Thermal management and control of a homogeneous charge compression ignition (HCCI) engineud

摘要

HCCI is the process which a relatively homogeneous mixture of air and fuel auto ignites through compression. HCCI engines can have high thermodynamic cycle efficiencies, with low levels of emissions of nitrogen oxides (NOx) and particulate matter (PM). However due to the nature of the combustion the operating envelope is quite small compared to conventional internal combustion engines.udA powertrain system centred on a supercharged HCCI engine with on-board thermal management was developed that extends the operating envelope of an HCCI engine. To achieve controlled auto-ignition across a wide range of engine conditions, a system for management of flow and temperature was installed at the air intake to enable the necessary regulation of temperatures and pressures at the inlet ports. The system includes a heat exchanger to heat the charge air, a supercharger to boost the charge air pressure, supercharger bypass and finally an intercooler, so that a wide range of combinations of pressures and temperatures can be achieved at the intake ports.udIn order to facilitate this control, a complete simulation model of the thermal system for a pressure-boosted multi-cylinder HCCI engine was developed. The model implements a dynamic mass and enthalpy balance model running in real time for the air intake system of the multi-cylinder HCCI gasoline engine and auxiliary components. The model is capable to calculate heat flux, mass flow, pressure and gas temperature distribution for the whole engine thermal management system however it does not take into account the turbulent nature of flow especially where hot and cold gas mix. Therefore an elaborate CFD model of the Thermal Management system has been compiled for evaluation of the computed flow field and analysis of the thermal system performance by the use of the CFD tool ANSYS CFX.....ud