Controlled Auto Ignition (CAI) uses compression heat to
auto ignite a homogeneous air/fuel mixture in an internal
combustion engine. Using internal exhaust gas recirculation
(IEGR) as an indirect control method, CAI
offers superior fuel economy and pollutant emission
reductions. Practically, this can readily be achieved by a
method of early exhaust valve closure and late inlet valve
opening to trap a large quantity of exhaust gas residuals
within the cylinder from one cycle to the next. However, it
has been found that the IEGR promoted CAI combustion
largely depends on the quantity and quality of the IEGR,
which in turn depends upon the combustion quality of
previous cycle, engine speed, load, etc. At low loads,
where the overall engine temperature is low, although an
extra large amount of IEGR has been used, CAI becomes
difficult to achieve. At high loads, the IEGR is much
hotter. The CAI combustion is so strong that it may
potentially be converted into detonation combustion. It is
difficult to control the CAI combustion quality without
external interferences. Engine coolant controls engine heat
transfer performance. By physically adjusting its
temperature, it was found in this research that IEGR promoted CAI combustion can be significantly extended
by increasing engine coolant temperature
