Dynamic Modeling of Residual-Affected Homogeneous Charge Compression Ignition Engines with Variable Valve Actuation

Abstract

One practical method for achieving homogeneous charge compression ignition (HCCI) in internal combustion engines is to modulate the valves to trap or reinduct exhaust gases, increasing the energy of the charge, and enabling autoignition. Controlling combustion phasing with valve modulation can be challenging, however, since any controller must operate through the chemical kinetics of HCCI and account for the cycle-to-cycle dynamics arising from the retained exhaust gas. This paper presents a simple model of the overall HCCI process that captures these fundamental aspects. The model uses an integrated Arrhenius rate expression to capture the importance of species concentrations and temperature on the ignition process and predict the start of combustion. The cycle-to-cycle dynamics, in turn, develop through mass exchange between a control volume representing the cylinder and a control mass modeling the exhaust manifold. Despite its simplicity, the model predicts combustion phasing, pressure evolution and work output for propane combustion experiments at levels of fidelity comparable to more complex representations. Transient responses to valve timing changes are also captured and, with minor modification, the model can, in principle, be extended to handle a variety of fuels.

A Simple HCCI Engine Model for Control

“…It is assumed that fuel reacts instantaneously at the crank angle where 50% of the heat is released (CA50). CA50 occurs ∆θ after the start of combustion θ SOC assuming that the combustion duration is found from equation (2). The in-cylinder pressure and temperature adhere to equations (9) and (10) until,…”

“…Several HCCI control-oriented models have been developed and most are DEM. A model including the effects of residuals induced by variable valve actuation is derived in [2]. The authors find that modeling ignition of the propaneair mixture using an integrated Arrhenius rate expression provides better results than using a temperature threshold or knock integral.…”

Real-time control oriented HCCI engine cycle-to-cycle dynamic modelling

“…The skeleton kinetic mechanism (SKM) method [12] and the heat release correlation method [10,13] . SKM is normally used for low molecular weight fuels or single component fuels, such as propane (C3H8) or ethanol (C2H5OH) [9,11] . This is because the reaction mechanisms of these fuels can be simplified by easy expressions, which generally contain 2 to 5 reaction steps and 5 to 10 reaction species [11] .…”

“…SKM is normally used for low molecular weight fuels or single component fuels, such as propane (C3H8) or ethanol (C2H5OH) [9,11] . This is because the reaction mechanisms of these fuels can be simplified by easy expressions, which generally contain 2 to 5 reaction steps and 5 to 10 reaction species [11] . However, due to the high complexity of gasoline even the simplest gasoline reaction mechanism currently still contains 69 steps and 38 reaction species [12] .…”

A Dynamic Simulation Strategy for PCCI Combustion Control Design

“…Among these, [5,20,21,26,28,39,42] can be mentioned. The standard procedure for creating a controller includes the modeling part as the first step [1,6,27,38,40]. Often these models differ in several aspects from models which include details of the combustion process, like three-dimensional Computational Fluid Dynamics (CFD) models [4,7,32,33].…”