On the Influence of Composition on the Thermally-Dominant Recompression HCCI Combustion Dynamics

Abstract

A zero dimensional, mean-value, control-oriented model for recompression homogeneous charge compression ignition (HCCI) combustion with two discrete states representing temperature and composition dynamics is presented. This model captures steady state magnitudes and trends in combustion phasing, residual gas fraction, and mass flows caused by sweeps in valve timings, fueling rate, and fuel injection timing. It is shown that the coupling of the composition state with the mainly thermally-driven combustion dynamics causes competing slow and fast dynamics that shape the transient response of the phasing. A decoupled version of the model, where composition does not affect combustion phasing, is also developed in an effort to further simplify the model. This version matches the steady state fidelity of the coupled model, but has a qualitatively different dynamical behavior. Both models exhibit complex behaviors such as limit cycles at extremely late phasing. Both realizations are valid contenders as low order steady state representations of HCCI behavior. High-fidelity transient data will be necessary to further clarify the necessity of including composition effects on combustion phasing.

Controlled Load and Speed Transitions in a Multicylinder Recompression HCCI Engine

“…The discrete-time model presented here extends the HCCI models developed for operating regimes with near-complete combustion and low cycle-tocycle variability in [8]- [10]. In general, combustion is to be maintained in these regions for driveability and fuel economy.…”

“…The HCCI model from [8]- [10] is presented in Section IV-A. This model is valid in the low CV dynamical region.…”

“…The nonlinear two-state HCCI combustion model state update equations from [8]- [10] are summarized as follows:…”

“…In this paper, θ soc is considered to be θ 02 , the engine crank angle at which 2% of the total heat release occurs. For more details, please refer to [8]- [10].…”

Model-Based Feedback Control for an Automated Transfer Out of SI Operation During SI to HCCI Transitions in Gasoline Engines

“…Recycling of exhaust gases can be achieved by internal EGR [7], wherein a variable valve timing (VVT) mechanism is used to transfer exhaust gas from one cycle to the next (residual gas), and also by external EGR [4], wherein the exhaust gas is routed back to the engine intake through piping in the air path. Recompression internal EGR is the assumed method of HCCI operation in this paper, which employs an early closure of the exhaust valve to trap residuals in the cylinder [8], though internal EGR by reinduction of exhaust gases can be used as well [9]. For a detailed description of HCCI combustion, see [1].…”