as (12) where N i = m i /MW i is the number of moles of species i. m i is the mass and MW i is the molecular weight.…”