n-Heptane is a straight-chain alkane that serves as the zero point of the octane rating scale (the 100 point is a 100% iso-octane). (Earlier post.)

They found that compound homogeneous charge compression ignition combustion with n-heptane port injection and alcohol direct injection exhibits a three-stage combustion process containing n-heptane low-temperature reactions; high-temperature reactions; and alcohol combustion.

The results show that compound homogeneous charge compression ignition combustion could successfully reach the full load of the prototype engine. The indicated thermal efficiency is very close to the prototype engine. However, their CO and hydrocarbon emissions are relatively higher.

It is worth noting that compound homogeneous charge compression ignition combustion with alcohol direct injection can reduce nitrogen oxide and soot emissions simultaneously. Nitrogen oxide emissions can be reduced below 100 ppm, and smoke opacity is below 15% at the full-load ranges. Moreover, with increasing oxygen content of directly injected fuels, soot emission of compound homogeneous charge compression ignition combustion decreases. Ethanol direct injection could make compound homogeneous charge compression ignition combustion nearly smoke free at the full-load ranges.

—Huang et al.

Resources

• Zhen Huang, Libin Ji, Dong Han, Zheng Yang, Xingcai Lu (2013) Experimental study on dual-fuel compound homogeneous charge compression ignition combustion. International Journal of Engine Research. doi: doi: 10.1177/1468087412440908