Noorpoor - Assistant Professor، Iran University of Science and Technology
Mohammad Aghsaee - MS Student، Iran University of Science and Technology
Ali Hamedani - MS Student، Iran University of Science and Technology

Homogeneous charge compression ignition (HCCI)is one of the alternatives to reduce significantly engine emissions for future regulations.This new alternative combustion process is mainly controlled by chemical kinetics in comparison with the conventional combustion in interna l combustion engines.In this paper,the effect of H 2 addition on ignition timing of a natural -gas HCCI engines have been investigated numerically by adopting a single-zone zero-dimensional model.The chemical kinetic mechanism incorporated the GRI-3.0 mechanism that considers 53 species and 325 reactions together.To simulate HCCI engine cycles,a variable volume computation has been performed by including the piston motion into the chemical reaction design,CHEMKIN,code.The SENKIN code used in order to simulate the in-cylinder combustion.It was found that an additive-free mixture did not ignite for the intake temperature of 500 K.A mixture containing a small quantity of additives at the same temperature was ignited.For a fixed quanti ty of additive,it was found that H 2 addition was effective in advancing the ignition timing.It was also found that the percentage of additive required to achieve a near TDC ignition timing increases linearly with the increase in the engine speed while decreases with the increase in the equivalence ratio.Furthermore,the addition of 24%mass of H 2 could ignite a mixture at an intake temperature of 450 K.

Homogeneous Charge Compression Ignition (HCCI),Che mical Kinetics,Methane-fuel,Additives