Effects of fuel additives on ignition timing of methane fuelled HCCI engine

Abstract

AbstractThe control of ignition is one of the most critical issues in HCCI engines. It has been shown that using fuel additives play a significant role in reducing engine emission to satisfy the mandated EPA regulation. In this paper, the effect of additives such as hydrogen (H2), hydrogen peroxide (H2O2), formaldehyde (CH2O) and ethane (C2H6) on the control of ignition in natural gas HCCI engines has been investigated. The SENKIN code used to simulate the in-cylinder chemical reactions. The overall engine was modelled in the engine cycle simulation code, GT-Power. Then, the combustion results from SENKIN were transferred to the engine model to investigate the overall engine performance characteristics of the HCCI engine using a developed interface code that linked the SENKIN to GT-Power. The computational model was validated by available experimental data. The results showed that the calculated data were relatively in good agreement with the experimental data. It was found that an additive free mixture was not ignited the mixture at an intake temperature of 500 K while a mixture containing a small quantity of additives at the same temperature was able to initiate chemical reaction. For a fixed quantity of additive, it was found that H2 addition was effective in advancing the ignition timing as is compared with the other three additives. The engine peak pressure has been moved to the location before top dead centre. It was also found that the percentage of additives required in achieving near TDC ignition, increases linearly with an increase in engine speed. It decreases with increasing equivalence ratio. A small addition of H2O2 ignites the mixture at an intake temperature of 450 K. Adding ethane does not help to initiate reaction at 450 K.Keywords: HOMOGENEOUS CHARGE COMPRESSION IGNITIONCHEMICAL KINETICSAUTOIGNITIONMETHANEADDITIVES