Homogeneous charge compression ignition (HCCI) using isooctane, ethanol and natural gas - A comparison with spark-ignition operation

摘要

The Homogeneous Charge Compression Ignition (HCCI) is the third alternative for combustion in the Internal Combustion (IC) engines. Here, a homogeneous charge is used as in a spark-ignited engine, but the charge is compressed to auto-ignition as in a diesel. The characteristics of HCCI were compared to SI using a 1.6-liter, single-cylinder engine with compression ratio 21:1 in HCCI mode and 12:1 in SI mode. Three different fuels were used; isooctane, ethanol and natural gas. Some remarkable results were noted in the experiments. The indicated efficiency of HCCI was much better than for SI operation. Very little NO{sub}x was generated with HCCI, eliminating the need for a lean NO{sub}x catalyst. However, HCCI generated more HC and CO than SI operation. Stable and efficient operation with HCCI could be obtained with λ=3 to λ=9 using isooctane or ethanol. Natural gas, with a higher octane number, required a richer mixture to run in HCCI mode.