Combustion chamber wall temperature measurement and modeling during transient HCCI operation

In this paper the combustion chamber wall temperature was measured by the use of thermographic phosphor. The temperature was monitored over a large time window covering a load transient. Wall temperature measurement provide helpful information in all engines. This temperature is for example needed when calculating heat losses to the walls. Most important is however the effect of the wall temperature on combustion. The walls can not heat up instantaneously and the slowly increasing wall temperature following a load transient will affect the combustion events sucseeding the transient. The HCCI combustion process is, due to its dependence on chemical kinetics more sensitive to wall temperature than Otto or Diesel engines. In depth knowledge about transient wall temperature could increase the understanding of transient HCCI control. A "black box" state space model was derived which is useful when predicting transient wall temperature. To produce a model the engine is run with the load described by a Pseudo Random Binary Sequence (PRBS). Standard system identification methodology was then applied to acquire a state space model which calculate the combustion chamber wall temperature given IMEP_n. Such a model is useful when controlling HCCI combustion and makes it possible to compensate the impact of wall temperature delay following a load transient.