The possibility of running homogeneous charge compression ignition in spark ignition and compression ignition small-scale engines

Homogeneous charge compression ignition (HCCI) is known as an advanced combustion system. Due to cost limitations, small-scale engines are not equipped with features and devices, such as variable valve timing, intake heater, etc. which facilitate HCCI combustion. This study implemented HCCI on two small-scale engines, 150 cc spark ignition (SI) and 224 cc compression ignition (CI) engines. Only minor modifications were made for keeping costs low. The compression ratio of the SI target engine was increased from 10.5 to 12.4 to enhance the compression temperature. A low-pressure injector was installed near the intake port for supplying fuel for HCCI operation both on the SI and CI target engines. From initial tests, kerosene and butanol were chosen as the major fuel for HCCI operation on SI and CI target engines, respectively. Then, a serial experiment was performed to identify methods for controlling HCCI combustion on small-scale engines. Results show that exhaust gas recirculation and blended fuel were suitable methods for controlling HCCI combustion phasing on small-scale engines and could successfully extend the torque range of HCCI combustion.