Question

Effect of compression ratio on ignition timming in hcci

Answer 1

The homogeneous charge compression ignition (HCCI) or controlled autoignition (CAI) combustion has often been considered a new combustion process amongst the numerous research papers published over the last decade. However, it has been around perhaps as long as the spark ignition (SI) combustion in gasoline engine and compression ignition (CI) combustion in diesel engines

In the case of gasoline engines, the HCCI combustion had been observed and was found responsible for the “after-run”/“run-on” phenomenon that many drivers had experienced with their carbureted gasoline engines in the sixties and seventies, when a spark ignition engine continued to run after the ignition was turned off

In the case of diesel engines, the hot-bulb oil engines were invented and developed over 100 years ago. In these engines, the raw oil was injected onto the surface of a heated chamber called hot-bulb. This early injection gives the fuel lots of time to vaporize and mix with air. The hot-bulb had to be heated on the outside for the start-up and once the engine had started, the hot-bulb was kept hot by using the burned gases. Later design placed injection through the connecting passage between the hot-bulb and the main chamber so that a more homogeneous mixture could be formed, resulting in auto-ignited homogeneous charge combustion