A review of hydrogen addition in an HCCI engine fueled with biofuels

In recent times, the homogeneous charge compression ignition (HCCI) engine has become the attention of the research community. It is due to its improved combustion technology that will benefit the environment and automotive sectors. The intensive research of HCCI combustion is in line with the current trend in renewable fuels demand such as biofuels. One of the advantages of an HCCI engine to operate with a wide range of fuels including gasoline, diesel, biofuels, and hydrogen makes the HCCI technology emerged as the next internal combustion engine candidate for commercialization. This engine is considered as the potential alternative engine to provide what SI (Spark Ignition) and CI (Compression Ignition) engines could not sufficiently offer. Other than its good volumetric efficiency, it produces cleaner combustion and lower emissions levels of NO_x and Particulate Matters (PM). Hydrogen is knowingly able to reduce emissions level in an internal combustion engine, but the performance will be greatly reduced and not work in stable condition if runs in a single fuel. However, when the hydrogen is combined with biofuels, the emissions levels can be attained, and engine efficiency can be better than that of the biodiesel in a single mode. The combination of hydrogen with biofuels in dual-fuel mode can be achieved by inducing the hydrogen through the air intake manifold. Several ignition control strategies are performed experimentally (e.g. hydrogen addition, dual-fuel mode and exhaust gas recirculation) and other issues associated with HCCI engines are also discussed in detail in this review paper.