Homogeneous charge compression ignition (HCCI) engines are drawing attracting attention as the next-generation’s internal combustion engine, mainly because of its very low NOx and soot emissions and also for improvement in engine efficiency. Much research has been carried out in order to go deeper in this combustion process using multizone models or CFD codes. These simulation tools, although they can give a detailed view of the combustion process, are very time consuming and the results depend a lot on the initial conditions. A previous step to be considered in the simulation of the HCCI process is a heat release law evaluated from results of the experiment and a zero-dimensional model. This paper focuses on the development of a new heat release rate (HRR) law that models the HCCI process when the combustion chamber is considered as a homogeneous volume. The parameters of this law have been adjusted through an optimization process that has allowed to fit the combustion chamber pressure. All the engine operative conditions from low to full load have been successfully simulated with this HRR law, with the maximum error in the estimation of combustion chamber pressure less than 2%.Ministerio de Ciencia y Eduación CTQ2007-68,026-CO2-02/PP
