Abstract
Keywords:
HCCI, EGR, NO, auto-ignition
Abstract:
Homogeneous Charge Compression Ignition (HCCI) combustion applied to the internal combustion engine could be a solution to decrease the polluting emissions, particularly the nitrogen oxides and the particle matter. One of the main problems of this particular combustion mode is the control of the ignition phasing during the cycle. Several methods exist to regulate the start of the combustion such as the variation of the intake temperature or the EGR (Exhaust Gas Recirculation) rate. It is thus important to know the effect of each re-injected chemical species on the combustion development. The effects of different laboratorysimulated EGR rates (with as main components air, CO2 and N2), the inlet temperature and the addition at the intake of few species like NO, CO and CH4 on the ignition delays were studied. HCCI combustion of various fuels was also tested at the fixed equivalence ratio of 0.3. The results show that EGR effect due to the dilution is to delay spontaneous combustions whereas the intake temperature has the opposite effect. CO and CH4 addition have negligible effect. A promoting effect of NO addition is checked via cold and main combustion delays. A zero-dimensional modelling is developed in order to predict ignition times. The results obtained in modelling study offer encouraging tendencies by comparison with the experimental tests.